io.jl

# This file is a part of Julia. License is MIT: https://julialang.org/license

## core text I/O ##

"""
    print([io::IO], xs...)

Write to `io` (or to the default output stream [`stdout`](@ref)
if `io` is not given) a canonical (un-decorated) text representation.
The representation used by `print` includes minimal formatting and tries to
avoid Julia-specific details.

`print` falls back to calling `show`, so most types should just define
`show`. Define `print` if your type has a separate "plain" representation.
For example, `show` displays strings with quotes, and `print` displays strings
without quotes.

[`string`](@ref) returns the output of `print` as a string.

# Examples
```jldoctest
julia> print("Hello World!")
Hello World!
julia> io = IOBuffer();

julia> print(io, "Hello", ' ', :World!)

julia> String(take!(io))
"Hello World!"
```
"""
function print(io::IO, x)
    lock(io)
    try
        show(io, x)
    finally
        unlock(io)
    end
    return nothing
end

function print(io::IO, xs...)
    lock(io)
    try
        for x in xs
            print(io, x)
        end
    finally
        unlock(io)
    end
    return nothing
end

"""
    println([io::IO], xs...)

Print (using [`print`](@ref)) `xs` followed by a newline.
If `io` is not supplied, prints to [`stdout`](@ref).

# Examples
```jldoctest
julia> println("Hello, world")
Hello, world

julia> io = IOBuffer();

julia> println(io, "Hello, world")

julia> String(take!(io))
"Hello, world\\n"
```
"""
println(io::IO, xs...) = print(io, xs..., "\n")

## conversion of general objects to strings ##

"""
    sprint(f::Function, args...; context=nothing, sizehint=0)

Call the given function with an I/O stream and the supplied extra arguments.
Everything written to this I/O stream is returned as a string.
`context` can be either an [`IOContext`](@ref) whose properties will be used,
or a `Pair` specifying a property and its value. `sizehint` suggests the capacity
of the buffer (in bytes).

The optional keyword argument `context` can be set to `:key=>value` pair
or an `IO` or [`IOContext`](@ref) object whose attributes are used for the I/O
stream passed to `f`.  The optional `sizehint` is a suggested size (in bytes)
to allocate for the buffer used to write the string.

# Examples
```jldoctest
julia> sprint(show, 66.66666; context=:compact => true)
"66.6667"

julia> sprint(showerror, BoundsError([1], 100))
"BoundsError: attempt to access 1-element Vector{Int64} at index [100]"
```
"""
function sprint(f::Function, args...; context=nothing, sizehint::Integer=0)
    s = IOBuffer(sizehint=sizehint)
    if context !== nothing
        f(IOContext(s, context), args...)
    else
        f(s, args...)
    end
    String(resize!(s.data, s.size))
end

function _str_sizehint(x)
    if x isa Float64
        return 20
    elseif x isa Float32
        return 12
    elseif x isa String || x isa SubString{String}
        return sizeof(x)
    elseif x isa Char
        return ncodeunits(x)
    else
        return 8
    end
end

function print_to_string(xs...)
    if isempty(xs)
        return ""
    end
    siz::Int = 0
    for x in xs
        siz += _str_sizehint(x)
    end
    # specialized for performance reasons
    s = IOBuffer(sizehint=siz)
    for x in xs
        print(s, x)
    end
    String(resize!(s.data, s.size))
end

function string_with_env(env, xs...)
    if isempty(xs)
        return ""
    end
    siz::Int = 0
    for x in xs
        siz += _str_sizehint(x)
    end
    # specialized for performance reasons
    s = IOBuffer(sizehint=siz)
    env_io = IOContext(s, env)
    for x in xs
        print(env_io, x)
    end
    String(resize!(s.data, s.size))
end

"""
    string(xs...)

Create a string from any values using the [`print`](@ref) function.

`string` should usually not be defined directly. Instead, define a method
`print(io::IO, x::MyType)`. If `string(x)` for a certain type needs to be
highly efficient, then it may make sense to add a method to `string` and
define `print(io::IO, x::MyType) = print(io, string(x))` to ensure the
functions are consistent.

