"""Add is_system column to comm_conversations and migrate notifications to system channel (B-NOTIF-*).

Adds is_system boolean to comm_conversations for system channel support.
Migrates existing notifications into the system channel as CommMessages.
Creates a view notifications_legacy as a compatibility layer over the old notifications table.

Revision ID: 0120
Revises: 0119
"""

from alembic import op
import sqlalchemy as sa

revision = "0120"
down_revision = "0119"
branch_labels = None
depends_on = None


def upgrade() -> None:
    # 1. Add is_system column to comm_conversations
    op.add_column(
        "comm_conversations",
        sa.Column("is_system", sa.Boolean(), nullable=False, server_default=sa.text("false")),
    )
    op.create_index(
        "ix_comm_conversations_tenant_system",
        "comm_conversations",
        ["tenant_id", "is_system"],
    )

    # 2. Create system channel per tenant (for tenants that have notifications)
    op.execute("""
        INSERT INTO comm_conversations (id, tenant_id, title, is_pinned, is_locked, is_direct, is_archived, is_system, created_by, created_by_type, metadata, created_at, updated_at)
        SELECT
            gen_random_uuid(),
            n.tenant_id,
            'System Channel',
            false,
            true,
            false,
            false,
            true,
            NULL,
            'system',
            '{}'::jsonb,
            NOW(),
            NOW()
        FROM (
            SELECT DISTINCT tenant_id FROM notifications WHERE deleted_at IS NULL
        ) n
        WHERE NOT EXISTS (
            SELECT 1 FROM comm_conversations cc
            WHERE cc.tenant_id = n.tenant_id AND cc.is_system = true AND cc.deleted_at IS NULL
        );
    """)

    # 3. Insert notifications as CommMessages in the system channel
    op.execute("""
        INSERT INTO comm_messages (id, tenant_id, conversation_id, sender_id, sender_type, content, content_format, metadata, created_at, updated_at)
        SELECT
            gen_random_uuid(),
            n.tenant_id,
            sc.id,
            n.user_id,
            'system',
            COALESCE(n.title, '') || CASE WHEN n.body IS NOT NULL THEN E'\n' || n.body ELSE '' END,
            'text',
            jsonb_build_object(
                'notification_type', n.type,
                'severity', 'info',
                'entity_ref', CASE WHEN n.entity_type IS NOT NULL THEN jsonb_build_object('entity_type', n.entity_type, 'entity_id', n.entity_id::text) ELSE NULL END,
                'migrated_from_notification', true,
                'original_notification_id', n.id::text
            ),
            n.created_at,
            COALESCE(n.read_at, n.created_at)
        FROM notifications n
        JOIN comm_conversations sc ON sc.tenant_id = n.tenant_id AND sc.is_system = true AND sc.deleted_at IS NULL
        WHERE n.deleted_at IS NULL;
    """)

    # 4. Insert text blocks for each migrated message
    op.execute("""
        INSERT INTO comm_message_blocks (id, tenant_id, message_id, block_type, block_data, sort_order)
        SELECT
            gen_random_uuid(),
            cm.tenant_id,
            cm.id,
            'text',
            jsonb_build_object('text', cm.content),
            0
        FROM comm_messages cm
        WHERE cm.metadata->>'migrated_from_notification' = 'true';
    """)

    # 5. Insert action_card blocks for messages with entity references
    op.execute("""
        INSERT INTO comm_message_blocks (id, tenant_id, message_id, block_type, block_data, sort_order)
        SELECT
            gen_random_uuid(),
            cm.tenant_id,
            cm.id,
            'action_card',
            jsonb_build_object(
                'label', 'Open',
                'entity_type', (cm.metadata->'entity_ref'->>'entity_type'),
                'entity_id', (cm.metadata->'entity_ref'->>'entity_id')
            ),
            1
        FROM comm_messages cm
        WHERE cm.metadata->>'migrated_from_notification' = 'true'
          AND cm.metadata->'entity_ref' IS NOT NULL;
    """)

    # 6. For read notifications, create CommMessageRead entries
    op.execute("""
        INSERT INTO comm_message_reads (id, tenant_id, conversation_id, user_id, last_read_msg_id, last_read_at)
        SELECT
            gen_random_uuid(),
            cm.tenant_id,
            cm.conversation_id,
            cm.sender_id,
            cm.id,
            COALESCE(n.read_at, n.created_at)
        FROM comm_messages cm
        JOIN notifications n ON n.id::text = cm.metadata->>'original_notification_id'
        WHERE cm.metadata->>'migrated_from_notification' = 'true'
          AND n.read_at IS NOT NULL
          AND n.deleted_at IS NULL;
    """)

    # 7. Create legacy view over notifications table for backward compatibility
    op.execute("DROP VIEW IF EXISTS notifications_legacy")
    op.execute("CREATE VIEW notifications_legacy AS SELECT * FROM notifications")


def downgrade() -> None:
    op.execute("DROP VIEW IF EXISTS notifications_legacy")
    op.execute("DELETE FROM comm_message_blocks WHERE message_id IN (SELECT id FROM comm_messages WHERE metadata->>'migrated_from_notification' = 'true')")
    op.execute("DELETE FROM comm_messages WHERE metadata->>'migrated_from_notification' = 'true'")
    op.execute("DELETE FROM comm_conversations WHERE is_system = true AND title = 'System Channel'")
    op.drop_index("ix_comm_conversations_tenant_system", table_name="comm_conversations")
    op.drop_column("comm_conversations", "is_system")