package agent

import (
	"context"
	"crypto/sha256"
	"fmt"
	"io"
	"log"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/gooseek/backend/pkg/storage"
)

const (
	photoCachePrefix    = "poi-photos"
	maxPhotoSize        = 5 * 1024 * 1024 // 5MB
	photoDownloadTimeout = 8 * time.Second
)

type PhotoCacheService struct {
	storage   *storage.MinioStorage
	client    *http.Client
	mu        sync.RWMutex
	memCache  map[string]string // sourceURL -> publicURL (in-memory for current session)
}

func NewPhotoCacheService(s *storage.MinioStorage) *PhotoCacheService {
	return &PhotoCacheService{
		storage: s,
		client: &http.Client{
			Timeout: photoDownloadTimeout,
			CheckRedirect: func(req *http.Request, via []*http.Request) error {
				if len(via) >= 3 {
					return http.ErrUseLastResponse
				}
				return nil
			},
		},
		memCache: make(map[string]string, 128),
	}
}

func (pc *PhotoCacheService) CachePhoto(ctx context.Context, citySlug, sourceURL string) (string, error) {
	pc.mu.RLock()
	if cached, ok := pc.memCache[sourceURL]; ok {
		pc.mu.RUnlock()
		return cached, nil
	}
	pc.mu.RUnlock()

	key := pc.buildKey(citySlug, sourceURL)

	exists, err := pc.storage.ObjectExists(ctx, key)
	if err == nil && exists {
		publicURL := pc.storage.GetPublicURL(key)
		if publicURL != "" {
			pc.mu.Lock()
			pc.memCache[sourceURL] = publicURL
			pc.mu.Unlock()
			return publicURL, nil
		}
	}

	body, contentType, err := pc.downloadImage(ctx, sourceURL)
	if err != nil {
		return "", fmt.Errorf("download failed: %w", err)
	}
	defer body.Close()

	limitedReader := io.LimitReader(body, maxPhotoSize)

	result, err := pc.storage.UploadWithKey(ctx, key, limitedReader, -1, contentType)
	if err != nil {
		return "", fmt.Errorf("upload to minio failed: %w", err)
	}

	publicURL := pc.storage.GetPublicURL(result.Key)
	if publicURL == "" {
		return "", fmt.Errorf("no public URL configured for storage")
	}

	pc.mu.Lock()
	pc.memCache[sourceURL] = publicURL
	pc.mu.Unlock()

	return publicURL, nil
}

func (pc *PhotoCacheService) CachePhotoBatch(ctx context.Context, citySlug string, sourceURLs []string) []string {
	results := make([]string, len(sourceURLs))
	var wg sync.WaitGroup

	for i, url := range sourceURLs {
		wg.Add(1)
		go func(idx int, srcURL string) {
			defer wg.Done()

			cacheCtx, cancel := context.WithTimeout(ctx, photoDownloadTimeout+2*time.Second)
			defer cancel()

			cached, err := pc.CachePhoto(cacheCtx, citySlug, srcURL)
			if err != nil {
				log.Printf("[photo-cache] failed to cache %s: %v", truncateURL(srcURL), err)
				results[idx] = srcURL
				return
			}
			results[idx] = cached
		}(i, url)
	}

	wg.Wait()
	return results
}

func (pc *PhotoCacheService) buildKey(citySlug, sourceURL string) string {
	hash := sha256.Sum256([]byte(sourceURL))
	hashStr := fmt.Sprintf("%x", hash[:12])

	ext := ".jpg"
	lower := strings.ToLower(sourceURL)
	switch {
	case strings.Contains(lower, ".png"):
		ext = ".png"
	case strings.Contains(lower, ".webp"):
		ext = ".webp"
	case strings.Contains(lower, ".gif"):
		ext = ".gif"
	}

	slug := sanitizeSlug(citySlug)
	return fmt.Sprintf("%s/%s/%s%s", photoCachePrefix, slug, hashStr, ext)
}

func (pc *PhotoCacheService) downloadImage(ctx context.Context, url string) (io.ReadCloser, string, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return nil, "", err
	}

	req.Header.Set("User-Agent", "Mozilla/5.0 (compatible; GooSeek/1.0)")
	req.Header.Set("Accept", "image/*")

	resp, err := pc.client.Do(req)
	if err != nil {
		return nil, "", err
	}

	if resp.StatusCode != http.StatusOK {
		resp.Body.Close()
		return nil, "", fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	contentType := resp.Header.Get("Content-Type")
	if contentType == "" {
		contentType = "image/jpeg"
	}

	if !strings.HasPrefix(contentType, "image/") {
		resp.Body.Close()
		return nil, "", fmt.Errorf("not an image: %s", contentType)
	}

	return resp.Body, contentType, nil
}

func sanitizeSlug(s string) string {
	s = strings.ToLower(strings.TrimSpace(s))
	s = strings.Map(func(r rune) rune {
		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '-' {
			return r
		}
		if (r >= 0x0400 && r <= 0x04FF) || r == '_' {
			return r
		}
		if r == ' ' {
			return '-'
		}
		return -1
	}, s)
	for strings.Contains(s, "--") {
		s = strings.ReplaceAll(s, "--", "-")
	}
	return strings.Trim(s, "-")
}

func truncateURL(u string) string {
	if len(u) > 80 {
		return u[:80] + "..."
	}
	return u
}