kiss

#!/bin/sh
# shellcheck source=/dev/null
#
# Simple package manager written in POSIX shell for https://kisslinux.xyz
#
# The MIT License (MIT)
#
# Copyright (c) 2019-2021 Dylan Araps
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

log() {
    printf '%b%s %b%s%b %s\n' \
        "$c1" "${3:-->}" "${c3}${2:+$c2}" "$1" "$c3" "$2" >&2
}

war() {
    log "$1" "$2" "${3:-WARNING}"
}

die() {
    log "$1" "$2" "${3:-ERROR}"
    exit 1
}

contains() {
    # Check if a "string list" contains a word.
    case " $1 " in *" $2 "*) return 0; esac; return 1
}

equ() {
    # Check if a string is equal to enother.
    # This replaces '[ "$var" = str ]' and '[ "$var" != str ]'.
    case $1 in "$2") return 0 ;; *) return 1; esac
}

ok() {
    # Check if a string is non-null.
    # This replaces '[ "$var" ]', '[ -n "$var" ]'.
    case $1 in '') return 1 ;; *) return 0; esac
}

null() {
    # Check if a string is non-null.
    # This replaces '[ -z "$var" ]'.
    case $1 in '') return 0 ;; *) return 1; esac
}

tmp_file() {
    # Create a uniquely named temporary file and store its absolute path
    # in a variable (_tmp_file).
    #
    # To prevent subshell usage and to handle cases where multiple files
    # are needed, this saves the last two temporary files to variables
    # for access by the caller (allowing 3 files at once).
    _tmp_file_pre_pre=$_tmp_file_pre
    _tmp_file_pre=$_tmp_file
    _tmp_file=$tmp_dir/$KISS_PID-$1-$2

    : > "$_tmp_file" || die "$1" "Failed to create temporary file"
}

tmp_file_copy() {
    # Create a uniquely named temporary file and make a duplicate of
    # the file in '$3' if it exists.
    tmp_file "$1" "$2"

    ! [ -f "$3" ] || cp -f "$3" "$_tmp_file"
}

prompt() {
    null "$1" || log "$1"

    log "Continue?: Press Enter to continue or Ctrl+C to abort"

    # korn-shell does not exit on interrupt of read.
    equ "$KISS_PROMPT" 0 || read -r _ || exit 1
}

mkcd() {
    mkdir -p "$@" && cd "$1"
}

fnr() {
    # Replace all occurrences of substrings with substrings. This
    # function takes pairs of arguments iterating two at a time
    # until everything has been replaced.
    _fnr=$1
    shift 1

    while :; do case $_fnr-$# in
        *"$1"*) _fnr=${_fnr%"$1"*}${2}${_fnr##*"$1"} ;;
           *-2) break ;;
             *) shift 2
    esac done
}

am_owner() {
    # Figure out if we need to change users to operate on
    # a given file or directory.
    inf=$(ls -ld "$1") ||
        die "Failed to file information for '$1'"

    # Split the ls output into fields.
    read -r _ _ user _ <<EOF
$inf
EOF

    equ "$LOGNAME/$user" "$user/$LOGNAME"
}

as_user() {
    printf 'Using '%s' (to become %s)\n' "$cmd_su" "$user"

    case ${cmd_su##*/} in
        su) "$cmd_su" -c "$* <&3" "$user" 3<&0 </dev/tty ;;
         *) "$cmd_su" -u "$user" -- "$@"
    esac
}

pkg_owner() {
    ok "$2" || { set +f; set -f -- "$1" "$sys_db"/*/manifest; }

    _owns=$(grep -lxF "$@")
    _owns=${_owns%/*}
    _owns=${_owns##*/}

    ok "$_owns"
}

resolve_path() {
    _rpath=$KISS_ROOT/${1#/}

    # Attempt to resolve symlinks by using 'cd'.
    # If this fails, fallback to the file's parent
    # directory.
    cd -P "${_rpath%/*}" 2>/dev/null || PWD=${_rpath%/*}

    # Final resolved path.
    _rpath=${PWD#"$KISS_ROOT"}/${_rpath##*/}

    cd "$OLDPWD"
}

run_hook() {
    # Run all hooks in KISS_HOOK (a colon separated
    # list of absolute file paths).
    IFS=:

    for hook in ${KISS_HOOK:-}; do case $hook in *?*)
        "$hook" "$@" || die "$1 hook failed: '$hook'"
    esac done

    unset IFS
}

run_hook_pkg() {
    # Run a hook from the package's database files.
    if [ -x "$sys_db/$2/$1" ]; then
        log "$2" "Running $1 hook"
        "$sys_db/$2/$1"

    elif [ -f "$sys_db/$2/$1" ]; then
        war "$2" "skipping $1 hook: not executable"
    fi
}

decompress() {
    case $1 in
        *.tbz|*.bz2) bzip2 -d ;;
        *.lzma)      lzma -dc ;;
        *.lz)        lzip -dc ;;
        *.tar)       cat      ;;
        *.tgz|*.gz)  gzip -d  ;;
        *.xz|*.txz)  xz -dcT0 ;;
        *.zst)       zstd -dc ;;
    esac < "$1"
}

sh256() {
    # There's no standard utility to generate sha256 checksums.
    # This is a simple wrapper around sha256sum, sha256, shasum,
    # openssl, digest, ... which will use whatever is available.
    #
    # All utilities must match 'sha256sum' output.
    #
    # Example: '<checksum>  <file>'

    # Filter out directories and anything which does not exist.
    for f do shift
        [ -d "$f" ] || [ ! -e "$f" ] || set -- "$@" "$f"
    done

    ! equ "$#" 0 || return 0

    # Set the arguments based on found sha256 utility.
    case ${cmd_sha##*/} in
        openssl) set -- dgst -sha256 -r "$@" ;;
         sha256) set -- -r "$@" ;;
         shasum) set -- -a 256 "$@" ;;
         digest) set -- -a sha256 "$@" ;;
    esac

    # This is now one call to the checksums command rather than
    # one per file. We also display errors now rather than not
    # (due to old runtime detection method).
    hash=$("$cmd_sha" "$@") || die "Failed to generate checksums"

    # Intentional, globbing disabled.
    # shellcheck disable=2046,2086
    set -- $hash

    # As the output is '<hash>  <file>' and the above list is
    # split on whitespace; we need to pop every 2nd element.
    for sum do case ${_i:-0} in
        0) _i=1; set -- "$@" "$sum" ;;
        1) _i=0
    esac; shift; done

    printf '%s\n' "$@"

    # Convert the list items to a newline separated string.
    IFS=$newline hash=$*
    unset IFS
}

pkg_find_version() {
    ver_pre=$repo_ver
    rel_pre=$repo_rel

    pkg_find "$@"

    read -r repo_ver repo_rel 2>/dev/null < "$repo_dir/version" ||
        die "$1" "Failed to read version file ($repo_dir/version)"

    ok "$repo_rel" ||
        die "$1" "Release field not found in version file"

    # This belongs somewhere else, for now it can live here.
    [ -x "$repo_dir/build" ] ||
        die "$pkg" "Build file not found or not executable"
}

pkg_find_version_split() {
    pkg_find_version "$@"

    # Split the version on '.+-_' to obtain individual components.
    IFS=.+-_ read -r repo_major repo_minor repo_patch repo_ident <<EOF
$repo_ver
EOF
}

pkg_find() {
    _pkg_find "$@" || die "'$1' not found"
}

_pkg_find() {
    # Figure out which repository a package belongs to by searching for
    # directories matching the package name in $KISS_PATH/*.
    set -- "$1" "$2" "$3" "${4:-"$KISS_PATH"}"
    IFS=:

    # Iterate over KISS_PATH, grabbing all directories which match the query.
    # Intentional.
    # shellcheck disable=2086
    for _find_path in $4 "${3:-$sys_db}"; do set +f
        for _find_pkg in "$_find_path/"$1; do
            test "${3:--d}" "$_find_pkg" && set -f -- "$@" "$_find_pkg"
        done
    done

    unset IFS

    # Show all search results if called from 'kiss search', else store the
    # values in variables. If there are 4 arguments, no package has been found.
    case $2-$# in
        *-4) return 1 ;;
         -*) repo_dir=$5 repo_name=${5##*/} ;;
          *) shift 4; printf '%s\n' "$@"
    esac
}

pkg_list_version() {
    # List installed packages. As the format is files and directories, this
    # just involves a simple for loop and file read.

