package textfmt

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

func mdTextToString(text Txt) string {
	var b bytes.Buffer
	renderMDText(&b, text)
	return b.String()
}

func mdCellTexts(rows []TableRow) [][]string {
	var texts [][]string
	for _, row := range rows {
		var rowTexts []string
		for _, cell := range row.cells {
			rowTexts = append(rowTexts, mdTextToString(cell.text))
		}

		texts = append(texts, rowTexts)
	}

	return texts
}

func mdEnsureHeaderTexts(h []string) []string {
	var hh []string
	for _, t := range h {
		if strings.TrimSpace(t) == "" {
			t = "\\-"
		}

		hh = append(hh, t)
	}

	return hh
}

func renderMDText(w io.Writer, text Txt) {
	if len(text.cat) > 0 {
		for i, tc := range text.cat {
			if i > 0 {
				write(w, " ")
			}

			renderMDText(w, tc)
		}

		return
	}

	if text.bold {
		write(w, "**")
	}

	if text.italic {
		write(w, "_")
	}

	defer func() {
		if text.italic {
			write(w, "_")
		}

		if text.bold {
			write(w, "**")
		}
	}()

	if text.link == "" {
		w, f := writeWith(w, singleLine(), escapeMarkdown())
		write(w, text.text)
		w, _ = f()
		return
	}

	if text.text == "" {
		w, f := writeWith(w, singleLine(), escapeMarkdown())
		write(w, text.link)
		w, _ = f()
		return
	}

	write(w, "[")
	w, f := writeWith(w, singleLine(), escapeMarkdown())
	write(w, text.text)
	w, _ = f()
	write(w, "](")
	w, f = writeWith(w, singleLine(), escapeMarkdown())
	write(w, text.link)
	w, _ = f()
	write(w, ")")
	w, _ = f()
}

func renderMDTitle(w io.Writer, e Entry) {
	hashes := e.titleLevel + 1
	if hashes > 6 {
		hashes = 6
	}

	write(w, timesn("#", hashes), " ")
	renderMDText(w, e.text)
}

func renderMDParagraphIndent(w io.Writer, e Entry) {
	var f func() (io.Writer, error)
	if e.wrapWidth > 0 {
		indentFirst := e.indent + e.indentFirst
		w, f = writeWith(w, wrapIndent(indentFirst, e.indent, e.wrapWidth, e.wrapWidth))
	}

	renderMDText(w, e.text)
	if f != nil {
		f()
	}
}

func renderMDParagraph(w io.Writer, e Entry) {
	e.indent = 0
	e.indentFirst = 0
	renderMDParagraphIndent(w, e)
}

func renderMDList(w io.Writer, e Entry) {
	e.indent = 2
	e.indentFirst = -2
	if e.wrapWidth > 2 {
		e.wrapWidth -= 2
	}

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

		write(w, "- ")
		p := itemToParagraph(e, item.text)
		renderMDParagraphIndent(w, p)
	}
}

func renderMDNumberedList(w io.Writer, e Entry) {
	maxDigits := numDigits(len(e.items))
	e.indent = maxDigits + 2
	e.indentFirst = 0 - maxDigits - 2
	if e.wrapWidth > maxDigits+2 {
		e.wrapWidth -= maxDigits + 2
	}

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

		write(w, padRight(fmt.Sprintf("%d.", i+1), maxDigits+2))
		p := itemToParagraph(e, item.text)
		renderMDParagraphIndent(w, p)
	}
}

func renderMDDefinitions(w io.Writer, e Entry) {
	for _, d := range e.definitions {
		e.items = append(
			e.items,
			Item(Cat(Text(fmt.Sprintf("%s:", d.name.text)), d.value)),
		)
	}

	renderMDList(w, e)
}

func renderMDNumberedDefinitions(w io.Writer, e Entry) {
	for _, d := range e.definitions {
		e.items = append(
			e.items,
			Item(Cat(Text(fmt.Sprintf("%s:", d.name.text)), d.value)),
		)
	}

