from datetime import datetime
from enum import Enum
from typing import TYPE_CHECKING, Optional

from sqlalchemy import (
    BigInteger,
    DateTime,
    ForeignKey,
    Index,
    Integer,
    String,
    UniqueConstraint,
    func,
)
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.database.session import Base

if TYPE_CHECKING:
    from app.backoffice.admin.models import Admin
    from app.user.models import User


class ChargeRequestStatus(str, Enum):
    PENDING = "pending"
    APPROVED = "approved"
    REJECTED = "rejected"
    CANCELLED = "cancelled"


class CreditTransactionType(str, Enum):
    CHARGE = "charge"
    CONSUME = "consume"
    REFUND = "refund"
    ADMIN_ADJUST = "admin_adjust"


class CreditChargeRequest(Base):
    __tablename__ = "credit_charge_request"
    __table_args__ = (
        Index("idx_credit_request_user_uuid", "user_uuid"),
        Index("idx_credit_request_status", "status"),
        Index("idx_credit_request_created_at", "created_at"),
        Index("idx_credit_request_status_created", "status", "created_at"),
        {
            "mysql_engine": "InnoDB",
            "mysql_charset": "utf8mb4",
            "mysql_collate": "utf8mb4_unicode_ci",
        },
    )

    id: Mapped[int] = mapped_column(
        BigInteger,
        primary_key=True,
        nullable=False,
        autoincrement=True,
        comment="고유 식별자",
    )

    user_uuid: Mapped[str] = mapped_column(
        String(36),
        ForeignKey("user.user_uuid", ondelete="CASCADE"),
        nullable=False,
        comment="사용자 UUID (user.user_uuid 참조)",
    )

    requested_amount: Mapped[int] = mapped_column(
        Integer,
        nullable=False,
        comment="요청 크레딧 수량 (양수)",
    )

    message: Mapped[Optional[str]] = mapped_column(
        String(500),
        nullable=True,
        comment="사용자 요청 메시지",
    )

    status: Mapped[str] = mapped_column(
        String(20),
        nullable=False,
        default=ChargeRequestStatus.PENDING,
        server_default="pending",
        comment="처리 상태 (pending/approved/rejected/cancelled)",
    )

    admin_id: Mapped[Optional[int]] = mapped_column(
        BigInteger,
        ForeignKey("admin.id", ondelete="SET NULL"),
        nullable=True,
        comment="처리한 백오피스 관리자 ID",
    )

    admin_note: Mapped[Optional[str]] = mapped_column(
        String(1000),
        nullable=True,
        comment="관리자 메모",
    )

    processed_at: Mapped[Optional[datetime]] = mapped_column(
        DateTime,
        nullable=True,
        comment="처리 일시",
    )

    created_at: Mapped[datetime] = mapped_column(
        DateTime,
        nullable=False,
        server_default=func.now(),
        comment="요청 일시",
    )

    updated_at: Mapped[datetime] = mapped_column(
        DateTime,
        nullable=False,
        server_default=func.now(),
        onupdate=func.now(),
        comment="수정 일시",
    )

    user: Mapped["User"] = relationship(
        "User",
        foreign_keys=[user_uuid],
        primaryjoin="CreditChargeRequest.user_uuid == User.user_uuid",
        back_populates="credit_requests",
        lazy="noload",
    )

    transactions: Mapped[list["CreditTransaction"]] = relationship(
        "CreditTransaction",
        back_populates="charge_request",
        lazy="noload",
    )

    admin: Mapped[Optional["Admin"]] = relationship(
        "Admin",
        foreign_keys=[admin_id],
        primaryjoin="CreditChargeRequest.admin_id == Admin.id",
        lazy="selectin",
    )

    def __repr__(self) -> str:
        return (
            f"<CreditChargeRequest("
            f"id={self.id}, user_uuid='{self.user_uuid}', "
            f"amount={self.requested_amount}, status='{self.status}'"
            f")>"
        )


