format.go

package toml

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"strconv"
	"strings"
	"time"
	"unicode/utf8"
)

type FormatRule func(*Formatter) error

// Set the character to indent lines. If tab is let to 0, tab character will
// be used otherwise one or multiple space(s)
func WithTab(tab int) FormatRule {
	return func(ft *Formatter) error {
		if tab >= 1 {
			ft.withTab = strings.Repeat(" ", tab)
		}
		return nil
	}
}

// Tell the formatter to keep empty table when rewritting the document.
func WithEmpty(with bool) FormatRule {
	return func(ft *Formatter) error {
		ft.withEmpty = with
		return nil
	}
}

// Tell the formatter to indent nested sub table(s). If not set, all tables will
// be aligned.
func WithNest(with bool) FormatRule {
	return func(ft *Formatter) error {
		ft.withNest = with
		return nil
	}
}

// Tell the formatter to keep comments from the original document when rewritting.
func WithComment(with bool) FormatRule {
	return func(ft *Formatter) error {
		ft.withComment = with
		return nil
	}
}

// Tell the formatter to keep the format of the values as found in the original
// document.
// Using this option disables other options that format values.
func WithRaw(with bool) FormatRule {
	return func(ft *Formatter) error {
		ft.withRaw = with
		return nil
	}
}

// Tell the formatter to reformat (array of) inline table(s) to (array of) regular table(s)
func WithInline(inline bool) FormatRule {
	return func(ft *Formatter) error {
		ft.withInline = inline
		return nil
	}
}

// Tell the formatter how to reformat arrays. By default, array with 0 or 1 element
// will always be written on the same line.
func WithArray(format string) FormatRule {
	return func(ft *Formatter) error {
		switch strings.ToLower(format) {
		case "", "mixed":
			ft.withArray = arrayMixed
		case "multi":
			ft.withArray = arrayMulti
		case "single":
			ft.withArray = arraySingle
		default:
			return fmt.Errorf("%s: unsupported array format", format)
		}
		return nil
	}
}

// Tell the formatter to use the precision of millisecond to use and if it is needed
// to convert offset datetime to UTC.
func WithTime(millis int, utc bool) FormatRule {
	return func(ft *Formatter) error {
		if millis > 9 {
			millis = 9
		}
		pattern := "2006-01-02 15:04:05"
		if millis > 0 {
			pattern += "." + strings.Repeat("0", millis)
		}
		pattern += "-07:00"
		ft.timeconv = formatTime(pattern, utc)
		return nil
	}
}

// Tell the formatter how to format floating point number and where to write an
// underscore to make it more readable (if needed)
func WithFloat(format string, underscore int) FormatRule {
	return func(ft *Formatter) error {
		var spec byte
		switch strings.ToLower(format) {
		case "e", "scientific":
			spec = 'e'
		case "", "f", "float":
			spec = 'f'
		case "g", "auto":
			spec = 'g'
		default:
			return fmt.Errorf("%s: unsupported specifier", format)
		}
		ft.floatconv = formatFloat(spec, underscore)
		return nil
	}
}

// Tell the formatter which base to use to rewrite integer number and where to write
// an underscore to make it more readable (if needed)
func WithNumber(format string, underscore int) FormatRule {
	return func(ft *Formatter) error {
		var (
			base   int
			prefix string
		)
		switch strings.ToLower(format) {
		case "x", "hexa", "hex":
			base, prefix = 16, "0x"
		case "o", "octal", "oct":
			base, prefix = 8, "0o"
		case "b", "binary", "bin":
			base, prefix = 2, "0b"
		case "", "d", "decimal", "dec":
			base = 10
		default:
			return fmt.Errorf("%s: unsupported base", format)
		}
		ft.intconv = formatInteger(base, underscore, prefix)
		return nil
	}
}

