package main

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strings"
	"sync"
)

//作者 bambuo
//时间 2021/7/19 19:40
//版本 1.0

const domain = ``
const save = ``

type ErrorDownload struct {
	Task  *Task
	Error error
}

type Task struct {
	NO  int
	url string
}

func readFile(domain, m3u8File string) (map[int]string, error) {
	in, err := os.OpenFile(m3u8File, os.O_RDONLY, os.ModePerm)
	if err != nil {
		return nil, err
	}
	reader := bufio.NewReader(in)
	var index = 1
	var tss = map[int]string{}
	for {
		line, _, err := reader.ReadLine()
		if err != nil {
			if err == io.EOF {
				break
			} else {
				return nil, err
			}
		}

		if len(line) == 0 || strings.HasPrefix(string(line), `#`) {
			continue
		}

		if strings.HasPrefix(string(line), `/`) {
			tss[index] = domain + string(line[1:])
		} else {
			tss[index] = domain + "/" + string(line[1:])
		}
		index++
	}
	return tss, nil
}

func download(task *Task, savePath string) *ErrorDownload {
	resp, err := http.Get(task.url)
	if err != nil {
		return &ErrorDownload{
			Task:  task,
			Error: err,
		}
	}
	defer resp.Body.Close()

	data, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return &ErrorDownload{
			Task:  task,
			Error: err,
		}
	}

	ext := path.Ext(task.url)
	join := filepath.Join(savePath, fmt.Sprintf("%d%s", task.NO, ext))

	out, err := os.Create(join)
	if err != nil {
		return &ErrorDownload{
			Task:  task,
			Error: err,
		}
	}
	defer out.Close()

	size, err := io.Copy(out, bytes.NewReader(data))
	if err != nil {
		return &ErrorDownload{
			Task:  task,
			Error: err,
		}
	}
	log.Println("URL:[", task.url, "] 下载完成，文件大小[", size, "]字节")
	return nil
}

func Download(domain, srcFile string) {
	tss, err := readFile(domain, srcFile)
	if err != nil {
		panic(err)
	}
	var group sync.WaitGroup
	var taskChan = make(chan *Task, 8)
	var errorChan = make(chan *ErrorDownload, len(tss))

	for i := 0; i < 8; i++ {
		group.Add(1)
		go func() {
			defer group.Done()

			for {
				url, ok := <-taskChan
				if !ok {
					return
				}
				err := download(url, save)
				if nil != err {
					errorChan <- err
				}
			}
		}()
	}

	for k, v := range tss {
		taskChan <- &Task{
			NO:  k,
			url: v,
		}
	}
	close(taskChan)

	group.Wait()
	close(errorChan)
}