"""Social graph: friendships, follows, blocks.

docs/planning/social.md §4/§5 (US-1). Friends = mutual (request -> accept),
Follow = one-way (no approval), Block = hard deny. This module is models +
schema only -- the request/accept/block business logic (idempotent
duplicate/self handling, removing an existing friendship/follow on block,
etc.) belongs to the API router task that depends on this one.
"""
import enum

from sqlalchemy import Column, Integer, ForeignKey, DateTime, UniqueConstraint
from sqlalchemy.dialects.postgresql import ENUM
from sqlalchemy.orm import relationship
from sqlalchemy.sql import func

from app.database import Base


class FriendshipStatus(str, enum.Enum):
    PENDING = "pending"
    ACCEPTED = "accepted"


class Friendship(Base):
    """A friend request, directional until accepted.

    ``requester_id`` sent the request to ``addressee_id``. Once accepted the
    friendship is mutual, but the row stays directional (who asked whom) for
    audit purposes; the API layer treats it as symmetric once accepted.
    """

    __tablename__ = "friendships"

    id = Column(Integer, primary_key=True, index=True)
    requester_id = Column(
        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    addressee_id = Column(
        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    status = Column(
        ENUM(
            FriendshipStatus,
            name="friendship_status",
            create_type=False,
            values_callable=lambda enum_cls: [e.value for e in enum_cls],
        ),
        nullable=False,
        default=FriendshipStatus.PENDING,
        server_default=FriendshipStatus.PENDING.value,
    )
    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False)

    requester = relationship("User", foreign_keys=[requester_id], back_populates="sent_friend_requests")
    addressee = relationship("User", foreign_keys=[addressee_id], back_populates="received_friend_requests")

    __table_args__ = (
        UniqueConstraint("requester_id", "addressee_id", name="uq_friendships_pair"),
    )


class Follow(Base):
    """A one-way follow relationship: ``follower_id`` follows ``followed_id``."""

    __tablename__ = "follows"

    id = Column(Integer, primary_key=True, index=True)
    follower_id = Column(
        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    followed_id = Column(
        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False)

    follower = relationship("User", foreign_keys=[follower_id], back_populates="following")
    followed = relationship("User", foreign_keys=[followed_id], back_populates="followers")

    __table_args__ = (
        UniqueConstraint("follower_id", "followed_id", name="uq_follows_pair"),
    )


class Block(Base):
    """A hard deny: ``blocker_id`` has blocked ``blocked_id``."""

    __tablename__ = "blocks"

    id = Column(Integer, primary_key=True, index=True)
    blocker_id = Column(
        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    blocked_id = Column(
        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False)

    blocker = relationship("User", foreign_keys=[blocker_id], back_populates="blocks_initiated")
    blocked = relationship("User", foreign_keys=[blocked_id], back_populates="blocked_by")

    __table_args__ = (
        UniqueConstraint("blocker_id", "blocked_id", name="uq_blocks_pair"),
    )