package main

import (
	"io"
	"os"
	"strings"
	"time"
)

const (
	EventCtrlC   = -2
	EventTimeOut = -1
)

type Watcher struct {
	ch       <-chan string
	lastline string
	ctrlc    <-chan struct{}
}

func NewWatcher(pty io.ReadWriter) *Watcher {
	pipeline := make(chan string, 1024)
	ctrlc := make(chan struct{}, 100)
	go func() {
		for {
			var buffer [1024]byte
			n, _ := os.Stdin.Read(buffer[:])
			B := buffer[:n]
			for i, b := range B {
				if b == '\x03' {
					ctrlc <- struct{}{}
					return
				} else if b == '\x08' {
					// On CMD.exe, Ctrl-H removes all input text.
					// ( The reason is unknown )
					// Therefore, replace Ctrl-H to Backspace-key
					buffer[i] = '\x7F'
				}
			}
			pty.Write(B)
		}
	}()
	go func() {
		for {
			var buffer [1024]byte
			n, err := pty.Read(buffer[:])
			if err != nil {
				close(pipeline)
				return
			}
			// If the code below spends a lot of time,
			// It hangs up to io.Copy(pty, os.Stdin)
			// The reason is unknown.
			b := buffer[:n]
			os.Stdout.Write(b)
			pipeline <- string(b)
		}
	}()

	return &Watcher{ch: pipeline, ctrlc: ctrlc}
}

func (W *Watcher) checkWords(token string, words []string) int {
	W.lastline += token
	for i, word := range words {
		if pos := strings.Index(W.lastline, word); pos >= 0 {
			W.lastline = W.lastline[pos+len(word):]
			return i
		}
	}
	newLinePos := strings.LastIndexByte(W.lastline, '\n')
	if newLinePos >= 0 {
		W.lastline = W.lastline[newLinePos+1:]
	}
	return -1

}

func (W *Watcher) Expect(words ...string) int {
	if found := W.checkWords("", words); found >= 0 {
		return found
	}
	for {
		select {
		case token := <-W.ch:
			if found := W.checkWords(token, words); found >= 0 {
				return found
			}
		case <-W.ctrlc:
			return EventCtrlC
		}
	}
}

func (W *Watcher) ExpectWithTimeout(d time.Duration, words ...string) int {
	if found := W.checkWords("", words); found >= 0 {
		return found
	}

	timer := time.NewTimer(d)
	defer timer.Stop()

	for {
		select {
		case token := <-W.ch:
			if found := W.checkWords(token, words); found >= 0 {
				return found
			}
		case <-timer.C:
			return EventTimeOut
		case <-W.ctrlc:
			return EventCtrlC
		}
	}
}