1 files changed, 55 insertions, 0 deletions
diff --git a/contrib/fs/file.go b/contrib/fs/file.go
new file mode 100644
index 0000000..cdcd1a9
--- /dev/null
+++ b/contrib/fs/file.go
@@ -0,0 +1,55 @@
+package fs
+
+import (
+	"context"
+	"io/fs"
+	"mime"
+	"strings"
+
+	"tildegit.org/tjp/gus/gemini"
+)
+
+// FileHandler builds a handler function which serves up a file system.
+func FileHandler(fileSystem fs.FS) gemini.Handler {
+	return func(ctx context.Context, req *gemini.Request) *gemini.Response {
+		file, err := fileSystem.Open(strings.TrimPrefix(req.Path, "/"))
+		if isNotFound(err) {
+			return gemini.NotFound("Resource does not exist.")
+		}
+		if err != nil {
+			return gemini.Failure(err)
+		}
+
+		isDir, err := fileIsDir(file)
+		if err != nil {
+			return gemini.Failure(err)
+		}
+
+		if isDir {
+			return gemini.NotFound("Resource does not exist.")
+		}
+
+		return gemini.Success(mediaType(req.Path), file)
+	}
+}
+
+func mediaType(filePath string) string {
+	if strings.HasSuffix(filePath, ".gmi") {
+		// This may not be present in the listings searched by mime.TypeByExtension,
+		// so provide a dedicated fast path for it here.
+		return "text/gemini"
+	}
+
+	slashIdx := strings.LastIndex(filePath, "/")
+	dotIdx := strings.LastIndex(filePath[slashIdx+1:], ".")
+	if dotIdx == -1 {
+		return "application/octet-stream"
+	}
+	ext := filePath[slashIdx+dotIdx:]
+
+	mtype := mime.TypeByExtension(ext)
+	if mtype == "" {
+		return "application/octet-stream"
+	}
+	return mtype
+}