from functools import lru_cache
from pathlib import Path

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


class Settings(BaseSettings):
    model_config = SettingsConfigDict(
        env_file=".env",
        env_prefix="KBQA_",
        extra="ignore",
    )

    app_name: str = "KBQA"
    debug: bool = False

    dashscope_api_key: str = ""
    dashscope_base_url: str = "https://dashscope.aliyuncs.com/compatible-mode/v1"
    chat_model: str = "qwen3.5-flash"
    embedding_model: str = "text-embedding-v4"
    embedding_dim: int = 1024

    database_url: str = "sqlite+aiosqlite:///./data/kbqa.sqlite3"
    milvus_uri: str = "./data/milvus/kbqa.db"
    raw_data_dir: Path = Path("./data/raw")

    chunk_size: int = Field(default=500, ge=1)
    chunk_overlap: int = Field(default=50, ge=0)
    retrieval_top_k: int = Field(default=5, ge=1, le=100)
    max_research_searches: int = Field(default=3, ge=1, le=10)
    max_sources: int = Field(default=8, ge=1, le=50)
    history_message_limit: int = Field(default=20, ge=1, le=200)
    max_upload_mib: int = Field(default=20, ge=1, le=1024)
    max_query_length: int = Field(default=10_000, ge=1, le=100_000)
    cors_origins: list[str] = [
        "http://localhost:5173",
        "http://127.0.0.1:5173",
    ]

    run_live_tests: bool = False
    live_test_file: Path | None = None

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


@lru_cache
def get_settings() -> Settings:
    return Settings()


def validate_live_settings(settings: Settings) -> None:
    missing: list[str] = []
    if not settings.dashscope_api_key:
        missing.append("KBQA_DASHSCOPE_API_KEY")
    if not settings.dashscope_base_url:
        missing.append("KBQA_DASHSCOPE_BASE_URL")
    if missing:
        joined = ", ".join(missing)
        raise RuntimeError(f"Missing live model configuration: {joined}")