providers/slice: Make the slice functions way better

providers/slice/slice.go

@@ -1,6 +1,6 @@
 package slice
 
-import "fmt"
+import "reflect"
 import "html/template"
 import "git.tebibyte.media/sashakoshka/step"
 
@@ -16,50 +16,34 @@ type Provider struct {
 // FuncMap fulfills the step.FuncProvider interface.
 func (this *Provider) FuncMap () template.FuncMap {
 	return template.FuncMap {
-		"sAppend": funcSAppend,
-		"iAppend": funcIAppend,
-		"fAppend": funcFAppend,
+		"list":   funcList,
+		"append": funcAppend,
 	}
 }
 
-func funcSAppend (slice any, addition string) []string {
-	switch slice := slice.(type) {
-	case []string:
-		newSlice := make([]string, len(slice) + 1)
-		copy(newSlice, slice)
-		newSlice[len(slice)] = addition
-		return newSlice
-	case string:
-		return []string { slice, addition }
-	default:
-		return funcSAppend(fmt.Sprint(slice), addition)
+func funcList (items ...reflect.Value) (reflect.Value, error) {
+	if len(items) == 0 { return reflect.Value { }, nil }
+	ty := items[0].Type()
+	list := reflect.MakeSlice(ty, len(items), len(items))
+	for index, item := range items {
+		if item.Type().AssignableTo(ty) {
+			return reflect.Value { }, step.ErrTypeMismatch
+		}
+		dest := list.Index(index)
+		dest.Set(item)
 	}
+	return list, nil
 }
 
-func funcIAppend (slice any, addition int) []int {
-	switch slice := slice.(type) {
-	case []int:
-		newSlice := make([]int, len(slice) + 1)
-		copy(newSlice, slice)
-		newSlice[len(slice)] = addition
-		return newSlice
-	case int:
-		return []int { slice, addition }
-	default:
-		return funcIAppend(0, addition)
-	}
-}
-
-func funcFAppend (slice any, addition float64) []float64 {
-	switch slice := slice.(type) {
-	case []float64:
-		newSlice := make([]float64, len(slice) + 1)
-		copy(newSlice, slice)
-		newSlice[len(slice)] = addition
-		return newSlice
-	case float64:
-		return []float64 { slice, addition }
-	default:
-		return funcFAppend(0, addition)
+func funcAppend (slice reflect.Value, items ...reflect.Value) (reflect.Value, error) {
+	if slice.Type().Kind() != reflect.Slice {
+		return reflect.Value { }, step.ErrTypeMismatch
 	}
+	if len(items) == 0 { return reflect.Value { }, nil }
+	ty := slice.Type().Elem()
+	end := slice.Len() + len(items)
+	list := reflect.MakeSlice(ty, end, end)
+	boundary := reflect.Copy(list, slice)
+	reflect.Copy(list.Slice(boundary, end), reflect.ValueOf(items))
+	return list, nil
 }