"""Central configuration (environment variables with the ``QUANTCORE_`` prefix, or a ``.env`` file).

Every service receives a :class:`Settings` instance -- nothing reads the environment on its own,
which keeps the services testable (tests pass a ``Settings(data_dir=tmp_path)``).
"""

from __future__ import annotations

import logging
from functools import lru_cache
from pathlib import Path

from pydantic import Field
from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    """Runtime settings of the quant core."""

    model_config = SettingsConfigDict(env_prefix="QUANTCORE_", env_file=".env", extra="ignore")

    # --- storage ---------------------------------------------------------------------------
    data_dir: Path = Field(default=Path("data"), description="Root of all persisted data.")

    # --- universe --------------------------------------------------------------------------
    n_us: int = Field(default=500, description="Largest N US stocks (S&P 500 candidates).")
    n_europe: int = Field(default=500, description="Largest N European stocks (STOXX 600 candidates).")
    history_start: str = Field(default="2004-12-01", description="First date requested from Yahoo.")
    required_history_from: str = Field(
        default="2005-01-31",
        description="A stock is kept only if it has a price on or before this date ('data since 2005').",
    )
    min_price_coverage: float = Field(
        default=0.90, description="Minimum share of union-calendar days with a price since the first date."
    )
    max_missing_run: int = Field(
        default=20, description="Longest tolerated gap (business days) in a price series since the required date."
    )

    # --- market conventions ----------------------------------------------------------------
    base_currency: str = Field(default="CHF", description="Portfolio / reporting currency.")
    home_market: str = Field(default="Switzerland", description="Home market of the investor.")
    risk_free_rate: float = Field(default=0.0, description="Annual risk-free rate in the base currency.")
    trading_days_per_year: int = 252
    weeks_per_year: int = 52

    # --- Yahoo access ----------------------------------------------------------------------
    yahoo_batch_size: int = Field(default=100, description="Tickers per bulk download request.")
    yahoo_timeout: float = Field(default=30.0, description="Seconds per HTTP request.")
    yahoo_max_retries: int = 4
    yahoo_backoff: float = Field(default=2.0, description="Base of the exponential back-off (seconds).")
    yahoo_info_pause: float = Field(default=0.15, description="Pause between ticker-info requests (s).")

    # --- cuOpt -----------------------------------------------------------------------------
    cuopt_url: str = Field(
        default="http://127.0.0.1:5000",
        description="cuOpt REST endpoint. The default is a cuOpt container on the same machine (the "
                    "standalone DGX Spark setup, deploy/apptainer/); point it elsewhere for a remote one.")
    cuopt_time_limit: float = Field(default=120.0, description="MILP time limit in seconds.")
    cuopt_poll_interval: float = 1.0
    cuopt_timeout: float = Field(default=900.0, description="Max seconds to wait for a solution.")
    cuopt_request_timeout: float = Field(default=60.0, description="Seconds per HTTP call to cuOpt.")
    cuopt_upload_seconds_per_mb: float = Field(
        default=1.0, description="Added to the submit timeout per MB of request body. cuOpt accepts about "
                                 "10 MB/s, so this is a 10x margin; a client-side timeout during the upload "
                                 "would otherwise surface as an aborted job.")
    solver_fallback: bool = Field(
        default=True, description="Fall back to the local HiGHS MILP solver (scipy) when cuOpt is unreachable."
    )
    cuopt_threads: int | None = Field(default=None, description="CPU threads of the cuOpt MIP solver (None: server default).")
    cuopt_msgpack: bool = Field(default=True, description="Send cuOpt requests as msgpack when the package is available.")

    # --- MILP tolerances (reproducibility) ---------------------------------------------------
    mip_rel_gap: float = Field(default=1e-4, description="Relative MIP gap for HiGHS and cuOpt.")
    mip_abs_gap: float = Field(default=0.01, description="Absolute MIP gap in money units (cuOpt).")

    # --- misc ------------------------------------------------------------------------------
    log_level: str = "INFO"
    api_host: str = Field(
        default="127.0.0.1",
        description="Interface `quantcore serve` binds to: localhost only by default; the Docker images "
                    "pass 0.0.0.0 to publish the port.")
    api_port: int = 5001
    enable_ui: bool = Field(
        default=True,
        description="Serve the static test bench at /ui/ (and redirect / to it). Set false for a "
                    "deployment that only exposes the JSON API and /docs -- the same image then "
                    "serves a front end built by someone else.",
    )

    # derived paths -------------------------------------------------------------------------
    @property
    def universe_dir(self) -> Path:
        return self.data_dir / "universe"

    @property
    def prices_dir(self) -> Path:
        return self.data_dir / "prices"

    @property
    def fx_dir(self) -> Path:
        return self.data_dir / "fx"

    @property
    def snapshots_dir(self) -> Path:
        return self.data_dir / "snapshots"

    @property
    def jobs_dir(self) -> Path:
        return self.data_dir / "jobs"

    def ensure_dirs(self) -> None:
        for d in (self.universe_dir, self.prices_dir, self.fx_dir, self.snapshots_dir, self.jobs_dir):
            d.mkdir(parents=True, exist_ok=True)


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    """Process-wide settings (cached). Tests construct :class:`Settings` directly instead."""
    settings = Settings()
    logging.basicConfig(
        level=getattr(logging, settings.log_level.upper(), logging.INFO),
        format="%(asctime)s %(levelname)s %(name)s: %(message)s",
    )
    return settings