from datetime import datetime
from typing import TYPE_CHECKING, List, Optional

from sqlalchemy import Boolean, DateTime, ForeignKey, Index, Integer, String, func
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.database.session import Base

if TYPE_CHECKING:
    from app.user.models import User
    from app.video.models import Video


class Comment(Base):
    """
    영상 댓글 테이블

    2-depth 구조 (최상위 댓글 + 대댓글 1단계).
    parent_id가 NULL이면 최상위 댓글, 값이 있으면 대댓글.
    작성자(user_uuid)는 DB에 저장하지만 API 응답에는 미노출 (익명 정책).
    """

    __tablename__ = "comment"
    __table_args__ = (
        Index("idx_comment_video_id", "video_id"),
        Index("idx_comment_user_uuid", "user_uuid"),
        Index("idx_comment_parent_id", "parent_id"),
        Index("idx_comment_is_deleted", "is_deleted"),
        {
            "mysql_engine": "InnoDB",
            "mysql_charset": "utf8mb4",
            "mysql_collate": "utf8mb4_unicode_ci",
        },
    )

    id: Mapped[int] = mapped_column(
        Integer, primary_key=True, autoincrement=True, comment="고유 식별자"
    )
    video_id: Mapped[int] = mapped_column(
        Integer,
        ForeignKey("video.id", ondelete="CASCADE"),
        nullable=False,
        comment="연결된 Video의 id",
    )
    user_uuid: Mapped[str] = mapped_column(
        ForeignKey("user.user_uuid", ondelete="CASCADE"),
        nullable=False,
        comment="작성자 UUID (응답 미노출, 권한 검증용)",
    )
    parent_id: Mapped[Optional[int]] = mapped_column(
        Integer,
        ForeignKey("comment.id", ondelete="CASCADE"),
        nullable=True,
        comment="NULL=최상위 댓글, 값=대댓글의 부모 id",
    )
    nickname: Mapped[Optional[str]] = mapped_column(
        String(50), nullable=True, comment="댓글 작성자 닉네임 (null이면 익명)"
    )
    content: Mapped[str] = mapped_column(
        String(100), nullable=False, comment="댓글 본문 (한글 기준 100자 이내)"
    )
    is_deleted: Mapped[bool] = mapped_column(
        Boolean, nullable=False, default=False, comment="소프트 삭제 여부"
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime,
        nullable=False,
        server_default=func.now(),
        comment="작성 일시",
    )

    video: Mapped["Video"] = relationship("Video", back_populates="comments")
    user: Mapped["User"] = relationship("User", back_populates="comments")
    parent: Mapped[Optional["Comment"]] = relationship(
        "Comment", remote_side=[id], back_populates="replies"
    )
    replies: Mapped[List["Comment"]] = relationship(
        "Comment",
        back_populates="parent",
        cascade="all, delete-orphan",
    )