From 4bb39c91990a00370de1b1e8a39fffe93df9a3c7 Mon Sep 17 00:00:00 2001
From: Mya Pitzeruse <j.mya.pitz@gmail.com>
Date: Wed, 25 May 2022 23:17:08 -0500
Subject: [PATCH] feat(catalog): support exporting catalog to different output
 formats

---
 README.md        | 33 ++++++++++++++++++++++++----
 catalog/serve.go | 57 +++++++++++++++++++++++++++++-------------------
 2 files changed, 64 insertions(+), 26 deletions(-)

diff --git a/README.md b/README.md
index 8c218ce..9e3ac43 100644
--- a/README.md
+++ b/README.md
@@ -2,8 +2,6 @@
 
 _The minimal, declarative service catalog._
 
-Pronounced "MC" as in the master of ceremonies.
-
 ## Background
 
 In the last three jobs I've worked at, it's always been a hassle trying to locate the various dashboards, documentation,
@@ -60,11 +58,38 @@ func main() {
 
 Once you've built your catalog, you can easily run a landing page by executing the catalog file.
 
-```
+```sh
 $ go run ./catalog.go
 ```
 
 This starts a web server for you to interact with on `localhost:8080`. If `:8080` is already in use, you can configure
 the bind address by passing the `-bind_address` flag with the desired host and port.
 
-![Screenshot](screenshot.png)
+<center>
+  <img src="screenshot.png" alt="Screenshot" width="72%"/>
+</center>
+
+### Exporting your catalog
+
+Instead of needing to compile a binary or host your catalog using `go run`, you can export your catalog to HTML or JSON.
+This makes it easy to drop into existing self-host platforms or leverage with other popular systems.
+
+```sh
+$ go run ./catalog.go -output html > index.html
+$ go run ./catalog.go -output json > catalog.json
+```
+
+### Protecting your catalog using oauth-proxy
+
+Regardless of how you host your catalog, you'll likely want to protect access to it. An easy way to do this is using the
+[oauth-proxy][] project. This project provides common OAuth2 client functionality to any project, making it easy to
+require authentication in order to access a system / project.
+
+<!-- TODO: write up guide and link to it from here -->
+
+Until I have more of a concrete guide, you can follow my setup [here](https://github.com/mjpitz/mjpitz/blob/main/infra/helm/catalog/values.yaml).
+A simple analogy to this deployment would be a docker compose file with two services, one for the oauth-proxy and the
+other for the catalog (bound to 127.0.0.1). Using the new `-output` functionality, this deployment could definitely
+be simplified.
+
+[oauth-proxy]: https://oauth2-proxy.github.io/oauth2-proxy
diff --git a/catalog/serve.go b/catalog/serve.go
index 729aa35..002f93b 100644
--- a/catalog/serve.go
+++ b/catalog/serve.go
@@ -6,10 +6,13 @@ package catalog
 import (
 	"bytes"
 	_ "embed"
+	"encoding/json"
 	"flag"
 	"html/template"
+	"io"
 	"log"
 	"net/http"
+	"os"
 	"time"
 
 	"github.com/mjpitz/emc/catalog/service"
@@ -18,6 +21,11 @@ import (
 //go:embed index.html.tpl
 var catalog string
 
+var funcs = map[string]any{
+	"mod": func(mod, v int) int { return v % mod },
+	"eq":  func(exp, act int) bool { return exp == act },
+}
+
 // Spec defines the requirements for hosting a catalog.
 type Spec struct {
 	Services []service.Spec
@@ -36,39 +44,44 @@ func Service(label string, options ...service.Option) Option {
 // Serve provides command line functionality for running the service catalog.
 func Serve(options ...Option) {
 	addr := flag.String("bind_address", "127.0.0.1:8080", "the address the service should bind to when serving content")
+	output := flag.String("output", "", "set to output the catalog to stdout (valid html, json)")
 	flag.Parse()
 
 	start := time.Now()
 
-	t := template.Must(template.New("catalog").
-		Funcs(map[string]any{
-			"mod": func(mod, v int) int {
-				return v % mod
-			},
-			"eq": func(exp, act int) bool {
-				return exp == act
-			},
-		}).
-		Parse(catalog))
-
 	spec := Spec{}
 	for _, opt := range options {
 		opt(&spec)
 	}
 
-	html := bytes.NewBuffer(nil)
-	err := t.Execute(html, spec)
-	if err != nil {
-		panic(err)
+	buffer := bytes.NewBuffer(nil)
+	var err error
+
+	switch {
+	case output == nil || *output == "" || *output == "html":
+		err = template.Must(template.New("catalog").Funcs(funcs).Parse(catalog)).Execute(buffer, spec)
+	case *output == "json":
+		err = json.NewEncoder(buffer).Encode(spec)
 	}
 
-	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		http.ServeContent(w, r, "", start, bytes.NewReader(html.Bytes()))
-	})
-
-	log.Printf("serving on %s\n", *addr)
-	err = http.ListenAndServe(*addr, http.DefaultServeMux)
 	if err != nil {
-		panic(err)
+		log.Fatal("failed to render output", err)
+	}
+
+	if output != nil && *output != "" {
+		_, err = io.Copy(os.Stdout, bytes.NewReader(buffer.Bytes()))
+		if err != nil {
+			log.Fatal("failed to write buffer to stdout", err)
+		}
+	} else {
+		http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+			http.ServeContent(w, r, "", start, bytes.NewReader(buffer.Bytes()))
+		})
+
+		log.Printf("serving on %s\n", *addr)
+		err = http.ListenAndServe(*addr, http.DefaultServeMux)
+		if err != nil {
+			log.Fatal("failed to serve content", err)
+		}
 	}
 }