from __future__ import annotations

import asyncio
import time
from typing import Any, Dict, List, Optional

from fastapi import APIRouter
from pydantic import BaseModel, Field, field_validator

from app.core.logger import get_logger
from app.core.thread_pool import thread_pool
from app.services.keys_extractor_service import KeysExtractor

logger = get_logger(__name__)

router = APIRouter()


class KeysExtractRequest(BaseModel):
    data: Any = Field(..., description="JSON object or array to search")
    key_names: Optional[List[str]] = Field(
        default=None,
        description=(
            "Key names to look up at any depth. Mutually exclusive with `query`; "
            "provide one of the two."
        ),
    )
    query: Optional[str] = Field(
        default=None,
        description=(
            "Extended JSONPath expression (parsed with `jsonpath_ng.ext`) used to "
            "select values. Supports filters, arithmetic and the union operator, e.g. "
            "`$.store.book[?price > 10].title`. Each match is returned with its "
            "full path inside the source document. Mutually exclusive with `key_names`."
        ),
    )
    result_limit: Optional[int] = Field(
        None,
        ge=1,
        description=(
            "Maximum results to return. For `key_names` mode this caps values per "
            "key; for `query` mode it caps the number of matches returned. "
            "Omit (or pass null) to return the full, uncapped result."
        ),
    )

    @field_validator("key_names")
    @classmethod
    def _validate_key_names(cls, v: Optional[List[str]]) -> Optional[List[str]]:
        if v is None:
            return v
        if not v:
            raise ValueError("key_names must be a non-empty list (omit it or supply a `query`)")
        for kn in v:
            if not isinstance(kn, str) or not kn:
                raise ValueError("each key_name must be a non-empty string")
        return v

    @field_validator("query")
    @classmethod
    def _validate_query(cls, v: Optional[str]) -> Optional[str]:
        if v is None:
            return v
        if not isinstance(v, str) or not v.strip():
            raise ValueError("query must be a non-empty string")
        return v


class KeysExtractResponse(BaseModel):
    success: bool
    time_ms: float
    data: Dict[str, Any]
    error_message: Optional[str] = None


class KeysExtractBatchRequest(BaseModel):
    requests: List[KeysExtractRequest] = Field(
        ...,
        min_length=1,
        max_length=50,
        description="List of extraction requests (1-50) to process concurrently",
    )


class KeysExtractBatchResponse(BaseModel):
    success: bool
    time_ms: float
    results: List[KeysExtractResponse]


def _error_response(start: float, message: str) -> KeysExtractResponse:
    return KeysExtractResponse(
        success=False,
        time_ms=round((time.perf_counter() - start) * 1000, 3),
        data={},
        error_message=message,
    )


async def _extract_single(body: KeysExtractRequest) -> KeysExtractResponse:
    start = time.perf_counter()
    has_key_names = bool(body.key_names)
    has_query = body.query is not None

    if has_key_names and has_query:
        return _error_response(start, "provide either `key_names` or `query`, not both")
    if not has_key_names and not has_query:
        return _error_response(start, "either `key_names` or `query` must be provided")
    if not isinstance(body.data, (dict, list)):
        return _error_response(start, "`data` must be a JSON object or array")

    try:
        loop = asyncio.get_running_loop()
        results = await loop.run_in_executor(
            thread_pool,
            KeysExtractor(body.data, body.key_names, body.result_limit, body.query).extract,
        )
    except (TypeError, ValueError) as exc:
        return _error_response(start, str(exc))
    except Exception as exc:
        return _error_response(start, f"extraction failed: {exc}")

    elapsed = round((time.perf_counter() - start) * 1000, 3)
    return KeysExtractResponse(
        success=True,
        time_ms=elapsed,
        data=results,
        error_message=None,
    )


@router.post(
    "/keys/extract",
    response_model=KeysExtractBatchResponse,
    tags=["Keys Extractor"],
    summary="Extract values from nested JSON objects (batch of up to 50 requests processed concurrently)",
)
async def extract_keys_batch(body: KeysExtractBatchRequest):
    """Process up to 50 extraction requests concurrently.

    Each request supports two modes:

    * **key_names** (default) -- recursively walk any JSON object/array and return
      every value attached to the supplied key names, regardless of how deeply
      nested they are. Returns ``{key_name: [values...]}``.

    * **query** -- run an extended JSONPath expression and return each match with
      its full path inside the source document. Returns
      ``{"matches": [{"path": "users.[0].role", "value": "admin"}, ...]}``.
    """
    start = time.perf_counter()
    logger.info("keys_extract_batch | start count=%d", len(body.requests))
    tasks = [_extract_single(req) for req in body.requests]
    results = await asyncio.gather(*tasks)
    elapsed = round((time.perf_counter() - start) * 1000, 3)
    all_ok = all(r.success for r in results)
    logger.info(
        "keys_extract_batch | done total=%d succeeded=%d time_ms=%s",
        len(results),
        sum(1 for r in results if r.success),
        elapsed,
    )
    return KeysExtractBatchResponse(success=all_ok, time_ms=elapsed, results=results)