"""support_tickets + support_ticket_messages — the IT help-desk (求助域).

Revision ID: 301
Revises: 300
Create Date: 2026-06-17

PR2 of the employee↔IT communication theme: the free-form "ask IT for help"
surface (closing the template-only dead-end) with a full ticket lifecycle and
a message timeline. All person/ticket FKs are built with the parent's
charset/collation (``id_type_for`` / ``table_kw_for``) so the inline FKs can't
trip error 3780 on prod TiDB.
"""
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 = "301"
down_revision = "300"
branch_labels = None
depends_on = None

TICKETS = "support_tickets"
MESSAGES = "support_ticket_messages"


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()
    persons_id = id_type_for("identity_persons")
    kw = table_kw_for("identity_persons")

    if not _table_exists(bind, TICKETS):
        op.create_table(
            TICKETS,
            sa.Column("id", persons_id, primary_key=True),
            sa.Column("ticket_number", sa.String(24), nullable=False),
            sa.Column("requester_id", persons_id, nullable=False),
            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("priority", sa.String(16), nullable=False, server_default="normal"),
            sa.Column("status", sa.String(24), nullable=False, server_default="open"),
            sa.Column("source", sa.String(16), nullable=False, server_default="web"),
            sa.Column("assignee_id", persons_id, nullable=True),
            sa.Column("resolution", sa.Text(), nullable=True),
            sa.Column("feishu_message_id", sa.String(64), 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("first_response_at", sa.DateTime(timezone=True), nullable=True),
            sa.Column("resolved_at", sa.DateTime(timezone=True), nullable=True),
            sa.Column("closed_at", sa.DateTime(timezone=True), nullable=True),
            sa.ForeignKeyConstraint(["requester_id"], ["identity_persons.id"], name="fk_support_tickets_requester"),
            sa.ForeignKeyConstraint(["assignee_id"], ["identity_persons.id"], name="fk_support_tickets_assignee"),
            sa.UniqueConstraint("ticket_number", name="uq_support_tickets_number"),
            **kw,
        )
        op.create_index("ix_support_tickets_requester", TICKETS, ["requester_id", "status"])
        op.create_index("ix_support_tickets_assignee", TICKETS, ["assignee_id", "status"])
        op.create_index("ix_support_tickets_status_created", TICKETS, ["status", "created_at"])

    if not _table_exists(bind, MESSAGES):
        op.create_table(
            MESSAGES,
            sa.Column("id", persons_id, primary_key=True),
            sa.Column("ticket_id", persons_id, nullable=False),
            sa.Column("author_id", persons_id, nullable=True),
            sa.Column("kind", sa.String(16), nullable=False, server_default="comment"),
            sa.Column("body", sa.Text(), nullable=False),
            sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
            sa.ForeignKeyConstraint(["ticket_id"], [f"{TICKETS}.id"], name="fk_support_ticket_messages_ticket"),
            sa.ForeignKeyConstraint(["author_id"], ["identity_persons.id"], name="fk_support_ticket_messages_author"),
            **kw,
        )
        op.create_index(
            "ix_support_ticket_messages_ticket", MESSAGES, ["ticket_id", "created_at"],
        )


def downgrade() -> None:
    op.drop_table(MESSAGES)
    op.drop_table(TICKETS)