package app

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"net/http"
	"path/filepath"
	"regexp"
	"strings"
	"time"
)

const maxUploadBytes int64 = 16 << 20

var mediaNamePattern = regexp.MustCompile(`^[0-9]+-[0-9]+(?:-av1(?:-thumb|-original)?|-im1(?:-thumb)?)?\.(?:gif|jpe?g|png|webp|mp3|wav|amr|m4a)$`)

// Android's recorder can emit an MP3 stream without an ID3 tag. Go's generic
// sniffer identifies only the ID3 form, so validate the first MPEG audio frame
// header as a fallback instead of rejecting a valid phone recording as binary.
func isMPEGAudioFrameHeader(header []byte) bool {
	if len(header) < 4 || header[0] != 0xff || header[1]&0xe0 != 0xe0 {
		return false
	}
	version := (header[1] >> 3) & 0x03
	layer := (header[1] >> 1) & 0x03
	bitrateIndex := (header[2] >> 4) & 0x0f
	sampleRateIndex := (header[2] >> 2) & 0x03
	return version != 0x01 && layer != 0 && bitrateIndex != 0 && bitrateIndex != 0x0f && sampleRateIndex != 0x03
}

func detectUploadContentType(header []byte) string {
	contentType := http.DetectContentType(header)
	if isMPEGAudioFrameHeader(header) {
		return "audio/mpeg"
	}
	return contentType
}

func mediaThumbnailURL(source string) string {
	if source == "" || strings.ContainsAny(source, "?#") {
		return source
	}
	lower := strings.ToLower(source)
	if strings.HasSuffix(lower, "-im1-thumb.jpg") {
		return source
	}
	for _, extension := range []string{".jpeg", ".jpg", ".png", ".webp", ".gif"} {
		if strings.HasSuffix(lower, "-im1"+extension) {
			return source[:len(source)-len(extension)] + "-thumb.jpg"
		}
	}
	return source
}

func (a *App) uploadMedia(w http.ResponseWriter, r *http.Request) {
	// Multipart boundaries and headers add a small amount of overhead. Keep the
	// actual file limit at 16 MiB without rejecting a file that is exactly at
	// that limit solely because of the multipart envelope.
	r.Body = http.MaxBytesReader(w, r.Body, maxUploadBytes+(1<<20))
	if err := r.ParseMultipartForm(maxUploadBytes); err != nil {
		fail(w, http.StatusBadRequest, 20001, "媒体文件不得超过 16MB")
		return
	}
	defer r.MultipartForm.RemoveAll()
	purpose := r.FormValue("purpose")
	if purpose != "" && purpose != "avatar" && purpose != "voice" {
		fail(w, http.StatusBadRequest, 20001, "上传用途无效")
		return
	}

	file, fileHeader, err := r.FormFile("file")
	if err != nil {
		fail(w, http.StatusBadRequest, 20001, "请选择媒体文件")
		return
	}
	defer file.Close()

	size, err := file.Seek(0, io.SeekEnd)
	if err != nil || size <= 0 || size > maxUploadBytes {
		fail(w, http.StatusBadRequest, 20001, "媒体文件大小无效或超过 16MB")
		return
	}
	if _, err = file.Seek(0, io.SeekStart); err != nil {
		fail(w, http.StatusBadRequest, 20001, "无法读取媒体文件")
		return
	}
	header := make([]byte, min(size, 512))
	read, err := io.ReadFull(file, header)
	if err != nil && err != io.ErrUnexpectedEOF {
		fail(w, http.StatusBadRequest, 20001, "无法读取媒体文件")
		return
	}
	header = header[:read]
	extensions := map[string]string{
		"image/gif":   ".gif",
		"image/jpeg":  ".jpg",
		"image/png":   ".png",
		"image/webp":  ".webp",
		"audio/mpeg":  ".mp3",
		"audio/mp3":   ".mp3",
		"audio/wav":   ".wav",
		"audio/x-wav": ".wav",
		"audio/amr":   ".amr",
		"audio/mp4":   ".m4a",
	}
	contentType := detectUploadContentType(header)
	extension, ok := extensions[contentType]
	if !ok {
		fail(w, http.StatusBadRequest, 20001, "仅支持常见图片或语音格式")
		return
	}

