import os
import shutil
import zipfile
import json
import time
from contextlib import asynccontextmanager
from typing import List, Dict, Any

from fastapi import FastAPI, UploadFile, File, HTTPException
from fastapi.responses import FileResponse
from huggingface_hub import HfApi, hf_hub_download, HfFileSystem

# --- Configuration ---
UPLOAD_DIR = "uploaded_files"
STATE_FILE_NAME = "processing_audio_state.json"  # Match the client's filename
STATE_FILE_PATH = os.path.join(os.getcwd(), STATE_FILE_NAME)
HF_DATASET_REPO = "samfred2/AT2"
HF_TOKEN = os.getenv("HF_TOKEN")

# Hardcoded variables for automation
# Both thresholds are now 100 as requested
ZIP_UPLOAD_THRESHOLD = 100
STATE_UPLOAD_THRESHOLD = 100

# Global state object (will be loaded from/saved to STATE_FILE_PATH)
app_state: Dict[str, Any] = {
    "total_files_uploaded": 0,
    "current_zip_version": 0,
    "files_since_last_zip": 0,
    "files_since_last_state_upload": 0,
}

# Global file states (client-managed processing state)
file_states_cache: Dict[str, Any] = {
    "next_download_index": 0,
    "file_states": {}
}

# --- Hugging Face Utility Functions ---

def get_hf_api() -> HfApi:
    """Returns an HfApi instance, raising an error if token is missing."""
    if not HF_TOKEN:
        raise ValueError("HF_TOKEN not found in environment variables.")
    return HfApi(token=HF_TOKEN)

def download_state_file_from_hf():
    """Downloads the state file from the Hugging Face dataset to the local path."""
    try:
        api = get_hf_api()
        # Use hf_hub_download for simple file download
        downloaded_path = hf_hub_download(
            repo_id=HF_DATASET_REPO,
            filename=STATE_FILE_NAME,
            repo_type="dataset",
            local_dir=os.path.dirname(STATE_FILE_PATH),
            local_dir_use_symlinks=False
        )
        print(f"Successfully downloaded state file to: {downloaded_path}")
        return True
    except ValueError:
        print("HF_TOKEN missing. Cannot download state file.")
        return False
    except Exception as e:
        # File not found is a common case for the first run
        if "404" in str(e):
            print("State file not found on Hugging Face. Will start with default state.")
        else:
            print(f"Error downloading state file: {e}")
        return False

def upload_file_to_huggingface(local_path: str, path_in_repo: str):
    """Uploads a single file to the specified Hugging Face dataset."""
    try:
        api = get_hf_api()
        api.upload_file(
            path_or_fileobj=local_path,
            path_in_repo=path_in_repo,
            repo_id=HF_DATASET_REPO,
            repo_type="dataset",
            token=HF_TOKEN,
            commit_message=f"Sync: {path_in_repo}"
        )
        print(f"Successfully uploaded {os.path.basename(local_path)} to {HF_DATASET_REPO} as {path_in_repo}")
        return True
    except ValueError:
        print("HF_TOKEN missing. Skipping upload.")
        return False
    except Exception as e:
        print(f"Hugging Face upload failed for {local_path}: {e}")
        return False

# --- State Management Functions ---

def load_state():
    """Loads application state from the local state file."""
    global app_state, file_states_cache
    if os.path.exists(STATE_FILE_PATH):
        try:
            with open(STATE_FILE_PATH, "r") as f:
                # Load the complete state file content
                state_content = json.load(f)
                
                # Load internal counters
                if "total_files_uploaded" in state_content:
                    app_state["total_files_uploaded"] = state_content["total_files_uploaded"]
                if "current_zip_version" in state_content:
                    app_state["current_zip_version"] = state_content["current_zip_version"]
                if "files_since_last_zip" in state_content:
                    app_state["files_since_last_zip"] = state_content["files_since_last_zip"]
                if "files_since_last_state_upload" in state_content:
                    app_state["files_since_last_state_upload"] = state_content["files_since_last_state_upload"]
                
                # Load file_states (client-managed processing state)
                if "file_states" in state_content:
                    file_states_cache["file_states"] = state_content["file_states"]
                if "next_download_index" in state_content:
                    file_states_cache["next_download_index"] = state_content["next_download_index"]
                    
            print(f"State loaded successfully: app_state={app_state}, file_states_cache={file_states_cache}")
        except Exception as e:
            print(f"Error loading state file: {e}. Using default state.")
    else:
        print("Local state file not found. Using default state.")

def save_state():
    """Saves both application state counters and file processing states to the local state file."""
    global app_state, file_states_cache
    try:
        # Combine both app_state counters and file_states into one JSON
        complete_state = {
            **app_state,  # Include all counters
            **file_states_cache  # Include file_states and next_download_index
        }
        
        with open(STATE_FILE_PATH, "w") as f:
            json.dump(complete_state, f, indent=4)
        print(f"Complete state saved to {STATE_FILE_PATH}.")
    except Exception as e:
        print(f"Error saving state file: {e}")

def upload_state_file_to_hf():
    """Saves the current app_state counters and uploads the state file to Hugging Face."""
    save_state()
    upload_file_to_huggingface(STATE_FILE_PATH, STATE_FILE_NAME)
    global app_state
    app_state["files_since_last_state_upload"] = 0

