flatmap: Flatten
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package flatmap
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import (
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"fmt"
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"reflect"
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)
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type Map map[string]string
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// Flatten takes a structure and turns into a flat map[string]string.
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//
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// Within the "thing" parameter, only primitive values are allowed. Structs are
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// not supported. Therefore, it can only be slices, maps, primitives, and
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// any combination of those together.
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//
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// See the tests for examples of what inputs are turned into.
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func Flatten(thing map[string]interface{}) map[string]string {
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result := make(map[string]string)
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for k, raw := range thing {
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flatten(result, k, reflect.ValueOf(raw))
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}
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return result
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}
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func flatten(result map[string]string, prefix string, v reflect.Value) {
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if v.Kind() == reflect.Interface {
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v = v.Elem()
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}
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switch v.Kind() {
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case reflect.Bool:
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if v.Bool() {
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result[prefix] = "true"
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} else {
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result[prefix] = "false"
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}
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case reflect.Int:
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result[prefix] = fmt.Sprintf("%d", v.Int())
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case reflect.Map:
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flattenMap(result, prefix, v)
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case reflect.Slice:
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flattenSlice(result, prefix, v)
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case reflect.String:
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result[prefix] = v.String()
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default:
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panic(fmt.Sprintf("Unknown: %s", v))
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}
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}
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func flattenMap(result map[string]string, prefix string, v reflect.Value) {
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for _, k := range v.MapKeys() {
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if k.Kind() == reflect.Interface {
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k = k.Elem()
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}
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if k.Kind() != reflect.String {
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panic(fmt.Sprintf("%s: map key is not string: %s", prefix, k))
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}
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flatten(result, fmt.Sprintf("%s.%s", prefix, k.String()), v.MapIndex(k))
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}
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}
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func flattenSlice(result map[string]string, prefix string, v reflect.Value) {
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prefix = prefix + "."
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result[prefix+"#"] = fmt.Sprintf("%d", v.Len())
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for i := 0; i < v.Len(); i++ {
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flatten(result, fmt.Sprintf("%s%d", prefix, i), v.Index(i))
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}
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}
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@ -0,0 +1,67 @@
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package flatmap
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import (
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"reflect"
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"testing"
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)
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func TestFlatten(t *testing.T) {
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cases := []struct {
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Input map[string]interface{}
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Output map[string]string
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}{
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{
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Input: map[string]interface{}{
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"foo": "bar",
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"bar": "baz",
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},
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Output: map[string]string{
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"foo": "bar",
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"bar": "baz",
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},
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},
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{
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Input: map[string]interface{}{
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"foo": []string{
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"one",
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"two",
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},
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},
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Output: map[string]string{
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"foo.#": "2",
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"foo.0": "one",
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"foo.1": "two",
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},
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},
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{
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Input: map[string]interface{}{
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"foo": []map[interface{}]interface{}{
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map[interface{}]interface{}{
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"name": "bar",
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"port": 3000,
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"enabled": true,
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},
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},
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},
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Output: map[string]string{
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"foo.#": "1",
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"foo.0.name": "bar",
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"foo.0.port": "3000",
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"foo.0.enabled": "true",
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},
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},
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}
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for _, tc := range cases {
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actual := Flatten(tc.Input)
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if !reflect.DeepEqual(actual, tc.Output) {
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t.Fatalf(
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"Input:\n\n%#v\n\nOutput:\n\n%#v\n\nExpected:\n\n%#v\n",
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tc.Input,
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actual,
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tc.Output)
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}
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}
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}
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