"""Move task tools into task backend resources without replaying existing tasks."""

from alembic import op
import sqlalchemy as sa
from sqlalchemy.dialects import postgresql


revision = "20261023_0027"
down_revision = "20261023_0026"
branch_labels = None
depends_on = None


def upgrade():
    op.create_table(
        "task_backend_resources",
        sa.Column("id", sa.String(40), primary_key=True),
        sa.Column("name", sa.String(128), nullable=False),
        sa.Column("type", sa.String(16), nullable=False),
        sa.Column("description", sa.String(2048), nullable=False),
        sa.Column("config", postgresql.JSONB(), nullable=False),
        sa.Column("secrets", postgresql.JSONB(), nullable=False),
        sa.Column("enabled", sa.Boolean(), nullable=False),
        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
        sa.CheckConstraint("type IN ('reasoner', 'opencode')", name="ck_task_backend_type"),
    )
    op.add_column("assistants", sa.Column("task_backend", postgresql.JSONB(), nullable=True))
    op.add_column("background_tasks", sa.Column("backend_id", sa.String(40), nullable=False, server_default=""))
    op.add_column("background_tasks", sa.Column("backend_type", sa.String(16), nullable=False, server_default="opencode"))
    # NULL preserves pre-migration observation-window semantics for historical tasks.
    op.add_column("background_tasks", sa.Column("deadline_at", sa.String(40), nullable=True))
    op.alter_column("background_tasks", "tool_id", server_default="")
    op.execute("""
        DO $$ BEGIN
            IF EXISTS (
                SELECT b.assistant_id FROM assistant_tool_bindings b JOIN tools t ON t.id=b.tool_id
                WHERE t.type='task' GROUP BY b.assistant_id HAVING count(*) > 1
            ) THEN RAISE EXCEPTION 'Task backend migration: an assistant has multiple task bindings; resolve before retrying'; END IF;
            IF EXISTS (
                SELECT 1 FROM assistant_tool_bindings b JOIN tools t ON t.id=b.tool_id
                JOIN assistants a ON a.id=b.assistant_id
                WHERE t.type='task' AND (a.type != 'prompt' OR a.runtime_mode != 'pipeline')
            ) THEN RAISE EXCEPTION 'Task backend migration: task bindings require Prompt Pipeline'; END IF;
        END $$
    """)
    # Resource IDs may retain the old tool prefix: IDs are local to each resource table.
    op.execute("""
        INSERT INTO task_backend_resources (id,name,type,description,config,secrets,enabled,created_at,updated_at)
        SELECT id,name,'opencode',description,
            jsonb_build_object(
                'url',definition->'config'->'url',
                'directory',definition->'config'->'directory',
                'username',COALESCE(definition->'config'->'username','\"opencode\"'::jsonb),
                'timeout_seconds',COALESCE(definition->'config'->'timeout_seconds',definition->'config'->'timeoutSeconds','600'::jsonb),
                'max_concurrency',1,'instructions','','agent','','model_provider_id','','model_id','','skills_note',''
            ), secrets,status='active',created_at,updated_at
        FROM tools WHERE type='task'
    """)
    op.execute("""
        UPDATE assistants a SET task_backend=jsonb_build_object(
            'backend_id', b.tool_id,
            'instruction_source',COALESCE(
                b.config->'argument_bindings'->'instruction',
                b.config->'argumentBindings'->'instruction',
                '{"source":"model"}'::jsonb
            ),
            'instructions',''
        )
        FROM assistant_tool_bindings b JOIN tools t ON t.id=b.tool_id
        WHERE a.id=b.assistant_id AND t.type='task'
    """)
    op.execute("UPDATE background_tasks SET backend_id=tool_id, backend_type='opencode'")
    op.execute("DELETE FROM assistant_tool_bindings WHERE tool_id IN (SELECT id FROM tools WHERE type='task')")
    op.execute("DELETE FROM tools WHERE type='task'")
    op.drop_constraint("ck_tools_external_type", "tools", type_="check")
    op.create_check_constraint("ck_tools_external_type", "tools", "type IN ('http', 'mcp', 'client')")


def downgrade():
    raise RuntimeError(
        "Task backend resources cannot be downgraded safely to task tools. "
        "Restore a pre-migration database backup to roll back this resource migration."
    )