    # Optional arguments can be passed to check for specific packages. If no
    # arguments are passed, list all.
    ok "$1" || { set +f; set -f -- "$sys_db"/*; }

    # Loop over each package and print its name and version.
    for _list_pkg do
        pkg_find_version "${_list_pkg##*/}" "" "" "$sys_db"

        printf '%s\n' "$repo_name $repo_ver-$repo_rel"
    done
}

pkg_cache() {
    # Find the tarball of a package using a glob. Use the user's set compression
    # method if found or first match of the below glob.
    pkg_find_version "$1"

    set +f -- "$bin_dir/$1@$repo_ver-$repo_rel.tar."
    set -f -- "$1$KISS_COMPRESS" "$1"*

    tar_file=$1

    # If the first match does not exist, use the second. If neither exist,
    # this function returns 1 and the caller handles the error.
    [ -f "$1" ] || { tar_file=$2; [ -f "$2" ]; }
}

pkg_source_resolve() {
    # Given a line of input from the sources file, return an absolute
    # path to the source if it already exists, error if not.
    ok "${2##\#*}" || { unset _res _des; return; }

    unset _des

    # Surround each replacement with substitutions to handled escaped markers.
    # First substitution turns '\MARKER' into ' ' (can't appear in sources as
    # they're already split on whitespace), second replaces 'MARKER' with its
    # value and the third, turns ' ' into 'MARKER' (dropping \\).
    fnr "${2%"${2##*[!/]}"}" \
        \\VERSION \  VERSION "$repo_ver"   \  VERSION \
        \\RELEASE \  RELEASE "$repo_rel"   \  RELEASE \
        \\MAJOR   \  MAJOR   "$repo_major" \  MAJOR \
        \\MINOR   \  MINOR   "$repo_minor" \  MINOR \
        \\PATCH   \  PATCH   "$repo_patch" \  PATCH \
        \\IDENT   \  IDENT   "$repo_ident" \  IDENT \
        \\PACKAGE \  PACKAGE "$repo_name"  \  PACKAGE

    set -- "$1" "$_fnr" "${3%"${3##*[!/]}"}" "$4"

    # Git repository.
    if null "${2##git+*}"; then
        _res=$2

    # Remote source (cached).
    elif [ -f "$src_dir/$1/${3:+"$3/"}${2##*/}" ]; then
        _res=$src_dir/$1/${3:+"$3/"}${2##*/}

    # Remote source.
    elif null "${2##*://*}"; then
        _res=url+$2
        _des=$src_dir/$1/${3:+"$3/"}${2##*/}

    # Local relative dir.
    elif [ -d "$repo_dir/$2" ]; then
        _res=$repo_dir/$2/.

    # Local absolute dir.
    elif [ -d "/${2##/}" ]; then
        _res=/${2##/}/.

    # Local relative file.
    elif [ -f "$repo_dir/$2" ]; then
        _res=$repo_dir/$2

    # Local absolute file.
    elif [ -f "/${2##/}" ]; then
        _res=/${2##/}

    else
        die "$1" "No local file '$_res'"
    fi

    ok "$4" || printf 'found %s\n' "$_res"
}

pkg_source() {
    # Download any remote package sources. The existence of local files is
    # also checked.
    pkg_find_version_split "$1"

    # Support packages without sources. Simply do nothing.
    [ -f "$repo_dir/sources" ] || return 0

    log "$1" "Reading sources"

    while read -r src dest || ok "$src"; do
        pkg_source_resolve "$1" "$src" "$dest" "$2"

        # arg1: pre-source
        # arg2: package name
        # arg3: verbatim source
        # arg4: resolved source
        run_hook pre-source "$1" "$src" "$_fnr"

        case $_res in url+*)
            # Create directory structure in source cache. This prevents cache
            # conflicts between identical sources with differing dests.
            mkcd "${_des%/*}"

            pkg_source_get "$_des" "${_res##url+}"
        esac

        # arg1: post-source
        # arg2: package name
        # arg3: verbatim source
        # arg4: resolved source
        run_hook post-source "$1" "$src" "${_des:-"$_res"}"
    done < "$repo_dir/sources"
}

pkg_source_get() {
    log "$repo_name" "Downloading $2"

    # Set the arguments based on found download utility.
    case ${cmd_get##*/} in
           curl) set -- -fLo "$@" ;;
           wget) set -- -O   "$@" ;;
         aria2c) set -- -o   "$@" ;;
    esac

    "$cmd_get" "$@" || {
        rm -f "$2"
        die "$repo_name" "Failed to download $3"
    }
}

pkg_source_git() {
    # This magic will shallow clone branches, commits or the
    # regular repository. It correctly handles cases where a
    # shallow clone is not possible.
    log "$repo_name" "Cloning $1"

    # Split the source into URL + OBJECT (branch or commit).
    url=$1 com=${url##*[@#]} com=${com#${url%[#@]*}}

    git init
    git remote add origin "${url%[#@]*}"
    git fetch -t --filter=tree:0 origin "$com" || git fetch -t
    git -c advice.detachedHead=0 checkout "${com:-FETCH_HEAD}"
}

pkg_source_tar() {
    # This is a portable shell implementation of GNU tar's
    # '--strip-components 1'. Use of this function denotes a
    # performance penalty.
    tmp_file "$repo_name" tarball
    tmp_file "$repo_name" tarball-manifest

    unset _seen

    decompress "$1" > "$_tmp_file_pre" ||
        die "$repo_name" "Failed to decompress $1"

    tar xf "$_tmp_file_pre" ||
        die "$repo_name" "Failed to extract $1"

    # The sort command filters out all duplicate top-level
    # directories from the tarball's manifest. This is an optimization
    # as we avoid looping (4000 times for Python(!)).
    tar tf "$_tmp_file_pre" | sort -ut / -k1,1 > "$_tmp_file" ||
        die "$repo_name" "Failed to extract manifest"

    # Iterate over all directories in the first level of the
    # tarball's manifest. Each directory is moved up a level.
    while IFS=/ read -r dir _; do case ${dir#.} in *?*)
        # Move the parent directory to prevent naming conflicts
        # with the to-be-moved children.
        mv -f "$dir" "$KISS_PID-$dir"

        # Move all children up a directory level. If the mv command
        # fails, fallback to copying the remainder of the files.
        #
        # We can't use '-exec {} +' with any arguments between
        # the '{}' and '+' as this is not POSIX. We must also
        # use '$0' and '$@' to reference all arguments.
        find "$KISS_PID-$dir/." ! -name . -prune \
            -exec sh -c 'mv -f "$0" "$@" .' {} + 2>/dev/null ||

        find "$KISS_PID-$dir/." ! -name . -prune \
            -exec sh -c 'cp -fRp "$0" "$@" .' {} +

        # Remove the directory now that all files have been
        # transferred out of it. This can't be a simple 'rmdir'
        # as we may leave files in here if any were copied.
        rm -rf "$KISS_PID-$dir"
    esac done < "$_tmp_file"

    # Remove the tarball now that we are done with it.
    rm -f "$_tmp_file_pre"
}

pkg_extract() {
    # Extract all source archives to the build directory and copy over any
    # local repository files.
    #
    # NOTE: repo_dir comes from caller.
    log "$1" "Extracting sources"

    # arg1: pre-extract
    # arg2: package name
    # arg3: path to DESTDIR
    run_hook pre-extract "$pkg" "$pkg_dir/$pkg"

    while read -r src dest || ok "$src"; do
        pkg_source_resolve "$1" "$src" "$dest" >/dev/null

