CREATE TABLE kuknos_settlements (
    id uuid PRIMARY KEY,
    source_service text NOT NULL CHECK (source_service <> ''),
    source_transaction_id text NOT NULL CHECK (source_transaction_id <> ''),
    idempotency_key text NOT NULL UNIQUE CHECK (idempotency_key <> ''),
    status text NOT NULL CHECK (status IN ('PENDING','SUBMITTED','CONFIRMED','RETRYABLE','MANUAL_REVIEW')),
    network text NOT NULL DEFAULT 'kuknos',
    signed_transaction_xdr text NOT NULL DEFAULT '',
    transaction_hash text NOT NULL DEFAULT '',
    attempts integer NOT NULL DEFAULT 0 CHECK (attempts >= 0),
    available_at timestamptz NOT NULL DEFAULT clock_timestamp(),
    locked_at timestamptz,
    locked_by text NOT NULL DEFAULT '',
    last_error text NOT NULL DEFAULT '',
    submitted_at timestamptz,
    confirmed_at timestamptz,
    manual_review_at timestamptz,
    created_at timestamptz NOT NULL DEFAULT clock_timestamp(),
    updated_at timestamptz NOT NULL DEFAULT clock_timestamp()
);

CREATE INDEX kuknos_settlements_due_idx ON kuknos_settlements (status, available_at);