BEGIN;

ALTER TABLE device_twin
    ADD COLUMN telemetry_sequence bigint NOT NULL DEFAULT 0 CHECK (telemetry_sequence >= 0),
    ADD COLUMN last_error_code varchar(80),
    ADD COLUMN last_error_severity varchar(16),
    ADD COLUMN last_error_at timestamptz;

CREATE TABLE device_telemetry_event (
    id               uuid PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id        uuid NOT NULL REFERENCES tenant(id),
    device_id        uuid NOT NULL,
    conversation_id  uuid,
    event_key        varchar(255) NOT NULL,
    sequence_no      bigint NOT NULL CHECK (sequence_no > 0),
    event_type       varchar(24) NOT NULL CHECK (event_type IN ('status','error','command_result')),
    occurred_at      timestamptz NOT NULL,
    payload_digest   char(64) NOT NULL,
    payload          jsonb NOT NULL CHECK (jsonb_typeof(payload)='object'),
    error_code       varchar(80),
    error_severity   varchar(16) CHECK (error_severity IS NULL OR error_severity IN ('warning','error','critical')),
    command_id       uuid REFERENCES device_command(id),
    received_at      timestamptz NOT NULL DEFAULT now(),
    CONSTRAINT device_telemetry_device_tenant_fk FOREIGN KEY (device_id,tenant_id)
        REFERENCES device(id,tenant_id),
    CONSTRAINT device_telemetry_conversation_tenant_fk FOREIGN KEY (conversation_id,tenant_id)
        REFERENCES conversation(id,tenant_id),
    CONSTRAINT device_telemetry_event_key UNIQUE (device_id,event_key),
    CONSTRAINT device_telemetry_sequence_key UNIQUE (device_id,sequence_no)
);

CREATE INDEX device_telemetry_time_idx ON device_telemetry_event(device_id,occurred_at DESC,id);
CREATE INDEX device_telemetry_conversation_idx ON device_telemetry_event(conversation_id,occurred_at DESC)
    WHERE conversation_id IS NOT NULL;
CREATE INDEX device_telemetry_error_idx ON device_telemetry_event(tenant_id,error_severity,occurred_at DESC)
    WHERE event_type='error';

COMMIT;