package api

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
	"github.com/kindredsystems/silo/internal/db"
)

// presignUploadRequest is the request body for generating a presigned upload URL.
type presignUploadRequest struct {
	Filename    string `json:"filename"`
	ContentType string `json:"content_type"`
	Size        int64  `json:"size"`
}

// HandlePresignUpload generates a presigned PUT URL for direct browser upload.
func (s *Server) HandlePresignUpload(w http.ResponseWriter, r *http.Request) {
	if s.storage == nil {
		writeError(w, http.StatusServiceUnavailable, "storage_unavailable", "File storage not configured")
		return
	}

	var req presignUploadRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid_json", err.Error())
		return
	}

	if req.Filename == "" {
		writeError(w, http.StatusBadRequest, "invalid_request", "Filename is required")
		return
	}
	if req.Size > 500*1024*1024 {
		writeError(w, http.StatusBadRequest, "invalid_request", "File size exceeds 500MB limit")
		return
	}
	if req.ContentType == "" {
		req.ContentType = "application/octet-stream"
	}

	// Generate a unique temp key
	id := uuid.New().String()
	objectKey := fmt.Sprintf("uploads/tmp/%s/%s", id, req.Filename)

	expiry := 15 * time.Minute
	u, err := s.storage.PresignPut(r.Context(), objectKey, expiry)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to generate presigned URL")
		writeError(w, http.StatusInternalServerError, "presign_failed", "Failed to generate upload URL")
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"object_key": objectKey,
		"upload_url": u.String(),
		"expires_at": time.Now().Add(expiry).Format(time.RFC3339),
	})
}

// itemFileResponse is the JSON representation of an item file attachment.
type itemFileResponse struct {
	ID          string `json:"id"`
	Filename    string `json:"filename"`
	ContentType string `json:"content_type"`
	Size        int64  `json:"size"`
	ObjectKey   string `json:"object_key"`
	CreatedAt   string `json:"created_at"`
}

func itemFileToResponse(f *db.ItemFile) itemFileResponse {
	return itemFileResponse{
		ID:          f.ID,
		Filename:    f.Filename,
		ContentType: f.ContentType,
		Size:        f.Size,
		ObjectKey:   f.ObjectKey,
		CreatedAt:   f.CreatedAt.Format(time.RFC3339),
	}
}

// HandleListItemFiles lists file attachments for an item.
func (s *Server) HandleListItemFiles(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	partNumber := chi.URLParam(r, "partNumber")

	item, err := s.items.GetByPartNumber(ctx, partNumber)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to get item")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to get item")
		return
	}
	if item == nil {
		writeError(w, http.StatusNotFound, "not_found", "Item not found")
		return
	}

	files, err := s.itemFiles.ListByItem(ctx, item.ID)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to list item files")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to list files")
		return
	}

	result := make([]itemFileResponse, 0, len(files))
	for _, f := range files {
		result = append(result, itemFileToResponse(f))
	}

	writeJSON(w, http.StatusOK, result)
}

// associateFileRequest is the request body for associating an uploaded file with an item.
type associateFileRequest struct {
	ObjectKey   string `json:"object_key"`
	Filename    string `json:"filename"`
	ContentType string `json:"content_type"`
	Size        int64  `json:"size"`
}

// HandleAssociateItemFile moves a temp upload to permanent storage and creates a DB record.
func (s *Server) HandleAssociateItemFile(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	partNumber := chi.URLParam(r, "partNumber")

	if s.storage == nil {
		writeError(w, http.StatusServiceUnavailable, "storage_unavailable", "File storage not configured")
		return
	}

	item, err := s.items.GetByPartNumber(ctx, partNumber)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to get item")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to get item")
		return
	}
	if item == nil {
		writeError(w, http.StatusNotFound, "not_found", "Item not found")
		return
	}

	var req associateFileRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid_json", err.Error())
		return
	}

	if req.ObjectKey == "" || req.Filename == "" {
		writeError(w, http.StatusBadRequest, "invalid_request", "object_key and filename are required")
		return
	}

	// Security: only allow associating files from the temp upload prefix
	if !strings.HasPrefix(req.ObjectKey, "uploads/tmp/") {
		writeError(w, http.StatusBadRequest, "invalid_request", "object_key must be a temp upload")
		return
	}

	if req.ContentType == "" {
		req.ContentType = "application/octet-stream"
	}

	// Create DB record first to get the file ID
	itemFile := &db.ItemFile{
		ItemID:      item.ID,
		Filename:    req.Filename,
		ContentType: req.ContentType,
		Size:        req.Size,
		ObjectKey:   "", // will be set after copy
	}

	// Generate permanent key
	fileID := uuid.New().String()
	permanentKey := fmt.Sprintf("items/%s/files/%s/%s", item.ID, fileID, req.Filename)

