package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

type Todo struct {
	ID        int       `json:"id"`
	Task      string    `json:"task"`
	Completed bool      `json:"completed"`
	CreatedAt time.Time `json:"created_at"`
}

type TodoList struct {
	Todos  []Todo `json:"todos"`
	NextID int    `json:"next_id"`
}

const (
	dataDir = ".todos"
	reset   = "\033[0m"
	red     = "\033[31m"
	green   = "\033[32m"
	yellow  = "\033[33m"
	blue    = "\033[34m"
	magenta = "\033[35m"
	cyan    = "\033[36m"
	bold    = "\033[1m"
)

var currentProject string

func main() {
	ensureDataDir()
	reader := bufio.NewReader(os.Stdin)

	currentProject = selectProject(reader)
	list := loadTodos(currentProject)

	for {
		printHeader()
		printMenu()

		input, _ := reader.ReadString('\n')
		choice := strings.TrimSpace(input)

		switch choice {
		case "1":
			addTodo(&list, reader)
		case "2":
			listTodos(&list)
		case "3":
			completeTodo(&list, reader)
		case "4":
			deleteTodo(&list, reader)
		case "5":
			currentProject = selectProject(reader)
			list = loadTodos(currentProject)
		case "6":
			listProjects()
		case "7":
			deleteProject(reader)
		case "8":
			fmt.Println(cyan + "Goodbye! ✨" + reset)
			return
		default:
			fmt.Println(red + "Invalid option" + reset)
		}
	}
}

func printHeader() {
	fmt.Println("\n" + strings.Repeat("=", 50))
	fmt.Printf("%s%s✓ Todo Manager%s\n", bold, cyan, reset)
	fmt.Printf("%sProject:%s %s%s%s\n", yellow, reset, green, currentProject, reset)
	fmt.Println(strings.Repeat("=", 50))
}

func printMenu() {
	fmt.Println("\n" + bold + "Actions:" + reset)
	fmt.Println(cyan + "1." + reset + " Add todo")
	fmt.Println(cyan + "2." + reset + " List todos")
	fmt.Println(cyan + "3." + reset + " Complete todo")
	fmt.Println(cyan + "4." + reset + " Delete todo")
	fmt.Println(magenta + "5." + reset + " Switch project")
	fmt.Println(magenta + "6." + reset + " List all projects")
	fmt.Println(red + "7." + reset + " Delete project")
	fmt.Println(yellow + "8." + reset + " Exit")
	fmt.Print("\n" + bold + "Choose: " + reset)
}

func selectProject(reader *bufio.Reader) string {
	projects := getProjects()

	fmt.Println("\n" + bold + cyan + "Available Projects:" + reset)
	if len(projects) == 0 {
		fmt.Println(yellow + "No projects found. Create a new one!" + reset)
	} else {
		for i, p := range projects {
			fmt.Printf("%s%d.%s %s\n", cyan, i+1, reset, p)
		}
	}

	fmt.Print("\n" + bold + "Enter project name (or number): " + reset)
	input, _ := reader.ReadString('\n')
	input = strings.TrimSpace(input)

	if input == "" {
		return "default"
	}

	// Check if input is a number
	if num, err := strconv.Atoi(input); err == nil && num > 0 && num <= len(projects) {
		return projects[num-1]
	}

	return input
}

func addTodo(list *TodoList, reader *bufio.Reader) {
	fmt.Print(bold + "Enter task: " + reset)
	task, _ := reader.ReadString('\n')
	task = strings.TrimSpace(task)

	if task == "" {
		fmt.Println(red + "Task cannot be empty" + reset)
		return
	}

	todo := Todo{
		ID:        list.NextID,
		Task:      task,
		Completed: false,
		CreatedAt: time.Now(),
	}

	list.Todos = append(list.Todos, todo)
	list.NextID++
	saveTodos(list, currentProject)
	fmt.Println(green + "✓ Todo added!" + reset)
}

func listTodos(list *TodoList) {
	if len(list.Todos) == 0 {
		fmt.Println(yellow + "\nNo todos yet! Add one to get started." + reset)
		return
	}

	completed := 0
	for _, todo := range list.Todos {
		if todo.Completed {
			completed++
		}
	}

	fmt.Printf("\n%s%sYour Todos%s (%d total, %d completed)\n", bold, cyan, reset, len(list.Todos), completed)
	fmt.Println(strings.Repeat("-", 50))

