"""Runtime configuration for the img2threejs Space.

All values come from environment variables. On Hugging Face Spaces the
``LLM_*`` variables are meant to be set as *Space Secrets* (Settings ->
Secrets); they are injected into the process environment at runtime.

The conventional ``ANTHROPIC_API_KEY`` / ``ANTHROPIC_BASE_URL`` /
``ANTHROPIC_MODEL`` names are honoured as fallbacks so the Space also works
when a deployer only sets those.

Nothing in this module may ever log or return the API key value.
"""

from __future__ import annotations

import math
import os
from dataclasses import dataclass, field


def _first(*names: str) -> str | None:
    for name in names:
        value = os.environ.get(name)
        if value and value.strip():
            return value.strip()
    return None


def _int(
    name: str,
    default: int,
    *,
    minimum: int | None = None,
    maximum: int | None = None,
) -> int:
    """Read an integer setting without allowing malformed or extreme input.

    Environment variables are an operational boundary, not trusted Python
    values.  Falling back on parse failure keeps the app bootable; clamping
    keeps an accidental value such as ``MAX_CONCURRENT_JOBS=-1`` from
    disabling a guard or allocating an unreasonable amount of work.
    """
    raw = os.environ.get(name)
    value = default
    if raw is not None:
        try:
            value = int(raw.strip())
        except (TypeError, ValueError):
            value = default
    if minimum is not None:
        value = max(minimum, value)
    if maximum is not None:
        value = min(maximum, value)
    return value


def _float(
    name: str,
    default: float,
    *,
    minimum: float | None = None,
    maximum: float | None = None,
) -> float:
    """Read a finite, optionally clamped floating-point setting."""
    raw = os.environ.get(name)
    value = default
    if raw is not None:
        try:
            parsed = float(raw.strip())
            value = parsed if math.isfinite(parsed) else default
        except (TypeError, ValueError):
            value = default
    if minimum is not None:
        value = max(minimum, value)
    if maximum is not None:
        value = min(maximum, value)
    return value


@dataclass(frozen=True)
class Settings:
    """Immutable runtime settings snapshot."""

    # --- LLM provider (Space Secrets) -------------------------------------
    llm_api_key: str | None = field(
        default_factory=lambda: _first("LLM_API_KEY", "ANTHROPIC_API_KEY", "ANTHROPIC_AUTH_TOKEN")
    )
    llm_base_url: str = field(
        default_factory=lambda: _first("LLM_BASE_URL", "ANTHROPIC_BASE_URL")
        or "https://api.anthropic.com"
    )
    llm_model: str | None = field(
        default_factory=lambda: _first("LLM_MODEL", "ANTHROPIC_MODEL")
    )
    # "anthropic" = Messages API only, "openai" = chat/completions only,
    # "auto" = anthropic first, fall back to openai on HTTP 404.
    llm_api_style: str = field(
        default_factory=lambda: (os.environ.get("LLM_API_STYLE") or "auto").strip().lower()
    )
    # Reasoning models (e.g. kimi-k3) spend thinking tokens inside this
    # budget. A real 16k response can truncate before the JSON closes, so the
    # hosted default leaves enough headroom for both reasoning and the spec.
    llm_max_tokens: int = field(
        default_factory=lambda: _int(
            "LLM_MAX_TOKENS", 32768, minimum=256, maximum=131_072
        )
    )
    llm_timeout_s: float = field(
        default_factory=lambda: _float(
            "LLM_TIMEOUT_S", 180.0, minimum=1.0, maximum=1800.0
        )
    )
    llm_max_retries: int = field(
        default_factory=lambda: _int("LLM_MAX_RETRIES", 2, minimum=0, maximum=10)
    )
    llm_referer: str | None = field(default_factory=lambda: _first("LLM_REFERER"))
    llm_title: str | None = field(default_factory=lambda: _first("LLM_TITLE"))

