"""
FastAPI Server for Invoice Information Extractor
Provides REST API for invoice processing
"""

from fastapi import FastAPI, File, UploadFile, HTTPException, Form
from fastapi.responses import JSONResponse, FileResponse
from fastapi.staticfiles import StaticFiles
from fastapi.middleware.cors import CORSMiddleware
from contextlib import asynccontextmanager
from typing import Optional
import tempfile
import os
import shutil

from config import API_TITLE, API_DESCRIPTION, API_VERSION
from model_manager import model_manager
from inference import InferenceProcessor


@asynccontextmanager
async def lifespan(app: FastAPI):
    """Lifecycle manager - loads models on startup"""
    print("🚀 Starting Invoice Information Extractor API...")
    print("=" * 60)
    
    # Load models on startup
    try:
        model_manager.load_models()
        print("=" * 60)
        print("✅ API is ready to accept requests!")
        print("=" * 60)
    except Exception as e:
        print(f"❌ Failed to load models: {str(e)}")
        raise
    
    yield
    
    # Cleanup on shutdown
    print("🛑 Shutting down API...")


# Initialize FastAPI app
app = FastAPI(
    title=API_TITLE,
    description=API_DESCRIPTION,
    version=API_VERSION,
    lifespan=lifespan
)

# Add CORS middleware
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Mount frontend static files if they exist
frontend_dist = os.path.join(os.path.dirname(__file__), "frontend", "dist")
if os.path.exists(frontend_dist):
    app.mount("/assets", StaticFiles(directory=os.path.join(frontend_dist, "assets")), name="assets")
    print(f"📂 Serving frontend from: {frontend_dist}")


@app.get("/")
async def root():
    """Root endpoint - Serve frontend or API information"""
    frontend_index = os.path.join(os.path.dirname(__file__), "frontend", "dist", "index.html")
    if os.path.exists(frontend_index):
        return FileResponse(frontend_index)
    
    # Fallback to API information
    return {
        "name": API_TITLE,
        "version": API_VERSION,
        "status": "running",
        "models_loaded": model_manager.is_loaded(),
        "endpoints": {
            "health": "/health",
            "process": "/process-invoice (POST)",
            "extract": "/extract (POST)",
            "docs": "/docs"
        }
    }


@app.get("/health")
async def health_check():
    """Health check endpoint"""
    return {
        "status": "healthy",
        "models_loaded": model_manager.is_loaded()
    }


@app.post("/extract")
async def extract_invoice(
    file: UploadFile = File(..., description="Invoice image file (JPG, PNG, JPEG)"),
    doc_id: Optional[str] = Form(None, description="Optional document identifier"),
    enhance_image: Optional[bool] = Form(False, description="Apply OpenCV enhancement preprocessing"),
    reasoning_mode: Optional[str] = Form("simple", description="VLM reasoning mode: 'simple' or 'reason'")
):
    """
    Extract information from invoice image
    
    **Parameters:**
    - **file**: Invoice image file (required)
    - **doc_id**: Optional document identifier (auto-generated from filename if not provided)
    
    **Returns:**
    - JSON with extracted fields, confidence scores, and metadata
    
    **Example Response:**
    ```json
    {
        "doc_id": "invoice_001",
        "fields": {
            "dealer_name": "ABC Tractors Pvt Ltd",
            "model_name": "Mahindra 575 DI",
            "horse_power": 50,
            "asset_cost": 525000,
            "signature": {"present": true, "bbox": [100, 200, 300, 250]},
            "stamp": {"present": true, "bbox": [400, 500, 500, 550]}
        },
        "confidence": 0.89,
        "processing_time_sec": 3.8,
        "cost_estimate_usd": 0.000528
    }
    ```
    """
    
    # Validate file type
    if file.content_type and not file.content_type.startswith("image/"):
        raise HTTPException(
            status_code=400,
            detail="File must be an image (JPG, PNG, JPEG)"
        )
    
