2 files changed, 172 insertions, 0 deletions
diff --git a/internal/pkg/labels/labels.go b/internal/pkg/labels/labels.go
new file mode 100644
index 0000000..f448fdf
--- /dev/null
+++ b/internal/pkg/labels/labels.go
@@ -0,0 +1,109 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package labels
+
+import (
+	"fmt"
+	"strings"
+)
+
+const (
+	SchemeHost   = "host"
+	SchemeDocker = "docker"
+	SchemeLXC    = "lxc"
+)
+
+type Label struct {
+	Name   string
+	Schema string
+	Arg    string
+}
+
+func Parse(str string) (*Label, error) {
+	splits := strings.SplitN(str, ":", 3)
+	label := &Label{
+		Name:   splits[0],
+		Schema: "host",
+		Arg:    "",
+	}
+	if len(splits) >= 2 {
+		label.Schema = splits[1]
+	}
+	if len(splits) >= 3 {
+		label.Arg = splits[2]
+	}
+	if label.Schema != SchemeHost && label.Schema != SchemeDocker && label.Schema != SchemeLXC {
+		return nil, fmt.Errorf("unsupported schema: %s", label.Schema)
+	}
+	return label, nil
+}
+
+type Labels []*Label
+
+func (l Labels) RequireDocker() bool {
+	for _, label := range l {
+		if label.Schema == SchemeDocker {
+			return true
+		}
+	}
+	return false
+}
+
+func (l Labels) PickPlatform(runsOn []string) string {
+	platforms := make(map[string]string, len(l))
+	for _, label := range l {
+		switch label.Schema {
+		case SchemeDocker:
+			// "//" will be ignored
+			platforms[label.Name] = strings.TrimPrefix(label.Arg, "//")
+		case SchemeHost:
+			platforms[label.Name] = "-self-hosted"
+		case SchemeLXC:
+			platforms[label.Name] = "lxc:" + strings.TrimPrefix(label.Arg, "//")
+		default:
+			// It should not happen, because Parse has checked it.
+			continue
+		}
+	}
+	for _, v := range runsOn {
+		if v, ok := platforms[v]; ok {
+			return v
+		}
+	}
+
+	// TODO: support multiple labels
+	// like:
+	//   ["ubuntu-22.04"] => "ubuntu:22.04"
+	//   ["with-gpu"] => "linux:with-gpu"
+	//   ["ubuntu-22.04", "with-gpu"] => "ubuntu:22.04_with-gpu"
+
+	// return default.
+	// So the runner receives a task with a label that the runner doesn't have,
+	// it happens when the user have edited the label of the runner in the web UI.
+	// TODO: it may be not correct, what if the runner is used as host mode only?
+	return "node:20-bullseye"
+}
+
+func (l Labels) Names() []string {
+	names := make([]string, 0, len(l))
+	for _, label := range l {
+		names = append(names, label.Name)
+	}
+	return names
+}
+
+func (l Labels) ToStrings() []string {
+	ls := make([]string, 0, len(l))
+	for _, label := range l {
+		lbl := label.Name
+		if label.Schema != "" {
+			lbl += ":" + label.Schema
+			if label.Arg != "" {
+				lbl += ":" + label.Arg
+			}
+		}
+		ls = append(ls, lbl)
+	}
+	return ls
+}
diff --git a/internal/pkg/labels/labels_test.go b/internal/pkg/labels/labels_test.go
new file mode 100644
index 0000000..e46a27b
--- /dev/null
+++ b/internal/pkg/labels/labels_test.go
@@ -0,0 +1,63 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package labels
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"gotest.tools/v3/assert"
+)
+
+func TestParse(t *testing.T) {
+	tests := []struct {
+		args    string
+		want    *Label
+		wantErr bool
+	}{
+		{
+			args: "ubuntu:docker://node:18",
+			want: &Label{
+				Name:   "ubuntu",
+				Schema: "docker",
+				Arg:    "//node:18",
+			},
+			wantErr: false,
+		},
+		{
+			args: "ubuntu:host",
+			want: &Label{
+				Name:   "ubuntu",
+				Schema: "host",
+				Arg:    "",
+			},
+			wantErr: false,
+		},
+		{
+			args: "ubuntu",
+			want: &Label{
+				Name:   "ubuntu",
+				Schema: "host",
+				Arg:    "",
+			},
+			wantErr: false,
+		},
+		{
+			args:    "ubuntu:vm:ubuntu-18.04",
+			want:    nil,
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.args, func(t *testing.T) {
+			got, err := Parse(tt.args)
+			if tt.wantErr {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+			assert.DeepEqual(t, got, tt.want)
+		})
+	}
+}