        # Create the source's directories if not null.
        null "$_res" || mkcd "$mak_dir/$1/$dest"

        case $_res in
            git+*)
                pkg_source_git "${_res##git+}"
            ;;

            *.tar|*.tar.??|*.tar.???|*.tar.????|*.t?z)
                pkg_source_tar "$_res"
            ;;

            *?*)
                cp -Rf "$_res" .
            ;;
        esac
    done < "$repo_dir/sources" || die "$1" "Failed to extract $_res"
}

pkg_depends() {
    # Resolve all dependencies and generate an ordered list. The deepest
    # dependencies are listed first and then the parents in reverse order.
    contains "$deps" "$1" || {
        # Filter out non-explicit, already installed packages.
        null "$3" || ok "$2" || contains "$explicit" "$1" ||
            ! [ -d "$sys_db/$1" ] || return

        # Detect circular dependencies and bail out.
        # Looks for multiple repeating patterns of (dep dep_parent) (5 is max).
        case " $4 " in
*" ${4##* } "*" $1 "\
*" ${4##* } "*" $1 "\
*" ${4##* } "*" $1 "\
*" ${4##* } "*" $1 "\
*" ${4##* } "*" $1 "\
*)
            die "Circular dependency detected $1 <> ${4##* }"
        esac

        ! _pkg_find "$1" || ! [ -e "$repo_dir/depends" ] ||

        # Recurse through the dependencies of the child packages.
        while read -r dep dep_type || ok "$dep"; do
            ok "${dep##\#*}" || continue

            pkg_depends "$dep" '' "$3" "$4 $1" "$dep_type"
        done < "$repo_dir/depends" || :

        # Add parent to dependencies list.
        if ! equ "$2" expl || { equ "$5" make && ! pkg_cache "$1"; }; then
            deps="$deps $1"
        fi
    }
}

pkg_order() {
    # Order a list of packages based on dependence and take into account
    # pre-built tarballs if this is to be called from 'kiss i'.
    unset order redro deps

    for pkg do case $pkg in
      /*@*.tar.*) deps="$deps $pkg" ;;
       *@*.tar.*) deps="$deps $ppwd/$pkg" ;;
             */*) die "Not a package' ($pkg)" ;;
               *) pkg_depends "$pkg" raw
    esac done

    # Filter the list, only keeping explicit packages. The purpose of these
    # two loops is to order the argument list based on dependence.
    for pkg in $deps; do case " $* " in *" $pkg "*|*" ${pkg##"$ppwd/"} "*)
        order="$order $pkg"
        redro="$pkg $redro"
    esac done

    unset deps
}

pkg_strip() {
    # Strip package binaries and libraries. This saves space on the system as
    # well as on the tarballs we ship for installation.
    [ -f "$mak_dir/$pkg/nostrip" ] || equ "$KISS_STRIP" 0 && return

    log "$1" "Stripping binaries and libraries"

    # Strip only files matching the below ELF types. This uses 'od' to print
    # the first 18 bytes of the file. This is the location of the ELF header
    # (up to the ELF type) and contains the type information we need.
    #
    # Static libraries (.a) are in reality AR archives which contain ELF
    # objects. We simply read from the same 18 bytes and assume that the AR
    # header equates to an archive containing objects (.o).
    #
    # Example ELF output ('003' is ELF type):
    # 0000000 177   E   L   F 002 001 001  \0  \0  \0  \0  \0  \0  \0  \0  \0
    # 0000020 003  \0
    # 0000022
    #
    # Example AR output (.a):
    # 0000000   !   <   a   r   c   h   >  \n   /
    # 0000020
    # 0000022
    while read -r file; do case $file in
        # Look only in these locations for files of interest (libraries,
        # programs, etc). This includes all subdirectories. Old behavior
        # would run od on all files (upwards of 4000 for Python).
        */sbin/?*|*/bin/?*|*/lib/?*|*/lib??/?*|*/lib???/?*|*/lib????/?*)

        case $(od -A o -t c -N 18 "$file") in
            # REL (object files (.o), static libraries (.a)).
            *177*E*L*F*0000020\ 001\ *|*\!*\<*a*r*c*h*\>*)
                strip -g -R .comment -R .note "$file"
            ;;

            # EXEC (binaries), DYN (shared libraries).
            # Shared libraries keep global symbols in a separate ELF section
            # called '.dynsym'. '--strip-all/-s' does not touch the dynamic
            # symbol entries which makes this safe to do.
            *177*E*L*F*0000020\ 00[23]\ *)
                strip -s -R .comment -R .note "$file"
            ;;
        esac
    esac done < "$pkg_dir/$1/$pkg_db/$1/manifest" 2>/dev/null || :
}

pkg_fix_deps() {
    # Dynamically look for missing runtime dependencies by checking each
    # binary and library with 'ldd'. This catches any extra libraries and or
    # dependencies pulled in by the package's build suite.
    log "$1" "looking for dependencies (using ${cmd_elf##*/})"

    tmp_file_copy "$1" depends depends
    tmp_file      "$1" depends-fixed

    set +f
    set -f -- "$sys_db/"*/manifest

    # False positive (not a write).
    # shellcheck disable=2094
    while read -r _file; do case $_file in
        # Look only in these locations for files of interest (libraries,
        # programs, etc). This includes all subdirectories. Old behavior
        # would run ldd on all files (upwards of 4000 for Python).
        */sbin/?*|*/bin/?*|*/lib/?*|*/lib??/?*|*/lib???/?*|*/lib????/?*)

        # The readelf mode requires ldd's output to resolve the library
        # path for a given file. If ldd fails, silently skip the file.
        ldd_buf=$(ldd -- "$_file" 2>/dev/null) || continue

        # Attempt to get information from readelf. If this fails (or we
        # are in ldd mode), do full ldd mode (which has the downside of
        # listing dependencies of dependencies (and so on)).
        elf_buf=$("$cmd_elf" -d "$_file" 2>/dev/null) || elf_buf=$ldd_buf

        # Iterate over the output of readelf or ldd, extract file names,
        # resolve their paths and finally, figure out their owner.
        while read -r lib; do case $lib in *NEEDED*\[*\]|*'=>'*)
            # readelf: 0x0000 (NEEDED) Shared library: [libjson-c.so.5]
            lib=${lib##*\[}
            lib=${lib%%\]*}

            # Resolve library path.
            # ldd: libjson-c.so.5 => /lib/libjson-c.so.5 ...
            case $cmd_elf in
                *readelf) lib=${ldd_buf#*"	$lib => "} ;;
                *)        lib=${lib##*=> } ;;
            esac
            lib=${lib%% *}

            # Skip files owned by libc and POSIX.
            case ${lib##*/} in
                ld-*           |\
                lib[cm].so*    |\
                libcrypt.so*   |\
                libdl.so*      |\
                libmvec.so*    |\
                libpthread.so* |\
                libresolv.so*  |\
                librt.so*      |\
                libtrace.so*   |\
                libutil.so*    |\
                libxnet.so*    |\
                ldd)
                    continue
            esac

            resolve_path "$lib"

            # Skip file if owned by current package
            ! pkg_owner -e "$_rpath" manifest ||
                continue

            ! pkg_owner -e "$_rpath" "$@" ||
                printf '%s\n' "$_owns"

        esac done <<EOF || :
$elf_buf
EOF
    esac done < manifest |

    # Sort the depends file (including the existing depends file) and
    # remove any duplicate entries. This can't take into account comments
    # so they remain rather than being replaced.
    sort -uk1,1 "$_tmp_file_pre" - > "$_tmp_file"

    # If the depends file was modified, show a diff and replace it.
    ! [ -s "$_tmp_file" ] || {
        diff -U 3 "$_tmp_file_pre" "$_tmp_file" 2>/dev/null || :

        # Replace the existing depends file if one exists, otherwise this
        # just moves the file to its final resting place.
        mv -f "$_tmp_file" depends