    # Validate file extension as fallback
    if file.filename:
        ext = os.path.splitext(file.filename)[1].lower()
        if ext not in ['.jpg', '.jpeg', '.png', '.gif', '.bmp', '.tiff', '.webp']:
            raise HTTPException(
                status_code=400,
                detail="File must be an image (JPG, PNG, JPEG, GIF, BMP, TIFF, WEBP)"
            )
    
    # Check if models are loaded
    if not model_manager.is_loaded():
        raise HTTPException(
            status_code=503,
            detail="Models not loaded. Please wait for server initialization."
        )
    
    # Save uploaded file to temporary location
    import time
    request_start = time.time()
    temp_file = None
    try:
        # Create temporary file
        io_start = time.time()
        suffix = os.path.splitext(file.filename)[1]
        with tempfile.NamedTemporaryFile(delete=False, suffix=suffix) as temp:
            temp_file = temp.name
            # Write uploaded file content
            shutil.copyfileobj(file.file, temp)
        io_time = round(time.time() - io_start, 3)
        
        # Use filename as doc_id if not provided
        if doc_id is None:
            doc_id = os.path.splitext(file.filename)[0]
        
        # Process invoice
        result = InferenceProcessor.process_invoice(temp_file, doc_id, enhance_image, reasoning_mode)
        
        # Add total request time (includes file I/O)
        result['total_request_time_sec'] = round(time.time() - request_start, 2)
        result['file_io_time_sec'] = io_time
        
        return JSONResponse(content=result, media_type="application/json; charset=utf-8")
        
    except Exception as e:
        raise HTTPException(
            status_code=500,
            detail=f"Error processing invoice: {str(e)}"
        )
    
    finally:
        # Clean up temporary file
        if temp_file and os.path.exists(temp_file):
            try:
                os.unlink(temp_file)
            except:
                pass
        
        # Close uploaded file
        file.file.close()


@app.post("/process-invoice")
async def process_invoice(
    file: UploadFile = File(..., description="Invoice image file"),
    enhance_image: Optional[bool] = Form(False, description="Apply OpenCV enhancement preprocessing"),
    reasoning_mode: Optional[str] = Form("simple", description="VLM reasoning mode: 'simple' or 'reason'")
):
    """
    Process a single invoice and return extracted information
    Simplified endpoint for frontend integration
    
    **Parameters:**
    - **file**: Invoice image file (required)
    - **enhance_image**: Apply OpenCV enhancement preprocessing (optional)
    - **reasoning_mode**: VLM reasoning mode: 'simple' for single-step, 'reason' for Chain of Thought (optional)
    
    **Returns:**
    - JSON with extracted_text, signature_coords, stamp_coords
    """
    
    # Validate file type
    if file.content_type and not file.content_type.startswith("image/"):
        raise HTTPException(
            status_code=400,
            detail="File must be an image"
        )
    
    # Check if models are loaded
    if not model_manager.is_loaded():
        raise HTTPException(
            status_code=503,
            detail="Models not loaded. Please wait for server initialization."
        )
    
    temp_file = None
    try:
        # Save uploaded file to temporary location
        suffix = os.path.splitext(file.filename)[1] if file.filename else '.jpg'
        with tempfile.NamedTemporaryFile(delete=False, suffix=suffix) as temp:
            temp_file = temp.name
            shutil.copyfileobj(file.file, temp)
        
        # Use filename as doc_id
        doc_id = os.path.splitext(file.filename)[0] if file.filename else "invoice"
        
        # Process invoice
        result = InferenceProcessor.process_invoice(temp_file, doc_id, enhance_image, reasoning_mode)
        
        # Extract fields from result
        fields = result.get("fields", {})
        signature_info = fields.get("signature", {})
        stamp_info = fields.get("stamp", {})
        