	for _, todo := range list.Todos {
		status := red + "[ ]" + reset
		taskColor := reset
		if todo.Completed {
			status = green + "[✓]" + reset
			taskColor = "\033[90m" // Gray
		}
		dateStr := todo.CreatedAt.Format("Jan 02")
		fmt.Printf("%s%d.%s %s %s%s%s %s(%s)%s\n",
			cyan, todo.ID, reset, status, taskColor, todo.Task, reset,
			yellow, dateStr, reset)
	}
}

func completeTodo(list *TodoList, reader *bufio.Reader) {
	listTodos(list)
	if len(list.Todos) == 0 {
		return
	}

	fmt.Print("\n" + bold + "Enter todo ID to complete: " + reset)
	input, _ := reader.ReadString('\n')
	id, err := strconv.Atoi(strings.TrimSpace(input))
	if err != nil {
		fmt.Println(red + "Invalid ID" + reset)
		return
	}

	for i := range list.Todos {
		if list.Todos[i].ID == id {
			list.Todos[i].Completed = true
			saveTodos(list, currentProject)
			fmt.Println(green + "✓ Todo completed!" + reset)
			return
		}
	}
	fmt.Println(red + "Todo not found" + reset)
}

func deleteTodo(list *TodoList, reader *bufio.Reader) {
	listTodos(list)
	if len(list.Todos) == 0 {
		return
	}

	fmt.Print("\n" + bold + "Enter todo ID to delete: " + reset)
	input, _ := reader.ReadString('\n')
	id, err := strconv.Atoi(strings.TrimSpace(input))
	if err != nil {
		fmt.Println(red + "Invalid ID" + reset)
		return
	}

	for i := range list.Todos {
		if list.Todos[i].ID == id {
			list.Todos = append(list.Todos[:i], list.Todos[i+1:]...)
			saveTodos(list, currentProject)
			fmt.Println(green + "✓ Todo deleted!" + reset)
			return
		}
	}
	fmt.Println(red + "Todo not found" + reset)
}

func listProjects() {
	projects := getProjects()
	fmt.Println("\n" + bold + cyan + "All Projects:" + reset)
	if len(projects) == 0 {
		fmt.Println(yellow + "No projects found" + reset)
		return
	}

	for _, p := range projects {
		if p == currentProject {
			fmt.Printf("%s→ %s%s (current)\n", green, p, reset)
		} else {
			fmt.Printf("  %s\n", p)
		}

		list := loadTodos(p)
		total := len(list.Todos)
		completed := 0
		for _, todo := range list.Todos {
			if todo.Completed {
				completed++
			}
		}
		fmt.Printf("    %s%d todos (%d completed)%s\n", yellow, total, completed, reset)
	}
}

func deleteProject(reader *bufio.Reader) {
	projects := getProjects()
	if len(projects) == 0 {
		fmt.Println(yellow + "No projects to delete" + reset)
		return
	}

	listProjects()
	fmt.Print("\n" + bold + red + "Enter project name to delete: " + reset)
	input, _ := reader.ReadString('\n')
	name := strings.TrimSpace(input)

	if name == "" {
		return
	}

	if name == currentProject {
		fmt.Println(red + "Cannot delete current project. Switch first." + reset)
		return
	}

	filename := filepath.Join(dataDir, name+".json")
	if err := os.Remove(filename); err != nil {
		fmt.Println(red + "Error deleting project" + reset)
		return
	}

	fmt.Println(green + "✓ Project deleted!" + reset)
}

func ensureDataDir() {
	if err := os.MkdirAll(dataDir, 0755); err != nil {
		fmt.Println(red + "Error creating data directory" + reset)
		os.Exit(1)
	}
}

func getProjects() []string {
	files, err := os.ReadDir(dataDir)
	if err != nil {
		return []string{}
	}

	var projects []string
	for _, file := range files {
		if !file.IsDir() && strings.HasSuffix(file.Name(), ".json") {
			projects = append(projects, strings.TrimSuffix(file.Name(), ".json"))
		}
	}
	return projects
}

func loadTodos(project string) TodoList {
	filename := filepath.Join(dataDir, project+".json")
	data, err := os.ReadFile(filename)
	if err != nil {
		return TodoList{Todos: []Todo{}, NextID: 1}
	}

	var list TodoList
	if err := json.Unmarshal(data, &list); err != nil {
		return TodoList{Todos: []Todo{}, NextID: 1}
	}
	return list
}

func saveTodos(list *TodoList, project string) {
	filename := filepath.Join(dataDir, project+".json")
	data, err := json.MarshalIndent(list, "", "  ")
	if err != nil {
		fmt.Println(red + "Error saving todos" + reset)
		return
	}

	if err := os.WriteFile(filename, data, 0644); err != nil {
		fmt.Println(red + "Error writing file" + reset)
	}
}