"""phase18 — add reported_by column to issues table

Background
----------
Issues created on the iPad by an inspector have no `assigned_to` value until
a director assigns them via the web portal.  The mobile API's list_issues
endpoint filtered inspectors to `assigned_to == user.id`, so their own
newly-submitted issues were invisible on the iPad until assigned.

This migration adds `reported_by INT NULL FK → users.id` so the API can
return issues the inspector either created OR was assigned to, without
a join to the inspections table.

The column is nullable for backward compatibility: existing issues created
before this migration will have reported_by = NULL and continue to surface
only via the assigned_to path.

Uses INFORMATION_SCHEMA existence check — safe to re-run (CLAUDE.md rules 16, 17).

Revision ID: phase18_issue_reported_by
Revises:     phase17_notification_event_type
"""

revision      = 'phase18_issue_reported_by'
down_revision = 'phase17_notification_event_type'
branch_labels = None
depends_on    = None

from alembic import op
import sqlalchemy as sa


def _column_exists(conn, table, column):
    result = conn.execute(sa.text(
        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS "
        "WHERE TABLE_SCHEMA = DATABASE() "
        "AND TABLE_NAME = :table AND COLUMN_NAME = :col"
    ), {"table": table, "col": column})
    return result.scalar() > 0


def _fk_exists(conn, table, constraint_name):
    result = conn.execute(sa.text(
        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS "
        "WHERE TABLE_SCHEMA = DATABASE() "
        "AND TABLE_NAME = :table AND CONSTRAINT_NAME = :name"
    ), {"table": table, "name": constraint_name})
    return result.scalar() > 0


def upgrade():
    bind = op.get_bind()

    if not _column_exists(bind, 'issues', 'reported_by'):
        op.execute(sa.text(
            "ALTER TABLE issues "
            "ADD COLUMN reported_by INT NULL, "
            "ADD CONSTRAINT fk_issues_reported_by "
            "    FOREIGN KEY (reported_by) REFERENCES users(id) "
            "    ON DELETE SET NULL"
        ))


def downgrade():
    bind = op.get_bind()

    if _fk_exists(bind, 'issues', 'fk_issues_reported_by'):
        op.execute(sa.text(
            "ALTER TABLE issues DROP FOREIGN KEY fk_issues_reported_by"
        ))

    if _column_exists(bind, 'issues', 'reported_by'):
        op.execute(sa.text(
            "ALTER TABLE issues DROP COLUMN reported_by"
        ))