from fastapi import FastAPI, UploadFile, File, Header, HTTPException, Query
from fastapi.responses import FileResponse
from ultralytics import YOLO
import shutil
import os
import cv2

app = FastAPI()

model = YOLO('yolov8n.pt') 

TEMP_FOLDER = "temp_files"
os.makedirs(TEMP_FOLDER, exist_ok=True)

MY_PASSWORD = "david-shavin"
MAX_DURATION_SECONDS = 30

@app.get("/")
def home():
    return {"message": "YOLOv8 Tracking API is Active"}

@app.post("/verify")
async def verify_password(x_password: str = Header(None)):
    if x_password != MY_PASSWORD:
        raise HTTPException(status_code=401, detail="Incorrect Password")
    return {"message": "Access Granted"}

@app.post("/track-video")
async def track_video(
    file: UploadFile = File(...), 
    x_password: str = Header(None),
    # NEW ARGUMENT: target_fps (defaults to 5 if not sent)
    target_fps: int = Query(5, ge=1, le=30) 
):
    # 1. Security Check
    if x_password != MY_PASSWORD:
        raise HTTPException(status_code=401, detail="Unauthorized")

    # 2. Save File
    input_path = os.path.join(TEMP_FOLDER, "input.mp4")
    with open(input_path, "wb") as buffer:
        shutil.copyfileobj(file.file, buffer)

    # 3. Calculate Stride based on Target FPS
    try:
        cap = cv2.VideoCapture(input_path)
        orig_fps = cap.get(cv2.CAP_PROP_FPS)
        frame_count = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
        duration = frame_count / orig_fps if orig_fps > 0 else 0
        cap.release()

        if duration > MAX_DURATION_SECONDS:
            os.remove(input_path)
            raise HTTPException(status_code=400, detail=f"Video too long ({int(duration)}s). Limit is {MAX_DURATION_SECONDS}s.")

        # --- RESAMPLING LOGIC ---
        # If video is 30fps and user wants 5fps: stride = 30/5 = 6 (Process every 6th frame)
        if orig_fps > 0:
            stride = int(orig_fps / target_fps)
            # Ensure stride is at least 1 (process every frame)
            if stride < 1: stride = 1
        else:
            stride = 1 # Fallback
            
        print(f"Original FPS: {orig_fps}, Target: {target_fps}, Calculated Stride: {stride}")

    except HTTPException as he:
        raise he
    except Exception as e:
        print(f"Metadata Error: {e}")
        stride = 1

    # 4. Processing
    try:
        results = model.track(
            source=input_path, 
            save=True, 
            project=TEMP_FOLDER, 
            name="tracking_result", 
            exist_ok=True,
            vid_stride=stride  # <--- Apply the calculated resampling
        )
        
        output_video_path = os.path.join(TEMP_FOLDER, "tracking_result", "input.avi")
        return FileResponse(output_video_path, media_type="video/x-msvideo", filename="tracked_video.avi")

    except Exception as e:
        raise HTTPException(status_code=500, detail=f"Processing Error: {str(e)}")