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skillpackage/frontmatter.go

@@ -0,0 +1,114 @@
+package skillpackage
+
+import (
+	"fmt"
+	"strings"
+
+	"gopkg.in/yaml.v3"
+)
+
+// ExtractSkillMDFrontMatterYAML returns the YAML source inside the first --- ... --- block and the markdown body.
+func ExtractSkillMDFrontMatterYAML(raw []byte) (fmYAML string, body string, err error) {
+	text := strings.TrimPrefix(string(raw), "\ufeff")
+	if strings.TrimSpace(text) == "" {
+		return "", "", fmt.Errorf("SKILL.md is empty")
+	}
+	lines := strings.Split(text, "\n")
+	if len(lines) < 2 || strings.TrimSpace(lines[0]) != "---" {
+		return "", "", fmt.Errorf("SKILL.md must start with YAML front matter (---) per Agent Skills standard")
+	}
+	var fmLines []string
+	i := 1
+	for i < len(lines) {
+		if strings.TrimSpace(lines[i]) == "---" {
+			break
+		}
+		fmLines = append(fmLines, lines[i])
+		i++
+	}
+	if i >= len(lines) {
+		return "", "", fmt.Errorf("SKILL.md: front matter must end with a line containing only ---")
+	}
+	body = strings.Join(lines[i+1:], "\n")
+	body = strings.TrimSpace(body)
+	fmYAML = strings.Join(fmLines, "\n")
+	return fmYAML, body, nil
+}
+
+// ParseSkillMD parses SKILL.md YAML head + body.
+func ParseSkillMD(raw []byte) (*SkillManifest, string, error) {
+	fmYAML, body, err := ExtractSkillMDFrontMatterYAML(raw)
+	if err != nil {
+		return nil, "", err
+	}
+	var m SkillManifest
+	if err := yaml.Unmarshal([]byte(fmYAML), &m); err != nil {
+		return nil, "", fmt.Errorf("SKILL.md front matter: %w", err)
+	}
+	return &m, body, nil
+}
+
+type skillFrontMatterExport struct {
+	Name          string         `yaml:"name"`
+	Description   string         `yaml:"description"`
+	License       string         `yaml:"license,omitempty"`
+	Compatibility string         `yaml:"compatibility,omitempty"`
+	Metadata      map[string]any `yaml:"metadata,omitempty"`
+	AllowedTools  string         `yaml:"allowed-tools,omitempty"`
+}
+
+// BuildSkillMD serializes SKILL.md per agentskills.io.
+func BuildSkillMD(m *SkillManifest, body string) ([]byte, error) {
+	if m == nil {
+		return nil, fmt.Errorf("nil manifest")
+	}
+	fm := skillFrontMatterExport{
+		Name:          strings.TrimSpace(m.Name),
+		Description:   strings.TrimSpace(m.Description),
+		License:       strings.TrimSpace(m.License),
+		Compatibility: strings.TrimSpace(m.Compatibility),
+		AllowedTools:  strings.TrimSpace(m.AllowedTools),
+	}
+	if len(m.Metadata) > 0 {
+		fm.Metadata = m.Metadata
+	}
+	head, err := yaml.Marshal(&fm)
+	if err != nil {
+		return nil, err
+	}
+	s := strings.TrimSpace(string(head))
+	out := "---\n" + s + "\n---\n\n" + strings.TrimSpace(body) + "\n"
+	return []byte(out), nil
+}
+
+func manifestTags(m *SkillManifest) []string {
+	if m == nil || m.Metadata == nil {
+		return nil
+	}
+	var out []string
+	if raw, ok := m.Metadata["tags"]; ok {
+		switch v := raw.(type) {
+		case []any:
+			for _, x := range v {
+				if s, ok := x.(string); ok && s != "" {
+					out = append(out, s)
+				}
+			}
+		case []string:
+			out = append(out, v...)
+		}
+	}
+	return out
+}
+
+func versionFromMetadata(m *SkillManifest) string {
+	if m == nil || m.Metadata == nil {
+		return ""
+	}
+	if v, ok := m.Metadata["version"]; ok {
+		if s, ok := v.(string); ok {
+			return strings.TrimSpace(s)
+		}
+	}
+	return ""
+}