# --- File Processing Functions ---

def zip_uploaded_files_versioned() -> str:
    """Zips all files in the upload directory (excluding state file) into a versioned zip file."""
    if not os.path.exists(UPLOAD_DIR) or not os.listdir(UPLOAD_DIR):
        print("No files to zip.")
        return None

    # Increment version and create filename
    global app_state
    app_state["current_zip_version"] += 1
    zip_filename = f"uploaded_files_{app_state['current_zip_version']}.zip"
    zip_path = os.path.join(os.getcwd(), zip_filename)
    
    exclude_file = STATE_FILE_NAME

    with zipfile.ZipFile(zip_path, 'w', zipfile.ZIP_DEFLATED) as zipf:
        for root, _, files in os.walk(UPLOAD_DIR):
            for file in files:
                file_path = os.path.join(root, file)
                # Only zip files that are NOT the state file
                if file != exclude_file:
                    # Add file to zip, preserving directory structure relative to UPLOAD_DIR
                    zipf.write(file_path, os.path.relpath(file_path, UPLOAD_DIR))
    
    print(f"Successfully created versioned zip file at: {zip_path}")
    return zip_path

def upload_zip_to_hf(zip_path: str):
    """Uploads the versioned zip file to the Hugging Face dataset."""
    if not zip_path or not os.path.exists(zip_path):
        print("Zip file not found. Skipping upload.")
        return

    upload_file_to_huggingface(zip_path, os.path.basename(zip_path))
    
    # Reset counter after successful upload
    global app_state
    app_state["files_since_last_zip"] = 0

def cleanup_upload_dir():
    """Removes the upload directory and its contents, but keeps the state file."""
    if os.path.exists(UPLOAD_DIR):
        for item in os.listdir(UPLOAD_DIR):
            item_path = os.path.join(UPLOAD_DIR, item)
            if os.path.isdir(item_path):
                shutil.rmtree(item_path)
            # Only remove files that are NOT the state file
            elif item != STATE_FILE_NAME:
                os.remove(item_path)
        print(f"Cleaned up files in {UPLOAD_DIR} directory (state file preserved).")

# --- Application Lifespan ---

@asynccontextmanager
async def lifespan(app: FastAPI):
    # Startup: 1. Ensure upload directory exists
    os.makedirs(UPLOAD_DIR, exist_ok=True)
    print(f"Application starting. Upload directory: {UPLOAD_DIR}")
    
    # Startup: 2. Download and load state (only internal counters are loaded here)
    # We rely on the /state/ endpoint to download the file_states from HF when needed.
    download_state_file_from_hf()
    load_state()
    print(f"Initial state counters: {app_state}")
    
    yield
    
    # Shutdown: 1. Upload state file (only internal counters are uploaded here)
    print("Application shutting down. Uploading final state counters...")
    upload_state_file_to_hf()
    
    # Shutdown: 2. Perform final zip and upload of any remaining files
    print("Performing final zip and upload...")
    zip_path = zip_uploaded_files_versioned()
    if zip_path:
        upload_zip_to_hf(zip_path)
        # Clean up the created zip file after upload
        os.remove(zip_path)
        
    # Shutdown: 3. Cleanup
    cleanup_upload_dir()
    print("Shutdown complete.")

# --- FastAPI App Initialization ---

app = FastAPI(
    title="Versioned File Uploader and Dataset Sync Service",
    description="A service for file management with versioned zipping and state persistence to Hugging Face.",
    version="2.0.0",
    lifespan=lifespan
)

# --- Endpoints ---

@app.post("/upload/")
async def upload_file(file: UploadFile = File(...)):
    """Upload a file to the server and trigger periodic tasks."""
    global app_state, file_states_cache
    
    # 1. Save the file
    try:
        file_path = os.path.join(UPLOAD_DIR, file.filename)
        
        # Check if file already exists to prevent overwriting without warning
        if os.path.exists(file_path):
            # Special handling for the state file: allow overwrite as it's a sync mechanism
            if file.filename != STATE_FILE_NAME:
                raise HTTPException(status_code=409, detail=f"File '{file.filename}' already exists.")

        try:
            # Write the uploaded file to the local UPLOAD_DIR
            with open(file_path, "wb") as buffer:
                shutil.copyfileobj(file.file, buffer)
        except Exception as e:
            raise HTTPException(status_code=500, detail=f"Could not write file to disk: {e}")
        
        # --- LOGIC FOR STATE FILE HANDLING ---
        if file.filename == STATE_FILE_NAME:
            print(f"Intercepted state file upload: {STATE_FILE_NAME}. Merging with cache...")
            # Read the uploaded state file and merge it with our cache
            try:
                with open(file_path, "r") as f:
                    uploaded_state = json.load(f)
                    
                # Merge the uploaded state into our cache
                if "file_states" in uploaded_state:
                    file_states_cache["file_states"] = uploaded_state["file_states"]
                if "next_download_index" in uploaded_state:
                    file_states_cache["next_download_index"] = uploaded_state["next_download_index"]
                
                # Save the merged state back to disk
                save_state()
                print(f"✅ State file merged: next_download_index={file_states_cache['next_download_index']}, file_states count={len(file_states_cache['file_states'])}")
            except Exception as e:
                print(f"Error processing uploaded state file: {e}")
            
            return {"filename": file.filename, "message": "State file successfully merged", "state": file_states_cache}
        # --- END LOGIC FOR STATE FILE HANDLING ---
        
        # 2. Update counters only after successful write of a non-state file (transcription JSON)
        app_state["total_files_uploaded"] += 1
        app_state["files_since_last_zip"] += 1
        app_state["files_since_last_state_upload"] += 1
        save_state() # Save both app_state and file_states
        
        print(f"✅ File uploaded: {file.filename} | files_since_last_zip={app_state['files_since_last_zip']}")
        
        # 3. Check for state file upload threshold (100 non-state file uploads)
        if app_state["files_since_last_state_upload"] >= STATE_UPLOAD_THRESHOLD:
            print(f"State upload threshold ({STATE_UPLOAD_THRESHOLD}) reached. Uploading state file...")
            upload_state_file_to_hf()
            
        # 4. Check for zip upload threshold (100 non-state file uploads)
        if app_state["files_since_last_zip"] >= ZIP_UPLOAD_THRESHOLD:
            print(f"Zip upload threshold ({ZIP_UPLOAD_THRESHOLD}) reached. Zipping and uploading files...")
            zip_path = zip_uploaded_files_versioned()
            if zip_path:
                upload_zip_to_hf(zip_path)
                os.remove(zip_path)
                cleanup_upload_dir()
                
        return {"filename": file.filename, "message": "File successfully uploaded", "state": app_state}
    except HTTPException:
        raise
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"An error occurred during upload: {e}")

@app.get("/download/{filename}")
async def download_file(filename: str):
    """Download a file from the server."""
    file_path = os.path.join(UPLOAD_DIR, filename)
    
    if not os.path.exists(file_path):
        raise HTTPException(status_code=404, detail="File not found")
    
    return FileResponse(
        path=file_path, 
        filename=filename, 
        media_type='application/octet-stream'
    )

@app.post("/sync_dataset/")
async def sync_dataset():
    """Manually trigger zipping of all uploaded files and uploading to the Hugging Face dataset."""
    print("Manual dataset sync triggered.")
    
    # 1. Upload state file (internal counters)
    upload_state_file_to_hf()
    
    # 2. Zip and upload files
    zip_path = zip_uploaded_files_versioned()
    if not zip_path:
        return {"message": "No files to sync. Upload directory is empty.", "state": app_state}
    
    upload_zip_to_hf(zip_path)
    
    # Clean up the created zip file after upload
    os.remove(zip_path)
    
    return {"message": "Files zipped and upload to Hugging Face dataset initiated.", "state": app_state}

@app.get("/files/")
async def list_files():
    """List all files currently available for download."""
    if not os.path.exists(UPLOAD_DIR):
        return {"files": []}
    
    # Exclude the state file from the list of downloadable files
    files = [f for f in os.listdir(UPLOAD_DIR) if f != STATE_FILE_NAME]
    return {"files": files, "state": app_state}

@app.get("/state/")
async def get_state():
    """
    Get the current application state (including file processing status).
    Returns both internal counters and client-managed file_states.
    """
    global file_states_cache
    
    # Return the merged state: app_state counters + file_states cache
    return_state = {
        **app_state,
        **file_states_cache
    }
    
    print(f"✅ Returning state: next_download_index={file_states_cache.get('next_download_index')}, file_states count={len(file_states_cache.get('file_states', {}))}")
    return {"state": return_state}

# --- Main execution block for testing/running ---
if __name__ == "__main__":
    import uvicorn
    # Set the token for local testing
    os.environ["HF_TOKEN"] = HF_TOKEN or "dummy_token_for_local_test"
    
    # Ensure UPLOAD_DIR exists before starting
    os.makedirs(UPLOAD_DIR, exist_ok=True)
    
    # Use a short timeout for local testing to simulate a quick run
    config = uvicorn.Config(app, host="0.0.0.0", port=8000, log_level="info")
    server = uvicorn.Server(config)
    
    # This block is for local testing and won't be used in the final sandbox execution
    # but is good practice for a runnable script.
    try:
        print("Starting server for local test...")
        # server.run() # Normally we would run this, but in the sandbox we use exec
        pass
    except KeyboardInterrupt:
        print("Server stopped by user.")
    finally:
        # Simulate cleanup that happens in the lifespan context manager
        # when running with uvicorn in a real environment.
        pass