Refactor rock, paper, scissors

lib/common.go

@@ -141,3 +141,21 @@ func SplitArgs(s string, n int) (args []string) {
 	}
 	return
 }
+
+func MapKeys[K comparable, V any](m map[K]V) []K {
+	keys := make([]K, 0, len(m))
+	for k := range m {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+func MapKey[K comparable, V comparable](m map[K]V, v V) K {
+	var r K
+	for k := range m {
+		if m[k] == v {
+			return k
+		}
+	}
+	return r
+}

lib/common_test.go

@@ -123,3 +123,37 @@ func TestSplitArgs(t *testing.T) {
 		}
 	}
 }
+
+func TestMapKeys(t *testing.T) {
+	tables := []struct {
+		m    map[string]int
+		want []string
+	}{
+		{map[string]int{"a": 0, "b": 1, "c": 3}, []string{"a", "b", "c"}},
+	}
+
+	for _, table := range tables {
+		if got, want := MapKeys(table.m), table.want; !reflect.DeepEqual(got, want) {
+			t.Errorf("got: %#v, want: %#v", got, want)
+		}
+	}
+}
+
+func TestMapKey(t *testing.T) {
+	tables := []struct {
+		m    map[string]int
+		n    int
+		want string
+	}{
+		{map[string]int{"a": 0, "b": 1, "c": 2}, 0, "a"},
+		{map[string]int{"a": 0, "b": 1, "c": 2}, 1, "b"},
+		{map[string]int{"a": 0, "b": 1, "c": 2}, 2, "c"},
+		{map[string]int{"a": 0, "b": 1, "c": 2, "d": 0}, 0, "a"},
+	}
+
+	for _, table := range tables {
+		if got, want := MapKey(table.m, table.n), table.want; got != want {
+			t.Errorf("got: %#v, want: %#v", got, want)
+		}
+	}
+}

lib/rand.go

@@ -37,3 +37,15 @@ func SeedMathRand() error {
 func RandInt(min int, max int) int {
 	return rand.Intn(max-min+1) + min
 }
+
+func MapRand[K comparable, V any](m map[K]V) V {
+	n := rand.Intn(len(m))
+	i := 0
+	for _, v := range m {
+		if i == n {
+			return v
+		}
+		i++
+	}
+	panic("unreachable")
+}