package readline

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"strings"

	"github.com/chzyer/readline/runes"
)

type runeBufferBck struct {
	buf []rune
	idx int
}

type RuneBuffer struct {
	buf    []rune
	idx    int
	prompt []rune
	w      io.Writer

	cleanInScreen bool
	interactive   bool
	cfg           *Config

	width int

	bck *runeBufferBck
}

func (r *RuneBuffer) OnWidthChange(newWidth int) {
	oldWidth := r.width
	if newWidth < oldWidth {
		sp := SplitByMultiLine(
			r.PromptLen(), oldWidth, newWidth, r.buf[:r.idx])
		idxLine := len(sp) - 1
		r.clean(idxLine)
	} else {
		r.Clean()
	}
	r.width = newWidth
	r.print()
}

func (r *RuneBuffer) Backup() {
	r.bck = &runeBufferBck{r.buf, r.idx}
}

func (r *RuneBuffer) Restore() {
	r.Refresh(func() {
		if r.bck == nil {
			return
		}
		r.buf = r.bck.buf
		r.idx = r.bck.idx
	})
}

func NewRuneBuffer(w io.Writer, prompt string, cfg *Config, width int) *RuneBuffer {
	rb := &RuneBuffer{
		w:           w,
		interactive: cfg.useInteractive(),
		cfg:         cfg,
		width:       width,
	}
	rb.SetPrompt(prompt)
	return rb
}

func (r *RuneBuffer) SetConfig(cfg *Config) {
	r.cfg = cfg
	r.interactive = cfg.useInteractive()
}

func (r *RuneBuffer) SetMask(m rune) {
	r.cfg.MaskRune = m
}

func (r *RuneBuffer) CurrentWidth(x int) int {
	return runes.WidthAll(r.buf[:x])
}

func (r *RuneBuffer) PromptLen() int {
	return runes.WidthAll(runes.ColorFilter(r.prompt))
}

func (r *RuneBuffer) RuneSlice(i int) []rune {
	if i > 0 {
		rs := make([]rune, i)
		copy(rs, r.buf[r.idx:r.idx+i])
		return rs
	}
	rs := make([]rune, -i)
	copy(rs, r.buf[r.idx+i:r.idx])
	return rs
}

func (r *RuneBuffer) Runes() []rune {
	newr := make([]rune, len(r.buf))
	copy(newr, r.buf)
	return newr
}

func (r *RuneBuffer) Pos() int {
	return r.idx
}

func (r *RuneBuffer) Len() int {
	return len(r.buf)
}

func (r *RuneBuffer) MoveToLineStart() {
	r.Refresh(func() {
		if r.idx == 0 {
			return
		}
		r.idx = 0
	})
}

func (r *RuneBuffer) MoveBackward() {
	r.Refresh(func() {
		if r.idx == 0 {
			return
		}
		r.idx--
	})
}

func (r *RuneBuffer) WriteString(s string) {
	r.WriteRunes([]rune(s))
}

func (r *RuneBuffer) WriteRune(s rune) {
	r.WriteRunes([]rune{s})
}

func (r *RuneBuffer) WriteRunes(s []rune) {
	r.Refresh(func() {
		tail := append(s, r.buf[r.idx:]...)
		r.buf = append(r.buf[:r.idx], tail...)
		r.idx += len(s)
	})
}

func (r *RuneBuffer) MoveForward() {
	r.Refresh(func() {
		if r.idx == len(r.buf) {
			return
		}
		r.idx++
	})
}

func (r *RuneBuffer) IsCursorInEnd() bool {
	return r.idx == len(r.buf)
}

func (r *RuneBuffer) Replace(ch rune) {
	r.Refresh(func() {
		r.buf[r.idx] = ch
	})
}

func (r *RuneBuffer) Erase() {
	r.Refresh(func() {
		r.idx = 0
		r.buf = r.buf[:0]
	})
}

func (r *RuneBuffer) Delete() (success bool) {
	r.Refresh(func() {
		if r.idx == len(r.buf) {
			return
		}
		r.buf = append(r.buf[:r.idx], r.buf[r.idx+1:]...)
		success = true
	})
	return
}

