CREATE TABLE alert_rules (
    id uuid PRIMARY KEY,
    schema_version integer NOT NULL CHECK (schema_version = 1),
    name text NOT NULL CHECK (length(name) BETWEEN 1 AND 160),
    enabled boolean NOT NULL DEFAULT false,
    severity text NOT NULL CHECK (severity IN ('attention', 'degraded', 'critical')),
    scope jsonb NOT NULL DEFAULT '{}'::jsonb,
    condition jsonb NOT NULL,
    evaluation_interval_seconds integer NOT NULL CHECK (evaluation_interval_seconds BETWEEN 5 AND 3600),
    pending_seconds integer NOT NULL CHECK (pending_seconds BETWEEN 0 AND 2592000),
    resolve_seconds integer NOT NULL CHECK (resolve_seconds BETWEEN 0 AND 2592000),
    unknown_behavior text NOT NULL CHECK (unknown_behavior IN ('retain-firing-as-unknown', 'become-unknown', 'ignore-short-gap')),
    group_by jsonb NOT NULL DEFAULT '[]'::jsonb,
    suppress_when jsonb NOT NULL DEFAULT '[]'::jsonb,
    message jsonb NOT NULL,
    current_version_id uuid,
    revision bigint NOT NULL DEFAULT 1 CHECK (revision > 0),
    created_by uuid REFERENCES users(id) ON DELETE SET NULL,
    created_at timestamptz NOT NULL DEFAULT now(),
    updated_at timestamptz NOT NULL DEFAULT now()
);

CREATE TABLE alert_rule_versions (
    id uuid PRIMARY KEY,
    rule_id uuid NOT NULL REFERENCES alert_rules(id) ON DELETE RESTRICT,
    version_number integer NOT NULL CHECK (version_number > 0),
    document jsonb NOT NULL,
    change_summary text NOT NULL DEFAULT '' CHECK (length(change_summary) <= 500),
    created_by uuid REFERENCES users(id) ON DELETE SET NULL,
    created_at timestamptz NOT NULL DEFAULT now(),
    UNIQUE (rule_id, version_number)
);

ALTER TABLE alert_rules
    ADD CONSTRAINT alert_rules_current_version_fk
    FOREIGN KEY (current_version_id) REFERENCES alert_rule_versions(id)
    ON DELETE RESTRICT DEFERRABLE INITIALLY DEFERRED;

CREATE INDEX alert_rules_enabled_idx ON alert_rules (enabled, evaluation_interval_seconds, updated_at DESC) WHERE enabled = true;
CREATE INDEX alert_rules_severity_idx ON alert_rules (severity, updated_at DESC);
CREATE INDEX alert_rule_versions_history_idx ON alert_rule_versions (rule_id, version_number DESC);