1 files changed, 102 insertions, 3 deletions
diff --git a/packages/taler-util/src/codec.ts b/packages/taler-util/src/codec.ts
index 8605ff335..678c3f092 100644
--- a/packages/taler-util/src/codec.ts
+++ b/packages/taler-util/src/codec.ts
@@ -14,12 +14,17 @@
  GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
  */
 
+import { j2s } from "./helpers.js";
+import { Logger } from "./logging.js";
+
 /**
  * Type-safe codecs for converting from/to JSON.
  */
 
 /* eslint-disable @typescript-eslint/ban-types */
 
+const logger = new Logger("codec.ts");
+
 /**
  * Error thrown when decoding fails.
  */
@@ -134,7 +139,7 @@ class UnionCodecBuilder<
   TargetType,
   TagPropertyLabel extends keyof TargetType,
   CommonBaseType,
-  PartialTargetType
+  PartialTargetType,
 > {
   private alternatives = new Map<any, Alternative>();
 
@@ -186,7 +191,7 @@ class UnionCodecBuilder<
           throw new DecodingError(
             `expected tag for ${objectDisplayName} at ${renderContext(
               c,
-            )}.${discriminator}`,
+            )}.${String(discriminator)}`,
           );
         }
         const alt = alternatives.get(d);
@@ -194,7 +199,7 @@ class UnionCodecBuilder<
           throw new DecodingError(
             `unknown tag for ${objectDisplayName} ${d} at ${renderContext(
               c,
-            )}.${discriminator}`,
+            )}.${String(discriminator)}`,
           );
         }
         const altDecoded = alt.codec.decode(x);
@@ -322,6 +327,74 @@ export function codecForString(): Codec<string> {
 }
 
 /**
+ * Return a codec for a value that must be a string.
+ */
+export function codecForStringURL(shouldEndWithSlash?: boolean): Codec<string> {
+  return {
+    decode(x: any, c?: Context): string {
+      if (typeof x !== "string") {
+        throw new DecodingError(
+          `expected string at ${renderContext(c)} but got ${typeof x}`,
+        );
+      }
+      if (shouldEndWithSlash && !x.endsWith("/")) {
+        throw new DecodingError(
+          `expected URL string that ends with slash at ${renderContext(
+            c,
+          )} but got ${x}`,
+        );
+      }
+      try {
+        const url = new URL(x);
+        return x;
+      } catch (e) {
+        if (e instanceof Error) {
+          throw new DecodingError(e.message);
+        } else {
+          throw new DecodingError(
+            `expected an URL string at ${renderContext(c)} but got "${x}"`,
+          );
+        }
+      }
+    },
+  };
+}
+
+/**
+ * Return a codec for a value that must be a string.
+ */
+export function codecForURL(shouldEndWithSlash?: boolean): Codec<URL> {
+  return {
+    decode(x: any, c?: Context): URL {
+      if (typeof x !== "string") {
+        throw new DecodingError(
+          `expected string at ${renderContext(c)} but got ${typeof x}`,
+        );
+      }
+      if (shouldEndWithSlash && !x.endsWith("/")) {
+        throw new DecodingError(
+          `expected URL string that ends with slash at ${renderContext(
+            c,
+          )} but got ${x}`,
+        );
+      }
+      try {
+        const url = new URL(x);
+        return url;
+      } catch (e) {
+        if (e instanceof Error) {
+          throw new DecodingError(e.message);
+        } else {
+          throw new DecodingError(
+            `expected an URL string at ${renderContext(c)} but got "${x}"`,
+          );
+        }
+      }
+    },
+  };
+}
+
+/**
  * Codec that allows any value.
  */
 export function codecForAny(): Codec<any> {
@@ -417,3 +490,29 @@ export function codecOptional<V>(innerCodec: Codec<V>): Codec<V | undefined> {
     },
   };
 }
+
+export type CodecType<T> = T extends Codec<infer X> ? X : any;
+
+export function codecForEither<T extends Array<Codec<unknown>>>(
+  ...alts: [...T]
+): Codec<CodecType<T[number]>> {
+  return {
+    decode(x: any, c?: Context): any {
+      for (const alt of alts) {
+        try {
+          return alt.decode(x, c);
+        } catch (e) {
+          continue;
+        }
+      }
+      if (logger.shouldLogTrace()) {
+        logger.trace(`offending value: ${j2s(x)}`);
+      }
+      throw new DecodingError(
+        `No alternative matched at at ${renderContext(c)}`,
+      );
+    },
+  };
+}
+
+const x = codecForEither(codecForString(), codecForNumber());