"""replace legacy task log fields with canonical Molecular CoT fields"""

from collections.abc import Sequence

import sqlalchemy as sa
from alembic import op

revision: str = "e4f5a6b7c8d9"
down_revision: str | Sequence[str] | None = "e3f4a5b6c7d8"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None


def upgrade() -> None:
    op.add_column("task_logs", sa.Column("trace_id", sa.String(64), nullable=False, server_default=""))
    op.add_column("task_logs", sa.Column("span_id", sa.String(128), nullable=True))
    op.add_column("task_logs", sa.Column("src", sa.String(255), nullable=False, server_default="task.system"))
    op.add_column("task_logs", sa.Column("marker", sa.String(16), nullable=False, server_default="REASON"))
    op.add_column("task_logs", sa.Column("intent", sa.Text(), nullable=False, server_default=""))
    op.add_column("task_logs", sa.Column("payload", sa.JSON(), nullable=True))
    op.add_column("task_logs", sa.Column("error", sa.Text(), nullable=True))
    bind = op.get_bind()
    bind.execute(sa.text("""
        UPDATE task_logs
        SET src = COALESCE(source, 'task.system'),
            intent = COALESCE(message, ''),
            marker = CASE WHEN UPPER(level) IN ('WARNING', 'ERROR') THEN 'EXPLORE' ELSE 'REASON' END,
            error = CASE WHEN UPPER(level) IN ('WARNING', 'ERROR') THEN COALESCE(message, 'Task event') ELSE NULL END
    """))
    if bind.dialect.name == "postgresql":
        bind.execute(sa.text("UPDATE task_logs SET payload = metadata_json::json WHERE metadata_json IS NOT NULL"))
    elif bind.dialect.name == "sqlite":
        bind.execute(sa.text("UPDATE task_logs SET payload = json(metadata_json) WHERE metadata_json IS NOT NULL AND json_valid(metadata_json)"))
    op.create_index("ix_task_logs_task_src", "task_logs", ["task_id", "src"])
    op.drop_index("ix_task_logs_task_source", table_name="task_logs")
    op.drop_column("task_logs", "source")
    op.drop_column("task_logs", "message")
    op.drop_column("task_logs", "metadata_json")
    for column in ("trace_id", "src", "marker", "intent"):
        op.alter_column("task_logs", column, server_default=None)


def downgrade() -> None:
    raise NotImplementedError("Canonical task log migration is a breaking migration")