"""Backfill + require FlowVersion.input_schema.

Revision ID: e8f3a1c2b4d6
Revises: c4d8f2a1e6b9
Create Date: 2026-09-30 00:00:00.000000

Pre-Phase-3 rows have input_schema NULL. Backfill them from the stored
langflow_json (same parser the write choke point uses); unparseable rows
get the textarea fallback so reads never crash. Then enforce NOT NULL.
"""

from collections.abc import Sequence

import sqlalchemy as sa
from alembic import op

# revision identifiers, used by Alembic.
revision: str = "e8f3a1c2b4d6"
down_revision: str | Sequence[str] | None = "c4d8f2a1e6b9"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None

_FALLBACK = {
    "json_schema": {"type": "object", "properties": {}},
    "ui_schema": {},
    "fallback": "textarea",
}


def _derive(langflow_json) -> dict:
    import json as stdlib_json

    try:
        from app.flows import input_schema as parser

        if isinstance(langflow_json, str):
            # SQLite stores JSON columns as TEXT; Postgres returns dict.
            langflow_json = stdlib_json.loads(langflow_json)
        return parser.extract_form_schema(langflow_json)
    except Exception:  # noqa: BLE001 -- backfill must never fail the migration
        return dict(_FALLBACK)


def upgrade() -> None:
    """Upgrade schema."""
    import json as stdlib_json

    connection = op.get_bind()
    rows = connection.execute(
        sa.text("SELECT id, langflow_json FROM flow_versions WHERE input_schema IS NULL")
    ).all()
    for row_id, langflow_json in rows:
        schema = _derive(langflow_json)
        connection.execute(
            sa.text("UPDATE flow_versions SET input_schema = :schema WHERE id = :id"),
            {"schema": stdlib_json.dumps(schema), "id": str(row_id)},
        )
    with op.batch_alter_table("flow_versions") as batch:
        batch.alter_column("input_schema", existing_type=sa.JSON(), nullable=False)


def downgrade() -> None:
    """Downgrade schema (data kept, nullability restored)."""
    with op.batch_alter_table("flow_versions") as batch:
        batch.alter_column("input_schema", existing_type=sa.JSON(), nullable=True)