        # Generate a new manifest as we may be the creator of the depends
        # file. This could otherwise be implemented by inserting a line
        # at the correct place in the existing manifest.
        pkg_manifest "${PWD##*/}" "$pkg_dir"
    }
}

pkg_manifest() {
    # Generate the package's manifest file. This is a list of each file
    # and directory inside the package. The file is used when uninstalling
    # packages, checking for package conflicts and for general debugging.
    log "$1" "Generating manifest"

    tmp_file "$1" manifest

    # Create a list of all files and directories. Append '/' to the end of
    # directories so they can be easily filtered out later. Also filter out
    # all libtool .la files and charset.alias.
    {
        printf '%s\n' "$2/$1/$pkg_db/$1/manifest"

        ! [ -d "$2/$1/etc" ] ||
            printf '%s\n' "$2/$1/$pkg_db/$1/etcsums"

        find "$2/$1" ! -path "$2/$1" -type d -exec printf '%s/\n' {} + \
            -o \( ! -type d -a ! -name \*.la -a ! -name charset.alias \) -print

    # Sort the output in reverse. Directories appear after their contents.
    } | sort -ur > "$_tmp_file"

    # Remove the prefix from each line.
    while read -r file; do
        printf '%s\n' "${file#"$2/$1"}"
    done < "$_tmp_file" > "$2/$1/$pkg_db/$1/manifest"
}

pkg_manifest_validate() {
    log "$1" "Checking if manifest valid"

    while read -r line; do
        [ -e "$tar_dir/$1$line" ] || [ -h "$tar_dir/$1$line" ] || {
            printf '%s\n' "$line"
            set -- "$@" "$line"
        }
    done < "$pkg_db/$1/manifest"

    case $# in [2-9]|[1-9][0-9]*)
        die "$1" "manifest contains $(($# - 1)) non-existent files"
    esac
}

pkg_manifest_replace() {
    # Replace the matching line in the manifest with the desired replacement.
    # This used to be a 'sed' call which turned out to be a little
    # error-prone in some cases. This new method is a tad slower but ensures
    # we never wipe the file due to a command error.
    tmp_file "$1" "manifest-replace-${2##*/}"

    while read -r line; do
        ! equ "$line" "$2" || line=$3

        printf '%s\n' "$line"
    done < "$sys_db/$1/manifest" | sort -r > "$_tmp_file"

    mv -f "$_tmp_file" "$sys_db/$1/manifest"
}

pkg_etcsums() {
    # Generate checksums for each configuration file in the package's /etc/
    # directory for use in "smart" handling of these files.
    log "$repo_name" "Generating etcsums"

    # Minor optimization - skip packages without /etc/.
    [ -d "$pkg_dir/$repo_name/etc" ] || return 0

    # Create a list of all files in etc but do it in reverse.
    while read -r etc; do case $etc in /etc/*[!/])
        set -- "$pkg_dir/$repo_name/$etc" "$@"
    esac done < manifest

    sh256 "$@" > etcsums
}

pkg_tar() {
    # Create a tarball from the built package's files. This tarball also
    # contains the package's database entry.
    #
    # NOTE: repo_ comes from caller.
    log "$1" "Creating tarball"

    _tar_file=$bin_dir/$1@$repo_ver-$repo_rel.tar.$KISS_COMPRESS

    # Use 'cd' to avoid needing tar's '-C' flag which may not be portable
    # across implementations.
    cd "$pkg_dir/$1"

    # Create a tarball from the contents of the built package.
    tar cf - . | case $KISS_COMPRESS in
        bz2)  bzip2 -z ;;
        gz)   gzip -6  ;;
        lzma) lzma -z  ;;
        lz)   lzip -z  ;;
        xz)   xz -zT0  ;;
        zst)  zstd -z  ;;
    esac > "$_tar_file"

    cd "$OLDPWD"

    log "$1" "Successfully created tarball"

    # arg1: post-package
    # arg2: package name
    # arg3: path to tarball
    run_hook post-package "$1" "$_tar_file"
}

pkg_build_all() {
    # Build packages and turn them into packaged tarballs.
    # Order the argument list and filter out duplicates.

    # Mark packages passed on the command-line explicit.
    # Also resolve dependencies for all explicit packages.
    for pkg do
        pkg_depends "$pkg" expl filter
        explicit="$explicit $pkg "
    done

    # If this is an update, don't always build explicitly passsed packages
    # and instead install pre-built binaries if they exist.
    ok "$pkg_update" || explicit_build=$explicit

    set --

    # If an explicit package is a dependency of another explicit package,
    # remove it from the explicit list.
    for pkg in $explicit; do
        contains "$deps" "$pkg" || set -- "$@" "$pkg"
    done
    explicit_cnt=$#
    explicit=$*

    log "Building: explicit: $*${deps:+, implicit: ${deps## }}"

    # Intentional, globbing disabled.
    # shellcheck disable=2046,2086
    set -- $deps "$@"

    # Ask for confirmation if extra packages need to be built.
    equ "$#" "$explicit_cnt" || prompt

    log "Checking for pre-built dependencies"

    # Install any pre-built dependencies if they exist in the binary
    # directory and are up to date.
    for pkg in "$@"; do
        if ! contains "$explicit_build" "$pkg" && pkg_cache "$pkg"; then
            log "$pkg" "Found pre-built binary"

            # Intended behavior.
            # shellcheck disable=2030,2031
            (export KISS_FORCE=1; args i "$tar_file")
        else
            set -- "$@" "$pkg"
        fi

        shift
    done

    for pkg do
        pkg_source "$pkg"

        ! [ -f "$repo_dir/sources" ] || pkg_verify "$pkg"
    done

    # Finally build and create tarballs for all passed packages and
    # dependencies.
    for pkg do
        log "$pkg" "Building package ($((_build_cur+=1))/$#)"

        pkg_find_version_split "$pkg"

        # arg1: queue-status
        # arg2: package name
        # arg3: number in queue
        # arg4: total in queue
        run_hook queue "$pkg" "$_build_cur" "$#"

        ! [ -f "$repo_dir/sources" ] || pkg_extract  "$pkg"

        pkg_build    "$pkg"
        pkg_manifest "$pkg" "$pkg_dir"
        pkg_strip    "$pkg"

        cd "$pkg_dir/$pkg/$pkg_db/$pkg"

        pkg_fix_deps "$pkg"
        pkg_etcsums
        pkg_tar      "$pkg"

        if ok "$pkg_update" || ! contains "$explicit" "$pkg"; then
            log "$pkg" "Needed as a dependency or has an update, installing"

            # Intended behavior.
            # shellcheck disable=2030,2031
            (export KISS_FORCE=1; args i "$pkg")
        fi
    done

    case $pkg_update in '')
        # Intentional, globbing disabled.
        # shellcheck disable=2046,2086
        ! prompt "Install built packages? [$explicit]" || (args i $explicit)
    esac
}

pkg_build() {
    # Install built packages to a directory under the package name to
    # avoid collisions with other packages.
    mkcd "$mak_dir/$1" "$pkg_dir/$1/$pkg_db"

    log "$1" "Starting build"

    # arg1: pre-build
    # arg2: package name
    # arg3: path to build directory
    run_hook pre-build "$1" "$mak_dir/$1"

    # Attempt to create the log file early so any permissions errors are caught
    # before the build starts. 'tee' is run in a pipe and POSIX shell has no
    # pipe-fail causing confusing behavior when tee fails.
    : > "$log_dir/$1-$time-$KISS_PID"

