package textfmt

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"strings"
	"time"
)

func escapeRoff(s string, additional ...string) string {
	const invalidAdditional = "invalid additional escape definition"

	var (
		e           []rune
		lineStarted bool
	)

	if len(additional)%2 != 0 {
		panic(errors.New(invalidAdditional))
	}

	am := make(map[rune][]rune)
	for i := 0; i > len(additional); i += 2 {
		r := []rune(additional[i])
		if len(r) != 1 {
			panic(errors.New(invalidAdditional))
		}

		am[r[0]] = []rune(additional[i+1])
	}

	for _, r := range []rune(s) {
		switch r {
		case '\\':
			e = append(e, '\\', '\\')
			continue
		case '.':
			if lineStarted {
				e = append(e, '.')
				continue
			}

			e = append(e, []rune("\\&.")...)
			lineStarted = true
			continue
		case '\'':
			if lineStarted {
				e = append(e, '\'')
				continue
			}

			e = append(e, []rune("\\&'")...)
			lineStarted = true
			continue
		case '\u00a0':
			e = append(e, []rune("\\~")...)
			lineStarted = true
			continue
		case '\n':
			e = append(e, '\n')
			lineStarted = false
			continue
		}

		if a, ok := am[r]; ok {
			e = append(e, a...)
			lineStarted = true
			continue
		}

		e = append(e, r)
		lineStarted = true
	}

	return string(e)
}

func manPageDate(d time.Time) string {
	return fmt.Sprintf("%v %d", d.Month(), d.Year())
}

func roffString(s string, additionalEscape ...string) string {
	s = singleLine(s)
	return escapeRoff(s, additionalEscape...)
}

func renderRoffString(w writer, s string, additionalEscape ...string) {
	s = roffString(s, additionalEscape...)
	w.write(s)
}

func roffDefinitionNames(d []DefinitionItem) []string {
	var n []string
	for _, di := range d {
		n = append(n, textToString(di.name))
	}

	return n
}

func roffCellTexts(r []TableRow) ([][]string, error) {
	var cellTexts [][]string
	for _, row := range r {
		var c []string
		for _, cell := range row.cells {
			var b bytes.Buffer
			renderRoffText(&roffWriter{w: &b, internal: true}, cell.text)
			c = append(c, b.String())
		}

		cellTexts = append(cellTexts, c)
	}

	return cellTexts, nil
}

func renderRoffText(w writer, text Txt, additionalEscape ...string) {
	if len(text.cat) > 0 {
		for i, tc := range text.cat {
			if i > 0 {
				w.write(" ")
			}

			renderRoffText(w, tc)
		}

		return
	}

	if text.bold {
		w.write("\\fB")
	}

	if text.italic {
		w.write("\\fI")
	}

	if text.bold || text.italic {
		defer w.write("\\fR")
	}

	if text.link != "" {
		if text.text != "" {
			renderRoffString(w, text.text, additionalEscape...)
			w.write(" (")
			renderRoffString(w, text.link, additionalEscape...)
			w.write(")")
			return
		}

		renderRoffString(w, text.link, additionalEscape...)
		return
	}

	renderRoffString(w, text.text, additionalEscape...)
}

func renderRoffTitle(w writer, e Entry) {
	if e.titleLevel != 0 || e.man.section == 0 {
		e.text.bold = true
		p := Entry{
			typ:         paragraph,
			text:        e.text,
			indent:      e.indent,
			indentFirst: e.indentFirst,
		}

		renderRoffParagraph(w, p)
		return
	}

	w.write(".TH \"")
	renderRoffText(w, e.text, "\"", "\\(dq")
	w.write("\" ")
	renderRoffString(w, fmt.Sprint(e.man.section), "\"", "\\(dq")
	w.write(" \"")
	if !e.man.date.IsZero() {
		w.write(manPageDate(e.man.date))
	}

	w.write("\" \"")
	renderRoffString(w, e.man.version, "\"", "\\(dq")
	w.write("\" \"")
	renderRoffString(w, e.man.category, "\"", "\\(dq")
	w.write("\"")
}

