package manage

import (
	"encoding/json"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"git.az-it.net/az/morz-infoboard/server/backend/internal/fileutil"
	"git.az-it.net/az/morz-infoboard/server/backend/internal/reqcontext"
	"git.az-it.net/az/morz-infoboard/server/backend/internal/store"
)

const maxUploadSize = 512 << 20 // 512 MB

// HandleListMedia returns all media assets for a tenant as JSON.
// restricted-Users sehen nur ihre eigenen Medien.
func HandleListMedia(tenants *store.TenantStore, media *store.MediaStore) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		tenant, err := tenants.Get(r.Context(), r.PathValue("tenantSlug"))
		if err != nil {
			http.Error(w, "tenant not found", http.StatusNotFound)
			return
		}
		u := reqcontext.UserFromContext(r.Context())
		ownerUserID := ""
		if u != nil && u.Role == "restricted" {
			ownerUserID = u.ID
		}
		assets, err := media.List(r.Context(), tenant.ID, ownerUserID)
		if err != nil {
			http.Error(w, "db error", http.StatusInternalServerError)
			return
		}
		if assets == nil {
			assets = []*store.MediaAsset{}
		}
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(assets) //nolint:errcheck
	}
}

// HandleUploadMedia handles multipart file upload and web-URL registration.
func HandleUploadMedia(tenants *store.TenantStore, media *store.MediaStore, uploadDir string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		tenant, err := tenants.Get(r.Context(), r.PathValue("tenantSlug"))
		if err != nil {
			http.Error(w, "tenant not found", http.StatusNotFound)
			return
		}
		tenantID := tenant.ID

		u := reqcontext.UserFromContext(r.Context())
		createdByUserID := ""
		if u != nil {
			createdByUserID = u.ID
		}

		// W3: MaxBytesReader begrenzt den gesamten Request-Body auf maxUploadSize.
		r.Body = http.MaxBytesReader(w, r.Body, maxUploadSize)
		if err := r.ParseMultipartForm(maxUploadSize); err != nil {
			http.Error(w, "request too large or not multipart", http.StatusBadRequest)
			return
		}

		assetType := strings.TrimSpace(r.FormValue("type"))
		title := strings.TrimSpace(r.FormValue("title"))

		switch assetType {
		case "web":
			url := strings.TrimSpace(r.FormValue("url"))
			if url == "" {
				http.Error(w, "url required for type=web", http.StatusBadRequest)
				return
			}
			if title == "" {
				title = url
			}
			asset, err := media.Create(r.Context(), tenantID, title, "web", "", url, "", createdByUserID, 0)
			if err != nil {
				http.Error(w, "db error", http.StatusInternalServerError)
				return
			}
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusCreated)
			json.NewEncoder(w).Encode(asset) //nolint:errcheck
			return

		case "image", "video", "pdf":
			file, header, err := r.FormFile("file")
			if err != nil {
				http.Error(w, "file required for type="+assetType, http.StatusBadRequest)
				return
			}
			defer file.Close()

			mimeType := header.Header.Get("Content-Type")
			if detectedType := mimeToAssetType(mimeType); detectedType != "" {
				assetType = detectedType
			}
			if title == "" {
				title = strings.TrimSuffix(header.Filename, filepath.Ext(header.Filename))
			}

			// V1+N6: Gemeinsame Upload-Funktion, tenant-spezifisches Verzeichnis.
			storagePath, size, err := fileutil.SaveUploadedFile(file, header.Filename, title, uploadDir, r.PathValue("tenantSlug"))
			if err != nil {
				http.Error(w, "storage error", http.StatusInternalServerError)
				return
			}

			asset, err := media.Create(r.Context(), tenantID, title, assetType, storagePath, "", mimeType, createdByUserID, size)
			if err != nil {
				http.Error(w, "db error", http.StatusInternalServerError)
				return
			}
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusCreated)
			json.NewEncoder(w).Encode(asset) //nolint:errcheck

		default:
			http.Error(w, "type must be one of: image, video, pdf, web", http.StatusBadRequest)
		}
	}
}

// HandleDeleteMedia deletes a media asset from the database (and file if local).
func HandleDeleteMedia(media *store.MediaStore, uploadDir string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id := r.PathValue("id")
		asset, err := media.Get(r.Context(), id)
		if err != nil {
			http.Error(w, "not found", http.StatusNotFound)
			return
		}

		// K3: Rolle-bewusste Berechtigungsprüfung.
		u := reqcontext.UserFromContext(r.Context())
		if u == nil || !canDeleteMedia(u, asset) {
			http.Error(w, "Forbidden", http.StatusForbidden)
			return
		}

		// Delete physical file if it's a local upload.
		if asset.StoragePath != "" {
			filename := filepath.Base(asset.StoragePath)
			os.Remove(filepath.Join(uploadDir, filename)) //nolint:errcheck
		}

		if err := media.Delete(r.Context(), id); err != nil {
			http.Error(w, "db error", http.StatusInternalServerError)
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

// mimeToAssetType leitet den Asset-Typ aus dem MIME-Type ab.
func mimeToAssetType(mime string) string {
	mime = strings.ToLower(strings.TrimSpace(mime))
	switch {
	case strings.HasPrefix(mime, "image/"):
		return "image"
	case strings.HasPrefix(mime, "video/"):
		return "video"
	case mime == "application/pdf":
		return "pdf"
	default:
		return ""
	}
}

func sanitize(s string) string {
	var b strings.Builder
	for _, r := range s {
		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') || r == '-' || r == '_' {
			b.WriteRune(r)
		} else {
			b.WriteRune('_')
		}
	}
	out := b.String()
	if len(out) > 40 {
		out = out[:40]
	}
	return out
}

// canDeleteMedia prüft ob User u das Medium asset löschen darf.
// admin:       immer erlaubt
// screen_user: Tenant-Match reicht
// restricted:  Tenant-Match UND Besitzer-Match
func canDeleteMedia(u *store.User, asset *store.MediaAsset) bool {
	if u.Role == "admin" {
		return true
	}
	if u.TenantID != asset.TenantID {
		return false
	}
	if u.Role == "restricted" {
		return asset.CreatedByUserID == u.ID
	}
	return true
}