// Tell the formatter which sequence of character to use to write the end of line.
func WithEOL(format string) FormatRule {
	return func(ft *Formatter) error {
		switch strings.ToLower(format) {
		case "crlf", "windows":
			ft.withEOL = "\r\n"
		case "lf", "linux", "":
			ft.withEOL = "\n"
		default:
			return fmt.Errorf("%s: unsupported eof", format)
		}
		return nil
	}
}

const (
	arrayMixed int = iota
	arraySingle
	arrayMulti
)

// Formatter is responsible to rewrite a TOML document according to the settings
// given by user.
type Formatter struct {
	doc    Node
	writer *bufio.Writer

	floatconv func(string) (string, error)
	intconv   func(string) (string, error)
	timeconv  func(string) (string, error)

	withArray   int
	withInline  bool
	withTab     string
	withEOL     string
	withEmpty   bool
	withComment bool
	withNest    bool
	currLevel   int
	withRaw     bool
}

// Create a new Formatter that will rewrite the TOML document doc according to the
// rules specify.
func NewFormatter(doc string, rules ...FormatRule) (*Formatter, error) {
	identity := func(str string) (string, error) {
		return str, nil
	}
	f := Formatter{
		floatconv:   identity,
		intconv:     identity,
		timeconv:    identity,
		withArray:   arrayMixed,
		withInline:  false,
		withEmpty:   false,
		withNest:    false,
		withComment: true,
		withTab:     "\t",
		withEOL:     "\n",
		withRaw:     false,
	}

	buf, err := ioutil.ReadFile(doc)
	if err != nil {
		return nil, err
	}
	f.doc, err = Parse(bytes.NewReader(buf))
	if err != nil {
		return nil, err
	}
	for _, rfn := range rules {
		if err := rfn(&f); err != nil {
			return nil, err
		}
	}
	return &f, nil
}

// Reformat the document
func (f *Formatter) Format(w io.Writer) error {
	f.writer = bufio.NewWriter(w)
	root, ok := f.doc.(*Table)
	if !ok {
		return fmt.Errorf("document not parsed properly")
	}
	if err := f.formatTable(root, nil); err != nil {
		return err
	}
	return f.writer.Flush()
}

func (f *Formatter) formatTable(curr *Table, paths []string) error {
	options := curr.listOptions()
	if f.withEmpty || len(options) > 0 {
		f.formatHeader(curr, paths)
		err := f.formatOptions(options, append(paths, curr.key.Literal))
		if err != nil {
			return nil
		}
		f.endLine()
	}
	if !curr.isRoot() && curr.kind.isContainer() {
		paths = append(paths, curr.key.Literal)
	}
	if f.canNest(curr) {
		f.enterLevel(false)
		defer f.leaveLevel(false)
	}
	for _, next := range curr.listTables() {
		if err := f.formatTable(next, paths); err != nil {
			return err
		}
	}
	return nil
}

func (f *Formatter) formatOptions(options []*Option, paths []string) error {
	type table struct {
		prefix string
		*Table
	}
	var (
		length  = longestKey(options)
		array   int
		inlines []table
	)
	for _, o := range options {
		if i, ok := o.value.(*Table); ok && f.withInline {
			i.kind = tableRegular
			i.key = o.key
			i.comment = o.comment
			inlines = append(inlines, table{Table: i})
			continue
		}
		if i, ok := o.value.(*Array); ok && f.withInline {
			var (
				a Array
				t = Table{kind: tableArray, key: o.key}
			)
			for _, n := range i.nodes {
				if nod, ok := n.(*Table); ok {
					nod.key = o.key
					nod.kind = tableItem
					t.nodes = append(t.nodes, nod)
				} else {
					a.nodes = append(a.nodes, n)
				}
			}
			if !t.isEmpty() {
				sub := table{Table: &t}
				if !a.isEmpty() {
					sub.prefix = fmt.Sprintf("\"#%d\"", array)
					array++
				}
				inlines = append(inlines, sub)
			}
			if a.isEmpty() {
				continue
			}
			o.value = &a
		}
		f.formatComment(o.comment.pre, true)
		f.beginLine()
		f.writeKey(o.key.Literal, length)
		if err := f.formatValue(o.value); err != nil {
			return err
		}
		f.formatComment(o.comment.post, false)
		f.endLine()
	}
	if len(inlines) > 0 {
		f.endLine()
		f.enterLevel(false)
		defer f.leaveLevel(false)
		for _, i := range inlines {
			parents := append([]string{}, paths...)
			if i.prefix != "" {
				parents = append(parents, i.prefix)
			}
			if err := f.formatTable(i.Table, parents); err != nil {
				return err
			}
		}
	}
	return nil
}

