package service

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"strconv"
	"time"

	"git.umbrella.haus/ae/notatest/pkg/data"
	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5/pgconn"
	"github.com/rs/zerolog/log"
	"golang.org/x/crypto/bcrypt"
)

type userCtxKey struct{}

// Stripped object that only contains non-critical data
type userResponse struct {
	ID        uuid.UUID  `json:"id"`
	Username  string     `json:"username"`
	CreatedAt *time.Time `json:"created_at"`
	UpdatedAt *time.Time `json:"updated_at"`
	IsAdmin   bool       `json:"is_admin"`
}

// Mockable database operations interface
type UserStore interface {
	CreateUser(ctx context.Context, arg data.CreateUserParams) (data.User, error)
	ListUsers(ctx context.Context) ([]data.User, error)
	GetUserByID(ctx context.Context, id uuid.UUID) (data.User, error)
	GetUserByUsername(ctx context.Context, username string) (data.User, error)
	UpdatePassword(ctx context.Context, arg data.UpdatePasswordParams) error
	DeleteUser(ctx context.Context, id uuid.UUID) error
	RevokeAllUserRefreshTokens(ctx context.Context, id uuid.UUID) error
}

type usersResource struct {
	JWTSecret string
	Users     UserStore
}

func (rs usersResource) Routes() chi.Router {
	r := chi.NewRouter()

	// Public routes (no tokens required)
	r.Post("/", rs.Create)     // POST /users - registration/signup
	r.Post("/login", rs.Login) // POST /users/login - login as existing user

	// Protected routes (access token required)
	r.Group(func(r chi.Router) {
		r.Use(requireAccessToken(rs.JWTSecret))

		// Admin only general routes
		r.Group(func(r chi.Router) {
			r.Use(adminOnlyMiddleware)
			r.Get("/", rs.List) // GET /users - list all users
		})

		// User specific routes
		r.Route("/{id}", func(r chi.Router) {
			r.Use(userCtx(rs.Users)) // DB -> req. context

			// Admin routes
			r.Route("/admin", func(r chi.Router) {
				r.Use(adminOnlyMiddleware)
				r.Get("/", rs.Get)            // GET /users/admin/{id} - get single user
				r.Delete("/", rs.AdminDelete) // DELETE /users/admin/{id} - delete user
			})

			// Owner routes
			r.Route("/owner", func(r chi.Router) {
				r.Use(ownerOnlyMiddleware)
				r.Put("/", rs.UpdatePassword) // PUT /users/owner/{id} - update user password
				r.Delete("/", rs.OwnerDelete) // DELETE /users/owner/{id} - delete user
			})
		})
	})

	return r
}

func (rs usersResource) Create(w http.ResponseWriter, r *http.Request) {
	type request struct {
		Username string `json:"username"`
		Password string `json:"password"`
	}

	var req request
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		respondError(w, http.StatusBadRequest, "Invalid request body")
		return
	}

	normalizedUsername := normalizeUsername(req.Username)
	if err := validateUsername(normalizedUsername); err != nil {
		respondError(w, http.StatusBadRequest, err.Error())
		return
	}

	if err := validatePassword(req.Password); err != nil {
		respondError(w, http.StatusBadRequest, err.Error())
		return
	}

	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(req.Password), bcrypt.DefaultCost)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to create user")
		return
	}

	user, err := rs.Users.CreateUser(r.Context(), data.CreateUserParams{
		Username:     normalizedUsername,
		PasswordHash: string(hashedPassword),
	})
	if err != nil {
		if isDuplicateEntry(err) {
			respondError(w, http.StatusConflict, "Username is already in use")
		} else {
			respondError(w, http.StatusInternalServerError, "Failed to create user")
		}
		return
	}

	respondJSON(w, http.StatusCreated, map[string]string{
		"id":       user.ID.String(),
		"username": user.Username,
	})
}

func (rs usersResource) Login(w http.ResponseWriter, r *http.Request) {
	type request struct {
		Username string `json:"username"`
		Password string `json:"password"`
	}

	var req request
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		respondError(w, http.StatusBadRequest, "Invalid request body")
		return
	}

	user, err := rs.Users.GetUserByUsername(r.Context(), normalizeUsername(req.Username))
	if err != nil {
		respondError(w, http.StatusUnauthorized, "Invalid credentials")
		return
	}

	if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(req.Password)); err != nil {
		respondError(w, http.StatusUnauthorized, "Invalid credentials")
		return
	}

	tokenPair, err := generateTokenPair(user.ID.String(), user.IsAdmin, rs.JWTSecret)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to generate tokens")
		return
	}

	// Set refresh token in HTTP-only cookie
	http.SetCookie(w, &http.Cookie{
		Name:     "refresh_token",
		Value:    tokenPair.RefreshToken,
		Path:     "/",
		MaxAge:   int(refreshTokenDuration.Seconds()),
		HttpOnly: true,
		Secure:   true,
		SameSite: http.SameSiteStrictMode,
	})

