package auth

import (
	"encoding/json"
	"errors"
	"net/http"
	"strings"
)

type Handler struct {
	service *Service
}

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

func (h *Handler) RegisterRoutes(mux *http.ServeMux) {
	mux.HandleFunc("POST /api/auth/register", h.Register)
	mux.HandleFunc("POST /api/auth/login", h.Login)
	mux.HandleFunc("POST /api/auth/logout", h.Logout)
	mux.HandleFunc("GET /api/auth/me", h.Me)
}

type credentialsRequest struct {
	Email    string `json:"email"`
	Password string `json:"password"`
	Name     string `json:"name"`
}

func (h *Handler) Register(w http.ResponseWriter, r *http.Request) {
	var request credentialsRequest
	if !decodeJSON(w, r, &request) {
		return
	}
	user, err := h.service.Register(r.Context(), request.Email, request.Password, request.Name)
	if err != nil {
		if errors.Is(err, ErrEmailTaken) {
			writeJSON(w, http.StatusConflict, map[string]string{"error": "email is already registered"})
			return
		}
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()})
		return
	}
	h.service.SetSession(w, user)
	writeJSON(w, http.StatusCreated, map[string]User{"user": user})
}

func (h *Handler) Login(w http.ResponseWriter, r *http.Request) {
	var request credentialsRequest
	if !decodeJSON(w, r, &request) {
		return
	}
	user, err := h.service.Login(r.Context(), request.Email, request.Password)
	if err != nil {
		if errors.Is(err, ErrInvalidCredentials) {
			writeJSON(w, http.StatusUnauthorized, map[string]string{"error": "invalid email or password"})
			return
		}
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not sign in"})
		return
	}
	h.service.SetSession(w, user)
	writeJSON(w, http.StatusOK, map[string]User{"user": user})
}

func (h *Handler) Logout(w http.ResponseWriter, _ *http.Request) {
	h.service.ClearSession(w)
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

func (h *Handler) Me(w http.ResponseWriter, r *http.Request) {
	user, err := h.service.UserFromRequest(r.Context(), r)
	if err != nil {
		writeJSON(w, http.StatusUnauthorized, map[string]string{"error": "authentication required"})
		return
	}
	writeJSON(w, http.StatusOK, map[string]User{"user": user})
}

func decodeJSON(w http.ResponseWriter, r *http.Request, target any) bool {
	if !strings.HasPrefix(r.Header.Get("Content-Type"), "application/json") {
		writeJSON(w, http.StatusUnsupportedMediaType, map[string]string{"error": "content type must be application/json"})
		return false
	}
	decoder := json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<20))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(target); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid JSON body"})
		return false
	}
	return true
}