"""FastAPI dependency injection — provides shared singletons to route handlers."""

from typing import Annotated

from fastapi import Depends

from navi.config import settings
from navi.context_providers._loader import ContextProviderRegistry
from navi.core import (
    Agent,
    BackendRegistry,
    PgSessionStore,
    ProfileRegistry,
    SessionStore,
    ToolRegistry,
    build_default_registries,
)
from navi.llm.ollama import OllamaBackend
from navi.memory import MemoryStore
from navi.workers import Worker, build_default_workers


def _make_session_store() -> SessionStore:
    if not settings.database_url:
        raise RuntimeError("DATABASE_URL is required. SQLite support has been removed.")
    return PgSessionStore(settings.database_url)


def _make_memory_store() -> MemoryStore:
    if not settings.database_url:
        raise RuntimeError("DATABASE_URL is required. SQLite support has been removed.")
    return MemoryStore(settings.database_url)


_memory_store: MemoryStore | None = None
_registries: tuple[ToolRegistry, ProfileRegistry, BackendRegistry, ContextProviderRegistry] | None = None


def get_memory_store() -> MemoryStore:
    global _memory_store
    if _memory_store is None:
        _memory_store = _make_memory_store()
    return _memory_store


def get_registries() -> tuple[ToolRegistry, ProfileRegistry, BackendRegistry, ContextProviderRegistry]:
    global _registries
    if _registries is None:
        _registries = build_default_registries(
            memory_store=get_memory_store(),
            session_store=get_session_store(),
        )
        # Wire embedding backend into memory store for vector search.
        # Uses a dedicated Ollama endpoint when configured, otherwise falls back
        # to the main chat backend.
        try:
            if settings.embedding_ollama_host:
                emb_backend = OllamaBackend(
                    model=settings.embedding_model,
                    host=settings.embedding_ollama_host,
                    api_key=settings.embedding_ollama_api_key,
                    timeout=settings.ollama_request_timeout,
                )
            else:
                emb_backend = _registries[2].get("ollama")
            if hasattr(_memory_store, "set_embedding_backend"):
                _memory_store.set_embedding_backend(emb_backend)
        except Exception:
            pass
    return _registries


def get_tool_registry() -> ToolRegistry:
    return get_registries()[0]


def get_profile_registry() -> ProfileRegistry:
    return get_registries()[1]


def get_backend_registry() -> BackendRegistry:
    return get_registries()[2]


def get_cp_registry() -> ContextProviderRegistry:
    return get_registries()[3]


_session_store: SessionStore | None = None
_workers: list[Worker] | None = None


def get_session_store() -> SessionStore:
    global _session_store
    if _session_store is None:
        _session_store = _make_session_store()
    return _session_store


def get_workers() -> list[Worker]:
    global _workers
    if _workers is None:
        _workers = build_default_workers()
    return _workers


def get_agent(
    session_store: Annotated[SessionStore, Depends(get_session_store)],
    profile_registry: Annotated[ProfileRegistry, Depends(get_profile_registry)],
    tool_registry: Annotated[ToolRegistry, Depends(get_tool_registry)],
    backend_registry: Annotated[BackendRegistry, Depends(get_backend_registry)],
    cp_registry: Annotated[ContextProviderRegistry, Depends(get_cp_registry)],
) -> Agent:
    return Agent(session_store, profile_registry, tool_registry, backend_registry,
                 workers=get_workers(), memory_store=get_memory_store(), cp_registry=cp_registry)