Merge pull request 'Add support for custom CSS files' (#11) from f/twins:custom-css into master

Reviewed-on: https://code.rocketnine.space/tslocum/twins/pulls/11

CONFIGURATION.md

@@ -98,6 +98,11 @@ Set this option to `true` to disable this feature.
 
 Pages are converted automatically by [gmitohtml](https://code.rocketnine.space/tslocum/gmitohtml).
 
+## StyleSheet
+
+Specify a custom CSS stylesheet file if you want to override the default. This only
+affects the `HTTPS` protocol (obviously).
+
 ### DisableSize
 
 The size of the response body is included in the media type header by default.
@@ -240,6 +245,7 @@ hosts:
   gemini.rocks:
     cert: /srv/gemini.rocks/data/cert.crt
     key: /srv/gemini.rocks/data/cert.key
+    stylesheet: /srv/gemini.rocks/styles.css # Custom CSS stylesheet
     paths:
       -
         path: ^/.*\.php$

config.go

@@ -66,6 +66,9 @@ type hostConfig struct {
 	Key   string
 	Paths []*pathConfig
 
+	// Custom CSS styles. If specified, it will be used for all paths in that host/domain.
+	StyleSheet string
+
 	cert *tls.Certificate
 }
 
@@ -84,6 +87,8 @@ type serverConfig struct {
 
 const cacheUnset = -1965
 
+var customCSS = make(map[string][]byte)
+
 var config *serverConfig
 
 func readconfig(configPath string) error {
@@ -210,6 +215,21 @@ func readconfig(configPath string) error {
 		}
 		host.cert = &cert
 
+		// Custom CSS stylesheets are precached in customCSS and used on HTTPS requests.
+		if host.StyleSheet != "" {
+			_, err := os.Stat(host.StyleSheet)
+			if os.IsNotExist(err) {
+				log.Printf("custom stylesheet '%v' not found, ignore it.", host.StyleSheet)
+			} else {
+				cssBytes, err := ioutil.ReadFile(host.StyleSheet)
+				if err != nil {
+					log.Printf("problems with stylesheet '%v': %v", host.StyleSheet, err.Error())
+				} else {
+					customCSS[hostname] = cssBytes
+				}
+			}
+		}
+
 		for _, serve := range host.Paths {
 			if serve.Path == "" {
 				log.Fatal("a path must be specified in each serve entry")

serve_https.go

@@ -38,6 +38,14 @@ func serveHTTPS(w http.ResponseWriter, r *http.Request) (int, int64, string) {
 		if r.Method == "HEAD" {
 			return status, 0, ""
 		}
+
+		// Do we have a custom CSS file? If so, we use this instead.
+		if css, found := customCSS[r.URL.Hostname()]; found {
+			w.Write(css)
+			return status, int64(len(css)), ""
+		}
+
+		// Default CSS
 		w.Write(cssBytes)
 		return status, int64(len(cssBytes)), ""
 	}