From e40d7a236cd3b0f8c6c772ff6c245dec48fd9dc1 Mon Sep 17 00:00:00 2001
From: Gregory Eremin <g@erem.in>
Date: Sat, 7 Jul 2018 14:11:33 +0200
Subject: [PATCH] Named parameters helpers

---
 dbc/named.go      | 66 ++++++++++++++++++++++++++++++++++++++
 dbc/named_test.go | 80 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 146 insertions(+)
 create mode 100644 dbc/named.go
 create mode 100644 dbc/named_test.go

diff --git a/dbc/named.go b/dbc/named.go
new file mode 100644
index 0000000..c97650c
--- /dev/null
+++ b/dbc/named.go
@@ -0,0 +1,66 @@
+package dbc
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/localhots/gobelt/reflect2"
+)
+
+type namedParams interface {
+	Get(name string) (val interface{}, ok bool)
+}
+
+var (
+	_ namedParams = namedParamsMap{}
+	_ namedParams = &namedParamsStruct{}
+)
+
+func newNamedParams(val interface{}) (namedParams, error) {
+	switch tval := val.(type) {
+	case map[string]interface{}:
+		return newNamedParamsMap(tval)
+	default:
+		return newNamedParamsStruct(val)
+	}
+}
+
+type namedParamsMap struct {
+	m map[string]interface{}
+}
+
+func newNamedParamsMap(m map[string]interface{}) (namedParamsMap, error) {
+	return namedParamsMap{m}, nil
+}
+
+func (p namedParamsMap) Get(name string) (val interface{}, ok bool) {
+	val, ok = p.m[name]
+	return
+}
+
+type namedParamsStruct struct {
+	s   reflect.Value
+	idx map[string]int
+}
+
+func newNamedParamsStruct(s interface{}) (*namedParamsStruct, error) {
+	val := reflect.ValueOf(s)
+	if val.Kind() == reflect.Ptr {
+		val = val.Elem()
+	}
+	if val.Kind() != reflect.Struct {
+		return nil, fmt.Errorf("Unsupported named parameters type: %T", s)
+	}
+	return &namedParamsStruct{
+		s:   val,
+		idx: reflect2.TagIndex(val.Type(), tagName),
+	}, nil
+}
+
+func (p *namedParamsStruct) Get(name string) (val interface{}, ok bool) {
+	i, ok := p.idx[name]
+	if !ok {
+		return nil, false
+	}
+	return p.s.Field(i).Interface(), true
+}
diff --git a/dbc/named_test.go b/dbc/named_test.go
new file mode 100644
index 0000000..048fa3b
--- /dev/null
+++ b/dbc/named_test.go
@@ -0,0 +1,80 @@
+package dbc
+
+import "testing"
+
+func TestNamedParamsMap(t *testing.T) {
+	m, err := newNamedParamsMap(map[string]interface{}{
+		"num": 1,
+		"str": "foo",
+	})
+	if err != nil {
+		t.Fatalf("Failed to create named params map: %v", err)
+	}
+	testNamedParams(t, m)
+}
+
+func TestNamedParamsStruct(t *testing.T) {
+	type dummy struct {
+		Num int    `db:"num"`
+		Str string `db:"str"`
+	}
+	m, err := newNamedParamsStruct(&dummy{Num: 1, Str: "foo"})
+	if err != nil {
+		t.Fatalf("Failed to create named params struct: %v", err)
+	}
+	testNamedParams(t, m)
+}
+
+func testNamedParams(t *testing.T, p namedParams) {
+	t.Helper()
+
+	v, ok := p.Get("num")
+	if !ok {
+		t.Error("num was not found")
+	}
+	if v != 1 {
+		t.Errorf("Expected num to equal 1, got %d", v)
+	}
+
+	v, ok = p.Get("str")
+	if !ok {
+		t.Error("num was not found")
+	}
+	if v != "foo" {
+		t.Errorf("Expected num to equal 'foo', got %q", v)
+	}
+
+	_, ok = p.Get("missing")
+	if ok {
+		t.Error("missing value reportedly found")
+	}
+}
+
+func BenchmarkNamedParamsMap(b *testing.B) {
+	m, err := newNamedParamsMap(map[string]interface{}{"foo": 1})
+	if err != nil {
+		b.Fatalf("Failed to create named params map: %v", err)
+	}
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		m.Get("foo")
+	}
+}
+
+func BenchmarkNamedParamsStruct(b *testing.B) {
+	type dummy struct {
+		Foo int `db:"foo"`
+	}
+	m, err := newNamedParamsStruct(&dummy{Foo: 1})
+	if err != nil {
+		b.Fatalf("Failed to create named params struct: %v", err)
+	}
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		m.Get("foo")
+	}
+}