-- ============================================================
-- Audit Trigger Migration — Run on production after 001
-- Adds per-field audit triggers to configuration_items
-- ============================================================
BEGIN;

-- Fine-grained audit: capture individual field changes
CREATE OR REPLACE FUNCTION audit_ci_fields_func()
RETURNS TRIGGER AS $$
DECLARE
    col TEXT;
    old_val TEXT;
    new_val TEXT;
BEGIN
    IF TG_OP = 'UPDATE' THEN
        FOR col IN SELECT unnest(ARRAY[
            'name', 'description', 'status', 'location_id',
            'serial_number', 'asset_tag', 'purchase_date', 'warranty_expiry',
            'tags'
        ])
        LOOP
            old_val := row_to_json(OLD) ->> col;
            new_val := row_to_json(NEW) ->> col;
            IF old_val IS DISTINCT FROM new_val THEN
                INSERT INTO changelog (ci_id, action, field_name, old_value, new_value, version, snapshot)
                VALUES (NEW.id, 'update', col, old_val, NEW.version, NEW.version, to_jsonb(NEW));
            END IF;
        END LOOP;

        -- JSONB attributes changes
        IF OLD.attributes IS DISTINCT FROM NEW.attributes THEN
            INSERT INTO changelog (ci_id, action, field_name, old_value, new_value, version, snapshot)
            VALUES (NEW.id, 'update', 'attributes', OLD.attributes::text, NEW.attributes::text, NEW.version, to_jsonb(NEW));
        END IF;

        NEW.updated_at = now();
        NEW.version = OLD.version + 1;
        RETURN NEW;
    END IF;
    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

DROP TRIGGER IF EXISTS trg_ci_audit ON configuration_items;
CREATE TRIGGER trg_ci_field_audit
    AFTER UPDATE ON configuration_items
    FOR EACH ROW
    EXECUTE FUNCTION audit_ci_fields_func();

-- Relationship audit
CREATE OR REPLACE FUNCTION audit_relationship_func()
RETURNS TRIGGER AS $$
BEGIN
    IF TG_OP = 'INSERT' THEN
        INSERT INTO changelog (ci_id, action, field_name, new_value, version, snapshot)
        VALUES (NEW.source_ci_id, 'relationship_add', NEW.relationship::text,
                NEW.target_ci_id::text, 0, to_jsonb(NEW));
        RETURN NEW;
    ELSIF TG_OP = 'DELETE' THEN
        INSERT INTO changelog (ci_id, action, field_name, old_value, version, snapshot)
        VALUES (OLD.source_ci_id, 'relationship_remove', OLD.relationship::text,
                OLD.target_ci_id::text, 0, to_jsonb(OLD));
        RETURN OLD;
    END IF;
    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER trg_relationship_audit
    AFTER INSERT OR DELETE ON ci_relationships
    FOR EACH ROW
    EXECUTE FUNCTION audit_relationship_func();

COMMIT;