    # Call the build script, log the output to the terminal and to a file.
    # There's no PIPEFAIL in POSIX shell so we must resort to tricks like kill.
    {
        # Give the script a modified environment. Define toolchain program
        # environment variables assuming a generic environment by default.
        #
        # Define DESTDIR, PREFIX and GOPATH to sane defaults as their use is
        # mandatory in anything using autotools, meson, cmake, etc.
        #
        # Define KISS_ROOT as the sanitized value used internally by the
        # package manager. This is safe to join with other paths.
        AR="${AR:-ar}" \
        CC="${CC:-cc}" \
        CXX="${CXX:-c++}" \
        NM="${NM:-nm}" \
        RANLIB="${RANLIB:-ranlib}" \
        DESTDIR="$pkg_dir/$1" \
        GOPATH="$PWD/go" \
        KISS_ROOT="$KISS_ROOT" \
        \
        "$repo_dir/build" "$pkg_dir/$1" "$repo_ver" 2>&1 || {
            log "$1" "Build failed"
            log "$1" "Log stored to $log_dir/$1-$time-$KISS_PID"

            # arg1: build-fail
            # arg2: package name
            # arg3: path to build directory
            run_hook build-fail "$pkg" "$mak_dir/$1"

            pkg_clean
            kill 0
        }
    } | tee "$log_dir/$1-$time-$KISS_PID"

    # Delete the log file if the build succeeded to prevent the directory
    # from filling very quickly with useless logs.
    equ "$KISS_KEEPLOG" 1 || rm -f "$log_dir/$1-$time-$KISS_PID"

    # Copy the repository files to the package directory.
    cp -LRf "$repo_dir" "$pkg_dir/$1/$pkg_db/"

    log "$1" "Successfully built package"

    # arg1: post-build
    # arg2: package name
    # arg3: path to DESTDIR
    run_hook post-build "$1" "$pkg_dir/$1"
}

pkg_checksums() {
    # Generate checksums for packages.
    #
    # NOTE: repo_ comes from caller.
    while read -r src dest || ok "$src"; do
        pkg_source_resolve "$repo_name" "$src" "$dest" >/dev/null

        case $_res in [!g][!i][!t][!+]*/*[!.])
            set -- "$@" "$_res"
        esac
    done < "$repo_dir/sources"

    sh256 "$@"
}

pkg_verify() {
    # Verify all package checksums. This is achieved by generating a new set
    # of checksums and then comparing those with the old set.
    #
    # NOTE: repo_dir comes from caller.
    log "$repo_name" "Verifying sources"

    # Generate a new set of checksums to compare against.
    pkg_checksums >/dev/null

    # Intentional, globbing disabled.
    # shellcheck disable=2038,2086
    set -- $hash

    # Only read checksums if we generated some.
    null "$1" ||

    # Check that the first column (separated by whitespace) match in both
    # checksum files. If any part of either file differs, mismatch. Abort.
    while read -r chk _ || ok "$1"; do
        printf '%s\n%s\n' "- ${chk:-missing}" "+ ${1:-no source}"

        case $1-${chk:-null} in
            "$chk-$1"|"$1-SKIP")
                # We have a match.
            ;;

            "$hash"-*|*)
                die "$repo_name" "Checksum mismatch"
            ;;
        esac

        shift "$(($# != 0))"
    done < "$repo_dir/checksums"
}

pkg_conflicts() {
    # Check to see if a package conflicts with another.
    # _pkg comes from the caller.
    log "$_pkg" "Checking for package conflicts"

    tmp_file "$_pkg" manifest-files
    tmp_file "$_pkg" found-conflicts

    # Filter the tarball's manifest and select only files. Resolve all
    # symlinks in file paths as well.
    while read -r file; do case $file in *[!/])
        resolve_path "$file"

        printf '%s\n' "$_rpath"
    esac done < "$PWD/$pkg_db/$_pkg/manifest" > "$_tmp_file_pre"

    cd "$tar_dir/$_pkg"
    set +f
    set -f "$sys_db"/*/manifest

    # Remove the current package from the manifest list.
    fnr " $* " " $sys_db/$_pkg/manifest " ""

    # Intentional, globbing disabled.
    # shellcheck disable=2046,2086
    set -- $_fnr

    # Return here if there is nothing to check conflicts against.
    ! equ "$#" 0 || return 0

    # Store the list of found conflicts in a file as we'll be using the
    # information multiple times. Storing things in the cache dir allows
    # us to be lazy as they'll be automatically removed on script end.
    grep -Fxf "$_tmp_file_pre" -- "$@" 2>/dev/null > "$_tmp_file" || :

    # Enable alternatives automatically if it is safe to do so.
    # This checks to see that the package that is about to be installed
    # doesn't overwrite anything it shouldn't in '/var/db/kiss/installed'.
    grep -q ":/var/db/kiss/installed/" "$_tmp_file" || safe=1

    if ! equ "$KISS_CHOICE" 1 && equ "$safe" 1 && [ -s "$_tmp_file" ]; then
        # This is a novel way of offering an "alternatives" system.
        # It is entirely dynamic and all "choices" are created and
        # destroyed on the fly.
        #
        # When a conflict is found between two packages, the file
        # is moved to a directory called "choices" and its name
        # changed to store its parent package and its intended
        # location.
        #
        # The package's manifest is then updated to reflect this
        # new location.
        #
        # The 'kiss alternatives' command parses this directory and
        # offers you the CHOICE of *swapping* entries in this
        # directory for those on the filesystem.
        #
        # The alternatives command does the same thing we do here,
        # it rewrites manifests and moves files around to make
        # this work.
        #
        # Pretty nifty huh?
        while IFS=: read -r _ con; do
            printf '%s\n' "Found conflict $con"

            # Create the "choices" directory inside of the tarball.
            # This directory will store the conflicting file.
            mkdir -p "$PWD/$cho_db"

            # Construct the file name of the "db" entry of the
            # conflicting file. (pkg_name>usr>bin>ls)
            fnr "$con" '/' '>'

            # Move the conflicting file to the choices directory
            # and name it according to the format above.
            mv -f "$PWD$con" "$PWD/$cho_db/$_pkg$_fnr" 2>/dev/null || {
                log "File must be in ${con%/*} and not a symlink to it"
                log "This usually occurs when a binary is installed to"
                die "/sbin instead of /usr/bin (example)"
            }
        done < "$_tmp_file"

        log "$_pkg" "Converted all conflicts to choices (kiss a)"

        # Rewrite the package's manifest to update its location
        # to its new spot (and name) in the choices directory.
        pkg_manifest "$_pkg" "$tar_dir"

    elif [ -s "$_tmp_file" ]; then
        log "Package '$_pkg' conflicts with another package" "" "!>"
        log "Run 'KISS_CHOICE=1 kiss i $_pkg' to add conflicts" "" "!>"
        die "as alternatives." "" "!>"
    fi
}

pkg_swap() {
    # Swap between package alternatives.
    [ -d "$sys_db/$1" ] || die "'$1' not found"

    fnr "$1$2" '/' '>'

    [ -f "$sys_ch/$_fnr" ] || [ -h "$sys_ch/$_fnr" ] ||
        die "Alternative '$1 ${2:-null}' doesn't exist"

    if [ -f "$KISS_ROOT$2" ]; then
        pkg_owner "/${2#/}" ||
            die "File '$2' exists on filesystem but isn't owned"

        log "Swapping '$2' from '$_owns' to '$1'"

        # Convert the current owner to an alternative and rewrite its manifest
        # file to reflect this.
        cp -Pf "$KISS_ROOT$2" "$sys_ch/$_owns>${_fnr#*>}"
        pkg_manifest_replace "$_owns" "$2" "/$cho_db/$_owns>${_fnr#*>}"
    fi

    # Convert the desired alternative to a real file and rewrite the manifest
    # file to reflect this. The reverse of above.
    mv -f "$sys_ch/$_fnr" "$KISS_ROOT/$2"
    pkg_manifest_replace "$1" "/$cho_db/$_fnr" "$2"
}

file_rwx() {
    # Convert the output of 'ls' (rwxrwx---) to octal. This is simply
    # a 1-9 loop with the second digit being the value of the field.
    #
    # NOTE: This drops setgid/setuid permissions and does not include
    # them in the conversion. This is intentional.
    rwx=$(ls -ld "$1") oct='' o=0

    for c in 14 22 31 44 52 61 74 82 91; do
        rwx=${rwx#?}

        case $rwx in
            [rwx]*): "$((o+=${c#?}))" ;;
             [st]*): "$((o+=1))" ;;
             [ST]*) ;;
        esac

        case $((${c%?} % 3)) in 0)
            oct=$oct$o o=0
        esac
    done
}

pkg_install_files() {
    # Copy files and create directories (preserving permissions).
    # The 'test $1' will run with '-z' for overwrite and '-e' for verify.
    while { read -r file && _file=$KISS_ROOT$file; } do case $file in
        */)
            # Skip directories if they already exist in the file system.
            # (Think /usr/bin, /usr/lib, etc).
            [ -d "$_file" ] || {
                file_rwx "$2/${file#/}"
                mkdir -m "$oct" "$_file"
            }
        ;;