    # --- pipeline behaviour ------------------------------------------------
    spec_repair_rounds: int = field(
        default_factory=lambda: _int("SPEC_REPAIR_ROUNDS", 3, minimum=0, maximum=10)
    )

    # --- HTTP / server ------------------------------------------------------
    port: int = field(
        default_factory=lambda: _int("PORT", 7860, minimum=1, maximum=65_535)
    )
    runs_dir: str = field(default_factory=lambda: os.environ.get("RUNS_DIR", "/tmp/i2t-runs"))
    # Gallery items are disk-backed and survive process restarts. Deployments
    # that need persistence across Space rebuilds should point GALLERY_DIR at
    # a mounted persistent volume (for example /data/gallery).
    gallery_dir: str = field(
        default_factory=lambda: _first("GALLERY_DIR") or "/tmp/i2t-gallery"
    )
    max_upload_bytes: int = field(
        default_factory=lambda: _int(
            "MAX_UPLOAD_BYTES", 10 * 1024 * 1024,
            minimum=64 * 1024, maximum=50 * 1024 * 1024,
        )
    )
    max_image_pixels: int = field(
        default_factory=lambda: _int(
            "MAX_IMAGE_PIXELS", 40_000_000, minimum=4096, maximum=100_000_000
        )
    )
    # Longest-side pixel cap for the normalised image handed to the forge
    # scripts (pure-Python per-pixel readers) and to the LLM.
    normalize_max_side: int = field(
        default_factory=lambda: _int(
            "NORMALIZE_MAX_SIDE", 1024, minimum=64, maximum=8192
        )
    )
    job_ttl_s: int = field(
        default_factory=lambda: _int(
            "JOB_TTL_S", 2 * 60 * 60, minimum=60, maximum=7 * 24 * 60 * 60
        )
    )
    # Wall-clock bound from job acceptance through the completed browser
    # bundle. Queue time is included. Optional Bucket publication has its own
    # shorter bound below so a storage outage cannot consume a worker forever.
    job_timeout_s: float = field(
        default_factory=lambda: _float(
            "JOB_TIMEOUT_S", 1800.0, minimum=30.0, maximum=3600.0
        )
    )
    gallery_publish_timeout_s: float = field(
        default_factory=lambda: _float(
            "GALLERY_PUBLISH_TIMEOUT_S", 120.0, minimum=5.0, maximum=600.0
        )
    )
    max_concurrent_jobs: int = field(
        default_factory=lambda: _int(
            "MAX_CONCURRENT_JOBS", 2, minimum=1, maximum=16
        )
    )
    # Hard cap on queued+running jobs (each pins its upload bytes in memory).
    max_in_flight_jobs: int = field(
        default_factory=lambda: _int(
            "MAX_IN_FLIGHT_JOBS", 8, minimum=1, maximum=64
        )
    )
    rate_limit_jobs_per_hour: int = field(
        default_factory=lambda: _int(
            "RATE_LIMIT_JOBS_PER_HOUR", 10, minimum=1, maximum=10_000
        )
    )

    # --- tooling ------------------------------------------------------------
    # esbuild 0.25+ ships a statically-linked native binary (no node needed
    # at runtime); the .bin path is an npm-managed symlink to it.
    esbuild_entry: str = field(
        default_factory=lambda: os.environ.get("ESBUILD_ENTRY", "node_modules/.bin/esbuild")
    )

    # --- informational -------------------------------------------------------
    space_id: str | None = field(default_factory=lambda: _first("SPACE_ID"))
    space_host: str | None = field(default_factory=lambda: _first("SPACE_HOST"))

    @property
    def llm_configured(self) -> bool:
        return bool(self.llm_api_key and self.llm_model)

    @property
    def missing_llm_vars(self) -> list[str]:
        missing: list[str] = []
        if not self.llm_api_key:
            missing.append("LLM_API_KEY")
        if not self.llm_model:
            missing.append("LLM_MODEL")
        return missing


def load_settings() -> Settings:
    return Settings()