feat(#90): improve conf retrieval

src/parser/config.ts

@@ -4,30 +4,52 @@ import path from 'path';
 
 type Config = {
     styles?: string;
+    port: number;
     /* eslint-disable-next-line @typescript-eslint/no-explicit-any */
     katexOptions?: any;
     pageTitle?: string;
     mdExtensions?: string[];
 };
-let config: Config = {};
+
+const defaultConfig: Config = {
+    port: 31622,
+};
 
 const configPaths = [
     path.join(homedir(), '.vivify', 'config.json'),
     path.join(homedir(), '.vivify.json'),
 ];
 
-for (const cp of configPaths) {
-    if (!fs.existsSync(cp)) continue;
-    try {
-        config = JSON.parse(fs.readFileSync(cp, 'utf8'));
-        break;
-    } catch {}
-}
-
-if (config.styles && config.styles.length > 0) {
-    const stylePath =
-        config.styles[0] === '~' ? path.join(homedir(), config.styles.slice(1)) : config.styles;
-    config.styles = fs.existsSync(stylePath) ? fs.readFileSync(stylePath, 'utf8') : '';
-}
-
-export default config;
+const envConfigs: [[string, keyof Config]] = [['VIV_PORT', 'port']];
+
+const getConfig = (): Config => {
+    let config = undefined;
+    // greedily get config
+    for (const cp of configPaths) {
+        if (!fs.existsSync(cp)) continue;
+        try {
+            config = JSON.parse(fs.readFileSync(cp, 'utf8'));
+            break;
+        } catch {}
+    }
+
+    if (config === undefined) return defaultConfig;
+
+    // get styles
+    if (config.styles && config.styles.length > 0) {
+        const stylePath =
+            config.styles[0] === '~' ? path.join(homedir(), config.styles.slice(1)) : config.styles;
+        config.styles = fs.existsSync(stylePath) ? fs.readFileSync(stylePath, 'utf8') : '';
+    }
+    // fill missing values from default config
+    for (const [key, value] of Object.entries(defaultConfig)) {
+        if (config[key] === undefined) config[key] = value;
+    }
+    // environment overrides
+    for (const [env, key] of envConfigs) {
+        if (process.env[env]) config[key] = process.env[env];
+    }
+    return config;
+};
+
+export default getConfig();