#!/usr/bin/env python3
"""Tasked — terminal todo list manager."""
import argparse, json, sys, os
from datetime import datetime, date
from pathlib import Path


def color(text, code):
    return f"\033[{code}m{text}\033[0m" if sys.stdout.isatty() else text


DATA_FILE = Path.home() / ".tasked.json"


def load_tasks():
    if DATA_FILE.exists():
        try:
            return json.loads(DATA_FILE.read_text())
        except json.JSONDecodeError:
            return []
    return []


def save_tasks(tasks):
    DATA_FILE.write_text(json.dumps(tasks, indent=2, default=str))


def next_id(tasks):
    return max([t.get("id", 0) for t in tasks], default=0) + 1


PRIORITY_COLORS = {
    "high": "31",
    "medium": "33",
    "low": "32",
}


def format_task(t, show_id=True):
    prefix = f"[{t['id']}] " if show_id else ""
    status = color("✓", "32") if t.get("done") else color("○", "31")
    pri = color(t.get("priority", "medium").upper()[:4],
                PRIORITY_COLORS.get(t.get("priority", "medium"), "37"))
    
    due = ""
    if t.get("due"):
        try:
            d = datetime.fromisoformat(t["due"]).date()
            delta = (d - date.today()).days
            if delta < 0:
                due = color(f" (OVERDUE {abs(delta)}d)", "31;1")
            elif delta == 0:
                due = color(" (DUE TODAY)", "33;1")
            elif delta == 1:
                due = color(" (due tomorrow)", "33")
            else:
                due = color(f" (due in {delta}d)", "90")
        except:
            due = f" ({t['due']})"
    
    cats = ""
    if t.get("categories"):
        cats = " " + " ".join(color(f"[{c}]", "36") for c in t["categories"])
    
    return f"  {status} {pri} {t['title']}{cats}{due}"


def cmd_add(args):
    tasks = load_tasks()
    task = {
        "id": next_id(tasks),
        "title": " ".join(args.title),
        "done": False,
        "priority": args.priority or "medium",
        "categories": args.category or [],
        "created": datetime.now().isoformat(),
        "due": None,
    }
    if args.due:
        task["due"] = args.due
    tasks.append(task)
    save_tasks(tasks)
    print(f"  {color('✓', '32')} Added task #{task['id']}: {task['title']}")


def cmd_list(args):
    tasks = load_tasks()
    if not tasks:
        print(f"  {color('No tasks found', '90')}")
        return
    
    # Filter
    if args.category:
        tasks = [t for t in tasks if args.category in t.get("categories", [])]
    if args.priority:
        tasks = [t for t in tasks if t.get("priority") == args.priority]
    
    # Separate done/not done
    pending = [t for t in tasks if not t.get("done")]
    completed = [t for t in tasks if t.get("done")]
    
    if args.all:
        show = tasks
    elif args.completed:
        show = completed
    else:
        show = pending
    
    if not show:
        print(f"  {color('No matching tasks', '90')}")
        return
    
    print(f"\n  {color('Tasks:', '1')} ({len(pending)} pending, {len(completed)} done)")
    print(f"  {color('─' * 40, '90')}")
    
    for t in show:
        print(format_task(t))
    
    print()


def cmd_done(args):
    tasks = load_tasks()
    found = False
    for t in tasks:
        if t["id"] == args.id:
            t["done"] = True
            t["completed_at"] = datetime.now().isoformat()
            found = True
            print(f"  {color('✓', '32')} Task #{args.id} completed!")
            break
    if not found:
        print(f"  {color('✗', '31')} Task #{args.id} not found")
    save_tasks(tasks)


def cmd_delete(args):
    tasks = load_tasks()
    before = len(tasks)
    tasks = [t for t in tasks if t["id"] != args.id]
    if len(tasks) < before:
        print(f"  {color('✓', '32')} Deleted task #{args.id}")
    else:
        print(f"  {color('✗', '31')} Task #{args.id} not found")
    save_tasks(tasks)


def cmd_clear(args):
    tasks = load_tasks()
    before = len(tasks)
    if args.done:
        tasks = [t for t in tasks if not t.get("done")]
        print(f"  {color('✓', '32')} Cleared {before - len(tasks)} completed tasks")
    else:
        tasks = []
        print(f"  {color('✓', '32')} Cleared all {before} tasks")
    save_tasks(tasks)


def cmd_stats(args):
    tasks = load_tasks()
    total = len(tasks)
    done = sum(1 for t in tasks if t.get("done"))
    pending = total - done
    
    categories = {}
    for t in tasks:
        for c in t.get("categories", []):
            categories[c] = categories.get(c, 0) + 1
    
    print(f"\n  {color('Task Statistics', '1')}")
    print(f"  {color('─' * 30, '90')}")
    print(f"  Total:     {total}")
    print(f"  Pending:   {color(str(pending), '33')}")
    print(f"  Completed: {color(str(done), '32')}")
    if categories:
        print(f"\n  {color('Categories:', '36')}")
        for c, count in sorted(categories.items()):
            print(f"    {c}: {count}")
    print()


def main():
    parser = argparse.ArgumentParser(
        description="Tasked — terminal todo list manager",
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog=(
            "Examples:\n"
            "  tasked add 'Fix login bug' -p high -c bug\n"
            "  tasked list\n"
            "  tasked list --category bug\n"
            "  tasked done 1\n"
            "  tasked delete 1\n"
            "  tasked clear --done\n"
            "  tasked stats\n"
        ),
    )
    parser.add_argument("--version", action="version",
                        version="tasked 1.0.0")

    sub = parser.add_subparsers(dest="command", required=True)

    a = sub.add_parser("add", help="Add a new task")
    a.add_argument("title", nargs="+", help="Task title")
    a.add_argument("-p", "--priority", choices=["high", "medium", "low"],
                   default="medium", help="Priority level")
    a.add_argument("-c", "--category", action="append",
                   help="Category tag (can be used multiple times)")
    a.add_argument("--due", help="Due date (YYYY-MM-DD)")

    l = sub.add_parser("list", help="List tasks")
    l.add_argument("--category", help="Filter by category")
    l.add_argument("--priority", choices=["high", "medium", "low"],
                   help="Filter by priority")
    l.add_argument("--all", action="store_true", help="Show all tasks")
    l.add_argument("--completed", action="store_true",
                   help="Show only completed")

    d = sub.add_parser("done", help="Mark task as complete")
    d.add_argument("id", type=int, help="Task ID")

    rm = sub.add_parser("delete", help="Delete a task")
    rm.add_argument("id", type=int, help="Task ID")

    c = sub.add_parser("clear", help="Clear tasks")
    c.add_argument("--done", action="store_true",
                   help="Clear only completed tasks")

    s = sub.add_parser("stats", help="Show task statistics")

    args = parser.parse_args()

    if args.command == "add":
        cmd_add(args)
    elif args.command == "list":
        cmd_list(args)
    elif args.command == "done":
        cmd_done(args)
    elif args.command == "delete":
        cmd_delete(args)
    elif args.command == "clear":
        cmd_clear(args)
    elif args.command == "stats":
        cmd_stats(args)


if __name__ == "__main__":
    main()