# Examples
```jldoctest
julia> string("a", 1, true)
"a1true"
```
"""
string(xs...) = print_to_string(xs...)

string(a::Symbol) = String(a)

# note: print uses an encoding determined by `io` (defaults to UTF-8), whereas
#       write uses an encoding determined by `s` (UTF-8 for `String`)
print(io::IO, s::AbstractString) = for c in s; print(io, c); end
write(io::IO, s::AbstractString) = (len = 0; for c in s; len += Int(write(io, c))::Int; end; len)
show(io::IO, s::AbstractString) = print_quoted(io, s)

# optimized methods to avoid iterating over chars
write(io::IO, s::Union{String,SubString{String}}) =
    GC.@preserve s Int(unsafe_write(io, pointer(s), reinterpret(UInt, sizeof(s))))::Int
print(io::IO, s::Union{String,SubString{String}}) = (write(io, s); nothing)

"""
    repr(x; context=nothing)

Create a string from any value using the [`show`](@ref) function.
You should not add methods to `repr`; define a `show` method instead.

The optional keyword argument `context` can be set to an `IO` or [`IOContext`](@ref)
object whose attributes are used for the I/O stream passed to `show`.

Note that `repr(x)` is usually similar to how the value of `x` would
be entered in Julia.  See also [`repr(MIME("text/plain"), x)`](@ref) to instead
return a "pretty-printed" version of `x` designed more for human consumption,
equivalent to the REPL display of `x`.

# Examples
```jldoctest
julia> repr(1)
"1"

julia> repr(zeros(3))
"[0.0, 0.0, 0.0]"

julia> repr(big(1/3))
"0.333333333333333314829616256247390992939472198486328125"

julia> repr(big(1/3), context=:compact => true)
"0.333333"

```
"""
repr(x; context=nothing) = sprint(show, x; context=context)

limitrepr(x) = repr(x, context = :limit=>true)

# IOBuffer views of a (byte)string:

"""
    IOBuffer(string::String)

Create a read-only `IOBuffer` on the data underlying the given string.

# Examples
```jldoctest
julia> io = IOBuffer("Haho");

julia> String(take!(io))
"Haho"

julia> String(take!(io))
"Haho"
```
"""
IOBuffer(str::String) = IOBuffer(unsafe_wrap(Vector{UInt8}, str))
IOBuffer(s::SubString{String}) = IOBuffer(view(unsafe_wrap(Vector{UInt8}, s.string), s.offset + 1 : s.offset + sizeof(s)))

# join is implemented using IO

"""
    join([io::IO,] strings [, delim [, last]])

Join an array of `strings` into a single string, inserting the given delimiter (if any) between
adjacent strings. If `last` is given, it will be used instead of `delim` between the last
two strings. If `io` is given, the result is written to `io` rather than returned
as a `String`.

`strings` can be any iterable over elements `x` which are convertible to strings
via `print(io::IOBuffer, x)`. `strings` will be printed to `io`.

# Examples
```jldoctest
julia> join(["apples", "bananas", "pineapples"], ", ", " and ")
"apples, bananas and pineapples"

julia> join([1,2,3,4,5])
"12345"
```
"""
function join(io::IO, strings, delim, last)
    first = true
    local prev
    for str in strings
        if @isdefined prev
            first ? (first = false) : print(io, delim)
            print(io, prev)
        end
        prev = str
    end
    if @isdefined prev
        first || print(io, last)
        print(io, prev)
    end
    nothing
end
function join(io::IO, strings, delim="")
    # Specialization of the above code when delim==last,
    # which lets us emit (compile) less code
    first = true
    for str in strings
        first ? (first = false) : print(io, delim)
        print(io, str)
    end
end

join(strings) = sprint(join, strings)
join(strings, delim) = sprint(join, strings, delim)
join(strings, delim, last) = sprint(join, strings, delim, last)

## string escaping & unescaping ##

need_full_hex(c::Union{Nothing, AbstractChar}) = c !== nothing && isxdigit(c)
escape_nul(c::Union{Nothing, AbstractChar}) =
    (c !== nothing && '0' <= c <= '7') ? "\\x00" : "\\0"

"""
    escape_string(str::AbstractString[, esc])::AbstractString
    escape_string(io, str::AbstractString[, esc::])::Nothing

General escaping of traditional C and Unicode escape sequences. The first form returns the
escaped string, the second prints the result to `io`.

