-- 元数据只保存结构模具与绑定，不保存任何业务实例值。
CREATE SCHEMA metadata AUTHORIZATION muse_maint;
GRANT USAGE ON SCHEMA metadata TO muse_app, muse_eval;

CREATE TABLE metadata.type_registry (
    type_id text PRIMARY KEY,
    definition jsonb NOT NULL,
    content_hash text NOT NULL,
    state text NOT NULL DEFAULT 'candidate' CHECK (state IN ('candidate', 'published')),
    policy_revision bigint NOT NULL DEFAULT 0 CHECK (policy_revision >= 0)
);
CREATE TABLE metadata.schema_version (
    schema_id text NOT NULL,
    schema_version bigint NOT NULL CHECK (schema_version > 0),
    type_id text NOT NULL REFERENCES metadata.type_registry(type_id),
    definition jsonb NOT NULL,
    content_hash text NOT NULL,
    state text NOT NULL CHECK (state IN ('candidate', 'published')),
    PRIMARY KEY (schema_id, schema_version)
);
CREATE TABLE metadata.work_extension (
    work_id text NOT NULL,
    schema_id text NOT NULL,
    base_version bigint NOT NULL,
    extension_version bigint NOT NULL CHECK (extension_version > 0),
    definition jsonb NOT NULL,
    content_hash text NOT NULL,
    state text NOT NULL CHECK (state IN ('candidate', 'published')),
    PRIMARY KEY (work_id, schema_id, base_version, extension_version),
    FOREIGN KEY (schema_id, base_version)
        REFERENCES metadata.schema_version(schema_id, schema_version)
);
CREATE TABLE metadata.policy_version (
    type_id text NOT NULL REFERENCES metadata.type_registry(type_id),
    version bigint NOT NULL CHECK (version > 0),
    definition jsonb NOT NULL,
    content_hash text NOT NULL,
    PRIMARY KEY (type_id, version)
);
CREATE TABLE metadata.schema_binding (
    target_ref text PRIMARY KEY,
    work_id text NOT NULL,
    type_id text NOT NULL REFERENCES metadata.type_registry(type_id),
    schema_id text NOT NULL,
    base_version bigint NOT NULL,
    extension_version bigint,
    effective_schema_hash text NOT NULL,
    revision bigint NOT NULL CHECK (revision > 0),
    FOREIGN KEY (schema_id, base_version)
        REFERENCES metadata.schema_version(schema_id, schema_version),
    FOREIGN KEY (work_id, schema_id, base_version, extension_version)
        REFERENCES metadata.work_extension(work_id, schema_id, base_version, extension_version)
);
CREATE TABLE metadata.activation_receipt (
    command_id text PRIMARY KEY,
    request_hash text NOT NULL,
    result jsonb NOT NULL,
    reviewed_by text NOT NULL,
    change_scope text NOT NULL,
    created_at timestamptz NOT NULL DEFAULT current_timestamp
);

-- 候选修改也必须产生新版本；发布只允许改变状态，正文定义永远不可原地覆盖。
CREATE FUNCTION metadata.immutable_definition() RETURNS trigger LANGUAGE plpgsql AS $$
BEGIN
    IF TG_OP = 'DELETE' THEN
        RAISE EXCEPTION '元数据历史版本不可删除';
    END IF;
    IF NEW.definition IS DISTINCT FROM OLD.definition
        OR NEW.content_hash IS DISTINCT FROM OLD.content_hash THEN
        RAISE EXCEPTION '元数据定义不可修改，必须新增版本';
    END IF;
    RETURN NEW;
END;
$$;
CREATE TRIGGER schema_immutable BEFORE UPDATE OR DELETE ON metadata.schema_version
FOR EACH ROW EXECUTE FUNCTION metadata.immutable_definition();
CREATE TRIGGER extension_immutable BEFORE UPDATE OR DELETE ON metadata.work_extension
FOR EACH ROW EXECUTE FUNCTION metadata.immutable_definition();
CREATE TRIGGER policy_immutable BEFORE UPDATE OR DELETE ON metadata.policy_version
FOR EACH ROW EXECUTE FUNCTION metadata.immutable_definition();

GRANT SELECT, INSERT, UPDATE ON ALL TABLES IN SCHEMA metadata TO muse_app;
GRANT SELECT ON ALL TABLES IN SCHEMA metadata TO muse_eval;