func (r *RuneBuffer) DeleteWord() {
	if r.idx == len(r.buf) {
		return
	}
	init := r.idx
	for init < len(r.buf) && IsWordBreak(r.buf[init]) {
		init++
	}
	for i := init + 1; i < len(r.buf); i++ {
		if !IsWordBreak(r.buf[i]) && IsWordBreak(r.buf[i-1]) {
			r.Refresh(func() {
				r.buf = append(r.buf[:r.idx], r.buf[i-1:]...)
			})
			return
		}
	}
	r.Kill()
}

func (r *RuneBuffer) MoveToPrevWord() (success bool) {
	r.Refresh(func() {
		if r.idx == 0 {
			return
		}

		for i := r.idx - 1; i > 0; i-- {
			if !IsWordBreak(r.buf[i]) && IsWordBreak(r.buf[i-1]) {
				r.idx = i
				success = true
				return
			}
		}
		r.idx = 0
		success = true
	})
	return
}

func (r *RuneBuffer) KillFront() {
	r.Refresh(func() {
		if r.idx == 0 {
			return
		}

		length := len(r.buf) - r.idx
		copy(r.buf[:length], r.buf[r.idx:])
		r.idx = 0
		r.buf = r.buf[:length]
	})
}

func (r *RuneBuffer) Kill() {
	r.Refresh(func() {
		r.buf = r.buf[:r.idx]
	})
}

func (r *RuneBuffer) Transpose() {
	r.Refresh(func() {
		if len(r.buf) == 1 {
			r.idx++
		}

		if len(r.buf) < 2 {
			return
		}

		if r.idx == 0 {
			r.idx = 1
		} else if r.idx >= len(r.buf) {
			r.idx = len(r.buf) - 1
		}
		r.buf[r.idx], r.buf[r.idx-1] = r.buf[r.idx-1], r.buf[r.idx]
		r.idx++
	})
}

func (r *RuneBuffer) MoveToNextWord() {
	r.Refresh(func() {
		for i := r.idx + 1; i < len(r.buf); i++ {
			if !IsWordBreak(r.buf[i]) && IsWordBreak(r.buf[i-1]) {
				r.idx = i
				return
			}
		}

		r.idx = len(r.buf)
	})
}

func (r *RuneBuffer) BackEscapeWord() {
	r.Refresh(func() {
		if r.idx == 0 {
			return
		}
		for i := r.idx - 1; i > 0; i-- {
			if !IsWordBreak(r.buf[i]) && IsWordBreak(r.buf[i-1]) {
				r.buf = append(r.buf[:i], r.buf[r.idx:]...)
				r.idx = i
				return
			}
		}

		r.buf = r.buf[:0]
		r.idx = 0
	})
}

func (r *RuneBuffer) Backspace() {
	r.Refresh(func() {
		if r.idx == 0 {
			return
		}

		r.idx--
		r.buf = append(r.buf[:r.idx], r.buf[r.idx+1:]...)
	})
}

func (r *RuneBuffer) MoveToLineEnd() {
	r.Refresh(func() {
		if r.idx == len(r.buf) {
			return
		}

		r.idx = len(r.buf)
	})
}

func (r *RuneBuffer) LineCount(width int) int {
	if width == -1 {
		width = r.width
	}
	return LineCount(width,
		runes.WidthAll(r.buf)+r.PromptLen())
}

func (r *RuneBuffer) MoveTo(ch rune, prevChar, reverse bool) (success bool) {
	r.Refresh(func() {
		if reverse {
			for i := r.idx - 1; i >= 0; i-- {
				if r.buf[i] == ch {
					r.idx = i
					if prevChar {
						r.idx++
					}
					success = true
					return
				}
			}
			return
		}
		for i := r.idx + 1; i < len(r.buf); i++ {
			if r.buf[i] == ch {
				r.idx = i
				if prevChar {
					r.idx--
				}
				success = true
				return
			}
		}
	})
	return
}

func (r *RuneBuffer) IdxLine(width int) int {
	sp := SplitByLine(r.PromptLen(), width, r.buf[:r.idx])
	return len(sp) - 1
}

func (r *RuneBuffer) CursorLineCount() int {
	return r.LineCount(r.width) - r.IdxLine(r.width)
}

