#!/usr/bin/env python3
"""Tiny CLI todo tracker. Data lives in ~/.todo.json."""

import argparse
import json
import os
from datetime import datetime, timezone

DEFAULT_PATH = os.path.expanduser("~/.todo.json")


def load(path=DEFAULT_PATH):
    if not os.path.exists(path):
        return []
    with open(path, "r", encoding="utf-8") as f:
        return json.load(f)


def save(items, path=DEFAULT_PATH):
    with open(path, "w", encoding="utf-8") as f:
        json.dump(items, f, indent=2)


def cmd_add(args):
    items = load()
    entry = {
        "id": max((i.get("id", 0) for i in items), default=0) + 1,
        "task": args.task,
        "done": False,
        "created": datetime.now(timezone.utc).isoformat(),
    }
    items.append(entry)
    save(items)
    print(f"added {entry['id']}: {args.task}")


def cmd_list(args):
    items = load()
    if args.done_only:
        items = [i for i in items if i.get("done")]
    elif not args.all:
        items = [i for i in items if not i.get("done")]
    for i in items:
        status = "x" if i.get("done") else " "
        print(f"[{status}] {i['id']}: {i['task']}")
    if not items:
        print("(none)")


def cmd_done(args):
    items = load()
    for i in items:
        if i.get("id") == args.id:
            i["done"] = True
            i["finished"] = datetime.now(timezone.utc).isoformat()
            save(items)
            print(f"done {i['id']}")
            return
    print(f"id {args.id} not found", flush=True)
    raise SystemExit(2)


def main():
    p = argparse.ArgumentParser(description="Tiny todo CLI")
    sub = p.add_subparsers(dest="cmd")
    a = sub.add_parser("add")
    a.add_argument("task", help="task text")
    sub.add_parser("list", help="show todos")
    sub.add_parser("all", help="show all including done")
    d = sub.add_parser("done", help="show done only or mark todo done by id")
    d.add_argument("id", type=int, nargs="?", help="todo id to mark done")
    args = p.parse_args()
    if args.cmd == "add":
        cmd_add(args)
    elif args.cmd == "list":
        cmd_list(args)
    elif args.cmd == "all":
        cmd_list(args)
    elif args.cmd == "done":
        if args.id is not None:
            cmd_done(args)
        else:
            args.done_only = True
            cmd_list(args)
    else:
        p.print_help()
        raise SystemExit(1)


if __name__ == "__main__":
    main()