Backslashes (`\\`) are escaped with a double-backslash (`"\\\\"`). Non-printable
characters are escaped either with their standard C escape codes, `"\\0"` for NUL (if
unambiguous), unicode code point (`"\\u"` prefix) or hex (`"\\x"` prefix).

The optional `esc` argument specifies any additional characters that should also be
escaped by a prepending backslash (`\"` is also escaped by default in the first form).

# Examples
```jldoctest
julia> escape_string("aaa\\nbbb")
"aaa\\\\nbbb"

julia> escape_string("\\xfe\\xff") # invalid utf-8
"\\\\xfe\\\\xff"

julia> escape_string(string('\\u2135','\\0')) # unambiguous
"ℵ\\\\0"

julia> escape_string(string('\\u2135','\\0','0')) # \\0 would be ambiguous
"ℵ\\\\x000"
```

## See also
[`unescape_string`](@ref) for the reverse operation.
"""
function escape_string(io::IO, s::AbstractString, esc="")
    a = Iterators.Stateful(s)
    for c::AbstractChar in a
        if c in esc
            print(io, '\\', c)
        elseif isascii(c)
            c == '\0'          ? print(io, escape_nul(peek(a)::Union{AbstractChar,Nothing})) :
            c == '\e'          ? print(io, "\\e") :
            c == '\\'          ? print(io, "\\\\") :
            '\a' <= c <= '\r'  ? print(io, '\\', "abtnvfr"[Int(c)-6]) :
            isprint(c)         ? print(io, c) :
                                 print(io, "\\x", string(UInt32(c), base = 16, pad = 2))
        elseif !isoverlong(c) && !ismalformed(c)
            isprint(c)         ? print(io, c) :
            c <= '\x7f'        ? print(io, "\\x", string(UInt32(c), base = 16, pad = 2)) :
            c <= '\uffff'      ? print(io, "\\u", string(UInt32(c), base = 16, pad = need_full_hex(peek(a)::Union{AbstractChar,Nothing}) ? 4 : 2)) :
                                 print(io, "\\U", string(UInt32(c), base = 16, pad = need_full_hex(peek(a)::Union{AbstractChar,Nothing}) ? 8 : 4))
        else # malformed or overlong
            u = bswap(reinterpret(UInt32, c)::UInt32)
            while true
                print(io, "\\x", string(u % UInt8, base = 16, pad = 2))
                (u >>= 8) == 0 && break
            end
        end
    end
end

escape_string(s::AbstractString, esc=('\"',)) = sprint(escape_string, s, esc, sizehint=lastindex(s))

function print_quoted(io, s::AbstractString)
    print(io, '"')
    escape_string(io, s, ('\"','$')) #"# work around syntax highlighting problem
    print(io, '"')
end

# general unescaping of traditional C and Unicode escape sequences

# TODO: handle unescaping invalid UTF-8 sequences
"""
    unescape_string(str::AbstractString, keep = ())::AbstractString
    unescape_string(io, s::AbstractString, keep = ())::Nothing

General unescaping of traditional C and Unicode escape sequences. The first form returns
the escaped string, the second prints the result to `io`.
The argument `keep` specifies a collection of characters which (along with backlashes) are
to be kept as they are.

