from functools import lru_cache
from pathlib import Path

from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    """Application settings sourced from environment / .env file."""

    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        extra="ignore",
    )

    yunke_base_url: str = "https://crm2.yunkecn.com"
    yunke_username: str = ""
    yunke_password: str = ""
    db_url: str = "mysql+asyncmy://user:pass@localhost:3306/yunke"
    redis_url: str = "redis://localhost:6379/0"
    media_dir: Path = Path("./media")
    # Fernet key for encrypting stored credentials. Required for real runs;
    # empty default lets tests construct Settings without a key.
    encryption_key: str = ""

    # Existing-session creds (optional; bypasses programmatic login — e.g. for
    # validation with a live browser session). Read from .env / environment.
    yk_userid: str = ""
    yk_company: str = ""
    yk_cookie: str = ""
    # Shared bearer token for the viewing API. Empty (default) -> auth DISABLED
    # (we trust the network boundary; this is a local/intranet tool). When set,
    # every API request must present this value via ``Authorization: Bearer
    # <token>`` or ``?token=<token>``. See app/api/auth.py.
    api_token: str = ""

    # Username/password for the SPA login page (``POST /api/auth/login``).
    # On success the login hands out the ``api_token`` above so the SPA can
    # act as a Bearer client; defaults keep local dev zero-config. Change both
    # in prod via ADMIN_USER / ADMIN_PASSWORD.
    admin_user: str = "admin"
    admin_password: str = "admin123"

    # Comma-separated list of allowed CORS origins for the viewing API. Empty
    # (default) -> only the dev fallback (``http://localhost:5173``) is allowed;
    # set ``CORS_ORIGINS=https://app.example.com`` in prod to lock cross-origin
    # access down to explicit origins. Never ``*`` (wildcard + credentialed APIs
    # are an open door; we accept no credentials but still restrict origins to
    # avoid reflecting arbitrary attacker-controlled origins in ``Acces-Control-
    # Allow-Origin``).
    cors_origins: str = ""

    # --- Anti-risk-control / stealth tuning ---------------------------------
    # Tuned 2026-08-11 after triggering 风控 during a heavy session (~500+
    # consecutive requests across groups/WA/voice-clips/SMS in ~1 hour).
    # The previous defaults (1.0s + 0.8s jitter = ~1.0..1.8s cadence) were
    # fast enough to trigger 云客's volume-based risk control when many
    # entities are synced back-to-back. New strategy: slower base cadence +
    # larger jitter (human-like irregularity) + hard per-run cap + longer
    # backoff with more retries (patience over aggression).
    # See app.session.yunke_client for the implementation.

    # Lower bound on seconds between successive upstream requests.
    # 2.0s base — roughly mimics a human clicking through pages (not a bot
    # hammering at 1 req/s). Combined with jitter this gives ~2.0..4.5s cadence.
    request_min_interval: float = 2.0
    # Random extra 0..jitter seconds. Large jitter (2.5s) ensures the cadence
    # is highly irregular — no periodic signature for 云客 to fingerprint.
    request_jitter: float = 2.5
    # Hard cap: 300 requests per run (~10 minutes at 2s avg). Prevents a
    # runaway sync from hammering 云客 for hours. 0 = unlimited (only for
    # manual debugging). A daily `sync --entity all` will likely need multiple
    # runs (or increase this cap) — by design, to stay under 风控 radar.
    max_requests_per_run: int = 300
    # Exponential backoff: start at 5s, double each retry, cap at 120s.
    # More patient than the old 2s/60s/4 — gives 云客 time to cool down.
    risk_backoff_base: float = 5.0
    risk_backoff_max: float = 120.0
    # 6 retries (was 4) — more chances to recover before giving up.
    # Total worst-case backoff: 5+10+20+40+80+120 = 275s (~4.6 min) before
    # the final attempt; generous recovery window.
    risk_backoff_attempts: int = 6


@lru_cache
def get_settings() -> Settings:
    """Return the process-wide Settings singleton."""
    return Settings()