from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.core.auth import hash_password, verify_password, create_access_token
from app.core.deps import get_current_user
from app.db.database import get_db
from app.db.models import ClassMembership, User
from app.schemas.auth import (
    ChangePasswordRequest,
    InviteCodeClassPreview,
    LoginRequest,
    RegisterRequest,
    SendEmailCodeRequest,
)
from app.schemas.user import TokenResponse, UserOut, build_user_out
from app.services.email_service import (
    send_account_activated_email,
    send_email_verification_code_email,
)
from app.services.email_verification_service import (
    ACTIVATION_EMAIL_PURPOSE,
    issue_email_verification_code,
    verify_email_code,
)
from app.services.member_activation_service import get_class_by_invite_code, validate_registration

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


@router.get("/invite-code/{invite_code}", response_model=InviteCodeClassPreview)
async def preview_invite_code_class(invite_code: str, db: AsyncSession = Depends(get_db)):
    class_ = await get_class_by_invite_code(db, invite_code.strip().upper())
    if class_ is None:
        raise HTTPException(status_code=404, detail="邀请码无效")
    return InviteCodeClassPreview(
        id=class_.id,
        name=class_.name,
        cohort_year=class_.cohort_year,
    )


@router.post("/email-verification-code")
async def send_activation_email_code(
    req: SendEmailCodeRequest,
    db: AsyncSession = Depends(get_db),
):
    existing = await db.execute(select(User).where(User.email == req.email))
    if existing.scalar_one_or_none():
        raise HTTPException(status_code=400, detail="该邮箱已注册")

    activation_target = await validate_registration(db, req.invite_code, req.student_id)
    if activation_target is None:
        raise HTTPException(status_code=400, detail="邀请码或学号无效，或账号已激活")

    code = await issue_email_verification_code(
        db,
        email=req.email,
        purpose=ACTIVATION_EMAIL_PURPOSE,
    )
    sent = await send_email_verification_code_email(req.email, code)
    if sent is False:
        raise HTTPException(status_code=500, detail="邮件发送失败，请检查邮件服务配置")
    return {"message": "验证码已发送，请查收邮箱"}


@router.post("/activate")
async def activate_account(req: RegisterRequest, db: AsyncSession = Depends(get_db)):
    # 1. Check if email is already in use
    existing = await db.execute(select(User).where(User.email == req.email))
    if existing.scalar_one_or_none():
        raise HTTPException(status_code=400, detail="该邮箱已注册")

    # 2. Validate invite_code + student_id against inactive class member
    activation_target = await validate_registration(db, req.invite_code, req.student_id)
    if activation_target is None:
        raise HTTPException(status_code=400, detail="邀请码或学号无效，或账号已激活")

    is_code_valid = await verify_email_code(
        db,
        email=req.email,
        code=req.email_code,
        purpose=ACTIVATION_EMAIL_PURPOSE,
    )
    if not is_code_valid:
        raise HTTPException(status_code=400, detail="邮箱验证码无效或已过期")

    user, class_id = activation_target
    user.email = req.email
    user.password_hash = hash_password(req.password)
    user.status = "approved"
    await db.commit()
    result = await db.execute(
        select(User)
        .options(
            selectinload(User.memberships),
            selectinload(User.memberships).selectinload(ClassMembership.class_),
        )
        .where(User.id == user.id)
    )
    user = result.scalar_one()
    user.set_active_membership(class_id)

    # 3. Issue token — activation and login in one step
    token = create_access_token({"sub": str(user.id), "role": user.role})
    await send_account_activated_email(req.email)
    return {
        "message": "账号激活成功",
        "token": token,
        "user": build_user_out(user, class_id),
    }


@router.post("/login", response_model=TokenResponse)
async def login(req: LoginRequest, db: AsyncSession = Depends(get_db)):
    result = await db.execute(
        select(User)
        .options(
            selectinload(User.memberships),
            selectinload(User.memberships).selectinload(ClassMembership.class_),
        )
        .where(User.email == req.email)
    )
    user = result.scalar_one_or_none()

    if user is None:
        raise HTTPException(status_code=401, detail="邮箱或密码错误")

    if user.status == "inactive":
        raise HTTPException(status_code=401, detail="账号尚未激活")

    if user.status == "disabled":
        raise HTTPException(status_code=401, detail="账号已被禁用")

    if not user.password_hash or not verify_password(req.password, user.password_hash):
        raise HTTPException(status_code=401, detail="邮箱或密码错误")

    token = create_access_token({"sub": str(user.id), "role": user.role})
    return TokenResponse(
        token=token,
        user=build_user_out(user),
    )


@router.get("/me", response_model=UserOut)
async def get_me(user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)):
    default_membership = user.get_default_membership()
    user_out = build_user_out(user, default_membership.class_id if default_membership else None)

    # Attach enabled_modules from active class
    if default_membership:
        from app.db.models import Class_
        from sqlalchemy import select

        result = await db.execute(select(Class_).where(Class_.id == default_membership.class_id))
        class_ = result.scalar_one_or_none()
        if class_:
            user_out.enabled_modules = class_.get_enabled_modules()

    return user_out


@router.put("/change-password")
async def change_password(
    req: ChangePasswordRequest,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    if not user.password_hash or not verify_password(req.old_password, user.password_hash):
        raise HTTPException(status_code=400, detail="Old password is incorrect")
    user.password_hash = hash_password(req.new_password)
    await db.commit()
    return {"message": "Password changed successfully"}