	if _, err = file.Seek(0, io.SeekStart); err != nil {
		fail(w, http.StatusBadRequest, 20001, "无法读取媒体文件")
		return
	}
	if err = a.validateStorageProviderConfig(r.Context()); err != nil {
		fail(w, http.StatusServiceUnavailable, 50001, "文件存储尚未正确配置")
		return
	}
	originalType, originalExtension, originalSize := contentType, extension, size
	isImage := strings.HasPrefix(contentType, "image/")
	if purpose == "voice" && isImage {
		fail(w, http.StatusBadRequest, 20001, "语音文件格式无效")
		return
	}
	var imageVariants avatarImages
	if isImage {
		imageVariants, err = createAvatarImages(r.Context(), file)
		if err != nil {
			if errors.Is(err, errAvatarBusy) {
				w.Header().Set("Retry-After", "2")
				fail(w, http.StatusServiceUnavailable, 50001, strings.ReplaceAll(err.Error(), "头像", "图片"))
			} else {
				fail(w, http.StatusBadRequest, 20001, strings.ReplaceAll(err.Error(), "头像", "图片"))
			}
			return
		}
	}
	if purpose == "avatar" {
		if !isImage {
			fail(w, http.StatusBadRequest, 20001, "头像必须是图片")
			return
		}
		contentType, extension, size = "image/jpeg", "-av1.jpg", int64(len(imageVariants.Display))
	} else if isImage {
		// Mark image uploads that have an immutable thumbnail sibling. The main
		// object remains byte-for-byte original for detail and preview screens.
		extension = "-im1" + originalExtension
	}

	provider := a.configPlain(r.Context(), "storage.provider", "local")
	name := fmt.Sprintf("%d-%d%s", current(r).ID, time.Now().UnixNano(), extension)
	objectKey := name
	if provider != "local" {
		prefix := strings.Trim(a.configPlain(r.Context(), "storage.object_prefix", "media"), "/")
		objectKey = fmt.Sprintf("%s/%s/%s", prefix, time.Now().Format("2006/01"), name)
	}
	mediaType := "audio"
	if strings.HasPrefix(contentType, "image/") {
		mediaType = "image"
	}

