"""support_kb_articles — self-growing help-desk knowledge base (求助域 PR4).

Revision ID: 302
Revises: 301
Create Date: 2026-06-17

Published articles are the AI copilot's deflection surface; an article can be
manually authored or AI-drafted from a resolved ticket (source='ai_ticket')
and then adopted (published) by an admin. FKs to identity_persons /
support_tickets are built with the parent collation (3780-safe).
"""
from __future__ import annotations

import sqlalchemy as sa

from alembic import op
from app.core.migration_helpers import id_type_for, table_kw_for

revision = "302"
down_revision = "301"
branch_labels = None
depends_on = None

TABLE = "support_kb_articles"


def _table_exists(bind, name: str) -> bool:
    return bind.execute(
        sa.text(
            "SELECT 1 FROM information_schema.TABLES "
            "WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = :n"
        ),
        {"n": name},
    ).scalar() is not None


def upgrade() -> None:
    bind = op.get_bind()
    if _table_exists(bind, TABLE):
        return
    pid = id_type_for("identity_persons")
    kw = table_kw_for("identity_persons")
    op.create_table(
        TABLE,
        sa.Column("id", pid, primary_key=True),
        sa.Column("title", sa.String(255), nullable=False),
        sa.Column("body", sa.Text(), nullable=False),
        sa.Column("category", sa.String(32), nullable=False, server_default="other"),
        sa.Column("status", sa.String(16), nullable=False, server_default="draft"),
        sa.Column("source", sa.String(16), nullable=False, server_default="manual"),
        sa.Column("source_ticket_id", pid, nullable=True),
        sa.Column("author_id", pid, nullable=True),
        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("published_at", sa.DateTime(timezone=True), nullable=True),
        sa.ForeignKeyConstraint(["source_ticket_id"], ["support_tickets.id"], name="fk_support_kb_ticket"),
        sa.ForeignKeyConstraint(["author_id"], ["identity_persons.id"], name="fk_support_kb_author"),
        **kw,
    )
    op.create_index("ix_support_kb_status", TABLE, ["status", "category"])


def downgrade() -> None:
    op.drop_table(TABLE)