	// Build response
	response := map[string]any{
		"access_token": tokenPair.AccessToken,
	}

	// Include user data if the client has requested it (`?includeUser=true`)
	if includeUser, _ := strconv.ParseBool(r.URL.Query().Get("includeUser")); includeUser {
		response["user"] = userResponse{
			ID:        user.ID,
			Username:  user.Username,
			CreatedAt: user.CreatedAt,
			UpdatedAt: user.UpdatedAt,
			IsAdmin:   user.IsAdmin,
		}
	}

	respondJSON(w, http.StatusOK, response)
}

func (rs usersResource) List(w http.ResponseWriter, r *http.Request) {
	users, err := rs.Users.ListUsers(r.Context())
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to retrieve users")
		return
	}

	// Output sanitization
	var output []map[string]any
	for _, user := range users {
		output = append(output, map[string]any{
			"id":         user.ID,
			"username":   user.Username,
			"created_at": user.CreatedAt,
			"updated_at": user.UpdatedAt,
		})
	}

	respondJSON(w, http.StatusOK, output)
}

func (rs usersResource) Get(w http.ResponseWriter, r *http.Request) {
	user, ok := r.Context().Value(userCtxKey{}).(data.User)
	if !ok {
		respondError(w, http.StatusNotFound, "User not found")
		return
	}

	respondJSON(w, http.StatusOK, map[string]any{
		"id":         user.ID,
		"username":   user.Username,
		"created_at": user.CreatedAt,
		"updated_at": user.UpdatedAt,
	})
}

func (rs usersResource) UpdatePassword(w http.ResponseWriter, r *http.Request) {
	type request struct {
		OldPassword string `json:"old_password"`
		NewPassword string `json:"new_password"`
	}

	var req request
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		respondError(w, http.StatusBadRequest, "Invalid request body")
		return
	}

	user, ok := r.Context().Value(userCtxKey{}).(data.User)
	if !ok {
		respondError(w, http.StatusNotFound, "User not found")
		return
	}

	// Verify the old password before allowing the update
	if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(req.OldPassword)); err != nil {
		respondError(w, http.StatusUnauthorized, "Invalid credentials")
		return
	}

	if err := validatePassword(req.NewPassword); err != nil {
		respondError(w, http.StatusBadRequest, err.Error())
		return
	}

	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(req.NewPassword), bcrypt.DefaultCost)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to update password")
		return
	}

	if err := rs.Users.UpdatePassword(r.Context(), data.UpdatePasswordParams{
		ID:           user.ID,
		PasswordHash: string(hashedPassword),
	}); err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to update password")
		return
	}

	if err := rs.Users.RevokeAllUserRefreshTokens(r.Context(), user.ID); err != nil {
		log.Error().Msgf("Failed to revoke refresh tokens: %s", err)
	}

	w.WriteHeader(http.StatusNoContent)
}

func (rs usersResource) AdminDelete(w http.ResponseWriter, r *http.Request) {
	user, ok := r.Context().Value(userCtxKey{}).(data.User)
	if !ok {
		respondError(w, http.StatusNotFound, "User not found")
		return
	}

	if err := rs.Users.DeleteUser(r.Context(), user.ID); err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to delete user")
		return
	}

	if err := rs.Users.RevokeAllUserRefreshTokens(r.Context(), user.ID); err != nil {
		log.Error().Msgf("Failed to revoke refresh tokens: %s", err)
	}

	w.WriteHeader(http.StatusNoContent)
}

func (rs usersResource) OwnerDelete(w http.ResponseWriter, r *http.Request) {
	type request struct {
		Password string `json:"password"`
	}

	var req request
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		respondError(w, http.StatusBadRequest, "Invalid request body")
		return
	}

	user, ok := r.Context().Value(userCtxKey{}).(data.User)
	if !ok {
		respondError(w, http.StatusNotFound, "User not found")
		return
	}

	// Verify the old password before allowing the deletion
	if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(req.Password)); err != nil {
		respondError(w, http.StatusUnauthorized, "Invalid credentials")
		return
	}

	err := rs.Users.DeleteUser(r.Context(), user.ID)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "Failed to delete user")
		return
	}

	if err := rs.Users.RevokeAllUserRefreshTokens(r.Context(), user.ID); err != nil {
		log.Error().Msgf("Failed to revoke refresh tokens: %s", err)
	}

	w.WriteHeader(http.StatusNoContent)
}

// Check if the given error is a PostgreSQL error for `unique_violation`, i.e. whether an entry
// with the given details already exists in the database table.
func isDuplicateEntry(err error) bool {
	var pgErr *pgconn.PgError
	if errors.As(err, &pgErr) {
		return pgErr.Code == "23505"
	}
	return false
}