Add env var support in config

README.md

@@ -9,6 +9,7 @@ GateH8 is a flexible and customizable API Gateway designed to proxy requests to
 - [Configuration Guide](#configuration-guide)
     - [General Settings](#general-settings)
     - [Path Variables and Wildcards](#path-variables-and-wildcards)
+    - [Environment Variables](#environment-variables)
     - [Virtual Hosts and Routes](#virtual-hosts-and-routes)
     - [Wildcard Domain Routing](#wildcard-domain-routing)
     - [CORS Settings](#cors-settings)
@@ -99,6 +100,10 @@ Additionally, GateH8 supports wildcards within path configurations. By using an
 
 The above configuration will match and route requests like `/products/1`, `/products/soap`, and so on.
 
+### Environment Variables
+
+GateH8 supports environment variables in the configuration file. This allows you to define dynamic values for your configuration, such as backend URLs, without having to hardcode them.
+
 ### Virtual Hosts and Routes
 
 Virtual hosts enable you to route traffic differently based on the domain of the incoming request.

config/config.go

@@ -82,17 +82,19 @@ type Config struct {
 // GetConfig reads the API Gateway's configuration from a JSON file and returns it.
 // It handles any issues with reading or parsing the configuration file.
 func GetConfig() (*Config, error) {
-	content, err := os.ReadFile("config.json")
+	rawConfig, err := os.ReadFile("config.json")
 	if err != nil {
 		return nil, fmt.Errorf("error reading config.json: %w", err)
 	}
 
+	rawConfig = replaceEnvVars(rawConfig)
+
 	config := new(Config) // Use new() to get a pointer directly, prevent local-to-heap migration.
-	if err = json.Unmarshal(content, config); err != nil {
+	if err = json.Unmarshal(rawConfig, config); err != nil {
 		return nil, fmt.Errorf("error parsing config.json: %w", err)
 	}
 
-	anyVhostWithSSL, allVhostsWithSSL := check(config)
+	anyVhostWithSSL, allVhostsWithSSL := checkVhostsWithTLS(config)
 
 	// If there's any vhost with TLS configured but not all of them have, then it's a config error.
 	if anyVhostWithSSL && !allVhostsWithSSL {
@@ -103,7 +105,18 @@ func GetConfig() (*Config, error) {
 	return config, nil
 }
 
-func check(config *Config) (bool, bool) {
+func replaceEnvVars(rawConfig []byte) []byte {
+	// replace ${path} with [[path]] to avoid env var replacement
+	rawConfig = []byte(strings.ReplaceAll(string(rawConfig), "${path}", "[[path]]"))
+	// replace env vars
+	rawConfig = []byte(os.ExpandEnv(string(rawConfig)))
+	// replace [[path]] with ${path} to restore original value
+	rawConfig = []byte(strings.ReplaceAll(string(rawConfig), "[[path]]", "${path}"))
+
+	return rawConfig
+}
+
+func checkVhostsWithTLS(config *Config) (bool, bool) {
 	// Check if any vhost has TLS configured
 	anyVhostWithSSL := false
 	allVhostsWithSSL := true