        *)
            # Skip directories and files which exist in verify mode.
            [ -d "$_file" ] || ! test "$1" "$_file" ||
                continue

            case $file in /etc/*[!/])
                # Handle /etc/ files in a special way (via a 3-way checksum) to
                # determine how these files should be installed. Do we overwrite
                # the existing file? Do we install it as $file.new to avoid
                # deleting user configuration? etc.
                #
                # This is more or less similar to Arch Linux's Pacman with the
                # user manually handling the .new files when and if they appear.
                pkg_etc || continue
            esac

            if [ -h "$_file" ]; then
                # Copy the file to the destination directory overwriting
                # any existing file.
                cp -fP "$2$file" "${_file%/*}/."

            else
                # Construct a temporary filename which is a) unique and
                # b) identifiable as related to the package manager.
                __tmp=${_file%/*}/__kiss-tmp-$_pkg-${file##*/}-$KISS_PID

                # Copy the file to the destination directory with the
                # temporary name created above.
                cp -fP "$2$file" "$__tmp" &&

                # Atomically move the temporary file to its final
                # destination. The running processes will either get
                # the old file or the new one.
                mv -f "$__tmp" "$_file"
            fi
    esac || return 1; done
}

pkg_remove_files() {
    # Remove a file list from the system. This function runs during package
    # installation and package removal. Combining the removals in these two
    # functions allows us to stop duplicating code.
    while read -r file; do
        case $file in /etc/?*[!/])
            sh256 "$KISS_ROOT/$file" >/dev/null

            read -r sum_pkg <&3 ||:

            equ "$hash" "$sum_pkg" || {
                printf 'Skipping %s (modified)\n' "$file"
                continue
            }
        esac

        _file=${KISS_ROOT:+"$KISS_ROOT/"}${file%%/}

        # Queue all directory symlinks for later removal.
        if [ -h "$_file" ] && [ -d "$_file" ]; then
            case $file in /*/*/)
                set -- "$@" "$_file"
            esac

        # Remove empty directories.
        elif [ -d "$_file" ]; then
            rmdir "$_file" 2>/dev/null || :

        # Remove everything else.
        else
            rm -f "$_file"
        fi
    done

    # Remove all broken directory symlinks.
    for sym do
        [ -e "$sym" ] || rm -f "$sym"
    done
}

pkg_etc() {
    sh256 "$tar_dir/$_pkg$file" "$KISS_ROOT$file" >/dev/null

    sum_new=${hash%%"$newline"*}
    sum_sys=${hash#*"$newline"}

    read -r sum_old <&3 2>/dev/null ||:

    # Compare the three checksums to determine what to do.
    case ${sum_old:-null}${sum_sys:-null}${sum_new} in
        # old = Y, sys = X, new = Y
        "${sum_new}${sum_sys}${sum_old}")
            return 1
        ;;

        # old = X, sys = X, new = X
        # old = X, sys = Y, new = Y
        # old = X, sys = X, new = Y
        "${sum_old}${sum_old}${sum_old}"|\
        "${sum_old:-null}${sum_sys}${sum_sys}"|\
        "${sum_sys}${sum_old}"*)

        ;;

        # All other cases.
        *)
            war "$_pkg" "saving $file as $file.new"
            _file=$_file.new
        ;;
    esac
}

pkg_removable() {
    # Check if a package is removable and die if it is not.
    # A package is removable when it has no dependents.
    log "$1" "Checking if package removable"

    cd "$sys_db"
    set +f

    ! grep -lFx -- "$1" */depends ||
        die "$1" "Not removable, has dependents"

    set -f
    cd "$OLDPWD"
}

pkg_remove() {
    # Remove a package and all of its files. The '/etc' directory is handled
    # differently and configuration files are *not* overwritten.
    [ -d "$sys_db/$1" ] || die "'$1' not installed"

    # Intended behavior.
    # shellcheck disable=2030,2031
    equ "$KISS_FORCE" 1  || pkg_removable "$1"

    # Block being able to abort the script with 'Ctrl+C' during removal.
    # Removes all risk of the user aborting a package removal leaving an
    # incomplete package installed.
    trap '' INT

    # arg1: pre-remove
    # arg2: package name
    # arg3: path to installed database
    run_hook_pkg pre-remove "$1"
    run_hook     pre-remove "$1" "$sys_db/$1"

    # Make a backup of any etcsums if they exist.
    tmp_file_copy "$1" etcsums-copy "$sys_db/$1/etcsums"

    log "$1" "Removing package"
    pkg_remove_files < "$sys_db/$1/manifest" 3< "$_tmp_file"

    # Reset 'trap' to its original value. Removal is done so
    # we no longer need to block 'Ctrl+C'.
    trap pkg_clean EXIT INT

    log "$1" "Removed successfully"
}

pkg_installable() {
    # Check if a package is removable and die if it is not.
    # A package is removable when all of its dependencies
    # are satisfied.
    log "$1" "Checking if package installable"

    # False positive.
    # shellcheck disable=2094
    ! [ -f "$2" ] ||

    while read -r dep dep_type || ok "$dep"; do
        case "$dep $dep_type" in [!\#]?*\ )
            ! [ -d "$sys_db/$dep" ] || continue

            printf '%s %s\n' "$dep" "$dep_type"

            set -- "$1" "$2" "$(($3 + 1))"
        esac
    done < "$2"

    case ${3:-0} in [1-9]*)
        die "$1" "Package not installable, missing $3 package(s)"
    esac
}

pkg_install() {
    # Install a built package tarball.
    #
    # Package installation works similarly to the method used by Slackware in
    # some of their tooling. It's not the obvious solution to the problem,
    # however it is the best solution at this given time.
    #
    # When an installation is an update to an existing package, instead of
    # removing the old version first we do something different.
    #
    # The new version is installed overwriting any files which it has in
    # common with the previously installed version of the package.
    #
    # A "diff" is then generated between the old and new versions and contains
    # any files existing in the old version but not the new version.
    #
    # The package manager then goes and removes these files which leaves us
    # with the new package version in the file system and all traces of the
    # old version gone.
    #
    # For good measure the package manager will then install the new package
    # an additional time. This is to ensure that the above diff didn't contain
    # anything incorrect.
    #
    # This is the better method as it is "seamless". An update to busybox won't
    # create a window in which there is no access to all of its utilities.

