from __future__ import annotations

import asyncio
import hashlib
import json as json_mod
from typing import Annotated, Any, Dict, Optional
from urllib.parse import urlparse

from fastapi import (
    APIRouter,
    Depends,
    File,
    Form,
    HTTPException,
    Query,
    UploadFile,
    status,
)
from fastapi.responses import PlainTextResponse

from app.api.deps import (
    get_converter_service,
    get_extraction_service,
    get_text_cleaner_service,
)
from app.config import get_settings
from app.core.logger import get_logger
from app.core.thread_pool import thread_pool as _thread_pool
from app.models.domain import ConversionError, count_tokens
from app.models.schemas import ConversionMetadata, ConversionResponse, UrlRequest
from app.services.converter_service import ConverterService
from app.services.extraction_service import ExtractionService
from app.services.text_cleaner_service import TextCleanerService
from app.utils.http_utils import DownloadError, download_url

router = APIRouter()
_logger = get_logger(__name__)
_settings = get_settings()
_MAX_UPLOAD_BYTES = _settings.max_upload_bytes


def _build_metadata(result) -> ConversionMetadata:
    return ConversionMetadata(
        source=result.source,
        char_count=result.char_count,
        word_count=result.word_count,
        line_count=result.line_count,
        file_size_bytes=result.file_size_bytes,
        mime_type=result.mime_type,
        content_hash=result.content_hash,
        token_estimate=result.token_estimate,
    )


async def _build_response(
    result,
    *,
    return_json: bool = False,
    filename: Optional[str] = None,
    raw_data: Optional[bytes] = None,
    mappings: Optional[Dict[str, Dict[str, Any]]] = None,
    json_schema: Optional[Dict[str, Any]] = None,
    schema_name: str = "extraction",
    extraction_service: ExtractionService = None,
    clean_content: bool = False,
    text_cleaner_service: TextCleanerService = None,
) -> ConversionResponse:
    json_content: Optional[Any] = None
    error_message: Optional[str] = None

    content = result.markdown
    if clean_content and text_cleaner_service:
        loop = asyncio.get_running_loop()
        content = await loop.run_in_executor(_thread_pool, text_cleaner_service.clean, content)

    if return_json and filename and extraction_service:
        loop = asyncio.get_running_loop()
        json_result = await loop.run_in_executor(
            _thread_pool,
            extraction_service.extract_structured,
            filename,
            content,
            mappings,
            raw_data,
            json_schema,
            schema_name,
        )
        if "error" in json_result:
            error_message = json_result["error"]
        else:
            json_content = json_result

    if clean_content and content != result.markdown:
        lines = content.splitlines()
        words = content.split()
        metadata = ConversionMetadata(
            source=result.source,
            char_count=len(content),
            word_count=len(words),
            line_count=len(lines),
            file_size_bytes=result.file_size_bytes,
            mime_type=result.mime_type,
            content_hash=hashlib.sha256(content.encode()).hexdigest(),
            token_estimate=max(1, count_tokens(content)),
        )
    else:
        metadata = _build_metadata(result)

    return ConversionResponse(
        success=True,
        time_ms=round(result.duration_ms, 3),
        content=content,
        return_json=return_json,
        json_content=json_content,
        metadata=metadata,
        error_message=error_message,
    )


def _raise_for_error(outcome: ConversionError) -> None:
    status_map = {
        "FileNotFoundError": status.HTTP_404_NOT_FOUND,
        "ValueError": status.HTTP_422_UNPROCESSABLE_ENTITY,
        "PermissionError": status.HTTP_403_FORBIDDEN,
    }
    code = status_map.get(outcome.error_type, status.HTTP_500_INTERNAL_SERVER_ERROR)
    raise HTTPException(
        status_code=code,
        detail={
            "success": False,
            "error_type": outcome.error_type,
            "message": outcome.message,
            "time_ms": round(outcome.duration_ms, 3),
        },
    )


@router.post(
    "/convert/file",
    response_model=ConversionResponse,
    summary="Convert uploaded file to Markdown",
)
async def convert_file(
    file: Annotated[UploadFile, File(description="File to convert")],
    plain_text: bool = Form(False),
    return_json: bool = Form(False),
    clean_content: bool = Query(False),
    mappings: Optional[str] = Form(None, description="JSON string with field mappings"),
    json_schema: Optional[str] = Form(None, description="JSON Schema for AI-based structured extraction"),
    schema_name: str = Form("extraction", description="Name for the JSON Schema"),
    converter_service: ConverterService = Depends(get_converter_service),
    extraction_service: ExtractionService = Depends(get_extraction_service),
    text_cleaner_service: TextCleanerService = Depends(get_text_cleaner_service),
):
    if file is None:
        raise HTTPException(status_code=400, detail={"success": False, "message": "No file provided."})

    parsed_mappings = None
    if mappings:
        try:
            parsed_mappings = json_mod.loads(mappings)
        except json_mod.JSONDecodeError:
            raise HTTPException(status_code=400, detail={"success": False, "message": "Invalid JSON in mappings parameter."})

    parsed_schema = None
    if json_schema:
        try:
            parsed_schema = json_mod.loads(json_schema)
        except json_mod.JSONDecodeError:
            raise HTTPException(status_code=400, detail={"success": False, "message": "Invalid JSON in json_schema parameter."})

