package api

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

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/render"
	"github.com/google/uuid"
)

func Whoami(w http.ResponseWriter, r *http.Request) {
	slog.Debug("user: entering Whoami handler")
	user, ok := r.Context().Value(userKey{}).(*User)
	if !ok || user == nil {
		slog.Debug("user: anonymous user")
		w.Write([]byte("anonymous"))
		return
	}

	slog.Debug("user: returning username", "userid", user.ID, "username", user.Name)
	w.Write([]byte(user.Name))
}

func LoginCtx(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		slog.Debug("user: entering LoginCtx middleware")
		userID, ok := r.Context().Value(userIDKey).(uuid.UUID)
		if !ok || userID == uuid.Nil {
			slog.Debug("user: no user ID provided, assuming anonymous user")
			next.ServeHTTP(w, r)
			return
		}

		slog.Debug("user: fetching user by ID", "user ID", userID)
		user, err := dbGetUser(userID.String())
		if err != nil {
			slog.Error("user: failed to fetch user by ID", "user ID", userID, "error", err)
			render.Render(w, r, ErrNotFound)
			return
		}

		slog.Debug("user: successfully fetched user", "user ID", user.ID, "username", user.Name)
		ctx := context.WithValue(r.Context(), userKey{}, user)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func ListUsers(w http.ResponseWriter, r *http.Request) {
	slog.Debug("user: entering ListUsers handler")
	dbUsers, err := dbGetAllUsers()
	if err != nil {
		slog.Error("user: failed to fetch users", "error", err)
		render.Render(w, r, ErrInternal(err))
		return
	}

	slog.Debug("user: successfully fetched users", "count", len(dbUsers))
	if err := render.RenderList(w, r, NewUserListResponse(dbUsers)); err != nil {
		slog.Error("user: failed to render user list response", "error", err)
		render.Render(w, r, ErrInternal(err))
		return
	}
}

func GetUser(w http.ResponseWriter, r *http.Request) {
	slog.Debug("user: entering GetUser handler")

	userID := chi.URLParam(r, "userID")
	parsed, err := uuid.Parse(userID)
	if err != nil {
		render.Render(w, r, ErrInvalidRequest(err))
		return
	}

	user, err := dbGetUser(parsed.String())
	if err != nil {
		if errors.Is(err, ErrUserNotFound) {
			render.Render(w, r, ErrNotFound)
		} else {
			slog.Error("user: failed to fetch user", "userid", parsed.String(), "error", err)
			render.Render(w, r, ErrInternal(err))
		}
		return
	}

	slog.Debug("user: rendering user", "userid", user.ID, "username", user.Name)
	if err := render.Render(w, r, NewUserPayloadResponse(user)); err != nil {
		slog.Error("user: failed to render user", "userid", parsed.String(), "error", err)
		render.Render(w, r, ErrInternal(err))
	}
}

func newUserID() uuid.UUID {
	return uuid.New()
}

func NewUser(w http.ResponseWriter, r *http.Request) {
	slog.Debug("user: entering NewUser handler")
	err := r.ParseMultipartForm(64 << 10)
	if err != nil {
		slog.Error("user: failed to parse multipartform", "error", err)
		http.Error(w, "Unable to parse form", http.StatusBadRequest)
		return
	}

	newUserName := r.FormValue("name")
	password := r.FormValue("password")
	if newUserName == "" || password == "" {
		slog.Error("user: username or password is empty")
		http.Error(w, "Username and password cannot be empty", http.StatusBadRequest)
		return
	}

	slog.Debug("user: hashing password for new user", "userName", newUserName)
	hashedPassword, err := hashPassword(password)
	if err != nil {
		slog.Error("user: failed to hash password", "error", err)
		http.Error(w, "Unable to hash password", http.StatusInternalServerError)
		return
	}

	newUser := User{
		ID:       newUserID(),
		Name:     newUserName,
		Password: hashedPassword,
	}

	slog.Debug("user: adding new user to database", "userID", newUser.ID, "userName", newUser.Name)
	err = dbAddUser(&newUser)
	if err != nil {
		slog.Error("user: failed to add new user", "userID", newUser.ID, "userName", newUser.Name, "error", err)
		render.Render(w, r, ErrInternal(err))
		return
	}

	slog.Debug("user: successfully added new user", "userID", newUser.ID, "userName", newUser.Name)
	render.Render(w, r, NewUserPayloadResponse(&newUser))
}

type User struct {
	ID       uuid.UUID `json:"id"`
	Name     string    `json:"name"`
	Password string    `json:"-"`
}

type userKey struct{}

type UserPayload struct {
	*User
}