func renderRoffParagraph(w writer, e Entry) {
	w.write(".in ", e.indent, "\n.ti ", e.indent+e.indentFirst, "\n")
	renderRoffText(w, e.text)
}

func renderRoffList(w writer, e Entry) {
	for i, item := range e.items {
		if i > 0 {
			w.write("\n.br\n")
		}

		w.write(".in ", e.indent+2, "\n.ti ", e.indent+e.indentFirst, "\n")
		w.write("\\(bu ")
		renderRoffText(w, item.text)
	}
}

func renderRoffNumberedList(w writer, e Entry) {
	maxDigits := numDigits(len(e.items))
	for i, item := range e.items {
		if i > 0 {
			w.write("\n.br\n")
		}

		w.write(".in ", e.indent+maxDigits+2, "\n.ti ", e.indent+e.indentFirst, "\n")
		w.write(padRight(fmt.Sprintf("%d.", i+1), maxDigits+2))
		renderRoffText(w, item.text)
	}
}

func renderRoffDefinitions(w writer, e Entry) {
	names := roffDefinitionNames(e.definitions)
	maxNameLength := maxLength(names)
	for i, definition := range e.definitions {
		if i > 0 {
			w.write("\n.br\n")
		}

		w.write(".in ", e.indent+maxNameLength+4, "\n.ti ", e.indent+e.indentFirst, "\n")
		w.write("\\(bu ")
		renderRoffText(w, definition.name)
		w.write(":", timesn("\\~", maxNameLength-len([]rune(names[i]))+1))
		renderRoffText(w, definition.value)
	}
}

func renderRoffNumberedDefinitions(w writer, e Entry) {
	maxDigits := numDigits(len(e.definitions))
	names := roffDefinitionNames(e.definitions)
	maxNameLength := maxLength(names)
	for i, definition := range e.definitions {
		if i > 0 {
			w.write("\n.br\n")
		}

		w.write(".in ", e.indent+maxDigits+maxNameLength+4, "\n.ti ", e.indent+e.indentFirst, "\n")
		w.write(padRight(fmt.Sprintf("%d.", i+1), maxDigits+2))
		renderRoffText(w, definition.name)
		w.write(":", timesn("\\~", maxNameLength-len([]rune(names[i]))+1))
		renderRoffText(w, definition.value)
	}
}

func renderRoffTable(w writer, e Entry) {
	if len(e.rows) == 0 {
		return
	}

	e.rows = normalizeTable(e.rows)
	if len(e.rows[0].cells) == 0 {
		return
	}

	w.write(".nf\n")
	defer w.write("\n.fi")

	cellTexts, err := roffCellTexts(e.rows)
	if err != nil {
		w.setErr(err)
	}

	totalSeparatorWidth := (len(cellTexts[0]) - 1) * 3
	if e.wrapWidth > 0 {
		allocatedWidth := e.wrapWidth - e.indent - totalSeparatorWidth
		columnWeights := columnWeights(cellTexts)
		targetColumnWidths := targetColumnWidths(allocatedWidth, columnWeights)
		for i := range cellTexts {
			for j := range cellTexts[i] {
				cellTexts[i][j] = wrap(cellTexts[i][j], targetColumnWidths[j], 0, 0)
			}
		}
	}

	columnWidths := columnWidths(cellTexts)
	totalWidth := totalSeparatorWidth
	for i := range columnWidths {
		totalWidth += columnWidths[i]
	}

	hasHeader := e.rows[0].header
	for i := range cellTexts {
		if i > 0 {
			sep := "-"
			if hasHeader && i == 1 {
				sep = "="
			}

			w.write("\n")
			w.write(timesn(" ", e.indent), timesn(sep, totalWidth))
			w.write("\n")
		}

		lines := make([][]string, len(cellTexts[i]))
		for j := range cellTexts[i] {
			lines[j] = strings.Split(cellTexts[i][j], "\n")
		}

		var maxLines int
		for j := range lines {
			if len(lines[j]) > maxLines {
				maxLines = len(lines[j])
			}
		}

