BEGIN;

CREATE TABLE external_dependency_probe_state (
    service_name          varchar(32) NOT NULL CHECK (service_name ~ '^[a-z][a-z0-9-]{1,31}$'),
    dependency            varchar(64) NOT NULL CHECK (dependency ~ '^[a-z][a-z0-9_]{1,63}$'),
    status                varchar(16) NOT NULL CHECK (status IN ('AVAILABLE','UNAVAILABLE')),
    checked_at            timestamptz NOT NULL,
    last_success_at       timestamptz,
    last_failure_at       timestamptz,
    last_error_code       varchar(80),
    latency_ms            bigint NOT NULL CHECK (latency_ms >= 0),
    probe_interval_ms     bigint NOT NULL CHECK (probe_interval_ms > 0),
    consecutive_failures  integer NOT NULL DEFAULT 0 CHECK (consecutive_failures >= 0),
    updated_at            timestamptz NOT NULL DEFAULT now(),
    PRIMARY KEY (service_name, dependency),
    CONSTRAINT external_probe_success_check CHECK (
        (status='AVAILABLE' AND last_success_at IS NOT NULL AND last_error_code IS NULL AND consecutive_failures=0) OR
        (status='UNAVAILABLE' AND last_failure_at IS NOT NULL AND last_error_code IS NOT NULL AND consecutive_failures>0)
    )
);

CREATE INDEX external_dependency_probe_status_idx
    ON external_dependency_probe_state(status, checked_at DESC);

COMMIT;