from __future__ import annotations

import os
import secrets
from datetime import timedelta
from pathlib import Path

from dotenv import dotenv_values

BASE_DIR = Path(__file__).resolve().parent.parent
DATA_DIR = BASE_DIR / "data"
STATIC_DIR = BASE_DIR / "static"
UPLOAD_DIR = BASE_DIR / "uploads"
IMAGE_DIR = STATIC_DIR / "images"


def load_local_environment() -> None:
    """加载本地配置，优先级为系统环境变量 > .env.local > .env。"""
    values = dotenv_values(BASE_DIR / ".env")
    overrides = dotenv_values(BASE_DIR / ".env.local")
    # .env.local 中的空值表示“沿用 .env”，避免本机模板清空密钥。
    values.update({key: value for key, value in overrides.items() if value})
    for key, value in values.items():
        if value:
            os.environ.setdefault(key, value)


load_local_environment()


def env_int(name: str, default: int) -> int:
    try:
        return int(os.environ.get(name, str(default)))
    except ValueError:
        return default


def env_bool(name: str, default: bool = False) -> bool:
    value = os.environ.get(name)
    if value is None:
        return default
    return value.strip().lower() in {"1", "true", "yes", "on"}


def app_env() -> str:
    return os.environ.get("APP_ENV", "development").strip().lower() or "development"


def database_url() -> str:
    """返回数据库地址，并将相对 SQLite 路径固定到项目目录。"""
    value = os.environ.get("DATABASE_URL", "").strip()
    if not value:
        return f"sqlite:///{DATA_DIR / 'pipe_survival_0331.db'}"
    prefix = "sqlite:///"
    if value.startswith(prefix) and not value.startswith("sqlite:////"):
        return f"sqlite:///{BASE_DIR / value.removeprefix(prefix)}"
    return value


class Config:
    APP_ENV = app_env()
    DEBUG = env_bool("DEBUG", APP_ENV in {"dev", "development", "local"})
    SECRET_KEY = os.environ.get("SECRET_KEY") or secrets.token_hex(32)
    SECRET_KEY_GENERATED = not bool(os.environ.get("SECRET_KEY"))
    SQLALCHEMY_DATABASE_URI = database_url()
    SQLALCHEMY_TRACK_MODIFICATIONS = False
    MAX_CONTENT_LENGTH = env_int("MAX_UPLOAD_BYTES", 16 * 1024 * 1024)
    SESSION_COOKIE_HTTPONLY = True
    SESSION_COOKIE_SAMESITE = "Lax"
    SESSION_COOKIE_SECURE = env_bool("SESSION_COOKIE_SECURE", APP_ENV == "production")
    # 仅在用户主动勾选“保持登录状态”时使用。
    REMEMBER_COOKIE_DURATION = timedelta(days=7)
    REMEMBER_COOKIE_HTTPONLY = True
    REMEMBER_COOKIE_SECURE = SESSION_COOKIE_SECURE
    REMEMBER_COOKIE_SAMESITE = "Lax"
    FUSION_MODEL_CORE_DIR = os.environ.get(
        "FUSION_MODEL_CORE_DIR",
        str(BASE_DIR / "model_core"),
    )
    ALLOW_REGISTRATION = env_bool("ALLOW_REGISTRATION", False)
    ADMIN_USERNAME = os.environ.get("ADMIN_USERNAME", "admin").strip() or "admin"
    ADMIN_PASSWORD = os.environ.get("ADMIN_PASSWORD")
    ADMIN_EMAIL = os.environ.get("ADMIN_EMAIL", "").strip().lower()
    APP_TIMEZONE = os.environ.get("APP_TIMEZONE", "Asia/Shanghai").strip() or "Asia/Shanghai"
    PASSWORD_RESET_TOKEN_MINUTES = env_int("PASSWORD_RESET_TOKEN_MINUTES", 30)
    RESEND_API_KEY = os.environ.get("RESEND_API_KEY", "").strip()
    RESEND_FROM_EMAIL = os.environ.get("RESEND_FROM_EMAIL", "").strip()
    EMAIL_CODE_MINUTES = env_int("EMAIL_CODE_MINUTES", 10)
    EMAIL_CODE_RESEND_SECONDS = env_int("EMAIL_CODE_RESEND_SECONDS", 60)
    EMAIL_CODE_MAX_ATTEMPTS = env_int("EMAIL_CODE_MAX_ATTEMPTS", 5)
    # 邮箱验证码通过后，可用于高风险操作的短时授权。
    FRESH_AUTH_MINUTES = env_int("FRESH_AUTH_MINUTES", 5)
    TRUSTED_DEVICE_DAYS = env_int("TRUSTED_DEVICE_DAYS", 30)


def ensure_dirs() -> None:
    for path in (DATA_DIR, STATIC_DIR, IMAGE_DIR, UPLOAD_DIR):
        path.mkdir(parents=True, exist_ok=True)