from fastapi import APIRouter, UploadFile, File, Form, HTTPException
from fastapi.responses import JSONResponse, FileResponse
from typing import Optional
import tempfile
import shutil
import os

from core.registry.loader import get_tasks
from core.execution.executor import execute_task


# =====================================================
# ROUTER BUILDER
# =====================================================

def build_api_router() -> APIRouter:
    """
    Dynamically builds API routes from TASK REGISTRY.

    Generated endpoints:

        POST /execute/{task}
        GET  /tasks
        GET  /health
    """

    router = APIRouter(tags=["API"])

    # =================================================
    # EXECUTE TASK
    # =================================================
    @router.post("/execute/{task_name}")
    async def execute(
        task_name: str,
        file: Optional[UploadFile] = File(None),
        url_input: Optional[str] = Form(None),
    ):
        """
        Universal execution endpoint.
        Accepts:
            - file upload
            - url_input
        """

        tasks = get_tasks()

        if task_name not in tasks:
            raise HTTPException(
                status_code=404,
                detail=f"Task '{task_name}' not found",
            )

        temp_path = None

        try:
            # -----------------------------------------
            # SAVE UPLOADED FILE
            # -----------------------------------------
            if file:
                suffix = os.path.splitext(file.filename)[1]

                with tempfile.NamedTemporaryFile(
                    delete=False,
                    suffix=suffix,
                ) as tmp:
                    shutil.copyfileobj(file.file, tmp)
                    temp_path = tmp.name

            # -----------------------------------------
            # BUILD INPUT PAYLOAD
            # -----------------------------------------
            payload = {
                "file_path": temp_path,
                "url_input": url_input,
            }

            # -----------------------------------------
            # EXECUTE TASK
            # -----------------------------------------
            result = await execute_task(task_name, payload)

            # -----------------------------------------
            # FILE RESPONSE
            # -----------------------------------------
            if isinstance(result, dict) and result.get("file"):
                output_file = result["file"]

                if os.path.exists(output_file):
                    return FileResponse(
                        output_file,
                        filename=os.path.basename(output_file),
                    )

            # -----------------------------------------
            # JSON RESPONSE
            # -----------------------------------------
            return JSONResponse(result)

        except Exception as e:
            raise HTTPException(
                status_code=500,
                detail=str(e),
            )

        finally:
            # -----------------------------------------
            # CLEANUP TEMP FILE
            # -----------------------------------------
            if temp_path and os.path.exists(temp_path):
                os.unlink(temp_path)

    # =================================================
    # TASK LIST
    # =================================================
    @router.get("/tasks")
    async def list_tasks():
        """
        Returns registry tasks.
        Used by UI and Docs builder.
        """

        tasks = get_tasks()

        return {
            name: {
                "category": getattr(t, "category", "general"),
                "description": getattr(t, "description", ""),
            }
            for name, t in tasks.items()
        }

    # =================================================
    # HEALTH CHECK
    # =================================================
    @router.get("/health")
    async def health():
        return {
            "status": "ok",
            "tasks_loaded": len(get_tasks()),
        }

    return router