	var bucket, publicURL string
	var storage mediaObjectStorage
	closeStorage := func() {}
	if provider == "local" {
		storage = localMediaStorage{directory: a.configPlain(r.Context(), "storage.local.directory", a.config.MediaDir)}
		baseURL := strings.TrimSpace(a.configPlain(r.Context(), "storage.local.public_base_url", ""))
		if baseURL == "" {
			scheme := strings.TrimSpace(strings.Split(r.Header.Get("X-Forwarded-Proto"), ",")[0])
			if scheme != "https" {
				scheme = "http"
			}
			baseURL = fmt.Sprintf("%s://%s/uploads", scheme, r.Host)
		}
		publicURL = storagePublicURL(baseURL, objectKey)
	} else {
		storage, closeStorage, err = a.newMediaObjectStorage(r.Context())
		if err != nil {
			log.Printf("storage provider init failed provider=%s error=%v", provider, err)
			fail(w, http.StatusServiceUnavailable, 50001, "文件存储连接初始化失败")
			return
		}
		defer closeStorage()
		bucket = storage.Bucket()
		publicURL = storagePublicURL(a.configPlain(r.Context(), "storage."+provider+".public_base_url", ""), objectKey)
	}
	if len(publicURL) > 500 || len(objectKey) > 500 {
		fail(w, http.StatusServiceUnavailable, 50001, "文件存储公开地址过长")
		return
	}
	objects := []mediaUploadObject{{Key: objectKey, ContentType: contentType, Size: size, Body: file}}
	var thumbnailURL, originalURL string
	if isImage {
		mainExtension := filepath.Ext(objectKey)
		stem := strings.TrimSuffix(objectKey, mainExtension)
		urlStem := strings.TrimSuffix(publicURL, mainExtension)
		thumbnailURL, originalURL = urlStem+"-thumb.jpg", urlStem+"-original"+originalExtension
		if len(thumbnailURL) > 500 || len(stem+"-thumb.jpg") > 500 || (purpose == "avatar" && (len(originalURL) > 500 || len(stem+"-original"+originalExtension) > 500)) {
			fail(w, http.StatusServiceUnavailable, 50001, "文件存储公开地址过长")
			return
		}
		// Publish the primary URL only once its thumbnail is available.
		if purpose == "avatar" {
			objects = []mediaUploadObject{
				{Key: stem + "-original" + originalExtension, ContentType: originalType, Size: originalSize, Body: file},
				{Key: stem + "-thumb.jpg", ContentType: "image/jpeg", Size: int64(len(imageVariants.Thumbnail)), Body: bytes.NewReader(imageVariants.Thumbnail)},
				{Key: objectKey, ContentType: contentType, Size: size, Body: bytes.NewReader(imageVariants.Display)},
			}
		} else {
			originalURL = ""
			objects = []mediaUploadObject{
				{Key: stem + "-thumb.jpg", ContentType: "image/jpeg", Size: int64(len(imageVariants.Thumbnail)), Body: bytes.NewReader(imageVariants.Thumbnail)},
				{Key: objectKey, ContentType: originalType, Size: originalSize, Body: file},
			}
		}
	}

	result, err := a.db.ExecContext(r.Context(), `INSERT INTO media_assets(owner_user_id,media_type,storage_provider,bucket,object_key,public_url,mime_type,file_size,moderation_status,status) VALUES(?,?,?,?,?,'',?,?,1,0)`, current(r).ID, mediaType, provider, bucket, objectKey, contentType, size)
	if err != nil {
		fail(w, http.StatusInternalServerError, 50001, "创建媒体记录失败")
		return
	}
	mediaID, _ := result.LastInsertId()
	cleanupRecord := func() {
		ctx, cancel := context.WithTimeout(context.WithoutCancel(r.Context()), 5*time.Second)
		defer cancel()
		_, _ = a.db.ExecContext(ctx, `DELETE FROM media_assets WHERE id=? AND status=0`, mediaID)
	}

	cleanupObjects, err := putMediaObjects(r.Context(), storage, objects)
	if err != nil {
		cleanupRecord()
		log.Printf("media upload failed provider=%s bucket=%s object=%s original=%q error=%v", provider, bucket, objectKey, filepath.Base(fileHeader.Filename), err)
		fail(w, http.StatusBadGateway, 50001, "文件上传失败，请检查存储配置后重试")
		return
	}
	if _, err = a.db.ExecContext(r.Context(), `UPDATE media_assets SET public_url=?,status=1 WHERE id=? AND status=0`, publicURL, mediaID); err != nil {
		cleanupObjects()
		cleanupRecord()
		fail(w, http.StatusInternalServerError, 50001, "完成媒体记录失败")
		return
	}
	reply(w, map[string]any{
		"id":           mediaID,
		"name":         name,
		"url":          publicURL,
		"provider":     provider,
		"objectKey":    objectKey,
		"thumbnailUrl": thumbnailURL,
		"originalUrl":  originalURL,
	})
}

func (a *App) serveMedia(w http.ResponseWriter, r *http.Request) {
	parts := strings.Split(strings.Trim(r.URL.Path, "/"), "/")
	name := parts[len(parts)-1]
	if !mediaNamePattern.MatchString(name) {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	directory := a.configPlain(r.Context(), "storage.local.directory", a.config.MediaDir)
	http.ServeFile(w, r, filepath.Join(directory, filepath.Base(name)))
}