	// Copy from temp to permanent location
	if err := s.storage.Copy(ctx, req.ObjectKey, permanentKey); err != nil {
		s.logger.Error().Err(err).Str("src", req.ObjectKey).Str("dst", permanentKey).Msg("failed to copy file")
		writeError(w, http.StatusInternalServerError, "copy_failed", "Failed to move file to permanent storage")
		return
	}

	// Delete the temp object (best-effort)
	_ = s.storage.Delete(ctx, req.ObjectKey)

	// Save DB record with permanent key
	itemFile.ObjectKey = permanentKey
	if err := s.itemFiles.Create(ctx, itemFile); err != nil {
		s.logger.Error().Err(err).Msg("failed to create item file record")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to save file record")
		return
	}

	s.logger.Info().
		Str("part_number", partNumber).
		Str("file_id", itemFile.ID).
		Str("filename", req.Filename).
		Int64("size", req.Size).
		Msg("file associated with item")

	writeJSON(w, http.StatusCreated, itemFileToResponse(itemFile))
}

// HandleDeleteItemFile deletes a file attachment and its storage object.
func (s *Server) HandleDeleteItemFile(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	partNumber := chi.URLParam(r, "partNumber")
	fileID := chi.URLParam(r, "fileId")

	item, err := s.items.GetByPartNumber(ctx, partNumber)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to get item")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to get item")
		return
	}
	if item == nil {
		writeError(w, http.StatusNotFound, "not_found", "Item not found")
		return
	}

	// Get the file record to find the storage key
	file, err := s.itemFiles.Get(ctx, fileID)
	if err != nil {
		writeError(w, http.StatusNotFound, "not_found", "File not found")
		return
	}

	// Verify the file belongs to this item
	if file.ItemID != item.ID {
		writeError(w, http.StatusNotFound, "not_found", "File not found")
		return
	}

	// Delete from storage (best-effort)
	if s.storage != nil {
		_ = s.storage.Delete(ctx, file.ObjectKey)
	}

	// Delete DB record
	if err := s.itemFiles.Delete(ctx, fileID); err != nil {
		s.logger.Error().Err(err).Msg("failed to delete item file record")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to delete file")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

// setThumbnailRequest is the request body for setting an item thumbnail.
type setThumbnailRequest struct {
	ObjectKey string `json:"object_key"`
}

// HandleSetItemThumbnail copies a temp upload to the item thumbnail location.
func (s *Server) HandleSetItemThumbnail(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	partNumber := chi.URLParam(r, "partNumber")

	if s.storage == nil {
		writeError(w, http.StatusServiceUnavailable, "storage_unavailable", "File storage not configured")
		return
	}

	item, err := s.items.GetByPartNumber(ctx, partNumber)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to get item")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to get item")
		return
	}
	if item == nil {
		writeError(w, http.StatusNotFound, "not_found", "Item not found")
		return
	}

	var req setThumbnailRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid_json", err.Error())
		return
	}

	if req.ObjectKey == "" {
		writeError(w, http.StatusBadRequest, "invalid_request", "object_key is required")
		return
	}

	// Security: only allow from temp upload prefix
	if !strings.HasPrefix(req.ObjectKey, "uploads/tmp/") {
		writeError(w, http.StatusBadRequest, "invalid_request", "object_key must be a temp upload")
		return
	}

	// Copy to permanent thumbnail location
	thumbnailKey := fmt.Sprintf("items/%s/thumbnail.png", item.ID)
	if err := s.storage.Copy(ctx, req.ObjectKey, thumbnailKey); err != nil {
		s.logger.Error().Err(err).Msg("failed to copy thumbnail")
		writeError(w, http.StatusInternalServerError, "copy_failed", "Failed to set thumbnail")
		return
	}

	// Delete temp object (best-effort)
	_ = s.storage.Delete(ctx, req.ObjectKey)

	// Update DB
	if err := s.items.SetThumbnailKey(ctx, item.ID, thumbnailKey); err != nil {
		s.logger.Error().Err(err).Msg("failed to update thumbnail key")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to save thumbnail")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

// storageBackend returns the configured storage backend name.
func (s *Server) storageBackend() string {
	return "filesystem"
}

// HandleUploadItemFile accepts a multipart file upload and stores it as an item attachment.
func (s *Server) HandleUploadItemFile(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	partNumber := chi.URLParam(r, "partNumber")

	if s.storage == nil {
		writeError(w, http.StatusServiceUnavailable, "storage_unavailable", "File storage not configured")
		return
	}

	item, err := s.items.GetByPartNumber(ctx, partNumber)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to get item")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to get item")
		return
	}
	if item == nil {
		writeError(w, http.StatusNotFound, "not_found", "Item not found")
		return
	}

