from collections.abc import Callable
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Protocol, cast

from pydantic_ai import Agent
from pydantic_ai.messages import (
    ModelMessage,
    ModelResponse,
    ToolCallPart,
    ToolReturnPart,
)
from pydantic_ai.models import Model

from haiku.rag.capabilities import RAGCapabilityBase
from haiku.rag.config.models import AppConfig
from haiku.rag.store.models.chunk import SearchResult
from haiku.rag.store.models.citation import Citation

CapabilityFactory = Callable[..., RAGCapabilityBase[Any]]


class _RagLikeState(Protocol):
    document_filter: str | None
    citation_index: dict[str, Citation]
    citations: list[str]
    searches: dict[str, list[SearchResult]]


@dataclass
class CapabilityRunResult:
    answer: str
    cited_uris: list[str] = field(default_factory=list)
    cited_chunk_ids: list[str] = field(default_factory=list)
    searched_uris: list[str] = field(default_factory=list)
    n_searches: int = 0
    n_executions: int = 0
    n_search_calls: int = 0
    n_rejected_searches: int = 0
    n_failed_tools: int = 0
    n_requests: int = 0
    budget_spent: bool = False


def _count_tool_traffic(
    messages: list[ModelMessage], namespace: str
) -> tuple[int, int, int, int]:
    """Count search calls, failed calls and model requests in a run.

    ``state.searches`` is keyed by query, so it collapses repeated queries and
    never records a call the capability refused. Counting the message history
    instead gives the real number of attempts.

    Failures are split by tool. Only the search tool fails for want of budget,
    whereas the code tool raises ``ToolFailed`` for any error in model-written
    Python, so counting every failure together would report a ``ZeroDivisionError``
    as budget exhaustion.
    """
    search_tool = f"{namespace}_search"
    search_calls = 0
    rejected_searches = 0
    failed_tools = 0
    requests = 0
    for message in messages:
        if isinstance(message, ModelResponse):
            requests += 1
            search_calls += sum(
                1
                for part in message.parts
                if isinstance(part, ToolCallPart) and part.tool_name == search_tool
            )
            continue
        for part in message.parts:
            if isinstance(part, ToolReturnPart) and part.outcome == "failed":
                failed_tools += 1
                if part.tool_name == search_tool:
                    rejected_searches += 1
    return search_calls, rejected_searches, failed_tools, requests


@dataclass
class _EvalDeps:
    state: dict[str, Any] = field(default_factory=dict)


async def run_capability_question(
    capability_factory: CapabilityFactory,
    db_path: Path,
    config: AppConfig,
    question: str,
    capability_model: str | Model,
    document_filter: str | None = None,
    request_limit: int | None = None,
) -> CapabilityRunResult:
    """Run a single question through a capability and return answer + retrieval data.

    Builds a native capability via ``capability_factory(db_path=..., config=...)``.
    After the run, citations and searched documents
    are extracted from the state for downstream eval scoring.

    The capability must produce a state with RAG-capability-shaped fields (citation
    index, searches, optional document filter) — i.e. ``RAGState`` or
    ``AnalysisState`` from ``haiku.rag.capabilities``.
    """
    capability = capability_factory(
        db_path=db_path,
        config=config,
        defer_loading=False,
    )
    if request_limit is not None:
        capability.request_limit = request_limit
    state = capability.state_type()
    typed = cast(_RagLikeState, state)
    if document_filter is not None:
        typed.document_filter = document_filter

    deps = _EvalDeps(state={capability.state_namespace: state.model_dump(mode="json")})
    agent = Agent(
        capability_model,
        deps_type=_EvalDeps,
        capabilities=[capability],
    )
    agent_result = await agent.run(question, deps=deps)
    state = capability.state_type.model_validate(deps.state[capability.state_namespace])
    typed = cast(_RagLikeState, state)

    cited_chunk_ids: list[str] = list(typed.citations)
    seen_cited: set[str] = set()
    cited_uris: list[str] = []
    for chunk_id in cited_chunk_ids:
        citation = typed.citation_index.get(chunk_id)
        if citation is None:
            continue
        if citation.document_uri not in seen_cited:
            seen_cited.add(citation.document_uri)
            cited_uris.append(citation.document_uri)

    seen_searched: set[str] = set()
    searched_uris: list[str] = []
    for results in typed.searches.values():
        for search_result in results:
            uri = search_result.document_uri
            if uri and uri not in seen_searched:
                seen_searched.add(uri)
                searched_uris.append(uri)

    executions = getattr(state, "executions", None)
    n_executions = len(executions) if executions is not None else 0

    n_search_calls, n_rejected_searches, n_failed_tools, n_requests = (
        _count_tool_traffic(agent_result.all_messages(), capability.state_namespace)
    )

    return CapabilityRunResult(
        answer=agent_result.output,
        cited_uris=cited_uris,
        cited_chunk_ids=cited_chunk_ids,
        searched_uris=searched_uris,
        n_searches=len(typed.searches),
        n_executions=n_executions,
        n_search_calls=n_search_calls,
        n_rejected_searches=n_rejected_searches,
        n_failed_tools=n_failed_tools,
        n_requests=n_requests,
        budget_spent=n_rejected_searches > 0,
    )