package textfmt

import (
	"code.squareroundforest.org/arpio/textedit"
	"errors"
)

type mdEscapeState struct {
	lineStarted     bool
	numberOnNewLine bool
	linkValue       bool
	linkClosed      bool
	linkOpen        bool
}

func escapeTeletypeEdit(r rune, s struct{}) ([]rune, struct{}) {
	if r >= 0x00 && r <= 0x1f && r != '\n' && r != '\t' {
		return []rune{0xb7}, s
	}

	if r >= 0x7f && r <= 0x9f {
		return []rune{0xb7}, s
	}

	return []rune{r}, s
}

func escapeTeletype() wrapper {
	return editor(
		textedit.Func(
			escapeTeletypeEdit,
			func(struct{}) []rune { return nil },
		),
	)
}

func escapeRoffEdit(additional ...string) func(rune, bool) ([]rune, bool) {
	const invalidAdditional = "invalid additional escape definition"
	if len(additional)%2 != 0 {
		panic(errors.New(invalidAdditional))
	}

	esc := map[rune][]rune{
		'\\':     []rune("\\\\"),
		'\u00a0': []rune("\\~"),
	}

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

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

	lsEsc := map[rune][]rune{
		'.':  []rune("\\&."),
		'\'': []rune("\\&'"),
	}

	return func(r rune, lineStarted bool) ([]rune, bool) {
		if r == '\n' {
			return []rune{'\n'}, false
		}

		replacement, replace := esc[r]
		if replace {
			return replacement, true
		}

		if lineStarted {
			return []rune{r}, true
		}

		replacement, replace = lsEsc[r]
		if replace {
			return replacement, true
		}

		return []rune{r}, true
	}
}

func escapeRoff(additional ...string) wrapper {
	return editor(
		textedit.Func(
			escapeRoffEdit(additional...),
			func(bool) []rune { return nil },
		),
	)
}

func escapeMarkdownEdit(r rune, s mdEscapeState) ([]rune, mdEscapeState) {
	var ret []rune
	switch r {
	case '\\', '`', '*', '_', '[', ']', '#', '<', '>':
		ret = append(ret, '\\', r)
	default:
		switch {
		case !s.lineStarted:
			switch r {
			case '+', '-':
				ret = append(ret, '\\', r)
			default:
				ret = append(ret, r)
			}
		case s.numberOnNewLine:
			switch r {
			case '.':
				ret = append(ret, '\\', r)
			default:
				ret = append(ret, r)
			}
		case s.linkClosed:
			switch r {
			case '(':
				ret = append(ret, '\\', r)
			default:
				ret = append(ret, r)
			}
		case s.linkValue:
			switch r {
			case ')':
				ret = append(ret, '\\', r)
			default:
				ret = append(ret, r)
			}
		default:
			ret = append(ret, r)
		}
	}

	s.numberOnNewLine = (!s.lineStarted || s.numberOnNewLine) && r >= '0' && r <= '9'
	s.lineStarted = r != '\n'
	s.linkValue = s.linkClosed && r == '(' || s.linkValue && r != ')'
	s.linkClosed = s.linkOpen && r == ']'
	s.linkOpen = !s.linkValue && r == '[' || s.linkOpen && r != ']'
	return ret, s
}

func escapeMarkdown() wrapper {
	return editor(
		textedit.Func(
			escapeMarkdownEdit,
			func(mdEscapeState) []rune { return nil },
		),
	)
}