Add configuration through environment variables

README.md

@@ -54,6 +54,8 @@ Once the code is compiled, the server can be started with `node server.js` in th
 The camera server can read a path to a config file from the `CONFIG_PATH` environment variable.
 This config file has to be in the json format and should have [this structure](./camera-server/example-config.json).
 
+Additionally each config key can be overwritten with an environment variable `CVH_CAMERA_CONFIG_<key>` (e.g. `CVH_CAMERA_CONFIG_cameraSlots` to overwrite the numbers of camera slots).
+
 Below is a description of the config file's properties:
 
 * `port`: The port on which the server will listen. Defaults to `5000`.

camera-server/src/config/config.ts

@@ -84,6 +84,33 @@ if (fileContent) {
     }
 }
 
+const ENV_CONFIG_PREFIX = 'CVH_CAMERA_CONFIG_';
+Object.keys(process.env).forEach((envKey) => {
+    if (envKey.startsWith(ENV_CONFIG_PREFIX)) {
+        const configKey = envKey.slice(ENV_CONFIG_PREFIX.length);
+        if (indexableConfig.hasOwnProperty(configKey)) {
+            const expectedType = typeof indexableConfig[configKey];
+            if (expectedType === 'string') {
+                indexableConfig[configKey] = process.env[envKey]!;
+            } else if (expectedType === 'number') {
+                const envValue = process.env[envKey]!;
+                const num = parseInt(envValue);
+                if (!isNaN(num)) {
+                    indexableConfig[configKey] = num;
+                } else {
+                    console.log(
+                        `Error: Config key ${configKey} from environment could not be parsed to a number`
+                    );
+                }
+            }
+        } else {
+            console.log(
+                `Error: Unknown config key ${configKey} in environment`
+            );
+        }
+    }
+});
+
 const config = indexableConfig as Config;
 if (config.notifyPath && !path.isAbsolute(config.notifyPath) && configPath) {
     config.notifyPath = path.resolve(