#!/usr/bin/env python3
import os
import re
import sys

base_dir = os.path.abspath(os.path.dirname(__file__))
todo_file = os.path.join(base_dir, "todo.md")


def add_task(task: str, parent=None):
    print(f"Adding task '{task}' to '{parent if parent else 'root'}'")
    todo = parse_todo()
    if parent and parent not in todo:
        print(f"Could not find parent task '{parent}' in root task list")
        exit(1)
    if parent:
        todo[parent]["sub_tasks"][task] = {"completed": False}
    else:
        todo[task] = {"completed": False, "sub_tasks": {}}
    write_todo(todo)


def list_tasks(parent=None):
    print(f"Listing tasks in '{parent if parent else 'root'}'")
    todo = parse_todo()
    if parent and parent not in todo:
        print(f"Could not find parent task '{parent}' in root task list")
        exit(1)
    if parent:
        todo = {parent: todo[parent]}
    print(build_todo(todo))


def complete_task(task, parent=None):
    print(f"Marking task '{task}' in '{parent if parent else 'root'}' as completed")
    todo = parse_todo()
    if parent:
        if parent not in todo:
            print(f"Could not find parent task '{parent}' in root task list")
            exit(1)
        if task not in todo[parent]["sub_tasks"]:
            print(f"Could not find task '{task}' in parent task '{parent}'")
            exit(1)
    if task not in todo:
        print(f"Could not find task '{task}' in root task list")
        exit(1)
    if parent:
        task = todo[parent]["sub_tasks"][task]
    else:
        task = todo[task]
    task["completed"] = True
    write_todo(todo)


def remove_task(task, parent=None):
    print(f"Removing task '{task}' from '{parent if parent else 'root'}'")
    todo = parse_todo()
    if parent:
        if parent not in todo:
            print(f"Could not find parent task '{parent}' in root task list")
            exit(1)
        if task not in todo[parent]["sub_tasks"]:
            print(f"Could not find task '{task}' in parent task '{parent}'")
            exit(1)
    if task not in todo:
        print(f"Could not find task '{task}' in root task list")
        exit(1)
    if parent:
        del todo[parent]["sub_tasks"][task]
    else:
        del todo[task]
    write_todo(todo)


def print_help():
    print("""Usage: todo.py [add|complete|remove] TASK [PARENT]
       todo.py list PARENT

    Manages todo.md file as a ToDo file""")


def parse_todo() -> dict[str, dict]:
    todo = {}
    with open(todo_file, "r") as f:
        lines = f.readlines()
        root_task = None
        for line in lines:
            if matches := re.match(r"^-\s+(\[(?P<status>[x ])]\s+)?(?P<task>.*)$", line.rstrip()):
                root_task_name = matches.group("task")
                root_task = {
                    "completed": matches.group("status") == "x",
                    "sub_tasks": {},
                }
                todo[root_task_name] = root_task
            elif matches := re.match(r"^\s+-\s+(\[(?P<status>[x ])]\s+)?(?P<task>.*)$", line.rstrip()):
                leaf_task = matches.group("task")
                root_task["sub_tasks"][leaf_task] = {
                    "completed": matches.group("status") == "x",
                }
    return todo


def build_todo(todo: dict[str, dict]) -> str:
    lines = ["# A ToDo list", ""]
    for task, task_data in todo.items():  # type: str, dict
        lines.append(f"- [{'x' if task_data["completed"] else ' '}] {task}")
        for leaf_task, leaf_task_data in task_data["sub_tasks"].items():
            lines.append(f"  - [{'x' if leaf_task_data["completed"] else ' '}] {leaf_task}")
    lines += [""]
    return "\n".join(lines)


def write_todo(todo: dict[str, dict]):
    with open(todo_file, "w") as f:
        f.write(build_todo(todo))


def main():
    if len(sys.argv) < 2:
        print_help()
        exit(1)

    match sys.argv[1]:
        case "help" | "--help" | "h" | "-h":
            print_help()
        case "list":
            match sys.argv[2:]:
                case [parent]:
                    list_tasks(parent)
                case _:
                    list_tasks()
        case "add" | "complete" | "remove" as task_name:
            task_func = f"{task_name}_task"
            match sys.argv[2:]:
                case [task]:
                    globals()[task_func](task)
                case [task, parent]:
                    globals()[task_func](task, parent)
                case _:
                    print_help()
                    exit(1)
        case _:
            print_help()
            exit(1)


if __name__ == "__main__":
    main()