-- Migration 009: Persistent Subscriptions
-- Adds support for persistent, correlation-based event subscriptions

CREATE TABLE IF NOT EXISTS persistent_subscriptions (
    id TEXT PRIMARY KEY,
    subscriber_id TEXT NOT NULL,
    correlation_id TEXT NOT NULL,
    event_types JSONB NOT NULL DEFAULT '[]'::jsonb,
    terminal_event_types JSONB NOT NULL DEFAULT '[]'::jsonb,
    delivery_mode INT NOT NULL DEFAULT 0,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    expires_at TIMESTAMPTZ NULL,
    completed_at TIMESTAMPTZ NULL,
    last_delivered_sequence BIGINT NOT NULL DEFAULT -1,
    status INT NOT NULL DEFAULT 0,
    connection_id TEXT NULL,
    data_source_id TEXT NULL
);

-- Index for looking up subscriptions by subscriber
CREATE INDEX IF NOT EXISTS idx_persistent_subscriptions_subscriber_id
    ON persistent_subscriptions (subscriber_id);

-- Index for looking up subscriptions by correlation ID (most common query)
CREATE INDEX IF NOT EXISTS idx_persistent_subscriptions_correlation_id
    ON persistent_subscriptions (correlation_id);

-- Index for looking up subscriptions by status
CREATE INDEX IF NOT EXISTS idx_persistent_subscriptions_status
    ON persistent_subscriptions (status);

-- Index for looking up subscriptions by connection ID
CREATE INDEX IF NOT EXISTS idx_persistent_subscriptions_connection_id
    ON persistent_subscriptions (connection_id)
    WHERE connection_id IS NOT NULL;

-- Index for finding expired subscriptions
CREATE INDEX IF NOT EXISTS idx_persistent_subscriptions_expires_at
    ON persistent_subscriptions (expires_at)
    WHERE expires_at IS NOT NULL AND status = 0; -- Active status

-- Composite index for active subscriptions by correlation (hot path)
CREATE INDEX IF NOT EXISTS idx_persistent_subscriptions_correlation_active
    ON persistent_subscriptions (correlation_id, status)
    WHERE status = 0;

COMMENT ON TABLE persistent_subscriptions IS 'Stores persistent event subscriptions that survive client disconnection';
COMMENT ON COLUMN persistent_subscriptions.id IS 'Unique subscription identifier';
COMMENT ON COLUMN persistent_subscriptions.subscriber_id IS 'User/client who owns this subscription';
COMMENT ON COLUMN persistent_subscriptions.correlation_id IS 'Correlation ID to filter events by';
COMMENT ON COLUMN persistent_subscriptions.event_types IS 'Array of event type names to deliver (empty = all)';
COMMENT ON COLUMN persistent_subscriptions.terminal_event_types IS 'Event types that complete the subscription';
COMMENT ON COLUMN persistent_subscriptions.delivery_mode IS 'How events are delivered: 0=Immediate, 1=Batched, 2=OnReconnect';
COMMENT ON COLUMN persistent_subscriptions.last_delivered_sequence IS 'Last event sequence successfully delivered';
COMMENT ON COLUMN persistent_subscriptions.status IS 'Subscription status: 0=Active, 1=Completed, 2=Expired, 3=Cancelled, 4=Paused';
COMMENT ON COLUMN persistent_subscriptions.connection_id IS 'Optional connection ID if client is currently connected';
COMMENT ON COLUMN persistent_subscriptions.data_source_id IS 'Optional data source ID for client-side routing';