"""Application settings loaded from config.yaml + env vars.

Priority (highest first):
  1. Environment variables (prefixed KDC_)
  2. configs/config.yaml
  3. Field defaults
"""

from __future__ import annotations

from functools import lru_cache
from pathlib import Path

import yaml
from pydantic import Field
from pydantic_settings import BaseSettings, SettingsConfigDict


class PathSettings(BaseSettings):
    pdf_dir: Path = Path("pdf")
    preview_dir: Path = Path("preview")
    metadata_dir: Path = Path("metadata")
    datasets_dir: Path = Path("datasets")
    dedup_registry: Path = Path("metadata/.dedup_registry.parquet")

    model_config = SettingsConfigDict(env_prefix="KDC_", extra="ignore")


class LoggingSettings(BaseSettings):
    level: str = "INFO"
    sink_file: Path | None = Path("logs/kdc.log")
    rotation: str = "10 MB"
    retention: str = "30 days"

    model_config = SettingsConfigDict(env_prefix="KDC_LOG_", extra="ignore")


class PreviewSettings(BaseSettings):
    dpi: int = Field(default=150, ge=72, le=600)
    format: str = "png"
    max_pages: int = Field(default=1, ge=1)
    quality: int = Field(default=90, ge=1, le=100)

    model_config = SettingsConfigDict(env_prefix="KDC_PREVIEW_", extra="ignore")


class MetadataSettings(BaseSettings):
    fallback_to_pypdf: bool = True
    min_file_size_kb: float = 1.0
    max_file_size_mb: float = 500.0

    model_config = SettingsConfigDict(env_prefix="KDC_METADATA_", extra="ignore")


class DedupSettings(BaseSettings):
    enabled: bool = True
    strategy: str = "sha256"

    model_config = SettingsConfigDict(env_prefix="KDC_DEDUP_", extra="ignore")


class HuggingFaceSettings(BaseSettings):
    repo_id: str = "Darachhat/khmer-document-corpus"
    token: str | None = None

    model_config = SettingsConfigDict(env_prefix="HF_", extra="ignore")


class Settings(BaseSettings):
    """Top-level aggregated settings."""

    paths: PathSettings = Field(default_factory=PathSettings)
    logging: LoggingSettings = Field(default_factory=LoggingSettings)
    preview: PreviewSettings = Field(default_factory=PreviewSettings)
    metadata: MetadataSettings = Field(default_factory=MetadataSettings)
    dedup: DedupSettings = Field(default_factory=DedupSettings)
    huggingface: HuggingFaceSettings = Field(default_factory=HuggingFaceSettings)

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

    @classmethod
    def from_yaml(cls, path: Path | None = None) -> Settings:
        """Load settings from a YAML file, falling back to defaults."""
        yaml_path = path or Path("configs/config.yaml")
        raw: dict = {}
        if yaml_path.exists():
            with yaml_path.open(encoding="utf-8") as f:
                raw = yaml.safe_load(f) or {}

        return cls(
            paths=PathSettings(**raw.get("paths", {})),
            logging=LoggingSettings(**raw.get("logging", {})),
            preview=PreviewSettings(**raw.get("preview", {})),
            metadata=MetadataSettings(**raw.get("metadata", {})),
            dedup=DedupSettings(**raw.get("dedup", {})),
            huggingface=HuggingFaceSettings(**raw.get("huggingface", {})),
        )


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    """Return the singleton Settings instance (cached after first call)."""
    return Settings.from_yaml()