        # Build text representation of extracted fields
        extracted_text_parts = []
        if fields.get("dealer_name"):
            extracted_text_parts.append(f"Dealer Name: {fields['dealer_name']}")
        if fields.get("model_name"):
            extracted_text_parts.append(f"Model Name: {fields['model_name']}")
        if fields.get("horse_power"):
            extracted_text_parts.append(f"Horse Power: {fields['horse_power']}")
        if fields.get("asset_cost"):
            extracted_text_parts.append(f"Asset Cost: {fields['asset_cost']}")
        
        extracted_text = "\n".join(extracted_text_parts) if extracted_text_parts else "No structured data extracted"
        
        # Get coordinates
        signature_coords = []
        if signature_info.get("present") and signature_info.get("bbox"):
            bbox = signature_info["bbox"]
            # Convert [x1, y1, x2, y2] format
            signature_coords = [[bbox[0], bbox[1], bbox[2], bbox[3]]]
        
        stamp_coords = []
        if stamp_info.get("present") and stamp_info.get("bbox"):
            bbox = stamp_info["bbox"]
            # Convert [x1, y1, x2, y2] format
            stamp_coords = [[bbox[0], bbox[1], bbox[2], bbox[3]]]
        
        # Return simplified response matching frontend expectations
        return JSONResponse(content={
            "extracted_text": extracted_text,
            "signature_coords": signature_coords,
            "stamp_coords": stamp_coords,
            "doc_id": result.get("doc_id", doc_id),
            "processing_time": result.get("processing_time_sec", 0),
            "confidence": result.get("confidence", 0),
            "cost_estimate_usd": result.get("cost_estimate_usd", 0),
            "fields": fields,  # Include raw fields for reference
            "timing_breakdown": result.get("timing_breakdown", {})  # Include timing info (with reasoning output if present)
        }, media_type="application/json; charset=utf-8")
        
    except Exception as e:
        raise HTTPException(
            status_code=500,
            detail=f"Error processing invoice: {str(e)}"
        )
    
    finally:
        # Clean up temporary file
        if temp_file and os.path.exists(temp_file):
            try:
                os.unlink(temp_file)
            except:
                pass
        
        # Close uploaded file
        file.file.close()


@app.post("/extract_batch")
async def extract_batch(
    files: list[UploadFile] = File(..., description="Multiple invoice images")
):
    """
    Extract information from multiple invoice images
    
    **Parameters:**
    - **files**: List of invoice image files
    
    **Returns:**
    - JSON array with results for each invoice
    """
    
    if not model_manager.is_loaded():
        raise HTTPException(
            status_code=503,
            detail="Models not loaded. Please wait for server initialization."
        )
    
    results = []
    temp_files = []
    
    try:
        for file in files:
            # Validate file type
            if not file.content_type.startswith("image/"):
                results.append({
                    "filename": file.filename,
                    "error": "File must be an image"
                })
                continue
            
            # Save to temp file
            suffix = os.path.splitext(file.filename)[1]
            with tempfile.NamedTemporaryFile(delete=False, suffix=suffix) as temp:
                temp_file = temp.name
                temp_files.append(temp_file)
                shutil.copyfileobj(file.file, temp)
            
            # Process
            try:
                doc_id = os.path.splitext(file.filename)[0]
                result = InferenceProcessor.process_invoice(temp_file, doc_id)
                results.append(result)
            except Exception as e:
                results.append({
                    "filename": file.filename,
                    "error": str(e)
                })
        
        return JSONResponse(content={"results": results}, media_type="application/json; charset=utf-8")
        
    finally:
        # Cleanup
        for temp_file in temp_files:
            if os.path.exists(temp_file):
                try:
                    os.unlink(temp_file)
                except:
                    pass
        
        for file in files:
            file.file.close()


if __name__ == "__main__":
    import uvicorn
    
    # Run server
    uvicorn.run(
        "app:app",
        host="0.0.0.0",
        port=7860,  # Hugging Face Spaces default port
        reload=False
    )