import secrets
import string
from datetime import datetime, timezone
from typing import Annotated
from fastapi import APIRouter, Depends, HTTPException, status, Request
from fastapi.security import OAuth2PasswordRequestForm
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select
from app.core.config import settings
from app.core.database import get_db
from app.core.rate_limit import limiter
from app.core.security import (
    verify_password,
    get_password_hash,
    create_access_token,
    create_refresh_token,
    decode_token,
    hash_token,
)
from app.models.user import User
from app.models.invite_code import InviteCode
from app.models.refresh_token import RefreshToken
from app.models.account import Account
from app.models.subscription import Subscription
from app.models.account_invite import AccountInvite
from app.schemas.user import UserCreate, UserResponse, UserLogin
from app.schemas.token import Token
from app.api.deps import get_current_active_user, get_refresh_token_payload

router = APIRouter(prefix="/auth", tags=["authentication"])


async def _store_refresh_token(db: AsyncSession, refresh_token_str: str, user_id) -> None:
    """Decode a refresh token JWT and store its hash in the database."""
    payload = decode_token(refresh_token_str)
    if payload and payload.get("jti"):
        token_record = RefreshToken(
            token_hash=hash_token(payload["jti"]),
            user_id=user_id,
            expires_at=datetime.fromtimestamp(payload["exp"], tz=timezone.utc),
        )
        db.add(token_record)


def _generate_display_code() -> str:
    """Generate a random 8-character alphanumeric display code."""
    chars = string.ascii_uppercase + string.digits
    return ''.join(secrets.choice(chars) for _ in range(8))


@router.post("/register", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
@limiter.limit("3/minute")
async def register(
    request: Request,
    user_data: UserCreate,
    db: Annotated[AsyncSession, Depends(get_db)]
):
    """Register a new user.

    Supports two flows:
    - account_invite_code: Join an existing account (bypasses platform invite gate)
    - invite_code: Platform invite code (when REQUIRE_INVITE_CODE is enabled)

    After user creation, if no account invite was used, a personal Account
    and free Subscription are created automatically.
    """
    # Check for account invite code FIRST — bypasses platform invite gate
    account_invite_record = None
    if user_data.account_invite_code:
        result = await db.execute(
            select(AccountInvite).where(
                AccountInvite.code == user_data.account_invite_code
            )
        )
        account_invite_record = result.scalar_one_or_none()

        if not account_invite_record:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Invalid account invite code"
            )

        if account_invite_record.is_used:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Account invite code has already been used"
            )

        if account_invite_record.is_expired:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Account invite code has expired"
            )

    # Validate platform invite code if required (skip if account invite was provided)
    invite_code_record = None
    if not account_invite_record and settings.REQUIRE_INVITE_CODE:
        if not user_data.invite_code:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Invite code is required"
            )

        # Look up invite code (case-insensitive)
        result = await db.execute(
            select(InviteCode).where(InviteCode.code == user_data.invite_code.upper())
        )
        invite_code_record = result.scalar_one_or_none()

        if not invite_code_record:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Invalid invite code"
            )

        if invite_code_record.is_used:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Invite code has already been used"
            )

        if invite_code_record.is_expired:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Invite code has expired"
            )

    # Check if email already exists
    result = await db.execute(select(User).where(User.email == user_data.email))
    existing_user = result.scalar_one_or_none()
    if existing_user:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Email already registered"
        )

    if account_invite_record:
        # Join existing account via account invite
        new_user = User(
            email=user_data.email,
            password_hash=get_password_hash(user_data.password),
            name=user_data.name,
            role="engineer",
            invite_code_id=invite_code_record.id if invite_code_record else None,
            account_id=account_invite_record.account_id,
            account_role=account_invite_record.role,
        )
        db.add(new_user)
        await db.flush()

        # Mark account invite as used
        account_invite_record.accepted_by_id = new_user.id
        account_invite_record.used_at = datetime.now(timezone.utc)
    else:
        # Create personal Account first (user needs account_id for NOT NULL constraint)
        new_account = Account(
            name=f"{user_data.name}'s Account",
            display_code=_generate_display_code(),
        )
        db.add(new_account)
        await db.flush()  # Get account ID

        new_user = User(
            email=user_data.email,
            password_hash=get_password_hash(user_data.password),
            name=user_data.name,
            role="engineer",
            invite_code_id=invite_code_record.id if invite_code_record else None,
            account_id=new_account.id,
            account_role="owner",
        )
        db.add(new_user)
        await db.flush()  # Get user ID

