from haiku.rag.config import AppConfig, get_config
from haiku.rag.reranking.base import RerankerBase
from haiku.rag.utils import check_api_key_supported


def get_reranker(config: AppConfig | None = None) -> RerankerBase | None:
    """Build the configured reranker, or None if reranking is disabled.

    A configured reranker whose optional dependency is missing raises: the
    provider modules import their dependency at module scope and name the
    extra to install.
    """
    config = config if config is not None else get_config()
    model = config.reranking.model
    if model is None:
        return None

    check_api_key_supported(model, {"vllm"})

    if config.reranking.multimodal and model.provider != "vllm":
        raise ValueError("reranking.multimodal is only supported on the vllm provider")

    if model.provider == "cohere":
        from haiku.rag.reranking.cohere import CohereReranker

        return CohereReranker(model.name)

    if model.provider == "vllm":
        if not model.base_url:
            raise ValueError("vLLM reranker requires base_url in reranking.model")
        from haiku.rag.reranking.vllm import VLLMReranker

        return VLLMReranker(model.name, model.base_url, api_key=model.api_key)

    if model.provider == "zeroentropy":
        from haiku.rag.reranking.zeroentropy import ZeroEntropyReranker

        return ZeroEntropyReranker(model.name or "zerank-1")

    if model.provider == "jina":
        from haiku.rag.reranking.jina import JinaReranker

        return JinaReranker(model.name or "jina-reranker-v3")

    if model.provider == "jina-local":
        from haiku.rag.reranking.jina_local import JinaLocalReranker

        return JinaLocalReranker(model.name or "jinaai/jina-reranker-v3")

    if model.provider == "cross-encoder":
        if not model.name:
            raise ValueError("cross-encoder reranker requires name in reranking.model")
        from haiku.rag.reranking.cross_encoder import CrossEncoderReranker

        return CrossEncoderReranker(model.name)

    raise ValueError(f"Unknown reranking provider: {model.provider}")