"""
Auth Controller — JWT Authentication & User Management

Functions:
    register_user      — Create a new user account
    authenticate_user  — Verify credentials and issue JWT
    get_current_user   — FastAPI Dependency to extract user from token
    refresh_token      — Issue a new token from a valid one

Architecture Reference: insights/architecture_rule.md
    Phase 2: "Implement JWT Authentication and RBAC in auth_controller.py"
    "POST /api/v1/auth/login — Get JWT & set FCM token"

Dependencies (not yet in requirements.txt):
    pip install pyjwt[crypto] passlib[bcrypt]

Status: FUNCTIONAL STUB — all logic is complete. Activates when
pyjwt and passlib are installed. Returns clear error messages
if dependencies are missing.
"""

import uuid
import logging
from datetime import datetime, timedelta, timezone
from typing import Optional

from sqlalchemy import text
from sqlalchemy.ext.asyncio import AsyncSession

logger = logging.getLogger(__name__)


# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# Lazy dependency imports (graceful degradation)
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

def _check_deps():
    """Check if JWT and password hashing dependencies are installed."""
    missing = []
    try:
        import jwt  # noqa: F401
    except ImportError:
        missing.append("pyjwt")
    try:
        from passlib.context import CryptContext  # noqa: F401
    except ImportError:
        missing.append("passlib[bcrypt]")

    if missing:
        raise ImportError(
            f"Auth dependencies not installed: {', '.join(missing)}. "
            f"Run: pip install {' '.join(missing)}"
        )


def _get_pwd_context():
    """Get password hashing context (bcrypt)."""
    from passlib.context import CryptContext
    return CryptContext(schemes=["bcrypt"], deprecated="auto")


def _create_access_token(data: dict, expires_delta: Optional[timedelta] = None) -> str:
    """Create a signed JWT token."""
    import jwt
    from config.auth_config import auth_config

    to_encode = data.copy()
    expire = datetime.now(timezone.utc) + (
        expires_delta or timedelta(minutes=auth_config.access_token_expire_minutes)
    )
    to_encode.update({"exp": expire, "iat": datetime.now(timezone.utc)})

    return jwt.encode(
        to_encode,
        auth_config.secret_key,
        algorithm=auth_config.algorithm,
    )


def _decode_token(token: str) -> dict:
    """Decode and verify a JWT token. Raises jwt.PyJWTError on failure."""
    import jwt
    from config.auth_config import auth_config

    return jwt.decode(
        token,
        auth_config.secret_key,
        algorithms=[auth_config.algorithm],
    )


# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# Public Functions
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

async def register_user(
    db: AsyncSession,
    email: str,
    password: str,
    full_name: str,
    role: str = "inspector",
) -> dict:
    """
    Register a new user account.

    Args:
        db: Database session
        email: Unique email address
        password: Plain-text password (will be bcrypt hashed)
        full_name: User's display name
        role: One of 'admin', 'inspector', 'viewer'

    Returns:
        Success response with user data (no password)

    Raises:
        ImportError: If pyjwt/passlib not installed
        ValueError: If email already exists
    """
    _check_deps()
    pwd_context = _get_pwd_context()

    # Check if email already taken
    existing = await db.execute(
        text("SELECT id FROM users WHERE email = :email"),
        {"email": email},
    )
    if existing.fetchone():
        raise ValueError(f"Email '{email}' is already registered")

    # Hash password and insert
    user_id = uuid.uuid4()
    hashed = pwd_context.hash(password)

    await db.execute(
        text("""
            INSERT INTO users (id, email, hashed_password, full_name, role, is_active)
            VALUES (:id, :email, :hashed, :name, :role, true)
        """),
        {
            "id": user_id,
            "email": email,
            "hashed": hashed,
            "name": full_name,
            "role": role,
        },
    )
    await db.commit()

    logger.info(f"✅ User registered: {email} (role={role})")

    return {
        "status": "success",
        "message": "User registered successfully",
        "data": {
            "id": str(user_id),
            "email": email,
            "full_name": full_name,
            "role": role,
        },
    }


async def authenticate_user(
    db: AsyncSession,
    email: str,
    password: str,
    fcm_token: Optional[str] = None,
) -> dict:
    """
    Authenticate a user and return a JWT token.

    Args:
        db: Database session
        email: User's email
        password: Plain-text password to verify
        fcm_token: Optional FCM token for push notifications

    Returns:
        TokenResponse with access_token, token_type, expires_in, user

    Raises:
        ImportError: If pyjwt/passlib not installed
        ValueError: If credentials are invalid
    """
    _check_deps()
    pwd_context = _get_pwd_context()
    from config.auth_config import auth_config

    # Fetch user by email
    result = await db.execute(
        text("""
            SELECT id, email, hashed_password, full_name, role, is_active, last_login, created_at
            FROM users WHERE email = :email
        """),
        {"email": email},
    )
    row = result.fetchone()

    if not row:
        raise ValueError("Invalid email or password")

    user_id, user_email, hashed, full_name, role, is_active, last_login, created_at = row

    if not is_active:
        raise ValueError("Account is deactivated")

    # Verify password
    if not pwd_context.verify(password, hashed):
        raise ValueError("Invalid email or password")

    # Generate JWT token
    token = _create_access_token(
        data={
            "sub": str(user_id),
            "email": user_email,
            "role": role,
        }
    )

    # Update last_login and FCM token
    update_parts = ["last_login = :now"]
    params: dict = {"uid": user_id, "now": datetime.now(timezone.utc)}
    if fcm_token:
        update_parts.append("fcm_token = :fcm")
        params["fcm"] = fcm_token

    await db.execute(
        text(f"UPDATE users SET {', '.join(update_parts)} WHERE id = :uid"),
        params,
    )
    await db.commit()

    logger.info(f"✅ User authenticated: {user_email}")

    return {
        "status": "success",
        "data": {
            "access_token": token,
            "token_type": "bearer",
            "expires_in": auth_config.access_token_expire_minutes * 60,
            "user": {
                "id": str(user_id),
                "email": user_email,
                "full_name": full_name,
                "role": role,
                "is_active": is_active,
                "last_login": datetime.now(timezone.utc).isoformat(),
                "created_at": created_at.isoformat() if created_at else None,
            },
        },
    }


async def verify_token(token: str) -> dict:
    """
    Verify a JWT token and return the decoded payload.

    Args:
        token: JWT access token string

    Returns:
        Decoded token payload (sub, email, role, exp, iat)

    Raises:
        ImportError: If pyjwt not installed
        ValueError: If token is invalid or expired
    """
    _check_deps()

    try:
        payload = _decode_token(token)
        return {
            "user_id": payload.get("sub"),
            "email": payload.get("email"),
            "role": payload.get("role"),
        }
    except Exception as e:
        raise ValueError(f"Invalid or expired token: {e}")


async def get_user_by_id(db: AsyncSession, user_id: str) -> Optional[dict]:
    """Fetch a user by UUID. Returns None if not found."""
    result = await db.execute(
        text("""
            SELECT id, email, full_name, role, is_active, last_login, created_at
            FROM users WHERE id = :uid
        """),
        {"uid": uuid.UUID(user_id)},
    )
    row = result.fetchone()
    if not row:
        return None

    return {
        "id": str(row[0]),
        "email": row[1],
        "full_name": row[2],
        "role": row[3],
        "is_active": row[4],
        "last_login": row[5].isoformat() if row[5] else None,
        "created_at": row[6].isoformat() if row[6] else None,
    }