package auth

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

	"github.com/food-ai/backend/internal/middleware"
)

const maxRequestBodySize = 1 << 20 // 1 MB

type Handler struct {
	service *Service
}

func NewHandler(service *Service) *Handler {
	return &Handler{service: service}
}

type loginRequest struct {
	FirebaseToken string `json:"firebase_token"`
}

type refreshRequest struct {
	RefreshToken string `json:"refresh_token"`
}

func (h *Handler) Login(w http.ResponseWriter, r *http.Request) {
	r.Body = http.MaxBytesReader(w, r.Body, maxRequestBodySize)
	var req loginRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeErrorJSON(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.FirebaseToken == "" {
		writeErrorJSON(w, http.StatusBadRequest, "firebase_token is required")
		return
	}

	resp, err := h.service.Login(r.Context(), req.FirebaseToken)
	if err != nil {
		writeErrorJSON(w, http.StatusUnauthorized, "authentication failed")
		return
	}

	writeJSON(w, http.StatusOK, resp)
}

func (h *Handler) Refresh(w http.ResponseWriter, r *http.Request) {
	r.Body = http.MaxBytesReader(w, r.Body, maxRequestBodySize)
	var req refreshRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeErrorJSON(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.RefreshToken == "" {
		writeErrorJSON(w, http.StatusBadRequest, "refresh_token is required")
		return
	}

	resp, err := h.service.Refresh(r.Context(), req.RefreshToken)
	if err != nil {
		writeErrorJSON(w, http.StatusUnauthorized, "invalid refresh token")
		return
	}

	writeJSON(w, http.StatusOK, resp)
}

func (h *Handler) Logout(w http.ResponseWriter, r *http.Request) {
	userID := middleware.UserIDFromCtx(r.Context())
	if userID == "" {
		writeErrorJSON(w, http.StatusUnauthorized, "unauthorized")
		return
	}

	if err := h.service.Logout(r.Context(), userID); err != nil {
		writeErrorJSON(w, http.StatusInternalServerError, "logout failed")
		return
	}

	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

type errorResponse struct {
	Error string `json:"error"`
}

func writeErrorJSON(w http.ResponseWriter, status int, msg string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if err := json.NewEncoder(w).Encode(errorResponse{Error: msg}); err != nil {
		slog.Error("failed to write error response", "err", err)
	}
}

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