// tasks is a tiny to-do list for the terminal.
//
//	tasks add Buy milk     add a task
//	tasks                  list open tasks
//	tasks done 2           mark task 2 as done
//	tasks all              list every task, including done ones
//	tasks clear            remove done tasks
package main

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

type task struct {
	Text    string    `json:"text"`
	Done    bool      `json:"done"`
	Created time.Time `json:"created"`
}

func file() string {
	home, err := os.UserHomeDir()
	if err != nil {
		home = "."
	}
	return filepath.Join(home, ".tasks.json")
}

func load() []task {
	var ts []task
	if b, err := os.ReadFile(file()); err == nil {
		json.Unmarshal(b, &ts)
	}
	return ts
}

func save(ts []task) {
	b, _ := json.MarshalIndent(ts, "", "  ")
	if err := os.WriteFile(file(), b, 0o644); err != nil {
		fmt.Fprintln(os.Stderr, "couldn't save tasks:", err)
		os.Exit(1)
	}
}

func list(ts []task, all bool) {
	shown := 0
	for i, t := range ts {
		if t.Done && !all {
			continue
		}
		box := "[ ]"
		if t.Done {
			box = "[x]"
		}
		fmt.Printf("%3d. %s %s\n", i+1, box, t.Text)
		shown++
	}
	if shown == 0 {
		fmt.Println("Nothing to do. Add a task with: tasks add <what to do>")
	}
}

func main() {
	ts := load()
	args := os.Args[1:]
	if len(args) == 0 {
		list(ts, false)
		return
	}
	switch args[0] {
	case "add":
		text := strings.TrimSpace(strings.Join(args[1:], " "))
		if text == "" {
			fmt.Println("What should the task say? Example: tasks add Call mom")
			os.Exit(1)
		}
		ts = append(ts, task{Text: text, Created: time.Now()})
		save(ts)
		fmt.Printf("Added task %d: %s\n", len(ts), text)
	case "done":
		if len(args) < 2 {
			fmt.Println("Which task? Example: tasks done 2")
			os.Exit(1)
		}
		n, err := strconv.Atoi(args[1])
		if err != nil || n < 1 || n > len(ts) {
			fmt.Println("There's no task with that number.")
			os.Exit(1)
		}
		ts[n-1].Done = true
		save(ts)
		fmt.Printf("Nice! Finished: %s\n", ts[n-1].Text)
	case "all":
		list(ts, true)
	case "clear":
		var open []task
		for _, t := range ts {
			if !t.Done {
				open = append(open, t)
			}
		}
		save(open)
		fmt.Printf("Removed %d finished task(s).\n", len(ts)-len(open))
	case "help", "-h", "--help":
		fmt.Println("Usage: tasks [add <text> | done <number> | all | clear]")
	default:
		fmt.Println("Unknown command. Try: tasks help")
		os.Exit(1)
	}
}