feat: support for custom templates (#129)

Adds a `-templates` flag that can be used to provide
an alternative directory with templates for Sally to use.
The new templates override the default set embedded in Sally.

This includes a new 404 template so that 404 errors
use the same theme as the rest of the website.

Additionally, for HTTP status >400,
this also sets the Cache-Control header
to discourage CDNs like Cloudflare from caching the page.

Resolves #125, #18 

1 files changed, 29 insertions, 1 deletions

diff --git a/main.go b/main.go
index 5d54071..522ecf8 100644
--- a/main.go
+++ b/main.go
@@ -5,12 +5,15 @@ package main // import "go.uber.org/sally"
 import (
 	"flag"
 	"fmt"
+	"html/template"
 	"log"
 	"net/http"
+	"path/filepath"
 )
 
 func main() {
 	yml := flag.String("yml", "sally.yaml", "yaml file to read config from")
+	tpls := flag.String("templates", "", "directory of .html templates to use")
 	port := flag.Int("port", 8080, "port to listen and serve on")
 	flag.Parse()
 
@@ -20,9 +23,34 @@ func main() {
 		log.Fatalf("Failed to parse %s: %v", *yml, err)
 	}
 
+	var templates *template.Template
+	if *tpls != "" {
+		log.Printf("Parsing templates at path: %s\n", *tpls)
+		templates, err = getCombinedTemplates(*tpls)
+		if err != nil {
+			log.Fatalf("Failed to parse templates at %s: %v", *tpls, err)
+		}
+	} else {
+		templates = _templates
+	}
+
 	log.Printf("Creating HTTP handler with config: %v", config)
-	handler := CreateHandler(config)
+	handler, err := CreateHandler(config, templates)
+	if err != nil {
+		log.Fatalf("Failed to create handler: %v", err)
+	}
 
 	log.Printf(`Starting HTTP handler on ":%d"`, *port)
 	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", *port), handler))
 }
+
+func getCombinedTemplates(dir string) (*template.Template, error) {
+	// Clones default templates to then merge with the user defined templates.
+	// This allows for the user to only override certain templates, but not all
+	// if they don't want.
+	templates, err := _templates.Clone()
+	if err != nil {
+		return nil, err
+	}
+	return templates.ParseGlob(filepath.Join(dir, "*.html"))
+}