Implemented symlinks and mimetype for serve

README.md

@@ -5,6 +5,9 @@ japanese for *stairs*. a minimal, fast file index server.
 single static binary. TOML config. sortable listings (name, type, size,
 modified).
 
+browser-renderable files (images, audio, video, text, PDF and friends) are
+served inline so they open in place; everything else is sent as a download.
+
 ## build
 
 ```sh

assets/index.html

@@ -166,7 +166,7 @@ footer a:hover {
 {{if .HasParent}}<tr><td><a href="../">../</a></td><td class="num ty">-</td><td class="num sz"></td><td class="num mod"></td></tr>{{end}}
 {{range .Rows}}
 <tr{{if .IsDir}} class="dir"{{end}}>
-<td><a href="{{.URL}}"{{if not .IsDir}} download{{end}}>{{.Name}}</a></td>
+<td><a href="{{.URL}}">{{.Name}}</a></td>
 <td class="num ty">{{.Type}}</td>
 <td class="num sz">{{if .IsDir}}-{{else}}{{.SizeS}}{{end}}</td>
 <td class="num mod">{{.ModS}}</td>

config.go

@@ -14,6 +14,7 @@ type Config struct {
 	Root           string `toml:"root"`
 	Hidden         bool   `toml:"hidden"`
 	Footer         string `toml:"footer"`
+	FollowSymlinks bool   `toml:"follow_symlinks"`
 }
 
 func loadConfig(path string) (*Config, error) {
@@ -22,9 +23,15 @@ func loadConfig(path string) (*Config, error) {
 		return nil, err
 	}
 	cfg := &Config{}
-	if err := toml.Unmarshal(b, cfg); err != nil {
+	md, err := toml.Decode(string(b), cfg)
+	if err != nil {
 		return nil, fmt.Errorf("%s: %w", path, err)
 	}
+	// follow_symlinks defaults to true: symlinks are served as a window onto
+	// their target, even outside root.
+	if !md.IsDefined("follow_symlinks") {
+		cfg.FollowSymlinks = true
+	}
 	if cfg.Root == "" {
 		return nil, errors.New(`config: "root" is required`)
 	}

config.toml

@@ -11,3 +11,7 @@ hidden = true
 
 # footer shown at the bottom of every page
 footer = "kaidan 1.0"
+
+# follow symlinks even when their target lies outside root. set to false to
+# keep the served tree confined to root (escaping symlinks then 404).
+follow_symlinks = true

server.go

@@ -5,6 +5,7 @@ import (
 	_ "embed"
 	"fmt"
 	"html/template"
+	"io"
 	"mime"
 	"net/http"
 	"net/url"
@@ -30,6 +31,7 @@ type server struct {
 	rootReal string // symlink-resolved root, used for containment checks
 	hidden   bool
 	footer   string
+	follow   bool // serve symlinks even when they point outside root
 	tpl      *template.Template
 }
 
@@ -43,6 +45,7 @@ func newServer(cfg *Config) *server {
 		rootReal: rootReal,
 		hidden:   cfg.Hidden,
 		footer:   cfg.Footer,
+		follow:   cfg.FollowSymlinks,
 		tpl:      template.Must(template.New("index").Parse(indexHTML)),
 	}
 }
@@ -111,7 +114,7 @@ func (s *server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		http.NotFound(w, r)
 		return
 	}
-	if realPath != s.rootReal && !strings.HasPrefix(realPath, s.rootReal+string(os.PathSeparator)) {
+	if !s.follow && realPath != s.rootReal && !strings.HasPrefix(realPath, s.rootReal+string(os.PathSeparator)) {
 		http.NotFound(w, r) // symlink escaping the served root
 		return
 	}
@@ -147,11 +150,48 @@ func (s *server) serveFile(w http.ResponseWriter, r *http.Request, path, name st
 		return
 	}
 	defer f.Close()
+	disp := "attachment"
+	if inlineFile(f, name) {
+		disp = "inline"
+	}
 	w.Header().Set("Content-Disposition",
-		mime.FormatMediaType("attachment", map[string]string{"filename": name}))
+		mime.FormatMediaType(disp, map[string]string{"filename": name}))
 	http.ServeContent(w, r, name, info.ModTime(), f)
 }
 
+func inlineFile(f *os.File, name string) bool {
+	if ct := mime.TypeByExtension(strings.ToLower(filepath.Ext(name))); ct != "" {
+		return inlineMIME(ct)
+	}
+	buf := make([]byte, 512)
+	n, err := f.Read(buf)
+	if _, serr := f.Seek(0, io.SeekStart); serr != nil {
+		return false
+	}
+	if err != nil && err != io.EOF {
+		return false
+	}
+	return inlineMIME(http.DetectContentType(buf[:n]))
+}
+
+func inlineMIME(ct string) bool {
+	if i := strings.IndexByte(ct, ';'); i >= 0 {
+		ct = strings.TrimSpace(ct[:i])
+	}
+	switch {
+	case strings.HasPrefix(ct, "image/"),
+		strings.HasPrefix(ct, "audio/"),
+		strings.HasPrefix(ct, "video/"),
+		strings.HasPrefix(ct, "text/"):
+		return ct != "text/html"
+	case ct == "application/pdf",
+		ct == "application/xml",
+		ct == "application/json":
+		return true
+	}
+	return false
+}
+
 func (s *server) serveListing(w http.ResponseWriter, r *http.Request, dirPath, urlPath string) {
 	entries, err := os.ReadDir(dirPath)
 	if err != nil {
@@ -176,20 +216,31 @@ func (s *server) serveListing(w http.ResponseWriter, r *http.Request, dirPath, u
 			continue
 		}
 		isDir := e.IsDir()
+		var size int64
+		var mod time.Time
+		if info, err := e.Info(); err == nil { // lstat: does not follow symlinks
+			mod = info.ModTime()
+			if !isDir {
+				size = info.Size()
+			}
+		}
+		if e.Type()&os.ModeSymlink != 0 {
+			if ti, err := os.Stat(filepath.Join(dirPath, name)); err == nil {
+				isDir = ti.IsDir()
+				mod = ti.ModTime()
+				if isDir {
+					size = 0
+				} else {
+					size = ti.Size()
+				}
+			}
+		}
 		typ := "-"
 		if isDir {
 			typ = "dir"
 		} else if ext := strings.TrimPrefix(filepath.Ext(name), "."); ext != "" {
 			typ = strings.ToLower(ext)
 		}
-		var size int64
-		var mod time.Time
-		if info, err := e.Info(); err == nil {
-			mod = info.ModTime()
-			if !isDir {
-				size = info.Size()
-			}
-		}
 		rows = append(rows, row{
 			Name:    name,
 			URL:     dirURL + url.PathEscape(name),