func (f *Formatter) formatValue(n Node) error {
	if n == nil {
		return nil
	}
	var err error
	switch n := n.(type) {
	case *Literal:
		if f.withRaw {
			f.writer.WriteString(n.token.Raw)
			break
		}
		err = f.formatLiteral(n)
	case *Array:
		err = f.formatArray(n)
	case *Table:
		err = f.formatInline(n)
	default:
		err = fmt.Errorf("unexpected value type %T", n)
	}
	return err
}

func (f *Formatter) formatLiteral(i *Literal) error {
	if i.token.isString() {
		f.formatString(i.token)
		return nil
	}
	str, err := f.convertValue(i.token)
	if err == nil {
		f.writer.WriteString(str)
	}
	return err
}

func (f *Formatter) formatString(tok Token) {
	var (
		isMulti bool
		quoting string
		escape  func(rune) (rune, bool)
	)
	switch tok.Type {
	case TokBasic:
		escape = escapeBasic
		quoting = "\""
	case TokBasicMulti:
		escape = escapeMulti
		quoting, isMulti = "\"\"\"", true
	case TokLiteral:
		quoting = "'"
	case TokLiteralMulti:
		quoting, isMulti = "'''", true
	default:
		return
	}
	f.writer.WriteString(quoting)
	if isMulti {
		f.endLine()
	}
	str := escapeString(tok.Literal, isMulti, escape)
	if isMulti && strings.IndexByte(str, newline) < 0 {
		str = textWrap(str)
	}
	f.writer.WriteString(str)
	f.writer.WriteString(quoting)
}

func textWrap(str string) string {
	var (
		scan = bufio.NewScanner(strings.NewReader(str))
		buf  strings.Builder
	)
	const (
		length = 72
		limit  = 8
	)
	scan.Split(func(data []byte, ateof bool) (int, []byte, error) {
		if ateof {
			return len(data), data, bufio.ErrFinalToken
		}
		var i, j int
		for i < length {
			x := bytes.IndexAny(data[i:], " \t.?,!;")
			if x < 0 {
				return 0, nil, nil
			}
			j, i = i, i+x+1
		}
		if i >= length+limit {
			i = j
		}
		return i, data[:i], nil
	})
	scan.Scan()
	for {
		buf.WriteString(scan.Text())
		if !scan.Scan() {
			break
		}
		buf.WriteRune(backslash)
		buf.WriteRune(newline)
	}
	return buf.String()
}

func escapeBasic(r rune) (rune, bool) {
	switch r {
	case backslash:
	case dquote:
	case newline:
		r = 'n'
	case tab:
		r = 't'
	case formfeed:
		r = 'f'
	case backspace:
		r = 'b'
	case carriage:
		r = 'r'
	default:
		return r, false
	}
	return r, true
}

func escapeMulti(r rune) (rune, bool) {
	switch r {
	case backslash:
	case dquote:
	case tab:
		r = 't'
	case formfeed:
		r = 'f'
	case backspace:
		r = 'b'
	case carriage:
		r = 'r'
	default:
		return r, false
	}
	return r, true
}

