#!/usr/bin/env python3
"""
Task queue utility functions.

Provides:
    list_tasks_by_status   - List tasks by status
    list_pending_tasks     - List tasks with pending status
    list_tasks_by_assignee - List tasks by assignee
    list_my_tasks          - List tasks assigned to current developer
    get_task_stats         - Get P0/P1/P2/P3 counts
"""

from __future__ import annotations

import json
from pathlib import Path

from .paths import (
    FILE_TASK_JSON,
    get_repo_root,
    get_developer,
    get_tasks_dir,
)


def _read_json_file(path: Path) -> dict | None:
    """Read and parse a JSON file."""
    try:
        return json.loads(path.read_text(encoding="utf-8"))
    except (FileNotFoundError, json.JSONDecodeError, OSError):
        return None


# =============================================================================
# Public Functions
# =============================================================================

def list_tasks_by_status(
    filter_status: str | None = None,
    repo_root: Path | None = None
) -> list[dict]:
    """List tasks by status.

    Args:
        filter_status: Optional status filter.
        repo_root: Repository root path. Defaults to auto-detected.

    Returns:
        List of task info dicts with keys: priority, id, title, status, assignee.
    """
    if repo_root is None:
        repo_root = get_repo_root()

    tasks_dir = get_tasks_dir(repo_root)
    results = []

    if not tasks_dir.is_dir():
        return results

    for d in tasks_dir.iterdir():
        if not d.is_dir() or d.name == "archive":
            continue

        task_json = d / FILE_TASK_JSON
        if not task_json.is_file():
            continue

        data = _read_json_file(task_json)
        if not data:
            continue

        task_id = data.get("id", "")
        title = data.get("title") or data.get("name", "")
        priority = data.get("priority", "P2")
        status = data.get("status", "planning")
        assignee = data.get("assignee", "-")

        # Apply filter
        if filter_status and status != filter_status:
            continue

        results.append({
            "priority": priority,
            "id": task_id,
            "title": title,
            "status": status,
            "assignee": assignee,
            "dir": d.name,
            "children": data.get("children", []),
            "parent": data.get("parent"),
        })

    return results


def list_pending_tasks(repo_root: Path | None = None) -> list[dict]:
    """List pending tasks.

    Args:
        repo_root: Repository root path. Defaults to auto-detected.

    Returns:
        List of task info dicts.
    """
    return list_tasks_by_status("planning", repo_root)


def list_tasks_by_assignee(
    assignee: str,
    filter_status: str | None = None,
    repo_root: Path | None = None
) -> list[dict]:
    """List tasks assigned to a specific developer.

    Args:
        assignee: Developer name.
        filter_status: Optional status filter.
        repo_root: Repository root path. Defaults to auto-detected.

    Returns:
        List of task info dicts.
    """
    if repo_root is None:
        repo_root = get_repo_root()

    tasks_dir = get_tasks_dir(repo_root)
    results = []

    if not tasks_dir.is_dir():
        return results

    for d in tasks_dir.iterdir():
        if not d.is_dir() or d.name == "archive":
            continue

        task_json = d / FILE_TASK_JSON
        if not task_json.is_file():
            continue

        data = _read_json_file(task_json)
        if not data:
            continue

        task_assignee = data.get("assignee", "-")

        # Apply assignee filter
        if task_assignee != assignee:
            continue

        task_id = data.get("id", "")
        title = data.get("title") or data.get("name", "")
        priority = data.get("priority", "P2")
        status = data.get("status", "planning")

        # Apply status filter
        if filter_status and status != filter_status:
            continue

        results.append({
            "priority": priority,
            "id": task_id,
            "title": title,
            "status": status,
            "assignee": task_assignee,
            "dir": d.name,
            "children": data.get("children", []),
            "parent": data.get("parent"),
        })

    return results


def list_my_tasks(
    filter_status: str | None = None,
    repo_root: Path | None = None
) -> list[dict]:
    """List tasks assigned to current developer.

    Args:
        filter_status: Optional status filter.
        repo_root: Repository root path. Defaults to auto-detected.

    Returns:
        List of task info dicts.

    Raises:
        ValueError: If developer not set.
    """
    if repo_root is None:
        repo_root = get_repo_root()

    developer = get_developer(repo_root)
    if not developer:
        raise ValueError("Developer not set")

    return list_tasks_by_assignee(developer, filter_status, repo_root)


def get_task_stats(repo_root: Path | None = None) -> dict[str, int]:
    """Get task statistics.

    Args:
        repo_root: Repository root path. Defaults to auto-detected.

    Returns:
        Dict with keys: P0, P1, P2, P3, Total.
    """
    if repo_root is None:
        repo_root = get_repo_root()

    tasks_dir = get_tasks_dir(repo_root)
    stats = {"P0": 0, "P1": 0, "P2": 0, "P3": 0, "Total": 0}

    if not tasks_dir.is_dir():
        return stats

    for d in tasks_dir.iterdir():
        if not d.is_dir() or d.name == "archive":
            continue

        task_json = d / FILE_TASK_JSON
        if not task_json.is_file():
            continue

        data = _read_json_file(task_json)
        if not data:
            continue

        priority = data.get("priority", "P2")
        if priority in stats:
            stats[priority] += 1
        stats["Total"] += 1

    return stats


def format_task_stats(stats: dict[str, int]) -> str:
    """Format task stats as string.

    Args:
        stats: Stats dict from get_task_stats.

    Returns:
        Formatted string like "P0:0 P1:1 P2:2 P3:0 Total:3".
    """
    return f"P0:{stats['P0']} P1:{stats['P1']} P2:{stats['P2']} P3:{stats['P3']} Total:{stats['Total']}"


# =============================================================================
# Main Entry (for testing)
# =============================================================================

if __name__ == "__main__":
    stats = get_task_stats()
    print(format_task_stats(stats))
    print()
    print("Pending tasks:")
    for task in list_pending_tasks():
        print(f"  {task['priority']}|{task['id']}|{task['title']}|{task['status']}|{task['assignee']}")