package configui

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
)

type State string

const (
	READY   State = "ready"
	ERROR   State = "error"
	STARTED State = "started"
	ENDED   State = "ended"
)

type Policy string

const (
	NO         Policy = "no"
	ONFAIL     Policy = "on-failure"
	ALWAYS     Policy = "always"
	UNLESSSTOP Policy = "unless-stopped"
)

type Oni struct {
	Name   string   `json:"name"`
	Cmd    string   `json:"cmd"`
	Dir    string   `json:"dir"`
	Args   []string `json:"args"`
	Envs   []string `json:"envs"`
	Policy Policy   `json:"policy"`

	PID     int    `json:"pid"`
	LogFile string `json:"log_file"`
	State   State  `json:"state"`
	Error   string `json:"error"`
	ManStop bool   `json:"manual_stop"`

	parent *ConfigUI
	cmd    *exec.Cmd
	start  chan struct{}
	buff   bytes.Buffer
	log    io.Writer

	listeners []io.Writer
}

func NewOni(name string, cui *ConfigUI) *Oni {
	var err error
	oni := &Oni{
		Policy:    NO,
		State:     READY,
		parent:    cui,
		start:     make(chan struct{}, 1),
		listeners: make([]io.Writer, 0),
	}
	if cui.LogPath != "" {
		logpath := filepath.Join(filepath.Dir(cui.LogPath), name+".log")
		oni.LogFile = logpath
		oni.log, err = os.OpenFile(logpath, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
		if err != nil {
			panic(err)
		}
	}
	return oni
}

func (oni *Oni) Start() error {
	if oni.Cmd == "" {
		return ErrorOniNotValid
	}
	select {
	case oni.start <- struct{}{}:
		defer func() {
			err := recover()
			if err != nil {
				oni.end(err)
			}
		}()
	default:
		return ErrorOniHasStarted
	}
	cmd := exec.Command(oni.Cmd, oni.Args...)
	cmd.Env = oni.Envs
	cmd.Dir = oni.Dir
	var out io.Writer
	if oni.LogFile != "" {
		out = io.MultiWriter(oni.log, &oni.buff)
	} else {
		out = &oni.buff
	}
	cmd.Stderr = out
	cmd.Stdout = out
	oni.cmd = cmd
	err := oni.cmd.Start()
	if err != nil {
		oni.end(err)
		return err
	}
	go oni.read()
	oni.PID = cmd.Process.Pid
	oni.State = STARTED
	go func() {
		oni.end(cmd.Wait())
	}()

	return nil
}

func (oni *Oni) Stop() error {
	if oni.cmd == nil {
		return nil
	}
	return oni.cmd.Process.Kill()
}

func (oni *Oni) end(v interface{}) {
	if v == nil {
		oni.State = ENDED
	} else {
		oni.Error = fmt.Sprint(v)
		oni.State = ERROR
	}
	if len(oni.start) == 1 {
		<-oni.start
	}
}

func (oni *Oni) read() {
	go func() {
		scanner := bufio.NewScanner(&oni.buff)
		for scanner.Scan() {
			if len(oni.listeners) == 0 {
				continue
			}
			w := io.MultiWriter(oni.listeners...)
			w.Write([]byte(scanner.Text()))
		}
	}()
}