The following escape sequences are recognised:
 - Escaped backslash (`\\\\`)
 - Escaped double-quote (`\\\"`)
 - Standard C escape sequences (`\\a`, `\\b`, `\\t`, `\\n`, `\\v`, `\\f`, `\\r`, `\\e`)
 - Unicode BMP code points (`\\u` with 1-4 trailing hex digits)
 - All Unicode code points (`\\U` with 1-8 trailing hex digits; max value = 0010ffff)
 - Hex bytes (`\\x` with 1-2 trailing hex digits)
 - Octal bytes (`\\` with 1-3 trailing octal digits)

# Examples
```jldoctest
julia> unescape_string("aaa\\\\nbbb") # C escape sequence
"aaa\\nbbb"

julia> unescape_string("\\\\u03c0") # unicode
"π"

julia> unescape_string("\\\\101") # octal
"A"

julia> unescape_string("aaa \\\\g \\\\n", ['g']) # using `keep` argument
"aaa \\\\g \\n"
```

## See also
[`escape_string`](@ref).
"""
function unescape_string(io::IO, s::AbstractString, keep = ())
    a = Iterators.Stateful(s)
    for c in a
        if !isempty(a) && c == '\\'
            c = popfirst!(a)
            if c in keep
                print(io, '\\', c)
            elseif c == 'x' || c == 'u' || c == 'U'
                n = k = 0
                m = c == 'x' ? 2 :
                    c == 'u' ? 4 : 8
                while (k += 1) <= m && !isempty(a)
                    nc = peek(a)
                    n = '0' <= nc <= '9' ? n<<4 + (nc-'0') :
                        'a' <= nc <= 'f' ? n<<4 + (nc-'a'+10) :
                        'A' <= nc <= 'F' ? n<<4 + (nc-'A'+10) : break
                    popfirst!(a)
                end
                if k == 1 || n > 0x10ffff
                    u = m == 4 ? 'u' : 'U'
                    throw(ArgumentError("invalid $(m == 2 ? "hex (\\x)" :
                                        "unicode (\\$u)") escape sequence"))
                end
                if m == 2 # \x escape sequence
                    write(io, UInt8(n))
                else
                    print(io, Char(n))
                end
            elseif '0' <= c <= '7'
                k = 1
                n = c-'0'
                while (k += 1) <= 3 && !isempty(a)
                    c = peek(a)
                    n = ('0' <= c <= '7') ? n<<3 + c-'0' : break
                    popfirst!(a)
                end
                if n > 255
                    throw(ArgumentError("octal escape sequence out of range"))
                end
                write(io, UInt8(n))
            else
                print(io, c == 'a' ? '\a' :
                          c == 'b' ? '\b' :
                          c == 't' ? '\t' :
                          c == 'n' ? '\n' :
                          c == 'v' ? '\v' :
                          c == 'f' ? '\f' :
                          c == 'r' ? '\r' :
                          c == 'e' ? '\e' :
                          (c == '\\' || c == '"') ? c :
                          throw(ArgumentError("invalid escape sequence \\$c")))
            end
        else
            print(io, c)
        end
    end
end
unescape_string(s::AbstractString, keep = ()) =
    sprint(unescape_string, s, keep; sizehint=lastindex(s))

"""
    @b_str

Create an immutable byte (`UInt8`) vector using string syntax.

# Examples
```jldoctest
julia> v = b"12\\x01\\x02"
4-element Base.CodeUnits{UInt8, String}:
 0x31
 0x32
 0x01
 0x02

julia> v[2]
0x32
```
"""
macro b_str(s)
    v = codeunits(unescape_string(s))
    QuoteNode(v)
end

"""
    @raw_str -> String

Create a raw string without interpolation and unescaping.
The exception is that quotation marks still must be escaped. Backslashes
escape both quotation marks and other backslashes, but only when a sequence
of backslashes precedes a quote character. Thus, 2n backslashes followed by
a quote encodes n backslashes and the end of the literal while 2n+1 backslashes
followed by a quote encodes n backslashes followed by a quote character.

# Examples
```jldoctest
julia> println(raw"\\ \$x")
\\ \$x

julia> println(raw"\\"")
"

julia> println(raw"\\\\\\"")
\\"

julia> println(raw"\\\\x \\\\\\"")
\\\\x \\"
```
"""
macro raw_str(s); s; end

"""
    escape_raw_string(s::AbstractString)
    escape_raw_string(io, s::AbstractString)

Escape a string in the manner used for parsing raw string literals.
For each double-quote (`"`) character in input string `s`, this
function counts the number _n_ of preceeding backslash (`\\`) characters,
and then increases there the number of backslashes from _n_ to 2_n_+1
(even for _n_ = 0). It also doubles a sequence of backslashes at the end
of the string.