class CreditTransaction(Base):
    __tablename__ = "credit_transaction"
    __table_args__ = (
        Index("idx_credit_tx_user_uuid", "user_uuid"),
        Index("idx_credit_tx_user_uuid_created", "user_uuid", "created_at"),
        Index("idx_credit_tx_type", "type"),
        Index("idx_credit_tx_related_request", "related_request_id"),
        # 작업 1건당 consume 1행 / refund 1행을 DB 레벨에서 보장하는 멱등 키.
        # MySQL 은 NULL 을 서로 다르게 취급하므로 job_type 이 NULL 인 기존
        # charge/admin_adjust 행은 이 제약의 영향을 받지 않는다.
        UniqueConstraint("job_type", "job_ref", "type", name="uq_credit_job"),
        {
            "mysql_engine": "InnoDB",
            "mysql_charset": "utf8mb4",
            "mysql_collate": "utf8mb4_unicode_ci",
        },
    )

    id: Mapped[int] = mapped_column(
        BigInteger,
        primary_key=True,
        nullable=False,
        autoincrement=True,
        comment="고유 식별자",
    )

    user_uuid: Mapped[str] = mapped_column(
        String(36),
        ForeignKey("user.user_uuid", ondelete="CASCADE"),
        nullable=False,
        comment="사용자 UUID",
    )

    amount: Mapped[int] = mapped_column(
        Integer,
        nullable=False,
        comment="변경 크레딧 수량 (충전 양수, 차감 음수)",
    )

    balance_after: Mapped[int] = mapped_column(
        Integer,
        nullable=False,
        comment="변경 직후 잔액",
    )

    type: Mapped[str] = mapped_column(
        String(20),
        nullable=False,
        comment="변경 유형 (charge/consume/refund/admin_adjust)",
    )

    reason: Mapped[Optional[str]] = mapped_column(
        String(255),
        nullable=True,
        comment="변경 사유",
    )

    admin_id: Mapped[Optional[int]] = mapped_column(
        BigInteger,
        ForeignKey("admin.id", ondelete="SET NULL"),
        nullable=True,
        comment="처리 관리자 ID (관리자 충전/차감 시)",
    )

    related_request_id: Mapped[Optional[int]] = mapped_column(
        BigInteger,
        ForeignKey("credit_charge_request.id", ondelete="SET NULL"),
        nullable=True,
        comment="연관 충전 요청 ID",
    )

    # ==========================================================================
    # 작업 기반 멱등 키 — (job_type, job_ref, type) 유니크
    # ==========================================================================
    # 사전차감 정책의 핵심. 생성 작업을 시작할 때 차감하고 실패 시 환불하는데,
    # 재시도·중복 요청·크래시 후 재처리에도 "작업 1건당 정확히 1번"을 보장해야 한다.
    # FK 를 걸지 않는 이유: 썰박스(ssul_task.id 숫자)와 영상(video.task_id UUID7 문자열)
    # 이라는 이질적인 두 작업 테이블을 하나의 컬럼이 가리키기 때문이다.
    job_type: Mapped[Optional[str]] = mapped_column(
        String(20),
        nullable=True,
        comment="차감 유발 작업 종류 (ssul/video). 충전·관리자 조정은 NULL",
    )

    job_ref: Mapped[Optional[str]] = mapped_column(
        String(64),
        nullable=True,
        comment="작업 식별자 (ssul_task.id 문자열 또는 video.task_id)",
    )

    created_at: Mapped[datetime] = mapped_column(
        DateTime,
        nullable=False,
        server_default=func.now(),
        comment="변경 일시",
    )

    user: Mapped["User"] = relationship(
        "User",
        foreign_keys=[user_uuid],
        primaryjoin="CreditTransaction.user_uuid == User.user_uuid",
        back_populates="credit_transactions",
        lazy="noload",
    )

    charge_request: Mapped[Optional[CreditChargeRequest]] = relationship(
        "CreditChargeRequest",
        back_populates="transactions",
        lazy="noload",
    )

    admin: Mapped[Optional["Admin"]] = relationship(
        "Admin",
        foreign_keys=[admin_id],
        primaryjoin="CreditTransaction.admin_id == Admin.id",
        lazy="selectin",
    )

    def __repr__(self) -> str:
        return (
            f"<CreditTransaction("
            f"id={self.id}, user_uuid='{self.user_uuid}', "
            f"amount={self.amount}, type='{self.type}'"
            f")>"
        )