Add TOML based config file

The config file may provide default values or user sepcific settings.

README.adoc

@@ -21,7 +21,36 @@ The request query parameter `d` can be used to request GitHub like patterns by s
 
 === Configuration
 
-Configuration is available by using environment variables.
+Configuration is available by using a config file or by using environment variables.
+
+==== Config file
+
+If config file `/etc/identicon/config.toml` exists, its configuration will be used on application start.
+
+Use application argument `-c` to use another file.
+....
+$ identicon -c ./config.toml
+....
+
+In addition to configuration for default values, the configuration file can also be used to create specific configs for users.
+
+....
+[defaults]
+color-scheme = "v2"     # Default color scheme
+
+[[users]]
+id = "me@example.com"   # The users ID in plain text
+alias = "42"            # The alias to be used, e.g. for mapping users to other IDs
+color-scheme = "gh"     # The color scheme to be used for this user
+pattern = "github"      # The pattern to be used for this user
+
+[[users]]
+...
+....
+
+If config file is not present, the application will ignore it. Using environment variables will override default settings.
+
+==== Environment Variables
 
 You can use `COLORSCHEME` to define the default color scheme to be used. Fallback value will be `v2`.
 

go.mod

@@ -1,5 +1,8 @@
 module idicon
 
-go 1.16
+go 1.17
 
-require github.com/gorilla/mux v1.8.0
+require (
+	github.com/BurntSushi/toml v1.0.0
+	github.com/gorilla/mux v1.8.0
+)

go.sum

@@ -1,2 +1,4 @@
+github.com/BurntSushi/toml v1.0.0 h1:dtDWrepsVPfW9H/4y7dDgFc2MBUSeJhlaDtK13CxFlU=
+github.com/BurntSushi/toml v1.0.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
 github.com/gorilla/mux v1.8.0 h1:i40aqfkR1h2SlN9hojwV5ZA91wcXFOvkdNIeFDP5koI=
 github.com/gorilla/mux v1.8.0/go.mod h1:DVbg23sWSpFRCP0SfiEN6jmj59UnW/n46BH5rLB71So=

idicon.go

@@ -3,6 +3,7 @@ package main
 import (
 	"crypto/md5"
 	"encoding/hex"
+	"flag"
 	"image"
 	"image/color"
 	"image/draw"
@@ -14,6 +15,7 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/BurntSushi/toml"
 	"github.com/gorilla/mux"
 )
 
@@ -133,12 +135,24 @@ func RequestHandler(w http.ResponseWriter, r *http.Request) {
 
 	colorScheme := r.URL.Query().Get("c")
 	if colorScheme == "" {
-		colorScheme = os.Getenv("COLORSCHEME")
+		colorScheme = config.Defaults.ColorScheme
 	}
 
 	pattern := r.URL.Query().Get("d")
 	if pattern == "" {
-		pattern = os.Getenv("PATTERN")
+		pattern = config.Defaults.Pattern
+	}
+
+	for _, userConfig := range config.Users {
+		if hashBytes(id) == hashBytes(userConfig.Id) {
+			id = userConfig.Alias
+			if len(userConfig.ColorScheme) > 0 {
+				colorScheme = userConfig.ColorScheme
+			}
+			if len(userConfig.Pattern) > 0 {
+				pattern = userConfig.Pattern
+			}
+		}
 	}
 
 	w.Header().Add("Content-Type", "image/png")
@@ -157,7 +171,54 @@ func RequestHandler(w http.ResponseWriter, r *http.Request) {
 
