From a3b9f399e142ea750718633a68ad249e29dcd171 Mon Sep 17 00:00:00 2001
From: Leon Mika <lmika@lmika.org>
Date: Fri, 24 Jan 2025 13:25:28 +1100
Subject: [PATCH] Added list:add

---
 ucl/builtins/lists.go      | 35 +++++++++++++++++++++++++++++++++++
 ucl/builtins/lists_test.go | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 ucl/builtins/lists.go
 create mode 100644 ucl/builtins/lists_test.go

diff --git a/ucl/builtins/lists.go b/ucl/builtins/lists.go
new file mode 100644
index 0000000..be3259d
--- /dev/null
+++ b/ucl/builtins/lists.go
@@ -0,0 +1,35 @@
+package builtins
+
+import (
+	"context"
+	"ucl.lmika.dev/ucl"
+)
+
+func Lists() ucl.Module {
+	return ucl.Module{
+		Name: "lists",
+		Builtins: map[string]ucl.BuiltinHandler{
+			"add": listAdd,
+		},
+	}
+}
+
+func listAdd(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var target ucl.ModListable
+
+	if err := args.Bind(&target); err != nil {
+		return nil, err
+	}
+
+	for args.NArgs() > 0 {
+		var obj ucl.Object
+		if err := args.Bind(&obj); err != nil {
+			return nil, err
+		}
+		if err := target.Insert(-1, obj); err != nil {
+			return nil, err
+		}
+	}
+
+	return target, nil
+}
diff --git a/ucl/builtins/lists_test.go b/ucl/builtins/lists_test.go
new file mode 100644
index 0000000..8d8b909
--- /dev/null
+++ b/ucl/builtins/lists_test.go
@@ -0,0 +1,37 @@
+package builtins_test
+
+import (
+	"context"
+	"github.com/stretchr/testify/assert"
+	"testing"
+	"ucl.lmika.dev/ucl"
+	"ucl.lmika.dev/ucl/builtins"
+)
+
+func TestLists_Add(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    any
+		wantErr bool
+	}{
+		{desc: "list add 1", eval: `lists:add [1 2 3] 4`, want: []any{1, 2, 3, 4}},
+		{desc: "list add 2", eval: `lists:add [1 2 3] 4 5`, want: []any{1, 2, 3, 4, 5}},
+		{desc: "list add 3", eval: `lists:add [1 2 3]`, want: []any{1, 2, 3}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Lists()),
+			)
+			res, err := inst.Eval(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}