package api

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/sandrodach/mindsift/internal/auth"
	"github.com/sandrodach/mindsift/internal/storage"
)

// Images and audio in notes. Uploads need write access to the note, reading needs read access to a note
// that shows the file. Files are served through the API with the normal login (the browser loads them
// with fetch and shows a blob: URL), never under a public link.

const mediaGrace = 24 * time.Hour // uploads not yet placed in a block are kept this long

func (s *Server) mediaRoot() string { return s.store.MediaRoot() }

func (s *Server) mediaPath(m *storage.Media) string { return s.store.MediaFilePath(m) }

// mediaLimit is the largest allowed file of a kind in bytes.
func (s *Server) mediaLimit(kind string) int64 {
	mb := s.cfg.Media.MaxImageMB
	if kind == "audio" {
		mb = s.cfg.Media.MaxAudioMB
	}
	if s.cfg.DemoMode && s.cfg.Media.DemoMaxMB < mb {
		mb = s.cfg.Media.DemoMaxMB
	}
	return int64(mb) << 20
}

var detectMedia = storage.DetectMedia

func (s *Server) canEditDoc(userID, docID string) bool {
	role := s.store.DocRole(userID, docID)
	return role == "owner" || role == "editor"
}

// storeMedia checks limits and writes the file; size limits must have been applied while reading.
func (s *Server) storeMedia(w http.ResponseWriter, userID, docID string, data []byte, declared, sourceURL string) (*storage.Media, bool) {
	mime, kind, ok := detectMedia(data, declared)
	if !ok {
		writeError(w, http.StatusUnsupportedMediaType, "Nicht unterstütztes Format (Bilder: JPEG, PNG, GIF, WebP; Audio: WebM, Ogg, MP3, WAV, M4A)")
		return nil, false
	}
	if limit := s.mediaLimit(kind); int64(len(data)) > limit {
		writeError(w, http.StatusRequestEntityTooLarge, fmt.Sprintf("Datei zu groß (höchstens %d MB)", limit>>20))
		return nil, false
	}
	if quota := int64(s.cfg.Media.QuotaMB) << 20; quota > 0 {
		used, _ := s.store.MediaUsage(userID)
		if used+int64(len(data)) > quota {
			writeError(w, http.StatusRequestEntityTooLarge, fmt.Sprintf("Speicherplatz für Medien aufgebraucht (%d MB)", s.cfg.Media.QuotaMB))
			return nil, false
		}
	}
	m, err := s.store.CreateMedia(docID, userID, kind, mime, int64(len(data)), sourceURL)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Datei konnte nicht gespeichert werden")
		return nil, false
	}
	path := s.mediaPath(m)
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err == nil {
		err = os.WriteFile(path, data, 0o644)
		if err == nil {
			return m, true
		}
		slog.Error("Mediendatei konnte nicht geschrieben werden", "path", path, "error", err)
	}
	_ = s.store.DeleteMediaRow(m.ID)
	writeError(w, http.StatusInternalServerError, "Datei konnte nicht gespeichert werden")
	return nil, false
}

func mediaResponse(m *storage.Media) map[string]interface{} {
	return map[string]interface{}{"id": m.ID, "kind": m.Kind, "mime": m.Mime, "size": m.Size, "url": "/api/v1/media/" + m.ID}
}

// handleUploadMedia: POST /documents/{id}/media (multipart, field "file")
func (s *Server) handleUploadMedia(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	docID := chi.URLParam(r, "id")
	if !s.canEditDoc(userID, docID) {
		writeError(w, http.StatusForbidden, "Keine Schreibrechte für diese Notiz")
		return
	}
	allowLongTransfer(w)
	file, header, err := r.FormFile("file")
	if err != nil {
		var tooBig *http.MaxBytesError
		if errors.As(err, &tooBig) {
			writeError(w, http.StatusRequestEntityTooLarge, "Datei zu groß")
			return
		}
		writeError(w, http.StatusBadRequest, "Keine Datei im Feld \"file\"")
		return
	}
	defer file.Close()
	data, err := io.ReadAll(file)
	if err != nil || len(data) == 0 {
		writeError(w, http.StatusBadRequest, "Datei konnte nicht gelesen werden")
		return
	}
	if m, ok := s.storeMedia(w, userID, docID, data, header.Header.Get("Content-Type"), ""); ok {
		writeJSON(w, http.StatusCreated, mediaResponse(m))
	}
}