 }
 
+type Config struct {
+	Defaults Defaults     `toml:"defaults"`
+	Users    []UserConfig `toml:"users"`
+}
+
+type Defaults struct {
+	ColorScheme string `toml:"color-scheme"`
+	Pattern     string `toml:"pattern"`
+}
+
+type UserConfig struct {
+	Id          string `toml:"id"`
+	Alias       string `toml:"alias"`
+	ColorScheme string `toml:"color-scheme"`
+	Pattern     string `toml:"pattern"`
+}
+
+var (
+	config Config
+)
+
+func configure(configFile string) {
+	if file, err := os.OpenFile(configFile, os.O_RDONLY, 0); err == nil {
+		c := &Config{}
+		_, err := toml.NewDecoder(file).Decode(c)
+		if err != nil {
+			log.Printf("Invalid config file '%s' - ignore it.\n", configFile)
+		}
+
+		defer file.Close()
+		config = *c
+	}
+
+	if os.Getenv("COLORSCHEME") != "" {
+		config.Defaults.ColorScheme = os.Getenv("COLORSCHEME")
+	}
+
+	if os.Getenv("PATTERN") != "" {
+		config.Defaults.Pattern = os.Getenv("PATTERN")
+	}
+}
+
 func main() {
+	configFile := flag.String("c", "/etc/idicon/config.toml", "-c <path to config file>")
+	flag.Parse()
+
+	configure(*configFile)
+
 	router := mux.NewRouter()
 	router.HandleFunc("/avatar/{id}", RequestHandler)
 	log.Println("Starting ...")

idicon_test.go

@@ -6,6 +6,7 @@ import (
 	"image/png"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"reflect"
 	"testing"
 
@@ -19,7 +20,10 @@ var v1 []byte
 var v2 []byte
 
 //go:embed testdata/1a79a4d60de6718e8e5b326e338ae533_gh.png
-var gh []byte
+var gh1 []byte
+
+//go:embed testdata/a1d0c6e83f027327d8461063f4ac58a6_gh.png
+var gh2 []byte
 
 func testRouter() *mux.Router {
 	router := mux.NewRouter()
@@ -78,7 +82,7 @@ func TestCorrectResponseForGHColorSchemeAndPattern(t *testing.T) {
 	rr := httptest.NewRecorder()
 	testRouter().ServeHTTP(rr, req)
 
-	if !reflect.DeepEqual(rr.Body.Bytes(), gh) {
+	if !reflect.DeepEqual(rr.Body.Bytes(), gh1) {
 		t.Errorf("returned image does not match expected image")
 	}
 }
@@ -108,6 +112,49 @@ func TestStringMatchesHash(t *testing.T) {
 	}
 }
 
+func TestUsesConfig(t *testing.T) {
+	configure("./testdata/testconfig.toml")
+
+	if config.Defaults.ColorScheme != "gh" ||
+		config.Users[0].Id != "example" ||
+		config.Users[0].Alias != "42" ||
+		config.Users[0].ColorScheme != "gh" ||
+		config.Users[0].Pattern != "github" {
+		t.Errorf("Config not applied as expected")
+	}
+}
+
+func TestUsesConfigWithEnvVar(t *testing.T) {
+	os.Setenv("COLORSCHEME", "v1")
+	os.Setenv("PATTERN", "default")
+
+	configure("./testdata/testconfig.toml")
+
+	if config.Defaults.ColorScheme != "v1" ||
+		config.Users[0].Id != "example" ||
+		config.Users[0].Alias != "42" ||
+		config.Users[0].ColorScheme != "gh" ||
+		config.Users[0].Pattern != "github" {
+		t.Errorf("Config not applied as expected")
+	}
+}
+
+func TestCorrectResponseForUserConfig(t *testing.T) {
+	configure("./testdata/testconfig.toml")
+
+	req, err := http.NewRequest("GET", "/avatar/example", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rr := httptest.NewRecorder()
+	testRouter().ServeHTTP(rr, req)
+
+	if !reflect.DeepEqual(rr.Body.Bytes(), gh2) {
+		t.Errorf("returned image does not match expected image for mapped alias '42'")
+	}
+}
+
 func TestHSLtoRGB(t *testing.T) {
 	red := hslToRgba(0, 100, 50)
 	if red.R != 255 || red.G != 0 || red.B != 0 {

testdata/testconfig.toml

@@ -0,0 +1,8 @@
+[defaults]
+color-scheme = "gh"
+
+[[users]]
+id = "example"
+alias = "42"
+color-scheme = "gh"
+pattern = "github"