chore: import upstream snapshot with attribution

internal/skillcontent/reader.go

@@ -0,0 +1,209 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+// Package skillcontent reads embedded skill content from an injected fs.FS
+// rooted at the skill list (entries like "lark-calendar/SKILL.md").
+package skillcontent
+
+import (
+	"io/fs"
+	"path"
+	"sort"
+	"strings"
+
+	"github.com/larksuite/cli/errs"
+	"gopkg.in/yaml.v3"
+)
+
+type Reader struct {
+	fsys fs.FS
+}
+
+func New(fsys fs.FS) *Reader { return &Reader{fsys: fsys} }
+
+type SkillInfo struct {
+	Name        string         `json:"name"`
+	Description string         `json:"description"`
+	Version     string         `json:"version,omitempty"`
+	Metadata    map[string]any `json:"metadata,omitempty"`
+}
+
+// DirEntry.Path is skill-prefixed (e.g. "lark-doc/references/x.md") so it can be
+// fed straight back into `read`.
+type DirEntry struct {
+	Path  string `json:"path"`
+	IsDir bool   `json:"is_dir"`
+}
+
+func (r *Reader) List() ([]SkillInfo, error) {
+	entries, err := fs.ReadDir(r.fsys, ".")
+	if err != nil {
+		return nil, errs.NewInternalError(errs.SubtypeFileIO, "failed to read embedded skills: %v", err)
+	}
+	out := make([]SkillInfo, 0, len(entries))
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		// Skip dirs that aren't real skills (no SKILL.md).
+		if info, ok := r.skillInfo(e.Name()); ok {
+			out = append(out, info)
+		}
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
+	return out, nil
+}
+
+func (r *Reader) skillInfo(name string) (SkillInfo, bool) {
+	data, err := fs.ReadFile(r.fsys, name+"/SKILL.md")
+	if err != nil {
+		return SkillInfo{}, false
+	}
+	desc, version, metadata := parseFrontmatter(data)
+	return SkillInfo{Name: name, Description: desc, Version: version, Metadata: metadata}, true
+}
+
+// ListPath lists one directory layer (no recursion) under "<name>" or
+// "<name>/<sub>", returning the entries and the cleaned path listed.
+func (r *Reader) ListPath(arg string) ([]DirEntry, string, error) {
+	name, sub := SplitArg(arg)
+	if err := r.ensureSkill(name); err != nil {
+		return nil, "", err
+	}
+	dir := name
+	if sub != "" {
+		cleaned, err := cleanSubPath(sub)
+		if err != nil {
+			return nil, "", err
+		}
+		dir = name + "/" + cleaned
+		info, err := fs.Stat(r.fsys, dir)
+		if err != nil {
+			return nil, "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+				"path %q not found in skill %q", sub, name).
+				WithHint("run 'lark-cli skills list " + name + "' to see files in this skill")
+		}
+		if !info.IsDir() {
+			return nil, "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+				"path %q is a file, not a directory; use 'lark-cli skills read %s/%s' to read it", sub, name, cleaned)
+		}
+	}
+	entries, err := fs.ReadDir(r.fsys, dir)
+	if err != nil {
+		return nil, "", errs.NewInternalError(errs.SubtypeFileIO,
+			"failed to read embedded skill content: %v", err)
+	}
+	out := make([]DirEntry, 0, len(entries))
+	for _, e := range entries {
+		out = append(out, DirEntry{Path: dir + "/" + e.Name(), IsDir: e.IsDir()})
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Path < out[j].Path })
+	return out, dir, nil
+}
+
+// SplitArg splits "<name>/<rest>" at the first separator; an argument with no
+// separator is a bare skill name (rest "").
+func SplitArg(arg string) (name, rest string) {
+	name, rest, _ = strings.Cut(arg, "/")
+	return name, rest
+}
+
+// parseFrontmatter best-effort-extracts the frontmatter fields; missing or
+// unparseable frontmatter yields ("", "", nil), never an error.
+func parseFrontmatter(skillMD []byte) (description, version string, metadata map[string]any) {
+	lines := strings.Split(string(skillMD), "\n")
+	if strings.TrimRight(lines[0], "\r") != "---" {
+		return "", "", nil
+	}
+	block := make([]string, 0, len(lines))
+	closed := false
+	for _, ln := range lines[1:] {
+		if strings.TrimRight(ln, "\r") == "---" {
+			closed = true
+			break
+		}
+		block = append(block, ln)
+	}
+	if !closed {
+		return "", "", nil
+	}
+	var fm struct {
+		Description string         `yaml:"description"`
+		Version     string         `yaml:"version"`
+		Metadata    map[string]any `yaml:"metadata"`
+	}
+	if err := yaml.Unmarshal([]byte(strings.Join(block, "\n")), &fm); err != nil {
+		return "", "", nil
+	}
+	return fm.Description, fm.Version, fm.Metadata
+}
+
+func (r *Reader) ReadSkill(name string) ([]byte, error) {
+	if err := r.ensureSkill(name); err != nil {
+		return nil, err
+	}
+	data, err := fs.ReadFile(r.fsys, name+"/SKILL.md")
+	if err != nil {
+		return nil, errs.NewInternalError(errs.SubtypeFileIO,
+			"failed to read embedded skill content: %v", err)
+	}
+	return data, nil
+}
+
+func (r *Reader) ensureSkill(name string) error {
+	if name == "" || strings.ContainsAny(name, `/\`) || name == "." || name == ".." {
+		return unknownSkill(name)
+	}
+	info, err := fs.Stat(r.fsys, name)
+	if err != nil || !info.IsDir() {
+		return unknownSkill(name)
+	}
+	return nil
+}
+
+func unknownSkill(name string) error {
+	return errs.NewValidationError(errs.SubtypeInvalidArgument, "unknown skill %q", name).
+		WithHint("run 'lark-cli skills list' to see available skills")
+}
+
+// cleanSubPath returns the cleaned form of relpath, rejecting absolute paths and
+// ".." escapes. relpath must be non-empty (callers handle the skill-root case).
+func cleanSubPath(relpath string) (string, error) {
+	cleaned := path.Clean(relpath)
+	// path.Clean only treats '/' as a separator, so a Windows-style "..\" prefix
+	// survives; reject it explicitly alongside "../".
+	if relpath == "" || path.IsAbs(relpath) || cleaned == "." ||
+		cleaned == ".." || strings.HasPrefix(cleaned, "../") || strings.HasPrefix(cleaned, `..\`) {
+		return "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+			"invalid path %q: must be a relative path without '..'", relpath)
+	}
+	return cleaned, nil
+}
+
+// ReadReference returns the bytes of <name>/<relpath> and the cleaned path.
+func (r *Reader) ReadReference(name, relpath string) ([]byte, string, error) {
+	if err := r.ensureSkill(name); err != nil {
+		return nil, "", err
+	}
+	cleaned, err := cleanSubPath(relpath)
+	if err != nil {
+		return nil, "", err
+	}
+	full := name + "/" + cleaned
+	info, err := fs.Stat(r.fsys, full)
+	if err != nil {
+		return nil, "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+			"reference %q not found in skill %q", relpath, name).
+			WithHint("run 'lark-cli skills list " + name + "' to see files in this skill")
+	}
+	if info.IsDir() {
+		return nil, "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+			"reference %q is a directory, not a file", relpath)
+	}
+	data, err := fs.ReadFile(r.fsys, full)
+	if err != nil {
+		return nil, "", errs.NewInternalError(errs.SubtypeFileIO,
+			"failed to read embedded skill content: %v", err)
+	}
+	return data, cleaned, nil
+}