"""
config.py — Centralised, validated configuration using Pydantic Settings.

All values are read from environment variables (or .env file).
Import the singleton `settings` anywhere in the project.
"""

from functools import lru_cache
from typing import Literal

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


class Settings(BaseSettings):
    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        case_sensitive=False,
        extra="ignore",
    )

    # ── LLM ──────────────────────────────────────────────────────────────
    groq_api_key: str = Field(..., description="Groq API key (free tier)")
    llm_model: str = Field("llama-3.3-70b-versatile", description="Groq chat model")
    stt_model: str = Field("whisper-large-v3-turbo", description="Groq Whisper STT model")
    tts_voice: str = Field("en-US-JennyNeural", description="Edge-TTS voice")

    # ── RAG ───────────────────────────────────────────────────────────────
    chroma_persist_dir: str = Field("./data/chroma_db")
    embedding_model: str = Field("all-MiniLM-L6-v2")
    docs_dir: str = Field("./data/sample_files")
    chunk_size: int = Field(500, ge=100, le=4000)
    chunk_overlap: int = Field(50, ge=0, le=500)

    # ── MCP Server ────────────────────────────────────────────────────────
    mcp_server_host: str = Field("0.0.0.0")
    mcp_server_port: int = Field(8000, ge=1024, le=65535)
    mcp_transport: Literal["sse", "stdio"] = Field("sse")

    # ── SQLite ────────────────────────────────────────────────────────────
    sqlite_db_path: str = Field("./data/database.db")

    # ── Audio ─────────────────────────────────────────────────────────────
    audio_sample_rate: int = Field(16000)
    audio_channels: int = Field(1)
    audio_silence_threshold: int = Field(500)
    audio_silence_duration_sec: float = Field(1.5)
    audio_min_speech_duration_sec: float = Field(0.5)

    # ── App ───────────────────────────────────────────────────────────────
    app_env: Literal["development", "production"] = Field("development")
    log_level: Literal["DEBUG", "INFO", "WARNING", "ERROR"] = Field("INFO")
    log_format: Literal["json", "console"] = Field("console")

    @field_validator("chunk_overlap")
    @classmethod
    def overlap_less_than_chunk(cls, v: int, info) -> int:
        chunk_size = info.data.get("chunk_size", 500)
        if v >= chunk_size:
            raise ValueError("chunk_overlap must be less than chunk_size")
        return v

    # NEW — works both locally and on HF Spaces
    @property
    def mcp_server_url(self) -> str:
        if self.is_production:
            return f"https://{self.mcp_server_host}/sse"
        return f"http://localhost:{self.mcp_server_port}/sse"

    @property
    def is_production(self) -> bool:
        return self.app_env == "production"


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    """Return the cached Settings singleton."""
    return Settings()  # type: ignore[call-arg]


# Convenience singleton — import this everywhere
settings = get_settings()