import logging
import os
from flask import Flask, redirect, url_for
from flask_migrate import Migrate
from zoneinfo import ZoneInfo

from app.config import DevelopmentConfig, ProductionConfig
from app.extensions import db, login_manager, scheduler
from app.services.scheduler import SchedulerService


def create_app() -> Flask:
    """
    Application factory creating the Flask app, loading config, registering blueprints,
    initializing extensions, and booting the scheduler.
    """
    app = Flask(__name__)

    config_name = os.getenv("FLASK_ENV", "development").lower()
    if config_name == "production":
        app_config = ProductionConfig()
    else:
        app_config = DevelopmentConfig()
    app.config.from_object(app_config)

    configure_logging(app)
    register_extensions(app)
    register_blueprints(app)
    register_template_filters(app)
    enable_scheduler = app.config.get("ENABLE_SCHEDULER", True) and os.getenv("FLASK_SKIP_SCHEDULER") != "1"
    if enable_scheduler:
        init_scheduler(app)
    else:
        app.logger.info("Scheduler not started (ENABLE_SCHEDULER=%s, FLASK_SKIP_SCHEDULER=%s)",
                        app.config.get("ENABLE_SCHEDULER", True), os.getenv("FLASK_SKIP_SCHEDULER"))

    @app.route("/")
    def index():
        return redirect(url_for("apis.list_apis"))

    return app


def configure_logging(app: Flask) -> None:
    log_level = logging.DEBUG if app.debug else logging.INFO
    logging.basicConfig(level=log_level, format="%(asctime)s [%(levelname)s] %(name)s: %(message)s")


def register_extensions(app: Flask) -> None:
    db.init_app(app)
    login_manager.init_app(app)
    Migrate(app, db)
    scheduler.init_app(app)


def register_blueprints(app: Flask) -> None:
    from app.views.auth import auth_bp
    from app.views.apis import apis_bp
    from app.views.logs import logs_bp

    app.register_blueprint(auth_bp)
    app.register_blueprint(apis_bp)
    app.register_blueprint(logs_bp)


def register_template_filters(app: Flask) -> None:
    @app.template_filter("cron_human")
    def cron_human(expr: str) -> str:
        """
        将常见的 5 字段 cron 表达式转换为简单中文描述，不能完全覆盖所有情况。
        """
        parts = expr.strip().split()
        if len(parts) != 5:
            return expr
        minute, hour, day, month, dow = parts

        # 每 N 分钟
        if minute.startswith("*/") and hour == "*" and day == "*" and month == "*" and dow == "*":
            return f"每 {minute[2:]} 分钟"

        # 整点或固定时间
        if minute.isdigit() and hour.isdigit() and day == "*" and month == "*" and dow in ("*", "?"):
            return f"每天 {hour.zfill(2)}:{minute.zfill(2)}"

        # 每 N 小时的整点
        if minute == "0" and hour.startswith("*/") and day == "*" and month == "*" and dow in ("*", "?"):
            return f"每 {hour[2:]} 小时整点"

        # 每月某日
        if minute.isdigit() and hour.isdigit() and day.isdigit() and month == "*" and dow in ("*", "?"):
            return f"每月 {day} 日 {hour.zfill(2)}:{minute.zfill(2)}"

        # 每周某天
        weekday_map = {"0": "周日", "1": "周一", "2": "周二", "3": "周三", "4": "周四", "5": "周五", "6": "周六", "7": "周日"}
        if minute.isdigit() and hour.isdigit() and day in ("*", "?") and month == "*" and dow not in ("*", "?"):
            label = weekday_map.get(dow, f"周{dow}")
            return f"每{label} {hour.zfill(2)}:{minute.zfill(2)}"

        return expr

    @app.template_filter("to_cst")
    def to_cst(dt, fmt: str = "%Y-%m-%d %H:%M:%S"):
        """
        将 UTC 时间转换为中国标准时间字符串，如果值为空则返回空字符串。
        """
        if not dt:
            return ""
        try:
            tz = ZoneInfo(app.config.get("SCHEDULER_TIMEZONE", "Asia/Shanghai"))
            # 如果是 naive datetime，认为是 UTC
            if dt.tzinfo is None:
                dt = dt.replace(tzinfo=ZoneInfo("UTC"))
            return dt.astimezone(tz).strftime(fmt)
        except Exception:
            return str(dt)


def init_scheduler(app: Flask) -> None:
    """
    Start APScheduler and load enabled jobs from database.
    """
    scheduler.start()
    with app.app_context():
        service = SchedulerService(scheduler)
        service.load_enabled_jobs()