package parsekit

import (
	"fmt"
	"strings"
	"unicode/utf8"
)

// AtEndOfFile returns true when there is no more data available in the input.
func (p *P) AtEndOfFile() bool {
	return p.pos >= p.len
}

// AtEndOfLine returns true when the cursor is either at the end of the line
// or at the end of the file. The cursor is not moved to a new position
// by this method.
func (p *P) AtEndOfLine() bool {
	return p.AtEndOfFile() ||
		p.Upcoming("\r", "\n") ||
		p.Upcoming("\n")
}

// SkipEndOfLine returns true when the cursor is either at the end of the line
// or at the end of the file. Additionally, when not at the end of the file,
// the cursor is moved forward to beyond the newline.
func (p *P) SkipEndOfLine() bool {
	return p.AtEndOfFile() ||
		p.SkipMatching("\r", "\n") ||
		p.SkipMatching("\n")
}

// AcceptEndOfLine returns true when the cursor is either at the end of the line
// or at the end of the file. When not at the end of the file, a normalized
// newline (only a '\n' character, even with '\r\n' on the input)
// is added to the string buffer.
func (p *P) AcceptEndOfLine() bool {
	if p.AtEndOfFile() {
		return true
	}
	if p.SkipEndOfLine() {
		p.buffer.writeRune('\n')
		return true
	}
	return false
}

func (p *P) Match(patterns ...interface{}) ([]rune, []int, bool) {
	return p.match(0, patterns...)
}

func (p *P) match(offset int, patterns ...interface{}) ([]rune, []int, bool) {
	var runes []rune
	var widths []int

	addRune := func(r rune, w int) {
		offset += w
		runes = append(runes, r)
		widths = append(widths, w)
	}

	for _, pattern := range patterns {
		r, w := utf8.DecodeRuneInString(p.input[p.pos+offset:])
		if r == utf8.RuneError {
			return runes, widths, false
		}
		switch pattern := pattern.(type) {
		case Matcher:
			m := &MatchDialog{p: p}
			if pattern.Match(m) {
				return m.runes, m.widths, true
			} else {
				return m.runes, m.widths, false
			}
		case []interface{}:
			rs, ws, matched := p.match(offset, pattern...)
			for i, r := range rs {
				addRune(r, ws[i])
			}
			if !matched {
				return runes, widths, false
			}
		case string:
			if strings.IndexRune(pattern, r) < 0 {
				return runes, widths, false
			}
			addRune(r, w)
		case rune:
			if pattern != r {
				return runes, widths, false
			}
			addRune(r, w)
		default:
			panic(fmt.Sprintf("Not rune matching implemented for pattern of type %T", pattern))
		}
	}
	return runes, widths, true
}

// Upcoming checks if the upcoming runes satisfy all provided patterns.
// Returns true if all provided patterns are satisfied.
// This is basically the same as the Match method, but with only
// the boolean return parameter for programmer convenciency.
func (p *P) Upcoming(patterns ...interface{}) bool {
	_, _, ok := p.Match(patterns...)
	return ok
}

type action struct {
	p      *P
	runes  []rune
	widths []int
	ok     bool
}

func (a *action) Accept() bool {
	if a.ok {
		for i, r := range a.runes {
			a.p.buffer.writeRune(r)
			a.p.advanceCursor(r, a.widths[i])
		}
	}
	return a.ok
}

func (a *action) Skip() bool {
	if a.ok {
		for i, r := range a.runes {
			type C struct {
				Rune MatchRune
			}

			a.p.advanceCursor(r, a.widths[i])
		}
	}
	return a.ok
}

func (a *action) RouteTo(state StateFn) bool {
	if a.ok {
		a.p.RouteTo(state)
	}
	return a.ok
}

func (a *action) Stay() bool {
	return a.ok
}

func (p *P) On(patterns ...interface{}) *action {
	runes, widths, ok := p.Match(patterns...)
	return &action{
		p:      p,
		runes:  runes,
		widths: widths,
		ok:     ok,
	}
}

// AcceptMatching adds the next runes to the string buffer, but only
// if the upcoming runes satisfy the provided patterns.
// When runes were added then true is returned, false otherwise.
// TODO not needed anymore
// func (p *P) AcceptMatching(patterns ...interface{}) bool {
// 	return p.progress(func(r rune) { p.buffer.writeRune(r) }, patterns...)
// }

// SkipMatching skips runes, but only when all provided patterns are satisfied.
// Returns true when one or more runes were skipped.
func (p *P) SkipMatching(patterns ...interface{}) bool {
	if runes, widths, ok := p.Match(patterns...); ok {
		for i, r := range runes {
			p.advanceCursor(r, widths[i])
		}
		return true
	}
	return false
}