from fastapi import FastAPI, HTTPException
from fastapi.responses import StreamingResponse
from pydantic import BaseModel
import os
import json
import time

app = FastAPI()

print("[Main] Backend service starting...")

class CompletionRequest(BaseModel):
    prefix: str
    suffix: str
    languageId: str = 'markdown'

def generate_stream(request: CompletionRequest):
    from prompt import build_prompt
    from llm import stream_openai
    
    start_time = time.time()
    print(f"[Main] ========== New Request ==========")
    print(f"[Main] prefix length: {len(request.prefix)}, suffix length: {len(request.suffix)}")
    print(f"[Main] languageId: {request.languageId}")
    print(f"[Main] Prefix (last 200 chars): '{request.prefix[-200:]}'")
    print(f"[Main] Suffix (first 200 chars): '{request.suffix[:200]}'")
    
    try:
        prompt = build_prompt(request.prefix, request.suffix)
        print(f"[Main] Built prompt length: {len(prompt)}")
        print(f"[Main] Prompt (first 300 chars): '{prompt[:300]}'")
        print(f"[Main] Prompt (last 200 chars): '{prompt[-200:]}'")
        
        async def gen():
            chunk_count = 0
            first_chunk_time = None
            try:
                async for chunk in stream_openai(prompt):
                    current_time = time.time()
                    if first_chunk_time is None:
                        first_chunk_time = current_time - start_time
                    chunk_count += 1
                    chunk_data = json.loads(chunk) if isinstance(chunk, str) else chunk
                    content_preview = chunk_data.get('content', '')[:50] if chunk_data.get('content') else ''
                    print(f"[Main] Chunk {chunk_count}: '{content_preview}'...")
                    yield f"data: {json.dumps(chunk_data)}\n\n"
                
                done_signal = {"done": True}
                total_time = time.time() - start_time
                print(f"[Main] Stream complete - total chunks: {chunk_count}, first chunk at: {first_chunk_time:.2f}s, total time: {total_time:.2f}s")
                yield f"data: {json.dumps(done_signal)}\n\n"
            except Exception as e:
                error_msg = {"error": str(e), "type": type(e).__name__}
                print(f"[Main] Generator error: {e}")
                yield f"data: {json.dumps(error_msg)}\n\n"
        return gen()
    except Exception as e:
        error_msg = {"error": str(e), "type": type(e).__name__}
        print(f"[Main] Error building prompt or calling LLM: {e}")
        yield f"data: {json.dumps(error_msg)}\n\n"

@app.post("/v1/completions")
async def create_completion(request: CompletionRequest):
    print(f"[Main] POST /v1/completions called at {time.time()}")
    return StreamingResponse(generate_stream(request), media_type="text/event-stream")

@app.get("/health")
async def health_check():
    return {"status": "healthy", "timestamp": time.time()}

if __name__ == "__main__":
    import uvicorn
    port = int(os.getenv('PORT', 8000))
    print(f"[Main] Starting server on http://0.0.0.0:{port}")
    uvicorn.run(app, host="0.0.0.0", port=port)