config/config_test.go

@@ -0,0 +1,199 @@
+package config
+
+import (
+	"os"
+	"reflect"
+	"testing"
+)
+
+func Test_replaceEnvVars(t *testing.T) {
+	type args struct {
+		rawConfig []byte
+	}
+	tests := []struct {
+		name     string
+		args     args
+		envName  string
+		envValue string
+		want     []byte
+	}{
+		{
+			name: "test",
+			args: args{
+				rawConfig: []byte(`{
+{
+  "apiGateway": {
+    "name": "MyAPIGateway",
+    "version": "1.0.0"
+  },
+  "vhosts": {
+    "*": {
+      "endpoints": [
+        {
+          "path": "/ws",
+          "backend": {
+            "url": "ws://127.0.0.1:8080/ws/$TEST"
+          },
+          "websocket": {
+            "readBufferSize": 1024,
+            "writeBufferSize": 1024,
+            "allowedOrigins": ["*"]
+          }
+        }
+      ]
+    }
+  }
+}
+}`),
+			},
+			envName:  "TEST",
+			envValue: "test",
+			want: []byte(`{
+{
+  "apiGateway": {
+    "name": "MyAPIGateway",
+    "version": "1.0.0"
+  },
+  "vhosts": {
+    "*": {
+      "endpoints": [
+        {
+          "path": "/ws",
+          "backend": {
+            "url": "ws://127.0.0.1:8080/ws/test"
+          },
+          "websocket": {
+            "readBufferSize": 1024,
+            "writeBufferSize": 1024,
+            "allowedOrigins": ["*"]
+          }
+        }
+      ]
+    }
+  }
+}
+}`),
+		},
+		{
+			name: "path",
+			args: args{
+				rawConfig: []byte(`{
+{
+  "apiGateway": {
+    "name": "MyAPIGateway",
+    "version": "1.0.0"
+  },
+  "vhosts": {
+    "*": {
+      "endpoints": [
+        {
+          "path": "/ws",
+          "backend": {
+            "url": "ws://127.0.0.1:8080/ws"
+          },
+          "websocket": {
+            "readBufferSize": 1024,
+            "writeBufferSize": 1024,
+            "allowedOrigins": ["*"]
+          }
+        }
+      ]
+    }
+  }
+}
+}`),
+			},
+			want: []byte(`{
+{
+  "apiGateway": {
+    "name": "MyAPIGateway",
+    "version": "1.0.0"
+  },
+  "vhosts": {
+    "*": {
+      "endpoints": [
+        {
+          "path": "/ws",
+          "backend": {
+            "url": "ws://127.0.0.1:8080/ws"
+          },
+          "websocket": {
+            "readBufferSize": 1024,
+            "writeBufferSize": 1024,
+            "allowedOrigins": ["*"]
+          }
+        }
+      ]
+    }
+  }
+}
+}`),
+			envName:  "path",
+			envValue: "test",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_ = os.Setenv(tt.envName, tt.envValue)
+			if got := replaceEnvVars(tt.args.rawConfig); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("replaceEnvVars() = %v, wantAny %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_checkVhostsWithTLS(t *testing.T) {
+	type args struct {
+		config *Config
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantAny bool
+		wantAll bool
+	}{
+		{
+			name: "test",
+			args: args{
+				config: &Config{Vhosts: map[string]Vhost{
+					"www.sample.org": {TLS: &TLSConfig{}},
+				}},
+			},
+			wantAny: true,
+			wantAll: true,
+		},
+		{
+			name: "test",
+			args: args{
+				config: &Config{Vhosts: map[string]Vhost{
+					"www.sample.org":  {TLS: &TLSConfig{}},
+					"www1.sample.org": {},
+				}},
+			},
+			wantAny: true,
+			wantAll: false,
+		},
+		{
+			name: "test",
+			args: args{
+				config: &Config{Vhosts: map[string]Vhost{
+					"www.sample.org":  {},
+					"www1.sample.org": {},
+				}},
+			},
+			wantAny: false,
+			wantAll: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, got1 := checkVhostsWithTLS(tt.args.config)
+			if got != tt.wantAny {
+				t.Errorf("checkVhostsWithTLS() got = %v, wantAny %v", got, tt.wantAny)
+			}
+			if got1 != tt.wantAll {
+				t.Errorf("checkVhostsWithTLS() got1 = %v, wantAny %v", got1, tt.wantAll)
+			}
+		})
+	}
+}

example/http/config.json

@@ -12,7 +12,7 @@
             "GET"
           ],
           "backend": {
-            "url": "http://nginx1/",
+            "url": "http://${HOST1}/",
             "timeout": 5000
           }
         },
@@ -22,7 +22,7 @@
             "GET"
           ],
           "backend": {
-            "url": "http://nginx2/",
+            "url": "http://${HOST2}/",
             "timeout": 5000
           }
         }

example/http/docker-compose.yml

@@ -1,8 +1,11 @@
 services:
   gateh8:
-    image: yarlson/gateh8:0.2.1
+    image: yarlson/gateh8:0.3.0
     ports:
       - "80:80"
+    environment:
+      - HOST1=nginx1
+      - HOST2=nginx2
     volumes:
       - ./config.json:/config.json
     command: ["-a", ":80"]

example/websockets/docker-compose.yml

@@ -1,6 +1,6 @@
 services:
   gateh8:
-    image: yarlson/gateh8:0.2.1
+    image: yarlson/gateh8:0.3.0
     ports:
       - "80:80"
     volumes: