import os
from typing import Optional, List
from datetime import datetime
from pathlib import Path

from fastapi import FastAPI, Depends, HTTPException, status, Request, Form
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from fastapi.staticfiles import StaticFiles
from fastapi.templating import Jinja2Templates
from fastapi.responses import RedirectResponse
from pydantic import BaseModel, EmailStr
from passlib.context import CryptContext

from sqlalchemy import create_engine, Column, Integer, String, Text, ForeignKey, TIMESTAMP
from sqlalchemy.sql import func
from sqlalchemy.orm import sessionmaker, declarative_base, relationship, Session

# ==========================================
# Database Configuration
# ==========================================
SQLALCHEMY_DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://postgres.nujbaaxesubgawnazmza:gVgyOv6DL9vkzGmh@aws-1-ap-south-1.pooler.supabase.com:6543/postgres")

engine = create_engine(
    SQLALCHEMY_DATABASE_URL,
    pool_pre_ping=True,
    pool_size=5,
    max_overflow=10,
    pool_recycle=300,
    connect_args={"connect_timeout": 10},
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()

def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()

# ==========================================
# Models
# ==========================================
class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True, index=True)
    name = Column(String(100), nullable=False)
    age = Column(Integer, nullable=False)
    address = Column(Text, nullable=False)
    email = Column(String(100), unique=True, index=True, nullable=False)
    mobile_number = Column(String(20), nullable=False)
    password_hash = Column(String(255), nullable=False)
    created_at = Column(TIMESTAMP, server_default=func.now())

    files = relationship("File", back_populates="owner")

class File(Base):
    __tablename__ = "files"

    id = Column(Integer, primary_key=True, index=True)
    filename = Column(String(255), nullable=False)
    file_type = Column(String(50), nullable=False)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
    upload_timestamp = Column(TIMESTAMP, server_default=func.now())

    owner = relationship("User", back_populates="files")

# ==========================================
# Schemas
# ==========================================
class UserCreate(BaseModel):
    name: str
    age: int
    address: str
    email: EmailStr
    mobile_number: str
    password: str

class UserLogin(BaseModel):
    email: EmailStr
    password: str

class UserResponse(BaseModel):
    id: int
    name: str
    email: str

    class Config:
        from_attributes = True

class Token(BaseModel):
    access_token: str
    token_type: str

class TokenData(BaseModel):
    email: Optional[str] = None

# ==========================================
# FastAPI App setup
# ==========================================

app = FastAPI(title="Task 1 API")

@app.on_event("startup")
def on_startup():
    """Create DB tables on startup — retry-safe."""
    try:
        Base.metadata.create_all(bind=engine)
        print("✅ Database tables created / verified.")
    except Exception as e:
        print(f"⚠️  Could not connect to database on startup: {e}")
        print("   The app will start anyway; DB operations will fail until the DB is reachable.")

# --- Static files & Templates ---
BASE_DIR = Path(__file__).resolve().parent
app.mount("/static", StaticFiles(directory=str(BASE_DIR / "static")), name="static")
templates = Jinja2Templates(directory=str(BASE_DIR / "templates"))

pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="api/login")

# --- Helper Functions ---
def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password[:72], hashed_password)

def get_password_hash(password):
    return pwd_context.hash(password[:72])

def get_user_by_email(db: Session, email: str):
    return db.query(User).filter(User.email == email).first()

# ==========================================
# JSON API Endpoints (prefixed with /api/)
# ==========================================
@app.post("/api/signup", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
def signup(user: UserCreate, db: Session = Depends(get_db)):
    db_user = get_user_by_email(db, email=user.email)
    if db_user:
        raise HTTPException(status_code=400, detail="Email already registered")
    
    hashed_password = get_password_hash(user.password)
    
    new_user = User(
        name=user.name,
        age=user.age,
        address=user.address,
        email=user.email,
        mobile_number=user.mobile_number,
        password_hash=hashed_password
    )
    
    db.add(new_user)
    db.commit()
    db.refresh(new_user)
    
    return new_user

@app.post("/api/login", response_model=Token)
def login(form_data: OAuth2PasswordRequestForm = Depends(), db: Session = Depends(get_db)):
    # OAuth2PasswordRequestForm uses 'username' and 'password'
    # We map 'username' to 'email' in our DB
    user = get_user_by_email(db, email=form_data.username)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid credentials",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    if not verify_password(form_data.password, user.password_hash):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid credentials",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    # In a real app we'd create a proper JWT token here
    # For simplicity, returning a simple token string
    access_token = f"fake-jwt-token-for-{user.email}"
    
    return {"access_token": access_token, "token_type": "bearer"}

@app.get("/api/users/me", response_model=UserResponse)
def read_users_me(token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)):
    # This is a mock function since we aren't decoding real JWTs yet
    email = token.replace("fake-jwt-token-for-", "")
    user = get_user_by_email(db, email=email)
    if user is None:
        raise HTTPException(status_code=401, detail="Invalid token")
    return user

# ==========================================
# File Handling Endpoints
# ==========================================

UPLOAD_DIR = "uploads"
os.makedirs(UPLOAD_DIR, exist_ok=True)
ALLOWED_EXTENSIONS = {".pdf", ".png", ".jpeg", ".jpg"}

from fastapi import UploadFile, File as FastAPIFile
from fastapi.responses import FileResponse
import shutil

@app.post("/api/upload")
async def upload_file(
    file: UploadFile = FastAPIFile(...),
    token: str = Depends(oauth2_scheme),
    db: Session = Depends(get_db)
):
    # Authenticate user
    email = token.replace("fake-jwt-token-for-", "")
    user = get_user_by_email(db, email=email)
    if not user:
        raise HTTPException(status_code=401, detail="Invalid token")

    # Validate file type
    file_ext = os.path.splitext(file.filename)[1].lower()
    if file_ext not in ALLOWED_EXTENSIONS:
        raise HTTPException(status_code=400, detail=f"Invalid file type. Allowed: {', '.join(ALLOWED_EXTENSIONS)}")

    # Generate custom filename
    custom_filename = f"{user.id}_{user.name.replace(' ', '_')}_{file.filename}"
    file_path = os.path.join(UPLOAD_DIR, custom_filename)

    # Save to disk
    with open(file_path, "wb") as buffer:
        shutil.copyfileobj(file.file, buffer)

    # Save metadata to database
    db_file = File(
        filename=custom_filename,
        file_type=file_ext,
        user_id=user.id
    )
    db.add(db_file)
    db.commit()
    db.refresh(db_file)

    return {"message": "File uploaded successfully", "file_id": db_file.id, "filename": custom_filename}


@app.get("/api/download/{file_id}")
async def download_file(
    file_id: int,
    token: str = Depends(oauth2_scheme),
    db: Session = Depends(get_db)
):
    # Authenticate user
    email = token.replace("fake-jwt-token-for-", "")
    user = get_user_by_email(db, email=email)
    if not user:
        raise HTTPException(status_code=401, detail="Invalid token")

    # Fetch file record (Ensuring users can only see their own files)
    file_record = db.query(File).filter(File.id == file_id, File.user_id == user.id).first()
    if not file_record:
        raise HTTPException(status_code=404, detail="File not found")

    file_path = os.path.join(UPLOAD_DIR, file_record.filename)
    if not os.path.exists(file_path):
        raise HTTPException(status_code=404, detail="File is missing on the server")

    return FileResponse(path=file_path, filename=file_record.filename)


# --- File metadata response schema ---
class FileMetaResponse(BaseModel):
    id: int
    filename: str
    file_type: str
    upload_timestamp: Optional[datetime] = None

    class Config:
        from_attributes = True


@app.get("/api/files", response_model=List[FileMetaResponse])
async def list_files(
    token: str = Depends(oauth2_scheme),
    db: Session = Depends(get_db)
):
    """List all files belonging to the authenticated user."""
    email = token.replace("fake-jwt-token-for-", "")
    user = get_user_by_email(db, email=email)
    if not user:
        raise HTTPException(status_code=401, detail="Invalid token")

    files = db.query(File).filter(File.user_id == user.id).all()
    return files


@app.put("/api/files/{file_id}")
async def update_file(
    file_id: int,
    file: UploadFile = FastAPIFile(...),
    token: str = Depends(oauth2_scheme),
    db: Session = Depends(get_db)
):
    """Replace an existing file with a new upload."""
    email = token.replace("fake-jwt-token-for-", "")
    user = get_user_by_email(db, email=email)
    if not user:
        raise HTTPException(status_code=401, detail="Invalid token")

    file_record = db.query(File).filter(File.id == file_id, File.user_id == user.id).first()
    if not file_record:
        raise HTTPException(status_code=404, detail="File not found")

    # Validate new file type
    file_ext = os.path.splitext(file.filename)[1].lower()
    if file_ext not in ALLOWED_EXTENSIONS:
        raise HTTPException(status_code=400, detail=f"Invalid file type. Allowed: {', '.join(ALLOWED_EXTENSIONS)}")

    # Remove old physical file
    old_path = os.path.join(UPLOAD_DIR, file_record.filename)
    if os.path.exists(old_path):
        os.remove(old_path)

    # Save new file
    custom_filename = f"{user.id}_{user.name.replace(' ', '_')}_{file.filename}"
    new_path = os.path.join(UPLOAD_DIR, custom_filename)
    with open(new_path, "wb") as buffer:
        shutil.copyfileobj(file.file, buffer)

    # Update DB record
    file_record.filename = custom_filename
    file_record.file_type = file_ext
    db.commit()
    db.refresh(file_record)

    return {"message": "File updated successfully", "file_id": file_record.id, "filename": custom_filename}


@app.delete("/api/files/{file_id}")
async def delete_file(
    file_id: int,
    token: str = Depends(oauth2_scheme),
    db: Session = Depends(get_db)
):
    """Delete a file record and its physical file."""
    email = token.replace("fake-jwt-token-for-", "")
    user = get_user_by_email(db, email=email)
    if not user:
        raise HTTPException(status_code=401, detail="Invalid token")

    file_record = db.query(File).filter(File.id == file_id, File.user_id == user.id).first()
    if not file_record:
        raise HTTPException(status_code=404, detail="File not found")

    # Remove physical file
    file_path = os.path.join(UPLOAD_DIR, file_record.filename)
    if os.path.exists(file_path):
        os.remove(file_path)

    db.delete(file_record)
    db.commit()

    return {"message": "File deleted successfully"}


# ==========================================================
# HTML Page Routes (Jinja2 Templates + cookie-based session)
# ==========================================================

def _get_current_user_from_cookie(request: Request, db: Session):
    """Read the auth token from a cookie and return the User or None."""
    token = request.cookies.get("access_token", "")
    if not token:
        return None
    email = token.replace("fake-jwt-token-for-", "")
    return get_user_by_email(db, email=email)


@app.get("/")
def root_redirect():
    return RedirectResponse(url="/login", status_code=302)


# ---- Sign-Up Page ----
@app.get("/signup")
def page_signup(request: Request):
    return templates.TemplateResponse("signup.html", {"request": request})


@app.post("/signup")
def page_signup_post(
    request: Request,
    name: str = Form(...),
    age: int = Form(...),
    address: str = Form(...),
    email: str = Form(...),
    mobile_number: str = Form(...),
    password: str = Form(...),
    db: Session = Depends(get_db),
):
    existing = get_user_by_email(db, email=email)
    if existing:
        return templates.TemplateResponse("signup.html", {
            "request": request,
            "message": "Email already registered",
            "msg_type": "error",
        })

    new_user = User(
        name=name, age=age, address=address,
        email=email, mobile_number=mobile_number,
        password_hash=get_password_hash(password),
    )
    db.add(new_user)
    db.commit()

    response = RedirectResponse(url="/login", status_code=302)
    return response


# ---- Login Page ----
@app.get("/login")
def page_login(request: Request):
    return templates.TemplateResponse("login.html", {"request": request})


@app.post("/login")
def page_login_post(
    request: Request,
    email: str = Form(...),
    password: str = Form(...),
    db: Session = Depends(get_db),
):
    user = get_user_by_email(db, email=email)
    if not user or not verify_password(password, user.password_hash):
        return templates.TemplateResponse("login.html", {
            "request": request,
            "message": "Invalid email or password",
            "msg_type": "error",
        })

    token = f"fake-jwt-token-for-{user.email}"
    response = RedirectResponse(url="/dashboard", status_code=302)
    response.set_cookie(key="access_token", value=token, httponly=True)
    return response


# ---- Dashboard ----
@app.get("/dashboard")
def page_dashboard(request: Request, db: Session = Depends(get_db)):
    user = _get_current_user_from_cookie(request, db)
    if not user:
        return RedirectResponse(url="/login", status_code=302)

    files = db.query(File).filter(File.user_id == user.id).all()
    return templates.TemplateResponse("dashboard.html", {
        "request": request,
        "user": user,
        "files": files,
    })


# ---- Upload from browser ----
@app.post("/upload")
async def page_upload(
    request: Request,
    file1: UploadFile = FastAPIFile(...),
    file2: Optional[UploadFile] = FastAPIFile(None),
    db: Session = Depends(get_db),
):
    user = _get_current_user_from_cookie(request, db)
    if not user:
        return RedirectResponse(url="/login", status_code=302)

    uploaded = 0
    for f in [file1, file2]:
        if f is None or f.filename == "":
            continue
        file_ext = os.path.splitext(f.filename)[1].lower()
        if file_ext not in ALLOWED_EXTENSIONS:
            continue  # silently skip invalid types
        custom_filename = f"{user.id}_{user.name.replace(' ', '_')}_{f.filename}"
        dest = os.path.join(UPLOAD_DIR, custom_filename)
        with open(dest, "wb") as buf:
            shutil.copyfileobj(f.file, buf)
        db_file = File(filename=custom_filename, file_type=file_ext, user_id=user.id)
        db.add(db_file)
        uploaded += 1

    db.commit()
    return RedirectResponse(url="/dashboard", status_code=302)


# ---- Download from browser ----
@app.get("/download/{file_id}")
async def page_download(file_id: int, request: Request, db: Session = Depends(get_db)):
    user = _get_current_user_from_cookie(request, db)
    if not user:
        return RedirectResponse(url="/login", status_code=302)

    file_record = db.query(File).filter(File.id == file_id, File.user_id == user.id).first()
    if not file_record:
        return RedirectResponse(url="/dashboard", status_code=302)

    file_path = os.path.join(UPLOAD_DIR, file_record.filename)
    if not os.path.exists(file_path):
        return RedirectResponse(url="/dashboard", status_code=302)

    from fastapi.responses import FileResponse as FR
    return FR(path=file_path, filename=file_record.filename)


# ---- Delete from browser ----
@app.get("/delete/{file_id}")
def page_delete(file_id: int, request: Request, db: Session = Depends(get_db)):
    user = _get_current_user_from_cookie(request, db)
    if not user:
        return RedirectResponse(url="/login", status_code=302)

    file_record = db.query(File).filter(File.id == file_id, File.user_id == user.id).first()
    if file_record:
        file_path = os.path.join(UPLOAD_DIR, file_record.filename)
        if os.path.exists(file_path):
            os.remove(file_path)
        db.delete(file_record)
        db.commit()

    return RedirectResponse(url="/dashboard", status_code=302)


# ---- Logout ----
@app.get("/logout")
def page_logout():
    response = RedirectResponse(url="/login", status_code=302)
    response.delete_cookie("access_token")
    return response