    # Install can also take the full path to a tarball. We don't need to check
    # the repository if this is the case.
    case $1 in
        *.tar.*)
            [ -f "$1" ] || die "File '$1' does not exist"

            tar_file=$1
            _pkg=${1##*/}
            _pkg=${_pkg%@*}
        ;;

        *)
            pkg_cache "$1" || die "$1" "Not yet built"
            _pkg=$1
        ;;
    esac

    mkcd "$tar_dir/$_pkg"

    # The tarball is extracted to a temporary directory where its contents are
    # then "installed" to the filesystem. Running this step as soon as possible
    # allows us to also check the validity of the tarball and bail out early
    # if needed.
    decompress "$tar_file" | tar xf -

    # Naively assume that the existence of a manifest file is all that
    # determines a valid KISS package from an invalid one. This should be a
    # fine assumption to make in 99.99% of cases.
    [ -f "$PWD/$pkg_db/$_pkg/manifest" ] || die "Not a valid KISS package"

    # Intended behavior.
    # shellcheck disable=2030,2031
    equ "$KISS_FORCE" 1 || {
        pkg_manifest_validate "$_pkg"
        pkg_installable "$_pkg" "$PWD/$pkg_db/$_pkg/depends"
    }

    # arg1: pre-install
    # arg2: package name
    # arg3: path to extracted package
    run_hook pre-install "$_pkg" "$PWD"

    pkg_conflicts

    log "$_pkg" "Installing package (${tar_file##*/})"

    # If the package is already installed (and this is an upgrade) make a
    # backup of the manifest and etcsums files.
    tmp_file_copy "$_pkg" manifest-copy "$sys_db/$_pkg/manifest"
    tmp_file_copy "$_pkg"  etcsums-copy "$sys_db/$_pkg/etcsums"
    tmp_file      "$_pkg" manifest-diff

    tar_man=$PWD/$pkg_db/$_pkg/manifest

    # Generate a list of files which exist in the currently installed manifest
    # but not in the newer (to be installed) manifest.
    grep -vFxf "$tar_man" "$_tmp_file_pre_pre" > "$_tmp_file" 2>/dev/null ||:

    # Reverse the manifest file so that we start shallow and go deeper as we
    # iterate over each item. This is needed so that directories are created
    # going down the tree.
    tmp_file "$_pkg" manifest-reverse
    sort "$tar_man" > "$_tmp_file"

    # Block being able to abort the script with Ctrl+C during installation.
    # Removes all risk of the user aborting a package installation leaving
    # an incomplete package installed.
    trap '' INT

    if
        # Install the package's files by iterating over its manifest.
        pkg_install_files -z "$PWD" < "$_tmp_file" 3< "$_tmp_file_pre_pre" &&

        # This is the aforementioned step removing any files from the old
        # version of the package if the installation is an update. Each file
        # type has to be specially handled to ensure no system breakage occurs.
        pkg_remove_files < "$_tmp_file_pre" 3< "$_tmp_file_pre_pre" &&

        # Install the package's files a second time to fix any mess caused by
        # the above removal of the previous version of the package.
        pkg_install_files -e "$PWD" < "$_tmp_file" 3< "$_tmp_file_pre_pre"

    then
        # Reset 'trap' to its original value. Installation is done so we no longer
        # need to block 'Ctrl+C'.
        trap pkg_clean EXIT INT

        # arg1: post-install
        # arg2: package name
        # arg3: path to installed package database
        run_hook_pkg post-install "$_pkg"
        run_hook     post-install "$_pkg" "$sys_db/$_pkg"

        log "$_pkg" "Installed successfully"

    else
        pkg_clean
        log "$_pkg" "Failed to install package." ERROR
        die "$_pkg" "Filesystem now dirty, manual repair needed."
    fi
}

pkg_update() {
    # Check all installed packages for updates. So long as the installed
    # version and the version in the repositories differ, it's considered
    # an update.
    log "Updating repositories"

    # Create a list of all repositories.
    # Intentional, globbing disabled.
    # shellcheck disable=2046,2086
    { IFS=:; set -- $KISS_PATH; unset IFS; }

    # Update each repository in '$KISS_PATH'.
    for repo do
        ok "$repo" || continue

        [ -d "$repo" ] || {
            log "$repo" " "
            printf 'Skipping repository, not a directory\n'
            continue
        }

        cd "$repo"

        git remote >/dev/null 2>&1 || {
            log "$repo" " "
            printf 'Skipping git pull, not a repository\n'
            continue
        }

        # Go to the repository's root directory.
        git_root=$(git rev-parse --show-toplevel)
        cd "${git_root:?"failed to find git root for '$PWD'"}"

        # Go to the real root directory if this is a submodule.
        git_root=$(git rev-parse --show-superproject-working-tree)
        cd "${git_root:-"$PWD"}"

        contains "$repos" "$PWD" || {
            repos="$repos $PWD "

            # arg1: pre-update
            # env:  PWD is path to repository
            run_hook pre-update

            # Display whether or not signature verification is enabled.
            _sig=$(git config --get --default false merge.verifySignatures)

            log "$PWD" "[verify: $_sig]"

            if ! am_owner "$PWD"; then
                log "$PWD" "Need '$user' to update"
                as_user git pull
                as_user git submodule update --remote --init -f
            else
                git pull
                git submodule update --remote --init -f
            fi

            # arg1: post-update
            # env:  PWD is path to repository
            run_hook post-update
        }
    done

    log "Checking for new package versions"

    set +f --

    for pkg in "$sys_db/"*; do
        pkg_find_version "${pkg##*/}" "" "" "$sys_db"
        pkg_find_version "${pkg##*/}"

        # Detect repository orphans (installed packages with no
        # associated repository).
        case $repo_dir in */var/db/kiss/installed/*)
            _repo_orp="$_repo_orp$newline${pkg##*/}"
        esac

        # Compare installed packages to repository packages.
        equ "$ver_pre-$rel_pre" "$repo_ver-$repo_rel" || {
            printf '%s\n' "${pkg##*/} $ver_pre-$rel_pre ==> $repo_ver-$repo_rel"
            set -- "$@" "${pkg##*/}"
        }
    done

    log "Checking for orphaned repository packages"
    case $_repo_orp in *?*)
        war "Packages without repository$_repo_orp"
    esac

    set -f
    pkg_update=1

    case " $* " in
        *" kiss "*)
            log "Detected package manager update"
            log "The package manager will be updated first"

            prompt
            pkg_build_all kiss

            log "Updated the package manager"
            log "Re-run 'kiss update' to update your system"
        ;;

        "  ")
            log "Everything is up to date"
        ;;

        *)
            log "Packages to update: $*"

            prompt
            pkg_order "$@"

            # Intentional, globbing disabled.
            # shellcheck disable=2046,2086
            pkg_build_all $order

            log "Updated all packages"
        ;;
    esac
}

pkg_clean() {
    # Clean up on exit or error. This removes everything related to the build.
    # If _KISS_LVL is (1) we are the top-level process - the entire cache will
    # be removed. If _KISS_LVL is any other value, remove only the tar directory.
    case ${KISS_DEBUG:-0}-${_KISS_LVL:-1} in
        0-1) rm -rf "$proc" ;;
        0-*) rm -rf "$tar_dir"
    esac
}

args() {
    # Parse script arguments manually. This is rather easy to do in our case
    # since the first argument is always an "action" and the arguments that
    # follow are all package names.
    action=$1
    shift "$(($# != 0))"

    # Ensure that arguments do not contain invalid characters. Wildcards can
    # not be used here as they would conflict with kiss extensions.
    case $action in
        a|alternatives)
            case $1 in *\**|*\!*|*\[*|*\ *|*\]*|*/*|*"$newline"*)
                die "Invalid argument: '!*[ ]/\\n' ($1)"
            esac
        ;;

        b|build|c|checksum|d|download|i|install|l|list|r|remove)
            for _arg do case ${action%%"${action#?}"}-$_arg in
                i-*\!*|i-*\**|i-*\[*|i-*\ *|i-*\]*|i-*"$newline"*)
                    die "Invalid argument: '!*[ ]\\n' ('$_arg')"
                ;;

                [!i]-*\!*|[!i]-*\**|[!i]-*\[*|[!i]-*\ *|\
                [!i]-*\]*|[!i]-*/*|[!i]-*"$newline"*)
                    die "Invalid argument: '!*[ ]/\\n' ('$_arg')"
                ;;
            esac done

            # When no arguments are given on the command-line, use the basename
            # of the current directory as the package name and add the parent
            # directory to the running process' KISS_PATH.
            case ${action%%"${action#?}"}-$# in [!l]-0)
                export KISS_PATH=${PWD%/*}:$KISS_PATH
                set -- "${PWD##*/}"
            esac

            # Order the argument list based on dependence.
            pkg_order "$@"

            # Intentional, globbing disabled.
            # shellcheck disable=2046,2086
            set -- $order
        ;;
    esac

