package readline

import (
	"os"

	. "gitea.zaclys.com/bvaudour/gob/option"
	"gitea.zaclys.com/bvaudour/gob/shell/console/atom"
)

type Readline struct {
	st *atom.State
}

func New() *Readline {
	return &Readline{
		st: atom.NewState(),
	}
}

func (rl *Readline) execChar(r atom.Char, isPassword bool) (fix, stop bool) {
	if stop = r == '\n' || r == '\r'; stop {
		fix = true
		return
	}

	if atom.IsPrintable(r) {
		rl.st.Insert(r)
		fix = true
		return
	}

	var noBeep bool
	switch r {
	case atom.Bs, atom.C_H: // Back
		noBeep, fix = rl.st.Back(), true
	case atom.C_W: // Back word
		noBeep, fix = rl.st.BackWord(), true
	case atom.C_D: // Del or reset line
		l := rl.st.BufferLen()
		if l == 0 {
			rl.st.Return()
			os.Exit(0)
		} else {
			noBeep, fix = rl.st.Del(), true
			rl.st.Restart()
		}
	case atom.C_U: // Remove BOL
		noBeep, fix = rl.st.RemoveBegin(), true
	case atom.C_K: // Remove EOL
		noBeep, fix = rl.st.RemoveEnd(), true
	case atom.C_A: // Move to BOL
		noBeep, fix = rl.st.Begin(), true
	case atom.C_E: // Move to EOL
		noBeep, fix = rl.st.End(), true
	case atom.C_B: // Move left
		noBeep, fix = rl.st.Left(), true
	case atom.C_F: // Move right
		noBeep, fix = rl.st.Right(), true
	case atom.C_T: // Transpose
		noBeep, fix = rl.st.Transpose(), true
	case atom.C_P: // Previous history
		if !isPassword {
			noBeep = rl.st.HistoryPrev()
		}
	case atom.C_N: // Next history
		if !isPassword {
			noBeep = rl.st.HistoryNext()
		}
	case atom.C_S: // Search history
		if !isPassword {
			noBeep = rl.st.SearchHistoryNext()
		}
	case atom.C_R: // Reverse search history
		if !isPassword {
			noBeep = rl.st.SearchHistoryPrev()
		}
	case atom.C_G, atom.Esc: // Cancel history
		noBeep, fix = rl.st.Cancel(), true
	case atom.C_Y: // Yank
		noBeep = rl.st.Yank()
	case atom.C_C: // Emergency stop
		rl.st.Return()
		os.Exit(1)
	}

	if !noBeep {
		rl.st.Beep()
	}

	return
}

func (rl *Readline) execSequence(s atom.Sequence, isPassword bool) (fix, stop bool) {
	var noBeep bool
	switch s {
	case atom.Up: // Previous history
		if !isPassword {
			l := rl.st.BufferLen()
			if l == 0 || rl.st.IsHistoryMode() {
				noBeep = rl.st.HistoryPrev()
			} else {
				noBeep = rl.st.SearchHistoryPrev()
			}
		}
	case atom.Down: // Next history
		if !isPassword {
			l := rl.st.BufferLen()
			if l == 0 || rl.st.IsHistoryMode() {
				noBeep = rl.st.HistoryNext()
			} else {
				noBeep = rl.st.SearchHistoryNext()
			}
		}
	case atom.Right: // Move right
		noBeep, fix = rl.st.Right(), true
	case atom.Left: // Move left
		noBeep, fix = rl.st.Left(), true
	case atom.Ins: // Toggle insert
		rl.st.ToggleReplace()
		noBeep = true
	case atom.Del: // Delete under cursor
		noBeep, fix = rl.st.Del(), true
	case atom.Home: // Move BOL
		noBeep, fix = rl.st.Begin(), true
	case atom.End: // Move EOL
		noBeep, fix = rl.st.End(), true
	case atom.A_Bs: // Delete begin of word
		noBeep, fix = rl.st.BackWord(), true
	case atom.A_D, atom.A_Del: // Delete end of word
		noBeep, fix = rl.st.DelWord(), true
	case atom.C_Right, atom.A_F: // Next word
		noBeep, fix = rl.st.NextWord(), true
	case atom.C_Left, atom.A_B: // Begin of word
		noBeep, fix = rl.st.PrevWord(), true
	case atom.A_Y: // Previous yank
		noBeep = rl.st.YankPrev()
	}

	if !noBeep {
		rl.st.Beep()
	}

	return
}

func (rl *Readline) prompt(p string, isPassword bool) (result Result[string]) {
	if err, ok := rl.st.SetPrompt(p).Get(); ok {
		return Err[string](err)
	}

	rl.st.Start()
	defer rl.st.Stop()

	var refresh func() Option[error]
	if isPassword {
		refresh = func() Option[error] { return rl.st.Print("", 0) }
	} else {
		refresh = func() Option[error] {
			str, cursor := rl.st.Buffer()
			return rl.st.Print(str, cursor)
		}
	}
	refresh()

	var fix, stop, isErr bool
	for {
		n := rl.st.Next()
		if err, ok := n.Err(); ok {
			result, isErr = Err[string](err), true
			break
		}

		key, _ := n.Ok()
		if s, ok := key.Sequence(); ok {
			fix, stop = rl.execSequence(s, isPassword)
		} else if c, ok := key.Char(); ok {
			fix, stop = rl.execChar(c, isPassword)
		}

		err := refresh()
		if e, ok := err.Get(); ok {
			result, isErr = Err[string](e), true
			break
		}

		if stop {
			break
		}

		if fix {
			rl.st.FixState()
		}
	}

	if !isErr {
		r, _ := rl.st.Buffer()
		result = Ok(r)
		if !isPassword && len(r) > 0 {
			rl.st.AppendHistory(r)
		}
	}

	rl.st.Clear()
	rl.st.FixState()
	rl.st.Return()

	return
}

// Prompt retourne la chaîne saisie.
func (rl *Readline) Prompt(p string) Result[string] { return rl.prompt(p, false) }

// PromptPassword agit comme Prompt mais n’affiche pas à l’écran ce qui est saisi.
func (rl *Readline) PromptPassword(p string) Result[string] { return rl.prompt(p, true) }

// Close ferme proprement le Readline.
func (rl *Readline) Close() Option[error] { return rl.st.Close() }