package m3u8

import (
	"bufio"
	"bytes"
	"io"
	"strings"
	"videoweb/pub/common/errors"
	"videoweb/pub/common/utils"
	"videoweb/pub/storage/proxy"
)

// TransformVtt 读取雪碧图 vtt 文件，并把其中的缩略图路径替换为图片 cdn 地址。
// 兼容现有 /laosiji 路径资源：laosiji 的 vtt 需移除 /laosiji 前缀后，从 lsjImageYuan 源站读取。
// imgCdn       图片 cdn 域名（缩略图访问地址）
// origDomain   普通媒资的源站域名
// lsjImageYuan 老司机图片源站域名（由 app/web 项目从配置 lsjMediaConf.imageYuan 传入）
func TransformVtt(name, imgCdn, origDomain, lsjImageYuan string) (buff []byte, err error) {
	if name == "" {
		err = errors.MakeWithMsg(errors.M3u8FileName, "vtt file name is empty")
		return
	}
	if imgCdn == "" || origDomain == "" {
		err = errors.MakeWithMsg(errors.DomainErr, "imgCdn or origDomain is empty")
		return
	}

	mediaVersion := proxy.AppendsMediaS3Version(name)
	if len(mediaVersion) > 0 {
		name = mediaVersion + name
	}

	originName := name
	if strings.Contains(name, "laosiji") {
		if lsjImageYuan == "" {
			err = errors.MakeWithMsg(errors.DomainErr, "lsjImageYuan is empty")
			return
		}
		originName = stripLaosijiPrefix(name)
		origDomain = lsjImageYuan
	}

	srcReader, err := readFromRedis(originName, origDomain)
	if err != nil {
		return
	}
	raw, err := io.ReadAll(srcReader)
	if err != nil {
		return nil, errors.MakeWithMsg(errors.M3u8Read, "read vtt reader fail: "+err.Error())
	}

	dirPath := utils.PathForInfo(name).Dir
	buff = rewriteVttWithCDN(raw, imgCdn, dirPath)
	return
}

func stripLaosijiPrefix(name string) string {
	p := strings.TrimPrefix(name, "/")
	p = strings.TrimPrefix(p, "laosiji")
	p = strings.TrimPrefix(p, "/")
	return p
}

func rewriteVttWithCDN(vttData []byte, imgCdn, dirPath string) []byte {
	imgCdn = strings.TrimRight(strings.TrimSpace(imgCdn), "/")

	var out bytes.Buffer
	scanner := bufio.NewScanner(bytes.NewReader(vttData))
	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)

	for scanner.Scan() {
		line := scanner.Text()
		trim := strings.TrimSpace(line)

		if idx := strings.Index(trim, "#xywh="); idx >= 0 {
			p := strings.TrimSpace(trim[:idx])
			xywh := trim[idx:]

			var newPath string
			switch {
			case strings.HasPrefix(p, "http://") || strings.HasPrefix(p, "https://"):
				newPath = p
			case strings.HasPrefix(p, "/"):
				newPath = imgCdn + p
			default:
				newPath = utils.JoinUrlPath(utils.JoinUrlPath(imgCdn, strings.TrimRight(dirPath, "/")), p)
			}
			out.WriteString(newPath + xywh + "\n")
			continue
		}

		out.WriteString(line + "\n")
	}

	return out.Bytes()
}