func escapeString(str string, multi bool, escape func(r rune) (rune, bool)) string {
	if escape == nil {
		return str
	}
	var (
		i  int
		b  strings.Builder
		ok bool
	)
	for i < len(str) {
		char, z := utf8.DecodeRuneInString(str[i:])
		if char == utf8.RuneError {
			break
		}
		if multi && char == dquote {
			i += z
			b.WriteRune(char)
			if char, z = utf8.DecodeRuneInString(str[i:]); char == dquote {
				i += z
				b.WriteRune(char)
				char, z = utf8.DecodeRuneInString(str[i:])
			}
		}
		if char, ok = escape(char); ok {
			b.WriteRune(backslash)
		}
		b.WriteRune(char)
		i += z
	}
	return b.String()
}

func (f *Formatter) convertValue(tok Token) (string, error) {
	switch tok.Type {
	default:
		return tok.Literal, nil
	case TokDatetime:
		return f.timeconv(tok.Literal)
	case TokInteger:
		return f.intconv(tok.Literal)
	case TokFloat:
		return f.floatconv(tok.Literal)
	}
}

func (f *Formatter) formatArray(a *Array) error {
	if len(a.nodes) <= 1 || f.withArray == arraySingle {
		return f.formatArrayLine(a)
	}
	if f.withArray == arrayMulti {
		return f.formatArrayMultiline(a)
	}
	if a.isMultiline() {
		return f.formatArrayMultiline(a)
	}
	return f.formatArrayLine(a)
}

func (f *Formatter) formatArrayMultiline(a *Array) error {
	retr := func(n Node) comment {
		var c comment
		switch n := n.(type) {
		case *Literal:
			c = n.comment
		case *Array:
			c = n.comment
		case *Table:
			c = n.comment
		}
		return c
	}
	f.enterArray()
	defer func() {
		f.leaveArray()
		f.beginLine()
		f.writer.WriteString("]")
	}()

	f.writer.WriteString("[")
	f.endLine()
	for _, n := range a.nodes {
		com := retr(n)
		f.formatComment(com.pre, true)
		f.beginLine()
		if err := f.formatValue(n); err != nil {
			return err
		}
		f.writer.WriteString(",")
		f.formatComment(com.post, false)
		f.endLine()
	}
	return nil
}

func (f *Formatter) formatArrayLine(a *Array) error {
	f.writer.WriteString("[")
	for i, n := range a.nodes {
		if err := f.formatValue(n); err != nil {
			return err
		}
		if i < len(a.nodes)-1 {
			f.writer.WriteString(", ")
		}
	}
	f.writer.WriteString("]")
	return nil
}

func (f *Formatter) formatInline(t *Table) error {
	defer func(array int) {
		f.withArray = array
	}(f.withArray)
	f.withArray = arraySingle
	f.writer.WriteString("{")
	for i, o := range t.listOptions() {
		if i > 0 {
			f.writer.WriteString(", ")
		}
		f.writeKey(o.key.Literal, 0)
		if err := f.formatValue(o.value); err != nil {
			return err
		}
	}
	f.writer.WriteString("}")
	return nil
}

func (f *Formatter) formatHeader(curr *Table, paths []string) error {
	if curr.isRoot() {
		return nil
	}
	if curr.kind != tableItem {
		paths = append(paths, curr.key.Literal)
	}
	f.formatComment(curr.comment.pre, true)
	switch str := strings.Join(paths, "."); curr.kind {
	case tableRegular, tableImplicit:
		f.writeRegularHeader(str)
	case tableItem:
		f.writeArrayHeader(str)
	default:
		return fmt.Errorf("%s: can not write header for %s", curr.kind, str)
	}
	f.formatComment(curr.comment.post, false)
	f.endLine()
	return nil
}

func (f *Formatter) formatComment(comment string, pre bool) error {
	if !f.withComment || comment == "" {
		return nil
	}
	scan := bufio.NewScanner(strings.NewReader(comment))
	for scan.Scan() {
		f.writeComment(scan.Text(), pre)
	}
	return scan.Err()
}

func (f *Formatter) enterArray() {
	f.enterLevel(true)
}

func (f *Formatter) leaveArray() {
	f.leaveLevel(true)
}

func (f *Formatter) enterLevel(force bool) {
	if f.withNest || force {
		f.currLevel++
	}
}

