package savedrecipe

import (
	"context"
	"encoding/json"
	"errors"
	"log/slog"
	"net/http"

	"github.com/food-ai/backend/internal/infra/middleware"
	"github.com/go-chi/chi/v5"
)

const maxBodySize = 1 << 20 // 1 MB

// SavedRecipeRepository is the data layer interface used by Handler.
type SavedRecipeRepository interface {
	Save(ctx context.Context, userID string, req SaveRequest) (*UserSavedRecipe, error)
	List(ctx context.Context, userID string) ([]*UserSavedRecipe, error)
	GetByID(ctx context.Context, userID, id string) (*UserSavedRecipe, error)
	Delete(ctx context.Context, userID, id string) error
}

// Handler handles HTTP requests for saved recipes.
type Handler struct {
	repo SavedRecipeRepository
}

// NewHandler creates a new Handler.
func NewHandler(repo SavedRecipeRepository) *Handler {
	return &Handler{repo: repo}
}

// Save handles POST /saved-recipes.
func (h *Handler) Save(w http.ResponseWriter, r *http.Request) {
	userID := middleware.UserIDFromCtx(r.Context())
	if userID == "" {
		writeErrorJSON(w, r, http.StatusUnauthorized, "unauthorized")
		return
	}

	r.Body = http.MaxBytesReader(w, r.Body, maxBodySize)
	var req SaveRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeErrorJSON(w, r, http.StatusBadRequest, "invalid request body")
		return
	}
	if req.Title == "" && req.RecipeID == "" {
		writeErrorJSON(w, r, http.StatusBadRequest, "title or recipe_id is required")
		return
	}

	rec, err := h.repo.Save(r.Context(), userID, req)
	if err != nil {
		slog.ErrorContext(r.Context(), "save recipe", "err", err)
		writeErrorJSON(w, r, http.StatusInternalServerError, "failed to save recipe")
		return
	}
	writeJSON(w, http.StatusCreated, rec)
}

// List handles GET /saved-recipes.
func (h *Handler) List(w http.ResponseWriter, r *http.Request) {
	userID := middleware.UserIDFromCtx(r.Context())
	if userID == "" {
		writeErrorJSON(w, r, http.StatusUnauthorized, "unauthorized")
		return
	}

	recipes, err := h.repo.List(r.Context(), userID)
	if err != nil {
		slog.ErrorContext(r.Context(), "list saved recipes", "err", err)
		writeErrorJSON(w, r, http.StatusInternalServerError, "failed to list saved recipes")
		return
	}
	if recipes == nil {
		recipes = []*UserSavedRecipe{}
	}
	writeJSON(w, http.StatusOK, recipes)
}

// GetByID handles GET /saved-recipes/{id}.
func (h *Handler) GetByID(w http.ResponseWriter, r *http.Request) {
	userID := middleware.UserIDFromCtx(r.Context())
	if userID == "" {
		writeErrorJSON(w, r, http.StatusUnauthorized, "unauthorized")
		return
	}

	id := chi.URLParam(r, "id")
	rec, err := h.repo.GetByID(r.Context(), userID, id)
	if err != nil {
		slog.ErrorContext(r.Context(), "get saved recipe", "id", id, "err", err)
		writeErrorJSON(w, r, http.StatusInternalServerError, "failed to get saved recipe")
		return
	}
	if rec == nil {
		writeErrorJSON(w, r, http.StatusNotFound, "recipe not found")
		return
	}
	writeJSON(w, http.StatusOK, rec)
}

// Delete handles DELETE /saved-recipes/{id}.
func (h *Handler) Delete(w http.ResponseWriter, r *http.Request) {
	userID := middleware.UserIDFromCtx(r.Context())
	if userID == "" {
		writeErrorJSON(w, r, http.StatusUnauthorized, "unauthorized")
		return
	}

	id := chi.URLParam(r, "id")
	if err := h.repo.Delete(r.Context(), userID, id); err != nil {
		if errors.Is(err, ErrNotFound) {
			writeErrorJSON(w, r, http.StatusNotFound, "recipe not found")
			return
		}
		slog.ErrorContext(r.Context(), "delete saved recipe", "id", id, "err", err)
		writeErrorJSON(w, r, http.StatusInternalServerError, "failed to delete recipe")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

type errorResponse struct {
	Error     string `json:"error"`
	RequestID string `json:"request_id,omitempty"`
}

func writeErrorJSON(w http.ResponseWriter, r *http.Request, status int, msg string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if encodeErr := json.NewEncoder(w).Encode(errorResponse{
		Error:     msg,
		RequestID: middleware.RequestIDFromCtx(r.Context()),
	}); encodeErr != nil {
		slog.ErrorContext(r.Context(), "write error response", "err", encodeErr)
	}
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if err := json.NewEncoder(w).Encode(v); err != nil {
		slog.Error("write JSON response", "err", err)
	}
}