add ChainInterceptors

interceptor.go

@@ -10,4 +10,25 @@ type InvokerFunc = func(ctx context.Context, sql string) error
 // InterceptorFunc is the function type of an interceptor. An interceptor should implement this function to fulfill it's purpose.
 type InterceptorFunc = func(ctx context.Context, sql string, invoker InvokerFunc) error
 
-// TODO: add some common interceptors
+func noopInterceptor(ctx context.Context, sql string, invoker InvokerFunc) error {
+	return invoker(ctx, sql)
+}
+
+// ChainInterceptors chains multiple interceptors into one interceptor.
+func ChainInterceptors(interceptors ...InterceptorFunc) InterceptorFunc {
+	if len(interceptors) == 0 {
+		return noopInterceptor
+	}
+	return func(ctx context.Context, sql string, invoker InvokerFunc) error {
+		var chain func(int, context.Context, string) error
+		chain = func(i int, ctx context.Context, sql string) error {
+			if i == len(interceptors) {
+				return invoker(ctx, sql)
+			}
+			return interceptors[i](ctx, sql, func(ctx context.Context, sql string) error {
+				return chain(i+1, ctx, sql)
+			})
+		}
+		return chain(0, ctx, sql)
+	}
+}

interceptor_test.go

@@ -0,0 +1,55 @@
+package sqlingo
+
+import (
+	"context"
+	"testing"
+)
+
+func TestChainInterceptors(t *testing.T) {
+	s := ""
+	i1 := func(ctx context.Context, sql string, invoker InvokerFunc) error {
+		s += "<i1>"
+		s += sql
+		defer func() {
+			s += "</i1>"
+		}()
+		return invoker(ctx, sql+"s1")
+	}
+	i2 := func(ctx context.Context, sql string, invoker InvokerFunc) error {
+		s += "<i2>"
+		s += sql
+		defer func() {
+			s += "</i2>"
+		}()
+		return invoker(ctx, sql+"s2")
+	}
+	chain := ChainInterceptors(i1, i2)
+	_ = chain(context.Background(), "sql", func(ctx context.Context, sql string) error {
+		s += "<invoker>"
+		s += sql
+		defer func() {
+			s += "</invoker>"
+		}()
+		return nil
+	})
+	if s != "<i1>sql<i2>sqls1<invoker>sqls1s2</invoker></i2></i1>" {
+		t.Error(s)
+	}
+}
+
+func TestEmptyChainInterceptors(t *testing.T) {
+	s := ""
+	chain := ChainInterceptors()
+	_ = chain(context.Background(), "sql", func(ctx context.Context, sql string) error {
+		s += "<invoker>"
+		defer func() {
+			s += "</invoker>"
+		}()
+		s += sql
+		return nil
+	})
+
+	if s != "<invoker>sql</invoker>" {
+		t.Error(s)
+	}
+}