"""add users table and user_id to follows

Revision ID: 0005
Revises: 0004
Create Date: 2026-03-01 00:00:00.000000

"""
from typing import Sequence, Union

import sqlalchemy as sa
from sqlalchemy.dialects.postgresql import JSONB
from alembic import op

revision: str = "0005"
down_revision: Union[str, None] = "0004"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    # 1. Clear existing global follows — they have no user and cannot be migrated
    op.execute("DELETE FROM follows")

    # 2. Create users table
    op.create_table(
        "users",
        sa.Column("id", sa.Integer(), autoincrement=True, nullable=False),
        sa.Column("email", sa.String(), nullable=False),
        sa.Column("hashed_password", sa.String(), nullable=False),
        sa.Column("is_admin", sa.Boolean(), nullable=False, server_default="false"),
        sa.Column("notification_prefs", JSONB(), nullable=False, server_default="{}"),
        sa.Column(
            "created_at",
            sa.DateTime(timezone=True),
            server_default=sa.text("now()"),
            nullable=True,
        ),
        sa.PrimaryKeyConstraint("id"),
    )
    op.create_index(op.f("ix_users_email"), "users", ["email"], unique=True)

    # 3. Add user_id to follows (nullable first, then tighten after FK is set)
    op.add_column("follows", sa.Column("user_id", sa.Integer(), nullable=True))

    # 4. FK constraint
    op.create_foreign_key(
        "fk_follows_user_id",
        "follows",
        "users",
        ["user_id"],
        ["id"],
        ondelete="CASCADE",
    )

    # 5. Drop old unique constraint and add user-scoped one
    op.drop_constraint("uq_follows_type_value", "follows", type_="unique")
    op.create_unique_constraint(
        "uq_follows_user_type_value",
        "follows",
        ["user_id", "follow_type", "follow_value"],
    )

    # 6. Make user_id NOT NULL (table is empty so this is safe)
    op.alter_column("follows", "user_id", nullable=False)


def downgrade() -> None:
    op.alter_column("follows", "user_id", nullable=True)
    op.drop_constraint("uq_follows_user_type_value", "follows", type_="unique")
    op.create_unique_constraint("uq_follows_type_value", "follows", ["follow_type", "follow_value"])
    op.drop_constraint("fk_follows_user_id", "follows", type_="foreignkey")
    op.drop_column("follows", "user_id")
    op.drop_index(op.f("ix_users_email"), table_name="users")
    op.drop_table("users")