Add loading yaml label template files (#22976)

Extract from #11669 and enhancement to #22585 to support exclusive
scoped labels in label templates

* Move label template functionality to label module
* Fix handling of color codes
* Add Advanced label template

3 files changed, 244 insertions, 0 deletions

diff --git a/modules/label/label.go b/modules/label/label.go
new file mode 100644
index 0000000000..d3ef0e1dc9
--- /dev/null
+++ b/modules/label/label.go
@@ -0,0 +1,46 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package label
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// colorPattern is a regexp which can validate label color
+var colorPattern = regexp.MustCompile("^#?(?:[0-9a-fA-F]{6}|[0-9a-fA-F]{3})$")
+
+// Label represents label information loaded from template
+type Label struct {
+	Name        string `yaml:"name"`
+	Color       string `yaml:"color"`
+	Description string `yaml:"description,omitempty"`
+	Exclusive   bool   `yaml:"exclusive,omitempty"`
+}
+
+// NormalizeColor normalizes a color string to a 6-character hex code
+func NormalizeColor(color string) (string, error) {
+	// normalize case
+	color = strings.TrimSpace(strings.ToLower(color))
+
+	// add leading hash
+	if len(color) == 6 || len(color) == 3 {
+		color = "#" + color
+	}
+
+	if !colorPattern.MatchString(color) {
+		return "", fmt.Errorf("bad color code: %s", color)
+	}
+
+	// convert 3-character shorthand into 6-character version
+	if len(color) == 4 {
+		r := color[1]
+		g := color[2]
+		b := color[3]
+		color = fmt.Sprintf("#%c%c%c%c%c%c", r, r, g, g, b, b)
+	}
+
+	return color, nil
+}
diff --git a/modules/label/parser.go b/modules/label/parser.go
new file mode 100644
index 0000000000..768c72a61b
--- /dev/null
+++ b/modules/label/parser.go
@@ -0,0 +1,126 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package label
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"code.gitea.io/gitea/modules/options"
+
+	"gopkg.in/yaml.v3"
+)
+
+type labelFile struct {
+	Labels []*Label `yaml:"labels"`
+}
+
+// ErrTemplateLoad represents a "ErrTemplateLoad" kind of error.
+type ErrTemplateLoad struct {
+	TemplateFile  string
+	OriginalError error
+}
+
+// IsErrTemplateLoad checks if an error is a ErrTemplateLoad.
+func IsErrTemplateLoad(err error) bool {
+	_, ok := err.(ErrTemplateLoad)
+	return ok
+}
+
+func (err ErrTemplateLoad) Error() string {
+	return fmt.Sprintf("Failed to load label template file '%s': %v", err.TemplateFile, err.OriginalError)
+}
+
+// GetTemplateFile loads the label template file by given name,
+// then parses and returns a list of name-color pairs and optionally description.
+func GetTemplateFile(name string) ([]*Label, error) {
+	data, err := options.GetRepoInitFile("label", name+".yaml")
+	if err == nil && len(data) > 0 {
+		return parseYamlFormat(name+".yaml", data)
+	}
+
+	data, err = options.GetRepoInitFile("label", name+".yml")
+	if err == nil && len(data) > 0 {
+		return parseYamlFormat(name+".yml", data)
+	}
+
+	data, err = options.GetRepoInitFile("label", name)
+	if err != nil {
+		return nil, ErrTemplateLoad{name, fmt.Errorf("GetRepoInitFile: %w", err)}
+	}
+
+	return parseLegacyFormat(name, data)
+}
+
+func parseYamlFormat(name string, data []byte) ([]*Label, error) {
+	lf := &labelFile{}
+
+	if err := yaml.Unmarshal(data, lf); err != nil {
+		return nil, err
+	}
+
+	// Validate label data and fix colors
+	for _, l := range lf.Labels {
+		l.Color = strings.TrimSpace(l.Color)
+		if len(l.Name) == 0 || len(l.Color) == 0 {
+			return nil, ErrTemplateLoad{name, errors.New("label name and color are required fields")}
+		}
+		color, err := NormalizeColor(l.Color)
+		if err != nil {
+			return nil, ErrTemplateLoad{name, fmt.Errorf("bad HTML color code '%s' in label: %s", l.Color, l.Name)}
