From 55cf8bbdc7ad2a3c40ed68a92cacfc7d817cc0a4 Mon Sep 17 00:00:00 2001
From: Ravi Suhag <suhag.ravi@gmail.com>
Date: Tue, 13 Sep 2022 00:25:21 -0500
Subject: [PATCH] feat: add spa package (#49)

* feat: add spa package

* chore:fix typo

* fix: remove spa type

* fix: remove panic

* fix: merge handlers
---
 go.mod        |  1 +
 go.sum        |  1 +
 spa/router.go | 32 ++++++++++++++++++++++++++++++++
 spa/spa.go    | 40 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 74 insertions(+)
 create mode 100644 spa/router.go
 create mode 100644 spa/spa.go

diff --git a/go.mod b/go.mod
index a69bb08..8f86f43 100644
--- a/go.mod
+++ b/go.mod
@@ -6,6 +6,7 @@ require (
 	github.com/AlecAivazis/survey/v2 v2.3.5
 	github.com/DATA-DOG/go-sqlmock v1.5.0
 	github.com/MakeNowJust/heredoc v1.0.0
+	github.com/NYTimes/gziphandler v1.1.1
 	github.com/Nvveen/Gotty v0.0.0-20120604004816-cd527374f1e5 // indirect
 	github.com/briandowns/spinner v1.18.0
 	github.com/cenkalti/backoff v2.2.1+incompatible // indirect
diff --git a/go.sum b/go.sum
index 0efa314..7a0be0f 100644
--- a/go.sum
+++ b/go.sum
@@ -106,6 +106,7 @@ github.com/Microsoft/hcsshim v0.9.2/go.mod h1:7pLA8lDk46WKDWlVsENo92gC0XFa8rbKfy
 github.com/Microsoft/hcsshim/test v0.0.0-20201218223536-d3e5debf77da/go.mod h1:5hlzMzRKMLyo42nCZ9oml8AdTlq/0cvIaBv6tK1RehU=
 github.com/Microsoft/hcsshim/test v0.0.0-20210227013316-43a75bb4edd3/go.mod h1:mw7qgWloBUl75W/gVH3cQszUg1+gUITj7D6NY7ywVnY=
 github.com/NYTimes/gziphandler v0.0.0-20170623195520-56545f4a5d46/go.mod h1:3wb06e3pkSAbeQ52E9H9iFoQsEEwGN64994WTCIhntQ=
+github.com/NYTimes/gziphandler v1.1.1 h1:ZUDjpQae29j0ryrS0u/B8HZfJBtBQHjqw2rQ2cqUQ3I=
 github.com/NYTimes/gziphandler v1.1.1/go.mod h1:n/CVRwUEOgIxrgPvAQhUUr9oeUtvrhMomdKFjzJNB0c=
 github.com/Netflix/go-expect v0.0.0-20220104043353-73e0943537d2 h1:+vx7roKuyA63nhn5WAunQHLTznkw5W8b1Xc0dNjp83s=
 github.com/Netflix/go-expect v0.0.0-20220104043353-73e0943537d2/go.mod h1:HBCaDeC1lPdgDeDbhX8XFpy1jqjK0IBG8W5K+xYqA0w=
diff --git a/spa/router.go b/spa/router.go
new file mode 100644
index 0000000..e0f4c14
--- /dev/null
+++ b/spa/router.go
@@ -0,0 +1,32 @@
+package spa
+
+import (
+	"errors"
+	"io/fs"
+	"net/http"
+)
+
+// router is the http filesystem which only serves files
+// and prevent the directory traversal.
+type router struct {
+	index string
+	fs    http.FileSystem
+}
+
+// Open inspects the URL path to locate a file within the static dir.
+// If a file is found, it will be served. If not, the file located at
+// the index path on the SPA handler will be served.
+func (r *router) Open(name string) (http.File, error) {
+	file, err := r.fs.Open(name)
+
+	if err == nil {
+		return file, nil
+	}
+	// Serve index if file does not exist.
+	if errors.Is(err, fs.ErrNotExist) {
+		file, err := r.fs.Open(r.index)
+		return file, err
+	}
+
+	return nil, err
+}
diff --git a/spa/spa.go b/spa/spa.go
new file mode 100644
index 0000000..5bda3fd
--- /dev/null
+++ b/spa/spa.go
@@ -0,0 +1,40 @@
+package spa
+
+import (
+	"embed"
+	"errors"
+	"fmt"
+	"io/fs"
+	"net/http"
+
+	"github.com/NYTimes/gziphandler"
+)
+
+// Handler return a file server http handler for single page
+// application. This handler can be mounted on your mux server.
+//
+// If gzip is set true, handler gzip the response body, for clients
+// which support it. Usually it also can be left to proxies like Nginx,
+// this method is useful when that's undesirable.
+func Handler(build embed.FS, dir string, index string, gzip bool) (http.Handler, error) {
+	fsys, err := fs.Sub(build, dir)
+	if err != nil {
+		return nil, fmt.Errorf("couldn't create sub filesystem: %w", err)
+	}
+
+	if _, err = fsys.Open(index); err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return nil, fmt.Errorf("ui is enabled but no index.html found: %w", err)
+		} else {
+			return nil, fmt.Errorf("ui assets error: %w", err)
+		}
+	}
+	router := &router{index: index, fs: http.FS(fsys)}
+
+	hlr := http.FileServer(router)
+
+	if !gzip {
+		return hlr, nil
+	}
+	return gziphandler.GzipHandler(hlr), nil
+}