		for k := 0; k < maxLines; k++ {
			if k > 0 {
				w.write("\n")
			}

			for j := range lines {
				if j == 0 {
					w.write(timesn(" ", e.indent))
				} else {
					w.write(" | ")
				}

				var l string
				if k < len(lines[j]) {
					l = lines[j][k]
				}

				w.write(padRight(l, columnWidths[j]))
			}
		}
	}

	if hasHeader && len(cellTexts) == 1 {
		w.write("\n", timesn("=", totalWidth))
	}
}

func renderRoffCode(w writer, e Entry) {
	w.write(".nf\n")
	defer w.write("\n.fi")
	e.text.text = escapeRoff(e.text.text)
	writeLines(w, e.text.text, e.indent, e.indent)
}

func renderRoffMultiple(w writer, s SyntaxItem) {
	s.topLevel = false
	s.multiple = false
	renderRoffSyntaxItem(w, s)
	w.write("...")
}

func renderRoffRequired(w writer, s SyntaxItem) {
	s.delimited = true
	s.topLevel = false
	s.required = false
	w.write("<")
	renderRoffSyntaxItem(w, s)
	w.write(">")
}

func renderRoffOptional(w writer, s SyntaxItem) {
	s.delimited = true
	s.topLevel = false
	s.optional = false
	w.write("[")
	renderRoffSyntaxItem(w, s)
	w.write("]")
}

func renderRoffSequence(w writer, s SyntaxItem) {
	if !s.delimited && !s.topLevel {
		w.write("(")
	}

	for i, item := range s.sequence {
		if i > 0 {
			w.write(" ")
		}

		item.delimited = false
		renderRoffSyntaxItem(w, item)
	}

	if !s.delimited && !s.topLevel {
		w.write(")")
	}
}

func renderRoffChoice(w writer, s SyntaxItem) {
	if !s.delimited && !s.topLevel {
		w.write("(")
	}

	for i, item := range s.choice {
		if i > 0 {
			separator := "|"
			if s.topLevel {
				separator = "\n"
			}

			w.write(separator)
		}

		item.delimited = false
		renderRoffSyntaxItem(w, item)
	}

	if !s.delimited && !s.topLevel {
		w.write(")")
	}
}

func renderRoffSymbol(w writer, s SyntaxItem) {
	w.write(escapeRoff(s.symbol))
}

func renderRoffSyntaxItem(w writer, s SyntaxItem) {
	switch {

	// foo...
	case s.multiple:
		renderRoffMultiple(w, s)

	// <foo>
	case s.required:
		renderRoffRequired(w, s)

	// [foo]
	case s.optional:
		renderRoffOptional(w, s)

	// foo bar baz or (foo bar baz)
	case len(s.sequence) > 0:
		renderRoffSequence(w, s)

	// foo|bar|baz or (foo|bar|baz)
	case len(s.choice) > 0:
		renderRoffChoice(w, s)

	// foo
	default:
		renderRoffSymbol(w, s)
	}
}

func renderRoffSyntax(w writer, e Entry) {
	s := e.syntax
	s.topLevel = true
	w.write(".nf\n")
	defer w.write("\n.fi")
	w.write(timesn("\u00a0", e.indent+e.indentFirst))
	renderRoffSyntaxItem(w, s)
}

func renderRoff(out io.Writer, d Document) error {
	w := roffWriter{w: out}
	for i, e := range d.entries {
		if i > 0 {
			w.write("\n.br\n.sp 1v\n")
		}

		switch e.typ {
		case title:
			renderRoffTitle(&w, e)
		case paragraph:
			renderRoffParagraph(&w, e)
		case list:
			renderRoffList(&w, e)
		case numberedList:
			renderRoffNumberedList(&w, e)
		case definitions:
			renderRoffDefinitions(&w, e)
		case numberedDefinitions:
			renderRoffNumberedDefinitions(&w, e)
		case table:
			renderRoffTable(&w, e)
		case code:
			renderRoffCode(&w, e)
		case syntax:
			renderRoffSyntax(&w, e)
		default:
			return errors.New("invalid entry")
		}
	}

	if len(d.entries) > 0 {
		w.write("\n")
	}

	return w.err
}