    _logger.info("Received request to convert file: %s", file.filename)
    raw = await file.read()
    if len(raw) > _MAX_UPLOAD_BYTES:
        _logger.error("File %s exceeds %s MB limit", file.filename, _settings.max_upload_mb)
        raise HTTPException(status_code=413, detail={"success": False, "message": f"File exceeds {_settings.max_upload_mb} MB limit."})

    loop = asyncio.get_running_loop()
    outcome = await loop.run_in_executor(_thread_pool, converter_service.convert_stream, raw, file.filename or "upload")
    if isinstance(outcome, ConversionError):
        _logger.error("Conversion failed for %s: %s", file.filename, outcome.message)
        _raise_for_error(outcome)

    _logger.info("Conversion successful for %s", file.filename)

    content = outcome.markdown
    if clean_content:
        content = await loop.run_in_executor(_thread_pool, text_cleaner_service.clean, content)

    if plain_text:
        return PlainTextResponse(content)

    response = await _build_response(
        outcome,
        return_json=return_json,
        filename=file.filename,
        raw_data=raw,
        mappings=parsed_mappings,
        json_schema=parsed_schema,
        schema_name=schema_name,
        extraction_service=extraction_service,
        clean_content=clean_content,
        text_cleaner_service=text_cleaner_service,
    )
    _logger.info("Request completed for %s", file.filename)
    return response


@router.post(
    "/convert/url",
    response_model=ConversionResponse,
    summary="Convert a URL to Markdown",
)
async def convert_url(
    body: UrlRequest,
    clean_content: bool = Query(False),
    converter_service: ConverterService = Depends(get_converter_service),
    extraction_service: ExtractionService = Depends(get_extraction_service),
    text_cleaner_service: TextCleanerService = Depends(get_text_cleaner_service),
):
    _logger.info("Received request to convert URL: %s", body.url)
    parsed = urlparse(body.url)
    filename = parsed.path.split("/")[-1] or "url_content"

    if body.return_json:
        try:
            _logger.info("Fetching URL for JSON extraction: %s", body.url)
            raw_data, _ = await download_url(
                body.url, timeout_seconds=30.0, max_size_bytes=_MAX_UPLOAD_BYTES
            )

            loop = asyncio.get_running_loop()
            outcome = await loop.run_in_executor(_thread_pool, converter_service.convert_stream, raw_data, filename)
            if isinstance(outcome, ConversionError):
                _logger.error("Conversion failed for URL %s: %s", body.url, outcome.message)
                _raise_for_error(outcome)

            _logger.info("Conversion successful for URL %s", body.url)
            response = await _build_response(
                outcome,
                return_json=body.return_json,
                filename=filename,
                raw_data=raw_data,
                mappings=body.mappings,
                json_schema=body.json_schema,
                schema_name=body.schema_name,
                extraction_service=extraction_service,
                clean_content=clean_content,
                text_cleaner_service=text_cleaner_service,
            )
            _logger.info("Request completed for URL %s", body.url)
            return response
        except DownloadError as exc:
            _logger.error("Failed to fetch URL %s: %s", body.url, exc)
            status_code = 413 if exc.is_size_error else 400
            message = f"File exceeds {_settings.max_upload_mb} MB limit." if exc.is_size_error else f"Failed to fetch URL: {exc}"
            raise HTTPException(status_code=status_code, detail={"success": False, "message": message})

    loop = asyncio.get_running_loop()
    outcome = await loop.run_in_executor(_thread_pool, converter_service.convert_url, body.url)
    if isinstance(outcome, ConversionError):
        _logger.error("Conversion failed for URL %s: %s", body.url, outcome.message)
        _raise_for_error(outcome)

    _logger.info("Conversion successful for URL %s", body.url)
    response = await _build_response(
        outcome,
        return_json=body.return_json,
        filename=filename,
        mappings=body.mappings,
        json_schema=body.json_schema,
        schema_name=body.schema_name,
        extraction_service=extraction_service,
        clean_content=clean_content,
        text_cleaner_service=text_cleaner_service,
    )
    _logger.info("Request completed for URL %s", body.url)
    return response