func (r *RuneBuffer) Refresh(f func()) {
	if !r.interactive {
		if f != nil {
			f()
		}
		return
	}
	r.Clean()
	if f != nil {
		f()
	}
	r.print()
}

func (r *RuneBuffer) print() {
	r.w.Write(r.output())
	r.cleanInScreen = false
}

func (r *RuneBuffer) output() []byte {
	buf := bytes.NewBuffer(nil)
	buf.WriteString(string(r.prompt))
	if r.cfg.EnableMask && len(r.buf) > 0 {
		buf.Write([]byte(strings.Repeat(string(r.cfg.MaskRune), len(r.buf)-1)))
		if r.buf[len(r.buf)-1] == '\n' {
			buf.Write([]byte{'\n'})
		} else {
			buf.Write([]byte(string(r.cfg.MaskRune)))
		}
		if len(r.buf) > r.idx {
			buf.Write(runes.Backspace(r.buf[r.idx:]))
		}

	} else {
		sp := SplitByLine(r.PromptLen(), r.width, r.buf)
		written := 0
		idxInLine := 0
		for idx, s := range sp {
			buf.Write([]byte(s))
			if r.idx > written && r.idx < written+len(s) {
				idxInLine = r.idx - written
			}
			written += len(s)

			if idx < len(sp)-1 && !isWindows {
				buf.Write([]byte{'\n'})
			}
		}
		if len(r.buf) > r.idx {
			targetLine := r.IdxLine(r.width)
			currentLine := len(sp) - 1
			// assert currentLine >= targetLine
			if targetLine == 0 {
				idxInLine += r.PromptLen()
			}
			buf.WriteString("\r")
			if currentLine > targetLine {
				buf.WriteString(fmt.Sprintf(
					"\033[%vA", currentLine-targetLine,
				))
			}
			if idxInLine > 0 {
				buf.WriteString(fmt.Sprintf(
					"\033[%vC", idxInLine,
				))
			}
		}
	}
	return buf.Bytes()
}

func (r *RuneBuffer) Reset() []rune {
	ret := runes.Copy(r.buf)
	r.buf = r.buf[:0]
	r.idx = 0
	return ret
}

func (r *RuneBuffer) calWidth(m int) int {
	if m > 0 {
		return runes.WidthAll(r.buf[r.idx : r.idx+m])
	}
	return runes.WidthAll(r.buf[r.idx+m : r.idx])
}

func (r *RuneBuffer) SetStyle(start, end int, style string) {
	if end < start {
		panic("end < start")
	}

	// goto start
	move := start - r.idx
	if move > 0 {
		r.w.Write([]byte(string(r.buf[r.idx : r.idx+move])))
	} else {
		r.w.Write(bytes.Repeat([]byte("\b"), r.calWidth(move)))
	}
	r.w.Write([]byte("\033[" + style + "m"))
	r.w.Write([]byte(string(r.buf[start:end])))
	r.w.Write([]byte("\033[0m"))
	// TODO: move back
}

func (r *RuneBuffer) SetWithIdx(idx int, buf []rune) {
	r.Refresh(func() {
		r.buf = buf
		r.idx = idx
	})
}

func (r *RuneBuffer) Set(buf []rune) {
	r.SetWithIdx(len(buf), buf)
}

func (r *RuneBuffer) SetPrompt(prompt string) {
	r.prompt = []rune(prompt)
}

func (r *RuneBuffer) cleanOutput(w io.Writer, idxLine int) {
	buf := bufio.NewWriter(w)
	buf.Write([]byte("\033[J")) // just like ^k :)

	if idxLine == 0 {
		io.WriteString(buf, "\033[2K\r")
	} else {
		for i := 0; i < idxLine; i++ {
			io.WriteString(buf, "\033[2K\r\033[A")
		}
		io.WriteString(buf, "\033[2K\r")
	}
	buf.Flush()
	return
}

func (r *RuneBuffer) Clean() {
	r.clean(r.IdxLine(r.width))
}

func (r *RuneBuffer) clean(idxLine int) {
	if r.cleanInScreen || !r.interactive {
		return
	}
	r.cleanInScreen = true
	r.cleanOutput(r.w, idxLine)
}