web/advanced: check if imported settings are valid

web/src/lib/settings/validate.ts

@@ -0,0 +1,85 @@
+import type { Optional } from '$lib/types/generic';
+import defaultSettings from './defaults'
+import {
+    downloadModeOptions,
+    filenameStyleOptions,
+    savingMethodOptions,
+    themeOptions,
+    videoQualityOptions,
+    youtubeVideoCodecOptions,
+    type PartialSettings,
+} from '$lib/types/settings';
+
+function validateTypes(input: unknown, reference = defaultSettings as unknown) {
+    if (typeof input === 'undefined')
+        return true;
+
+    if (typeof input !== typeof reference)
+        return false;
+
+    if (typeof reference !== 'object')
+        return true;
+
+    if (reference === null || input === null)
+        return input === reference;
+
+    if (Array.isArray(reference)) {
+        // TODO: we dont expect the reference array to hold any
+        //       elements, but we should at maybe check whether
+        //       the input array types are all matching.
+        return true;
+    }
+
+    // we know that `input` is an `object` based on the first
+    // two `if`s, but for some reason typescript doesn't.  :)
+    if (typeof input !== 'object')
+        return false;
+
+    const keys = new Set([
+        ...Object.keys(input),
+        ...Object.keys(reference)
+    ]);
+
+    for (const key of keys) {
+        const _input = input as Record<string, unknown>;
+        const _reference = reference as Record<string, unknown>;
+
+        if (!validateTypes(_input[key], _reference[key])) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+function validateLiteral(value: Optional<string>, allowed: readonly string[]) {
+    return value === undefined || allowed.includes(value);
+}
+
+function validateLiterals(literals: [Optional<string>, readonly string[]][]) {
+    for (const [ value, allowed ] of literals) {
+        if (!validateLiteral(value, allowed))
+            return false;
+    }
+
+    return true;
+}
+
+// performs a basic check on an "untrusted" settings object.
+export function validateSettings(settings: PartialSettings) {
+    if (!settings?.schemaVersion) {
+        return false;
+    }
+
+    return (
+        validateTypes(settings)
+        && validateLiterals([
+            [ settings?.appearance?.theme      , themeOptions ],
+            [ settings?.save?.downloadMode     , downloadModeOptions ],
+            [ settings?.save?.filenameStyle    , filenameStyleOptions ],
+            [ settings?.save?.videoQuality     , videoQualityOptions ],
+            [ settings?.save?.youtubeVideoCodec, youtubeVideoCodecOptions ],
+            [ settings?.save?.savingMethod     , savingMethodOptions ]
+        ])
+    );
+}