from __future__ import annotations

from functools import lru_cache
from typing import Literal, Protocol

from pydantic import BaseModel

from app.core.config import get_settings

EvidenceState = Literal["grounded", "insufficient", "unavailable"]


class SourceCard(BaseModel):
    document_id: str
    title: str
    version: str
    section: str
    excerpt: str


class GroundedAnswer(BaseModel):
    answer: str
    evidence_state: EvidenceState
    sources: list[SourceCard]
    provider: str
    correlation_id: str


class KnowledgeHealth(BaseModel):
    provider: str
    available: bool
    detail: str
    tenant: str
    workspace: str
    collection: str
    # A provider may be healthy without exposing a corpus-size endpoint. `None` means
    # unknown, never "zero procedures".
    document_count: int | None


class KnowledgeProvider(Protocol):
    name: str

    def health(self, language: str = "en-GB") -> KnowledgeHealth: ...

    def ask(
        self, question: str, correlation_id: str, language: str = "en-GB"
    ) -> GroundedAnswer: ...


@lru_cache
def get_knowledge_provider() -> KnowledgeProvider:
    settings = get_settings()
    if settings.knowledge_provider == "ragcore":
        from app.services.knowledge.ragcore import RAGcoreKnowledgeProvider

        return RAGcoreKnowledgeProvider()
    from app.services.knowledge.demo import DemoKnowledgeProvider

    return DemoKnowledgeProvider()