    # Need to increment _KISS_LVL here to ensure we don't wipe the cache
    # early by non-asroot invocations.
    export _KISS_LVL=$((_KISS_LVL + 1))

    # Rerun the script as root with a fixed environment if needed. We sadly
    # can't run singular functions as root so this is needed.
    #
    # Intended behavior.
    # shellcheck disable=2030,2031
    case $action in a|alternatives|i|install|r|remove)
        if ok "$1" && ! am_owner "$KISS_ROOT/"; then
            as_user env \
                LOGNAME="$user" \
                HOME="$HOME" \
                XDG_CACHE_HOME="$XDG_CACHE_HOME" \
                KISS_COMPRESS="$KISS_COMPRESS" \
                KISS_PATH="$KISS_PATH" \
                KISS_FORCE="$KISS_FORCE" \
                KISS_ROOT="$KISS_ROOT" \
                KISS_CHOICE="$KISS_CHOICE" \
                KISS_COLOR="$KISS_COLOR" \
                KISS_TMPDIR="$KISS_TMPDIR" \
                KISS_PID="$KISS_PID" \
                _KISS_LVL="$_KISS_LVL" \
                "$0" "$action" "$@"
            return
        fi
    esac

    # Actions can be abbreviated to their first letter. This saves keystrokes
    # once you memorize the commands.
    case $action in
        a|alternatives)
            if equ "$1" -; then
                while read -r pkg path; do
                    pkg_swap "$pkg" "$path"
                done

            elif ok "$1"; then
                pkg_swap "$@"

            else
                # Go over each alternative and format the file
                # name for listing. (pkg_name>usr>bin>ls)
                set +f; for pkg in "$sys_ch/"*; do
                    fnr "${pkg##*/}" '>' '/'
                    printf '%s %s\n' "${_fnr%%/*}" "/${_fnr#*/}"
                done
            fi
        ;;

        c|checksum)
            for pkg do
                pkg_source "$pkg" c

                [ -f "$repo_dir/sources" ] || continue

                pkg_checksums

                if ok "$hash"; then
                    printf '%s\n' "$hash" > "$repo_dir/checksums"
                    log "$pkg" "Generated checksums"

                else
                    log "$pkg" "No sources needing checksums"
                fi
            done
        ;;

        i|install)  for pkg do pkg_install "$pkg"; done ;;
        b|build)    pkg_build_all "${@:?No packages installed}" ;;
        d|download) for pkg do pkg_source "$pkg"; done ;;
        l|list)     pkg_list_version "$@" ;;
        r|remove)   for pkg in $redro; do pkg_remove "$pkg"; done ;;
        s|search)   for pkg do pkg_find "$pkg" all; done ;;
        u|update)   pkg_update ;;
        v|version)  printf '5.5.16\n' ;;

        '')
            log 'kiss [a|b|c|d|i|l|r|s|u|v] [pkg]...'
            log 'alternatives List and swap to alternatives'
            log 'build        Build a package'
            log 'checksum     Generate checksums'
            log 'download     Pre-download all sources'
            log 'install      Install a package'
            log 'list         List installed packages'
            log 'remove       Remove a package'
            log 'search       Search for a package'
            log 'update       Update the system'
            log 'version      Package manager version'

            printf '\nRun "kiss help-ext" to see all actions\n'
        ;;

        help-ext)
            log 'Installed extensions (kiss-* in PATH)'

            # Intentional, globbing disabled.
            # shellcheck disable=2046,2030,2031
            set -- $(pkg_find kiss-\* all -x "$PATH")

            # To align descriptions figure out which extension has the longest
            # name by doing a simple 'name > max ? name : max' on the basename
            # of the path with 'kiss-' stripped as well.
            #
            # This also removes any duplicates found in '$PATH', picking the
            # first match.
            for path do p=${path#*/kiss-}
                case " $seen " in
                    *" $p "*) shift ;;
                    *) seen=" $seen $p " max=$((${#p} > max ? ${#p}+1 : max))
                esac
            done

            IFS=\#$IFS

            # Print each extension, grab its description from the second line
            # in the file and align the output based on the above max.
            for path do
                # Open the extension as a file descriptor.
                exec 3< "$path"

                # Grab the second line in the extension.
                { read -r _ && read -r _ cmt; } <&3

                printf "%b->%b %-${max}s %s\\n" \
                    "$c1" "$c3" "${path#*/kiss-}" "$cmt"
            done >&2
        ;;

        *)
            pkg_find "kiss-$action*" "" -x "$PATH"
            "$repo_dir" "$@"
        ;;
    esac
}

create_tmp_dirs() {
    # Root directory.
    KISS_ROOT=${KISS_ROOT%"${KISS_ROOT##*[!/]}"}

    # This allows for automatic setup of a KISS chroot and will
    # do nothing on a normal system.
    mkdir -p "$KISS_ROOT/" 2>/dev/null || :

    # System package database.
    sys_db=$KISS_ROOT/${pkg_db:=var/db/kiss/installed}
    sys_ch=$KISS_ROOT/${cho_db:=var/db/kiss/choices}

    # Top-level cache directory.
    cac_dir=${XDG_CACHE_HOME:-"${HOME%"${HOME##*[!/]}"}/.cache"}
    cac_dir=${cac_dir%"${cac_dir##*[!/]}"}/kiss

    # Persistent cache directories.
    src_dir=$cac_dir/sources
    log_dir=$cac_dir/logs/${time%-*}
    bin_dir=$cac_dir/bin

    # Top-level Temporary cache directory.
    proc=${KISS_TMPDIR:="$cac_dir/proc"}
    proc=${proc%"${proc##*[!/]}"}/$KISS_PID

    # Temporary cache directories.
    mak_dir=$proc/build
    pkg_dir=$proc/pkg
    tar_dir=$proc/extract
    tmp_dir=$proc/tmp

    mkdir -p "$src_dir" "$log_dir" "$bin_dir" \
             "$mak_dir" "$pkg_dir" "$tar_dir" "$tmp_dir"
}

main() {
    # Globally disable globbing and enable exit-on-error.
    set -ef

    # Color can be disabled via the environment variable KISS_COLOR. Colors are
    # also automatically disabled if output is being used in a pipe/redirection.
    equ "$KISS_COLOR" 0 || ! [ -t 2 ] ||
        c1='\033[1;33m' c2='\033[1;34m' c3='\033[m'

    # Store the original working directory to ensure that relative paths
    # passed by the user on the command-line properly resolve to locations
    # in the filesystem.
    ppwd=$PWD

    # Never know when you're gonna need one of these.
    newline="
"

    # Defaults for environment variables.
    : "${KISS_COMPRESS:=gz}"
    : "${KISS_PID:=$$}"
    : "${LOGNAME:?POSIX requires LOGNAME be set}"

    # Figure out which 'sudo' command to use based on the user's choice or what
    # is available on the system.
    cmd_su=${KISS_SU:-su}

    # Figure out which utility is available to dump elf information.
    cmd_elf=${KISS_ELF:-"$(
        command -v readelf      ||
        command -v eu-readelf   ||
        command -v llvm-readelf
    )"} || cmd_elf=ldd

    # Figure out which sha256 utility is available.
    cmd_sha=${KISS_SHA:-"$(
        command -v openssl   ||
        command -v sha256sum ||
        command -v sha256    ||
        command -v shasum    ||
        command -v digest
    )"} || die "No sha256 utility found"

    # Figure out which download utility is available.
    cmd_get=${KISS_GET:-"$(
        command -v curl ||
        command -v wget ||
        command -v aria2c
    )"} || die "No download utility found (curl, wget, aria2c)"

    # Store the date and time of script invocation to be used as the name of
    # the log files the package manager creates uring builds.
    time=$(date +%Y-%m-%d-%H:%M)

    create_tmp_dirs

    # Catch errors and ensure that build files and directories are cleaned
    # up before we die. This occurs on 'Ctrl+C' as well as success and error.
    trap pkg_clean EXIT INT

    args "$@"
}

main "$@"