	// Parse multipart form (max 500MB)
	if err := r.ParseMultipartForm(500 << 20); err != nil {
		writeError(w, http.StatusBadRequest, "invalid_form", err.Error())
		return
	}

	file, header, err := r.FormFile("file")
	if err != nil {
		writeError(w, http.StatusBadRequest, "missing_file", "File is required")
		return
	}
	defer file.Close()

	contentType := header.Header.Get("Content-Type")
	if contentType == "" {
		contentType = "application/octet-stream"
	}

	// Generate permanent key
	fileID := uuid.New().String()
	permanentKey := fmt.Sprintf("items/%s/files/%s/%s", item.ID, fileID, header.Filename)

	// Write directly to storage
	result, err := s.storage.Put(ctx, permanentKey, file, header.Size, contentType)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to upload file")
		writeError(w, http.StatusInternalServerError, "upload_failed", "Failed to store file")
		return
	}

	// Create DB record
	itemFile := &db.ItemFile{
		ItemID:         item.ID,
		Filename:       header.Filename,
		ContentType:    contentType,
		Size:           result.Size,
		ObjectKey:      permanentKey,
		StorageBackend: s.storageBackend(),
	}
	if err := s.itemFiles.Create(ctx, itemFile); err != nil {
		s.logger.Error().Err(err).Msg("failed to create item file record")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to save file record")
		return
	}

	s.logger.Info().
		Str("part_number", partNumber).
		Str("file_id", itemFile.ID).
		Str("filename", header.Filename).
		Int64("size", result.Size).
		Msg("file uploaded to item")

	writeJSON(w, http.StatusCreated, itemFileToResponse(itemFile))
}

// HandleUploadItemThumbnail accepts a multipart file upload and sets it as the item thumbnail.
func (s *Server) HandleUploadItemThumbnail(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	partNumber := chi.URLParam(r, "partNumber")

	if s.storage == nil {
		writeError(w, http.StatusServiceUnavailable, "storage_unavailable", "File storage not configured")
		return
	}

	item, err := s.items.GetByPartNumber(ctx, partNumber)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to get item")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to get item")
		return
	}
	if item == nil {
		writeError(w, http.StatusNotFound, "not_found", "Item not found")
		return
	}

	// Parse multipart form (max 10MB for thumbnails)
	if err := r.ParseMultipartForm(10 << 20); err != nil {
		writeError(w, http.StatusBadRequest, "invalid_form", err.Error())
		return
	}

	file, header, err := r.FormFile("file")
	if err != nil {
		writeError(w, http.StatusBadRequest, "missing_file", "File is required")
		return
	}
	defer file.Close()

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

	thumbnailKey := fmt.Sprintf("items/%s/thumbnail.png", item.ID)

	if _, err := s.storage.Put(ctx, thumbnailKey, file, header.Size, contentType); err != nil {
		s.logger.Error().Err(err).Msg("failed to upload thumbnail")
		writeError(w, http.StatusInternalServerError, "upload_failed", "Failed to store thumbnail")
		return
	}

	if err := s.items.SetThumbnailKey(ctx, item.ID, thumbnailKey); err != nil {
		s.logger.Error().Err(err).Msg("failed to update thumbnail key")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to save thumbnail")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

// HandleDownloadItemFile streams an item file attachment to the client.
func (s *Server) HandleDownloadItemFile(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	partNumber := chi.URLParam(r, "partNumber")
	fileID := chi.URLParam(r, "fileId")

	if s.storage == nil {
		writeError(w, http.StatusServiceUnavailable, "storage_unavailable", "File storage not configured")
		return
	}

	item, err := s.items.GetByPartNumber(ctx, partNumber)
	if err != nil || item == nil {
		writeError(w, http.StatusNotFound, "not_found", "Item not found")
		return
	}

	file, err := s.itemFiles.Get(ctx, fileID)
	if err != nil {
		writeError(w, http.StatusNotFound, "not_found", "File not found")
		return
	}

	if file.ItemID != item.ID {
		writeError(w, http.StatusNotFound, "not_found", "File not found")
		return
	}

	reader, err := s.storage.Get(ctx, file.ObjectKey)
	if err != nil {
		s.logger.Error().Err(err).Str("key", file.ObjectKey).Msg("failed to get file")
		writeError(w, http.StatusInternalServerError, "download_failed", "Failed to retrieve file")
		return
	}
	defer reader.Close()

	w.Header().Set("Content-Type", file.ContentType)
	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, file.Filename))
	if file.Size > 0 {
		w.Header().Set("Content-Length", strconv.FormatInt(file.Size, 10))
	}

	io.Copy(w, reader)
}