// handleFetchMedia: POST /documents/{id}/media/fetch {url} copies an external image, so readers of the
// note do not contact the other server and the image stays when it disappears there.
func (s *Server) handleFetchMedia(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	docID := chi.URLParam(r, "id")
	if !s.canEditDoc(userID, docID) {
		writeError(w, http.StatusForbidden, "Keine Schreibrechte für diese Notiz")
		return
	}
	var req struct {
		URL string `json:"url"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || strings.TrimSpace(req.URL) == "" {
		writeError(w, http.StatusBadRequest, "Bild-URL erforderlich")
		return
	}
	src := strings.TrimSpace(req.URL)
	// Same protection as alarm webhooks: https only, no addresses in the server's own network
	if err := validateWebhookURL(src, false, false); err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	limit := s.mediaLimit("image")
	httpReq, _ := http.NewRequestWithContext(r.Context(), http.MethodGet, src, nil)
	httpReq.Header.Set("Accept", "image/*")
	httpReq.Header.Set("User-Agent", "MindSift (image copy)")
	resp, err := guardedClient(false).Do(httpReq)
	if err != nil {
		writeError(w, http.StatusBadGateway, "Bild konnte nicht geladen werden")
		return
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		writeError(w, http.StatusBadGateway, fmt.Sprintf("Bild konnte nicht geladen werden (HTTP %d)", resp.StatusCode))
		return
	}
	data, err := io.ReadAll(io.LimitReader(resp.Body, limit+1))
	if err != nil {
		writeError(w, http.StatusBadGateway, "Bild konnte nicht geladen werden")
		return
	}
	if int64(len(data)) > limit {
		writeError(w, http.StatusRequestEntityTooLarge, fmt.Sprintf("Bild zu groß (höchstens %d MB)", limit>>20))
		return
	}
	if _, kind, ok := detectMedia(data, ""); !ok || kind != "image" {
		writeError(w, http.StatusUnsupportedMediaType, "Unter dieser Adresse liegt kein Bild (JPEG, PNG, GIF, WebP)")
		return
	}
	if m, ok := s.storeMedia(w, userID, docID, data, "", src); ok {
		writeJSON(w, http.StatusCreated, mediaResponse(m))
	}
}

// canReadMedia: the user may read the note the file was uploaded to, or a note whose blocks show it
// (e.g. a block copied into another note).
func (s *Server) canReadMedia(userID string, m *storage.Media) bool {
	if s.store.DocRole(userID, m.DocID) != "" {
		return true
	}
	docs, _ := s.store.MediaReferencedIn(m.ID)
	for _, d := range docs {
		if s.store.DocRole(userID, d) != "" {
			return true
		}
	}
	return false
}

// handleGetMedia: GET /media/{id} with range requests (seeking in audio).
func (s *Server) handleGetMedia(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	m, err := s.store.GetMedia(chi.URLParam(r, "id"))
	if err != nil || !s.canReadMedia(userID, m) {
		writeError(w, http.StatusNotFound, storage.ErrMediaNotFound.Error())
		return
	}
	f, err := os.Open(s.mediaPath(m))
	if err != nil {
		writeError(w, http.StatusNotFound, storage.ErrMediaNotFound.Error())
		return
	}
	defer f.Close()
	allowLongTransfer(w)
	w.Header().Set("Content-Type", m.Mime)
	// The content of an ID never changes; the login is checked on every request anyway
	w.Header().Set("Cache-Control", "private, max-age=31536000, immutable")
	w.Header().Set("Content-Security-Policy", "default-src 'none'; sandbox")
	created, _ := time.Parse(time.RFC3339, m.CreatedAt)
	http.ServeContent(w, r, "", created, f)
}

// compactMedia deletes files no block mentions any more (after the grace time) and their folders.
func (s *Server) compactMedia(now time.Time) {
	orphans, err := s.store.UnreferencedMedia(now.Add(-mediaGrace))
	if err != nil {
		slog.Error("Aufräumen der Mediendateien fehlgeschlagen", "error", err)
		return
	}
	for i := range orphans {
		m := &orphans[i]
		if err := os.Remove(s.mediaPath(m)); err != nil && !os.IsNotExist(err) {
			slog.Warn("Mediendatei konnte nicht gelöscht werden", "id", m.ID, "error", err)
			continue
		}
		_ = s.store.DeleteMediaRow(m.ID)
		_ = os.Remove(filepath.Dir(s.mediaPath(m))) // only succeeds when the folder is empty
	}
	if len(orphans) > 0 {
		slog.Info("Nicht mehr verwendete Mediendateien gelöscht", "count", len(orphans))
	}
}

// bodyLimit for uploads: the largest kind plus room for the multipart envelope
func (s *Server) mediaUploadLimit() int64 {
	img, audio := s.mediaLimit("image"), s.mediaLimit("audio")
	if audio > img {
		return audio + 1<<20
	}
	return img + 1<<20
}