func (f *Formatter) leaveLevel(force bool) {
	if f.withNest || force {
		f.currLevel--
	}
}

func (f *Formatter) canNest(curr *Table) bool {
	if curr.isRoot() {
		return false
	}
	if curr.kind == tableImplicit && !f.withEmpty {
		return false
	}
	return curr.kind.canNest()
}

func (f *Formatter) writeKey(str string, length int) {
	n, _ := f.writer.WriteString(str)
	if length > 0 {
		f.writer.WriteString(strings.Repeat(" ", length-n))
	}
	f.writer.WriteString(" = ")
}

func (f *Formatter) writeComment(str string, pre bool) {
	if pre {
		f.beginLine()
	} else {
		f.writer.WriteString(" ")
	}
	f.writer.WriteString("# ")
	f.writer.WriteString(str)
	if pre {
		f.endLine()
	}
}

func (f *Formatter) writeRegularHeader(str string) {
	f.beginLine()
	f.writer.WriteString("[")
	f.writer.WriteString(str)
	f.writer.WriteString("]")
}

func (f *Formatter) writeArrayHeader(str string) {
	f.beginLine()
	f.writer.WriteString("[[")
	f.writer.WriteString(str)
	f.writer.WriteString("]]")
}

func (f *Formatter) endLine() {
	f.writer.WriteString(f.withEOL)
}

func (f *Formatter) beginLine() {
	if f.currLevel == 0 {
		return
	}
	f.writer.WriteString(strings.Repeat(f.withTab, f.currLevel))
}

func longestKey(options []*Option) int {
	var length int
	for _, o := range options {
		n := len(o.key.Literal)
		if length == 0 || length < n {
			length = n
		}
	}
	return length
}

func formatString(str string) string {
	return str
}

func formatTime(pattern string, utc bool) func(string) (string, error) {
	if pattern == "" {
		pattern = time.RFC3339
	}
	return func(str string) (string, error) {
		var (
			when time.Time
			err  error
		)
		for _, pat := range makeAllPatterns() {
			when, err = time.Parse(pat, str)
			if err == nil {
				break
			}
		}
		if err != nil {
			return "", err
		}
		if utc {
			when = when.UTC()
		}
		return when.Format(pattern), nil
	}
}

func formatFloat(specifier byte, underscore int) func(string) (string, error) {
	return func(str string) (string, error) {
		f, err := strconv.ParseFloat(str, 64)
		if err != nil {
			return "", err
		}
		str = strconv.FormatFloat(f, specifier, -1, 64)
		return withUnderscore(str, underscore), nil
	}
}

func formatInteger(base, underscore int, prefix string) func(string) (string, error) {
	return func(str string) (string, error) {
		n, err := strconv.ParseInt(str, 0, 64)
		if err != nil {
			return "", err
		}
		str = strconv.FormatInt(n, base)
		return prefix + withUnderscore(str, underscore), nil
	}
}

func withUnderscore(str string, every int) string {
	if every == 0 || len(str) < every {
		return str
	}
	x := strings.Index(str, ".")
	if x < 0 {
		return insertUnderscore(str, every)
	}
	part := insertUnderscore(str[:x], every) + "."
	str = str[x+1:]
	x = strings.IndexAny(str, "eE")
	if x < 0 {
		return part + insertUnderscore(str, every)
	}
	part += insertUnderscore(str[:x], every)
	part += "e"
	if str[x+1] == '+' || str[x+1] == '-' {
		x++
		part += string(str[x])
	}
	return part + insertUnderscore(str[x+1:], every)
}

func insertUnderscore(str string, every int) string {
	if len(str) <= every {
		return str
	}
	var (
		i   = len(str) % every
		buf bytes.Buffer
	)
	if i > 0 {
		buf.WriteString(str[:i])
		buf.WriteString("_")
	}
	for i < len(str) && i+every < len(str) {
		buf.WriteString(str[i : i+every])
		buf.WriteString("_")
		i += every
	}
	buf.WriteString(str[i:])
	return buf.String()
}