package service

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/hex"
	"errors"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/freefire/jiang13-bbs/model"
)

const (
	BrandLogoMaxBytes    = 2 << 20   // 2 MiB
	BrandFaviconMaxBytes = 512 << 10 // 512 KiB
	brandMaxDim          = 2048
)

// ErrBrandFileMissing 设置了合法 URL 但磁盘上没有对应文件
var ErrBrandFileMissing = errors.New("品牌图文件不存在")

type brandFormat struct {
	ext  string
	mime string
	svg  bool
	ico  bool
}

func brandMaxBytes(slot string) int64 {
	if slot == BrandSlotFavicon {
		return BrandFaviconMaxBytes
	}
	return BrandLogoMaxBytes
}

func detectBrandFormat(data []byte, slot string) (brandFormat, error) {
	logo := slot != BrandSlotFavicon
	too := "仅支持 PNG / WebP / SVG"
	if !logo {
		too = "仅支持 PNG / WebP / SVG / ICO"
	}
	fail := errors.New(too)
	if len(data) >= 8 && string(data[0:8]) == "\x89PNG\r\n\x1a\n" {
		return brandFormat{ext: ".png", mime: "image/png"}, nil
	}
	if len(data) >= 12 && string(data[0:4]) == "RIFF" && string(data[8:12]) == "WEBP" {
		return brandFormat{ext: ".webp", mime: "image/webp"}, nil
	}
	if !logo && len(data) >= 4 && data[0] == 0 && data[1] == 0 && data[2] == 1 && data[3] == 0 {
		return brandFormat{ext: ".ico", mime: "image/x-icon", ico: true}, nil
	}
	if looksLikeSVG(data) {
		return brandFormat{ext: ".svg", mime: "image/svg+xml", svg: true}, nil
	}
	return brandFormat{}, fail
}

func looksLikeSVG(data []byte) bool {
	s := strings.ToLower(string(data))
	if !strings.Contains(s, "<svg") {
		return false
	}
	if strings.Contains(s, "<script") || strings.Contains(s, "javascript:") {
		return false
	}
	if strings.Contains(s, "onload=") || strings.Contains(s, "onerror=") {
		return false
	}
	return true
}

// SaveBrand 把品牌图落到 uploads/brand，不写站点设置
func (s *UploadService) SaveBrand(slot string, src io.Reader) (string, error) {
	slot, ok := NormalizeBrandSlot(slot)
	if !ok {
		return "", errors.New("无效的品牌图位置")
	}
	if src == nil {
		return "", errors.New("文件为空")
	}
	maxB := brandMaxBytes(slot)
	data, err := io.ReadAll(io.LimitReader(src, maxB+1))
	if err != nil {
		return "", errors.New("读取图片失败")
	}
	if len(data) == 0 {
		return "", errors.New("文件为空")
	}
	if int64(len(data)) > maxB {
		if slot == BrandSlotFavicon {
			return "", errors.New("Favicon 不能超过 512KB")
		}
		return "", errors.New("Logo 不能超过 2MB")
	}
	format, err := detectBrandFormat(data, slot)
	if err != nil {
		return "", err
	}
	if !format.svg && !format.ico {
		w, h, derr := decodeImageSizeReader(bytes.NewReader(data), format.mime)
		if derr != nil {
			return "", derr
		}
		if w < 1 || h < 1 || w > brandMaxDim || h > brandMaxDim {
			return "", errors.New("图片尺寸超出限制")
		}
	}

	if err := os.MkdirAll(filepath.Join(s.dir, "brand"), 0o755); err != nil {
		return "", err
	}
	nameBytes := make([]byte, 16)
	if _, err := rand.Read(nameBytes); err != nil {
		return "", err
	}
	filename := hex.EncodeToString(nameBytes) + format.ext
	fullPath := filepath.Join(s.dir, "brand", filename)
	if err := os.WriteFile(fullPath, data, 0o644); err != nil {
		return "", err
	}
	return "/uploads/brand/" + filename, nil
}

// CopyBrandFromMedia 把当前用户媒体库里的一张图复制进品牌目录，不写站点设置
func (s *UploadService) CopyBrandFromMedia(userID, attachmentID uint, slot string) (string, error) {
	if _, ok := NormalizeBrandSlot(slot); !ok {
		return "", errors.New("无效的品牌图位置")
	}
	var att model.Attachment
	if err := s.db.Where("id = ? AND user_id = ?", attachmentID, userID).First(&att).Error; err != nil {
		return "", errors.New("图片不存在或不属于你")
	}
	if strings.HasPrefix(att.URL, "/api/media/") && s.ops != nil {
		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
		defer cancel()
		r, _, e := s.ops.OpenObject(ctx, RemoteObjectID(att.URL), true)
		if e != nil {
			return "", e
		}
		defer r.Close()
		return s.SaveBrand(slot, r)
	}
	abs, ok := s.safeUploadPath(att.URL)
	if !ok {
		return "", errors.New("无效的图片地址")
	}
	f, err := os.Open(abs)
	if err != nil {
		return "", errors.New("读取图片失败")
	}
	defer f.Close()
	return s.SaveBrand(slot, f)
}

func (s *UploadService) safeUploadPath(url string) (string, bool) {
	rel := strings.TrimPrefix(strings.TrimSpace(url), "/uploads/")
	if rel == "" || rel == url || strings.Contains(rel, "..") {
		return "", false
	}
	abs := filepath.Join(s.dir, filepath.FromSlash(rel))
	root := filepath.Clean(s.dir)
	clean := filepath.Clean(abs)
	if clean != root && !strings.HasPrefix(clean, root+string(os.PathSeparator)) {
		return "", false
	}
	return clean, true
}

// BrandFileExists 确认 URL 对应文件在 brand 目录内
func (s *UploadService) BrandFileExists(url string) bool {
	rel := BrandRelPath(url)
	if rel == "" {
		return false
	}
	abs := filepath.Join(s.dir, filepath.FromSlash(rel))
	info, err := os.Stat(abs)
	return err == nil && !info.IsDir()
}

// RemoveBrandIfUnused 旧品牌图不再被任一槽位引用时删除
func (s *UploadService) RemoveBrandIfUnused(oldURL, light, dark, favicon string) {
	if oldURL == "" || oldURL == light || oldURL == dark || oldURL == favicon {
		return
	}
	rel := BrandRelPath(oldURL)
	if rel == "" {
		return
	}
	abs := filepath.Join(s.dir, filepath.FromSlash(rel))
	if err := os.Remove(abs); err != nil && !os.IsNotExist(err) {
		log.Printf("[upload] 删除品牌图失败 path=%s: %v", abs, err)
	}
}