package main

import (
	"embed"
	"log"
	"math/rand"
	"net/http"
	"strconv"

	"jxs.me/todogo/views"
)

//go:embed public/*
var publicFS embed.FS

type Todo struct {
	Id        string
	Title     string
	Completed bool
}

func filterSlice[T any](xs []T, pred func(T) bool) []T {
	result := make([]T, 0, len(xs))
	for _, element := range xs {
		if pred(element) {
			result = append(result, element)
		}

	}

	return result
}

func countSlice[T any](xs []T, pred func(T) bool) int {
	count := 0
	for _, element := range xs {
		if pred(element) {
			count += 1
		}
	}

	return count
}

type server struct {
	views  *views.Views
	router *http.ServeMux
	todos  []Todo
}

func newServer() *server {
	srv := &server{
		views:  views.New(),
		router: http.NewServeMux(),
		todos:  make([]Todo, 0, 10),
	}
	srv.routes()

	return srv
}

func (s *server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	s.router.ServeHTTP(w, r)
}

func (s *server) AddTodo(t Todo) {
	s.todos = append(s.todos, t)
}

func (s *server) HandleList() http.HandlerFunc {
	type viewModel struct {
		Todos      []Todo
		Only       string
		Incomplete int
	}

	list := s.views.Renderer("list.html")

	return func(w http.ResponseWriter, r *http.Request) {
		q := r.URL.Query()
		renderTodos := s.todos
		only := q.Get("only")

		if only == "active" {
			renderTodos = filterSlice(s.todos, func(todo Todo) bool { return !todo.Completed })
		}

		if only == "completed" {
			renderTodos = filterSlice(s.todos, func(todo Todo) bool { return todo.Completed })
		}

		incomplete := countSlice(s.todos, func(todo Todo) bool { return !todo.Completed })

		vm := viewModel{
			Todos:      renderTodos,
			Only:       only,
			Incomplete: incomplete,
		}
		list(w, r, vm)
	}
}

func (s *server) HandleCreate() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		title := r.Form.Get("title")
		s.AddTodo(Todo{
			Id:    strconv.Itoa(rand.Int()),
			Title: title,
		})

		http.Redirect(w, r, "/", http.StatusSeeOther)
	}
}

func (s *server) HandleToggle() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id := r.Form.Get("id")
		for i, todo := range s.todos {
			if todo.Id == id {
				todo.Completed = !todo.Completed
				s.todos[i] = todo
			}
		}

		http.Redirect(w, r, "/", http.StatusSeeOther)
	}
}

func (s *server) HandleDestroy() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id := r.Form.Get("id")
		s.todos = filterSlice(s.todos, func(t Todo) bool { return t.Id != id })

		http.Redirect(w, r, "/", http.StatusSeeOther)
	}
}

func (s *server) HandleClear() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		s.todos = filterSlice(s.todos, func(t Todo) bool { return !t.Completed })

		http.Redirect(w, r, "/", http.StatusSeeOther)
	}
}

func (s *server) routes() {
	s.router.Handle("/public/", http.FileServer(http.FS(publicFS)))
	s.router.HandleFunc("/", WithMethod("GET", s.HandleList()))
	s.router.HandleFunc("/todo", WithForm(WithMethod("POST", s.HandleCreate())))
	s.router.HandleFunc("/toggle", WithForm(WithMethod("POST", s.HandleToggle())))
	s.router.HandleFunc("/destroy", WithForm(WithMethod("POST", s.HandleDestroy())))
	s.router.HandleFunc("/clear", WithMethod("POST", s.HandleClear()))
}

func run() error {
	srv := newServer()

	log.Print("Running on 8080")
	return http.ListenAndServe(":8080", srv)
}

func main() {
	log.Fatal(run())
}