	renderMDNumberedList(w, e)
}

func renderMDTable(w io.Writer, e Entry) {
	e.rows = normalizeTable(e.rows)
	e.rows = ensureHeader(e.rows)
	if len(e.rows) == 0 || len(e.rows[0].cells) == 0 {
		return
	}

	headerTexts := mdCellTexts(e.rows[:1])
	cellTexts := mdCellTexts(e.rows[1:])
	headerTexts[0] = mdEnsureHeaderTexts(headerTexts[0])
	columns := columnWidths(headerTexts)
	cellColumns := columnWidths(cellTexts)
	if len(cellColumns) > 0 {
		for i := range columns {
			if cellColumns[i] > columns[i] {
				columns[i] = cellColumns[i]
			}
		}
	}

	write(w, "|")
	for i, h := range headerTexts[0] {
		write(w, " ", padRight(h, columns[i]))
		write(w, " |")
	}

	write(w, "\n|")
	for _, c := range columns {
		write(w, timesn("-", c+1))
		write(w, "-|")
	}

	for _, row := range cellTexts {
		write(w, "\n|")
		for i, cell := range row {
			write(w, " ", padRight(cell, columns[i]))
			write(w, " |")
		}
	}
}

func renderMDCode(w io.Writer, e Entry) {
	write(w, "```\n")
	write(w, e.text.text)
	write(w, "\n```")
}

func renderMDMultiple(w io.Writer, s SyntaxItem) {
	s.topLevel = false
	s.multiple = false
	renderMDSyntaxItem(w, s)
	write(w, "...")
}

func renderMDRequired(w io.Writer, s SyntaxItem) {
	s.delimited = true
	s.topLevel = false
	s.required = false
	write(w, "<")
	renderMDSyntaxItem(w, s)
	write(w, ">")
}

func renderMDOptional(w io.Writer, s SyntaxItem) {
	s.delimited = true
	s.topLevel = false
	s.optional = false
	write(w, "[")
	renderMDSyntaxItem(w, s)
	write(w, "]")
}

func renderMDSequence(w io.Writer, s SyntaxItem) {
	if !s.delimited && !s.topLevel {
		write(w, "(")
	}

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

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

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

func renderMDChoice(w io.Writer, s SyntaxItem) {
	if !s.delimited && !s.topLevel {
		write(w, "(")
	}

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

			write(w, separator)
		}

		item.delimited = false
		item.topLevel = s.topLevel
		renderMDSyntaxItem(w, item)
	}

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

func renderMDSymbol(w io.Writer, s SyntaxItem) {
	w, f := writeWith(w, escapeMarkdown())
	write(w, s.symbol)
	f()
}

func renderMDSyntaxItem(w io.Writer, s SyntaxItem) {
	switch {

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

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

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

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

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

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

func renderMDSyntax(w io.Writer, e Entry) {
	s := e.syntax
	s.topLevel = true
	write(w, "```\n")
	renderMDSyntaxItem(w, s)
	write(w, "\n```")
}

func renderMarkdown(out io.Writer, d Document) error {
	w, f := writeWith(out, mdNBSP(), errorHandler)
	for i, e := range d.entries {
		if i > 0 {
			write(w, "\n\n")
		}

		switch e.typ {
		case title:
			renderMDTitle(w, e)
		case paragraph:
			renderMDParagraph(w, e)
		case list:
			renderMDList(w, e)
		case numberedList:
			renderMDNumberedList(w, e)
		case definitions:
			renderMDDefinitions(w, e)
		case numberedDefinitions:
			renderMDNumberedDefinitions(w, e)
		case table:
			renderMDTable(w, e)
		case code:
			renderMDCode(w, e)
		case syntax:
			renderMDSyntax(w, e)
		default:
			return errors.New("invalid entry")
		}
	}

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

	_, err := f()
	return err
}