        # Now set account owner and create subscription
        new_account.owner_id = new_user.id

        new_subscription = Subscription(
            account_id=new_account.id,
            plan="free",
            status="active",
        )
        db.add(new_subscription)

    # Mark platform invite code as used
    if invite_code_record:
        invite_code_record.used_by_id = new_user.id
        invite_code_record.used_at = datetime.now(timezone.utc)

    await db.commit()
    await db.refresh(new_user)

    return new_user


@router.post("/login", response_model=Token)
@limiter.limit("5/minute")
async def login(
    request: Request,
    form_data: Annotated[OAuth2PasswordRequestForm, Depends()],
    db: Annotated[AsyncSession, Depends(get_db)]
):
    """Login and get access token."""
    # Find user by email
    result = await db.execute(select(User).where(User.email == form_data.username))
    user = result.scalar_one_or_none()

    if not user or not verify_password(form_data.password, user.password_hash):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect email or password",
            headers={"WWW-Authenticate": "Bearer"},
        )

    # Update last login
    user.last_login = datetime.now(timezone.utc)

    # Create tokens
    access_token = create_access_token(data={"sub": str(user.id)})
    refresh_token_str = create_refresh_token(data={"sub": str(user.id)})

    # Store refresh token hash in DB
    await _store_refresh_token(db, refresh_token_str, user.id)
    await db.commit()

    return Token(
        access_token=access_token,
        refresh_token=refresh_token_str,
        token_type="bearer"
    )


@router.post("/login/json", response_model=Token)
@limiter.limit("5/minute")
async def login_json(
    request: Request,
    credentials: UserLogin,
    db: Annotated[AsyncSession, Depends(get_db)]
):
    """Login with JSON body (alternative to form data)."""
    result = await db.execute(select(User).where(User.email == credentials.email))
    user = result.scalar_one_or_none()

    if not user or not verify_password(credentials.password, user.password_hash):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect email or password"
        )

    user.last_login = datetime.now(timezone.utc)

    access_token = create_access_token(data={"sub": str(user.id)})
    refresh_token_str = create_refresh_token(data={"sub": str(user.id)})

    # Store refresh token hash in DB
    await _store_refresh_token(db, refresh_token_str, user.id)
    await db.commit()

    return Token(
        access_token=access_token,
        refresh_token=refresh_token_str,
        token_type="bearer"
    )


@router.post("/refresh", response_model=Token)
@limiter.limit("10/minute")
async def refresh_token(
    request: Request,
    payload: Annotated[dict, Depends(get_refresh_token_payload)],
    db: Annotated[AsyncSession, Depends(get_db)]
):
    """Refresh access token using refresh token (rotation: old token is revoked)."""
    user_id = payload.get("sub")
    jti = payload.get("jti")

    # Validate refresh token hasn't been revoked
    if jti:
        token_hash = hash_token(jti)
        result = await db.execute(
            select(RefreshToken).where(RefreshToken.token_hash == token_hash)
        )
        stored_token = result.scalar_one_or_none()

        if stored_token and stored_token.is_revoked:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Refresh token has been revoked"
            )

        # Revoke the old refresh token (token rotation)
        if stored_token:
            stored_token.revoked_at = datetime.now(timezone.utc)

    result = await db.execute(select(User).where(User.id == user_id))
    user = result.scalar_one_or_none()

    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="User not found"
        )

    access_token = create_access_token(data={"sub": str(user.id)})
    new_refresh_token_str = create_refresh_token(data={"sub": str(user.id)})

    # Store new refresh token
    await _store_refresh_token(db, new_refresh_token_str, user.id)
    await db.commit()

    return Token(
        access_token=access_token,
        refresh_token=new_refresh_token_str,
        token_type="bearer"
    )


@router.get("/me", response_model=UserResponse)
async def get_me(
    current_user: Annotated[User, Depends(get_current_active_user)]
):
    """Get current authenticated user."""
    return current_user


@router.post("/logout")
async def logout(
    payload: Annotated[dict, Depends(get_refresh_token_payload)],
    db: Annotated[AsyncSession, Depends(get_db)]
):
    """Logout user by revoking the refresh token."""
    jti = payload.get("jti")
    if jti:
        token_hash = hash_token(jti)
        result = await db.execute(
            select(RefreshToken).where(RefreshToken.token_hash == token_hash)
        )
        stored_token = result.scalar_one_or_none()
        if stored_token and not stored_token.is_revoked:
            stored_token.revoked_at = datetime.now(timezone.utc)
            await db.commit()

    return {"message": "Successfully logged out"}