+		}
+		l.Color = color
+	}
+
+	return lf.Labels, nil
+}
+
+func parseLegacyFormat(name string, data []byte) ([]*Label, error) {
+	lines := strings.Split(string(data), "\n")
+	list := make([]*Label, 0, len(lines))
+	for i := 0; i < len(lines); i++ {
+		line := strings.TrimSpace(lines[i])
+		if len(line) == 0 {
+			continue
+		}
+
+		parts, description, _ := strings.Cut(line, ";")
+
+		color, name, ok := strings.Cut(parts, " ")
+		if !ok {
+			return nil, ErrTemplateLoad{name, fmt.Errorf("line is malformed: %s", line)}
+		}
+
+		color, err := NormalizeColor(color)
+		if err != nil {
+			return nil, ErrTemplateLoad{name, fmt.Errorf("bad HTML color code '%s' in line: %s", color, line)}
+		}
+
+		list = append(list, &Label{
+			Name:        strings.TrimSpace(name),
+			Color:       color,
+			Description: strings.TrimSpace(description),
+		})
+	}
+
+	return list, nil
+}
+
+// LoadFormatted loads the labels' list of a template file as a string separated by comma
+func LoadFormatted(name string) (string, error) {
+	var buf strings.Builder
+	list, err := GetTemplateFile(name)
+	if err != nil {
+		return "", err
+	}
+
+	for i := 0; i < len(list); i++ {
+		if i > 0 {
+			buf.WriteString(", ")
+		}
+		buf.WriteString(list[i].Name)
+	}
+	return buf.String(), nil
+}
diff --git a/modules/label/parser_test.go b/modules/label/parser_test.go
new file mode 100644
index 0000000000..5c8042f668
--- /dev/null
+++ b/modules/label/parser_test.go
@@ -0,0 +1,72 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package label
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestYamlParser(t *testing.T) {
+	data := []byte(`labels:
+  - name: priority/low
+    exclusive: true
+    color: "#0000ee"
+    description: "Low priority"
+  - name: priority/medium
+    exclusive: true
+    color: "0e0"
+    description: "Medium priority"
+  - name: priority/high
+    exclusive: true
+    color: "#ee0000"
+    description: "High priority"
+  - name: type/bug
+    color: "#f00"
+    description: "Bug"`)
+
+	labels, err := parseYamlFormat("test", data)
+	require.NoError(t, err)
+	require.Len(t, labels, 4)
+	assert.Equal(t, "priority/low", labels[0].Name)
+	assert.True(t, labels[0].Exclusive)
+	assert.Equal(t, "#0000ee", labels[0].Color)
+	assert.Equal(t, "Low priority", labels[0].Description)
+	assert.Equal(t, "priority/medium", labels[1].Name)
+	assert.True(t, labels[1].Exclusive)
+	assert.Equal(t, "#00ee00", labels[1].Color)
+	assert.Equal(t, "Medium priority", labels[1].Description)
+	assert.Equal(t, "priority/high", labels[2].Name)
+	assert.True(t, labels[2].Exclusive)
+	assert.Equal(t, "#ee0000", labels[2].Color)
+	assert.Equal(t, "High priority", labels[2].Description)
+	assert.Equal(t, "type/bug", labels[3].Name)
+	assert.False(t, labels[3].Exclusive)
+	assert.Equal(t, "#ff0000", labels[3].Color)
+	assert.Equal(t, "Bug", labels[3].Description)
+}
+
+func TestLegacyParser(t *testing.T) {
+	data := []byte(`#ee0701 bug   ;   Something is not working
+#cccccc   duplicate ; This issue or pull request already exists
+#84b6eb enhancement`)
+
+	labels, err := parseLegacyFormat("test", data)
+	require.NoError(t, err)
+	require.Len(t, labels, 3)
+	assert.Equal(t, "bug", labels[0].Name)
+	assert.False(t, labels[0].Exclusive)
+	assert.Equal(t, "#ee0701", labels[0].Color)
+	assert.Equal(t, "Something is not working", labels[0].Description)
+	assert.Equal(t, "duplicate", labels[1].Name)
+	assert.False(t, labels[1].Exclusive)
+	assert.Equal(t, "#cccccc", labels[1].Color)
+	assert.Equal(t, "This issue or pull request already exists", labels[1].Description)
+	assert.Equal(t, "enhancement", labels[2].Name)
+	assert.False(t, labels[2].Exclusive)
+	assert.Equal(t, "#84b6eb", labels[2].Color)
+	assert.Empty(t, labels[2].Description)
+}