package httpapi

import (
	"errors"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"time"

	"git.azzamo.net/Michilis/Spanglish/photo-api/internal/storage"
)

const presignExpiry = 15 * time.Minute

// serveFile delivers photo bytes after re-running the gallery access check.
// S3: 302 to a short-lived presigned URL; local: streamed directly.
func (s *Server) serveFile(w http.ResponseWriter, r *http.Request) {
	variant := r.PathValue("variant")
	if variant != "thumb" && variant != "preview" && variant != "original" {
		writeError(w, http.StatusNotFound, "Not Found")
		return
	}
	p, err := s.db.GetPhoto(r.Context(), r.PathValue("photoId"))
	if err != nil {
		writeStoreError(w, err, "Photo not found")
		return
	}
	g, err := s.db.GetGallery(r.Context(), p.GalleryID)
	if err != nil {
		writeStoreError(w, err, "Photo not found")
		return
	}
	user := s.optionalUser(r)
	token := r.URL.Query().Get("token")
	if denial := s.authorize(r, g, user, token); denial != nil {
		writeError(w, denial.status, denial.msg)
		return
	}
	isAdmin := user != nil && user.IsAdmin()

	var key, contentType, downloadName string
	switch variant {
	case "thumb":
		key, contentType = p.ThumbKey, "image/jpeg"
	case "preview":
		key, contentType = p.PreviewKey, "image/jpeg"
	case "original":
		key, contentType = p.OriginalKey, p.ContentType
		downloadName = p.OriginalFilename
		if downloadName == "" {
			downloadName = p.ID + extForContentType(p.ContentType)
		}
	}
	if key == "" {
		// Variant not generated yet (photo still processing).
		writeError(w, http.StatusNotFound, "Not ready")
		return
	}
	// Non-ready originals stay admin-only so uploads that fail processing
	// never leak to viewers.
	if p.Status != "ready" && !isAdmin {
		writeError(w, http.StatusNotFound, "Not ready")
		return
	}

	if url, err := s.storage.PresignGet(r.Context(), key, downloadName, contentType, presignExpiry); err == nil {
		http.Redirect(w, r, url, http.StatusFound)
		return
	} else if !errors.Is(err, storage.ErrNoPresign) {
		log.Printf("Error: presign %s: %v", key, err)
		writeError(w, http.StatusInternalServerError, "Internal Server Error")
		return
	}

	reader, size, err := s.storage.Open(r.Context(), key)
	if err != nil {
		if os.IsNotExist(err) {
			writeError(w, http.StatusNotFound, "Not Found")
			return
		}
		log.Printf("Error: open %s: %v", key, err)
		writeError(w, http.StatusInternalServerError, "Internal Server Error")
		return
	}
	defer reader.Close()

	w.Header().Set("Content-Type", contentType)
	w.Header().Set("Content-Length", fmt.Sprintf("%d", size))
	w.Header().Set("X-Content-Type-Options", "nosniff")
	// Keys are immutable (new upload = new key), so private caching is safe
	// even though access is checked per request.
	w.Header().Set("Cache-Control", "private, max-age=86400")
	if downloadName != "" {
		w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%q", downloadName))
	}
	if _, err := io.Copy(w, reader); err != nil {
		log.Printf("stream %s: %v", key, err)
	}
}

func extForContentType(ct string) string {
	switch ct {
	case "image/jpeg":
		return ".jpg"
	case "image/png":
		return ".png"
	case "image/gif":
		return ".gif"
	case "image/webp":
		return ".webp"
	case "image/heic":
		return ".heic"
	}
	return ""
}