This escaping convention is used in raw strings and other non-standard
string literals. (It also happens to be the escaping convention
expected by the Microsoft C/C++ compiler runtime when it parses a
command-line string into the argv[] array.)

See also: [`escape_string`](@ref)
"""
function escape_raw_string(io, str::AbstractString)
    escapes = 0
    for c in str
        if c == '\\'
            escapes += 1
        else
            if c == '"'
                # if one or more backslashes are followed by
                # a double quote then escape all backslashes
                # and the double quote
                escapes = escapes * 2 + 1
            end
            while escapes > 0
                write(io, '\\')
                escapes -= 1
            end
            escapes = 0
            write(io, c)
        end
    end
    # also escape any trailing backslashes,
    # so they do not affect the closing quote
    while escapes > 0
        write(io, '\\')
        write(io, '\\')
        escapes -= 1
    end
end
escape_raw_string(str::AbstractString) = sprint(escape_raw_string, str;
                                                sizehint = lastindex(str) + 2)

## multiline strings ##

"""
    indentation(str::AbstractString; tabwidth=8) -> (Int, Bool)

Calculate the width of leading white space. Return the width and a flag to indicate
if the string is empty.

# Examples
```jldoctest
julia> Base.indentation("")
(0, true)

julia> Base.indentation("  a")
(2, false)

julia> Base.indentation("\\ta"; tabwidth=3)
(3, false)
```
"""
function indentation(str::AbstractString; tabwidth=8)
    count = 0
    for ch in str
        if ch == ' '
            count += 1
        elseif ch == '\t'
            count = div(count + tabwidth, tabwidth) * tabwidth
        else
            return count, false
        end
    end
    count, true
end

"""
    unindent(str::AbstractString, indent::Int; tabwidth=8)

Remove leading indentation from string.

# Examples
```jldoctest
julia> Base.unindent("   a\\n   b", 2)
" a\\n b"

julia> Base.unindent("\\ta\\n\\tb", 2, tabwidth=8)
"      a\\n      b"
```
"""
function unindent(str::AbstractString, indent::Int; tabwidth=8)
    indent == 0 && return str
    # Note: this loses the type of the original string
    buf = IOBuffer(sizehint=sizeof(str))
    cutting = true
    col = 0     # current column (0 based)
    for ch in str
        if cutting
            if ch == ' '
                col += 1
            elseif ch == '\t'
                col = div(col + tabwidth, tabwidth) * tabwidth
            elseif ch == '\n'
                # Now we need to output enough indentation
                for i = 1:col-indent
                    print(buf, ' ')
                end
                col = 0
                print(buf, '\n')
            else
                cutting = false
                # Now we need to output enough indentation to get to
                # correct place
                for i = 1:col-indent
                    print(buf, ' ')
                end
                col += 1
                print(buf, ch)
            end
        elseif ch == '\t'       # Handle internal tabs
            upd = div(col + tabwidth, tabwidth) * tabwidth
            # output the number of spaces that would have been seen
            # with original indentation
            for i = 1:(upd-col)
                print(buf, ' ')
            end
            col = upd
        elseif ch == '\n'
            cutting = true
            col = 0
            print(buf, '\n')
        else
            col += 1
            print(buf, ch)
        end
    end
    # If we were still "cutting" when we hit the end of the string,
    # we need to output the right number of spaces for the indentation
    if cutting
        for i = 1:col-indent
            print(buf, ' ')
        end
    end
    String(take!(buf))
end

function String(a::AbstractVector{Char})
    n = 0
    for v in a
        n += ncodeunits(v)
    end
    out = _string_n(n)
    offs = 1
    for v in a
        offs += __unsafe_string!(out, v, offs)
    end
    return out
end

function String(chars::AbstractVector{<:AbstractChar})
    sprint(sizehint=length(chars)) do io
        for c in chars
            print(io, c)
        end
    end
end