refactor: Simplify supportsMediaTypeConversion arguments.

src/storage/conversion/ChainedConverter.ts

@@ -1,7 +1,7 @@
 import type { Representation } from '../../ldp/representation/Representation';
 import type { ValuePreferences } from '../../ldp/representation/RepresentationPreferences';
 import { getLoggerFor } from '../../logging/LogUtil';
-import { supportsConversion, matchesMediaType } from './ConversionUtil';
+import { matchesMediaType } from './ConversionUtil';
 import type { RepresentationConverterArgs } from './RepresentationConverter';
 import { TypedRepresentationConverter } from './TypedRepresentationConverter';
 
@@ -43,12 +43,6 @@ export class ChainedConverter extends TypedRepresentationConverter {
     return this.last.getOutputTypes();
   }
 
-  public async canHandle(input: RepresentationConverterArgs): Promise<void> {
-    // We assume a chain can be constructed, otherwise there would be a configuration issue
-    // So we only check if the input can be parsed and the preferred type can be written
-    supportsConversion(input, await this.first.getInputTypes(), await this.last.getOutputTypes());
-  }
-
   public async handle(input: RepresentationConverterArgs): Promise<Representation> {
     const args = { ...input };
     for (let i = 0; i < this.converters.length - 1; ++i) {

src/storage/conversion/ConversionUtil.ts

@@ -1,9 +1,7 @@
 import type { ValuePreferences } from '../../ldp/representation/RepresentationPreferences';
 import { INTERNAL_ALL } from '../../util/ContentTypes';
-import { BadRequestHttpError } from '../../util/errors/BadRequestHttpError';
 import { InternalServerError } from '../../util/errors/InternalServerError';
 import { NotImplementedHttpError } from '../../util/errors/NotImplementedHttpError';
-import type { RepresentationConverterArgs } from './RepresentationConverter';
 
 /**
  * Filters media types based on the given preferences.
@@ -91,20 +89,20 @@ export const matchesMediaType = (mediaA: string, mediaB: string): boolean => {
  *  - Checks if the input type is supported by the parser.
  *  - Checks if the parser can produce one of the preferred output types.
  * Throws an error with details if conversion is not possible.
- * @param request - Incoming arguments.
- * @param supportedIn - Media types that can be parsed by the converter.
- * @param supportedOut - Media types that can be produced by the converter.
+ * @param inputType - Actual input type.
+ * @param outputTypes - Acceptable output types.
+ * @param convertorIn - Media types that can be parsed by the converter.
+ * @param convertorOut - Media types that can be produced by the converter.
  */
-export const supportsConversion = (request: RepresentationConverterArgs, supportedIn: ValuePreferences,
-  supportedOut: ValuePreferences): void => {
-  const inType = request.representation.metadata.contentType;
-  if (!inType) {
-    throw new BadRequestHttpError('No content type indicated on request.');
-  }
-  if (!Object.keys(supportedIn).some((type): boolean => matchesMediaType(inType, type)) ||
-     matchingMediaTypes(request.preferences.type, supportedOut).length === 0) {
+export const supportsMediaTypeConversion = (
+  inputType = 'unknown', outputTypes: ValuePreferences = {},
+  convertorIn: ValuePreferences = {}, convertorOut: ValuePreferences = {},
+): void => {
+  if (!Object.keys(convertorIn).some((type): boolean => matchesMediaType(inputType, type)) ||
+     matchingMediaTypes(outputTypes, convertorOut).length === 0) {
     throw new NotImplementedHttpError(
-      `Can only convert from ${Object.keys(supportedIn)} to ${Object.keys(supportedOut)}.`,
+      `Cannot convert from ${inputType} to ${Object.keys(outputTypes)
+      }, only from ${Object.keys(convertorIn)} to ${Object.keys(convertorOut)}.`,
     );
   }
 };

src/storage/conversion/TypedRepresentationConverter.ts

@@ -1,5 +1,5 @@
 import type { ValuePreferences } from '../../ldp/representation/RepresentationPreferences';
-import { supportsConversion } from './ConversionUtil';
+import { supportsMediaTypeConversion } from './ConversionUtil';
 import { RepresentationConverter } from './RepresentationConverter';
 import type { RepresentationConverterArgs } from './RepresentationConverter';
 
@@ -22,7 +22,8 @@ export abstract class TypedRepresentationConverter extends RepresentationConvert
    */
   public async canHandle(args: RepresentationConverterArgs): Promise<void> {
     const types = [ this.getInputTypes(), this.getOutputTypes() ];
+    const { contentType } = args.representation.metadata;
     const [ inputTypes, outputTypes ] = await Promise.all(types);
-    supportsConversion(args, inputTypes, outputTypes);
+    supportsMediaTypeConversion(contentType, args.preferences.type, inputTypes, outputTypes);
   }
 }

test/unit/storage/conversion/ConversionUtil.test.ts

@@ -1,63 +1,34 @@
-import type { Representation } from '../../../../src/ldp/representation/Representation';
-import { RepresentationMetadata } from '../../../../src/ldp/representation/RepresentationMetadata';
-import type {
-  ValuePreferences,
-  RepresentationPreferences,
-} from '../../../../src/ldp/representation/RepresentationPreferences';
-import type { ResourceIdentifier } from '../../../../src/ldp/representation/ResourceIdentifier';
+import type { ValuePreferences } from '../../../../src/ldp/representation/RepresentationPreferences';
 import {
   matchesMediaType,
   matchingMediaTypes,
-  supportsConversion,
+  supportsMediaTypeConversion,
 } from '../../../../src/storage/conversion/ConversionUtil';
 import { InternalServerError } from '../../../../src/util/errors/InternalServerError';
 
 describe('ConversionUtil', (): void => {
-  const identifier: ResourceIdentifier = { path: 'path' };
-  let representation: Representation;
-  let metadata: RepresentationMetadata;
+  describe('supportsMediaTypeConversion', (): void => {
+    it('requires preferences.', async(): Promise<void> => {
+      expect((): any => supportsMediaTypeConversion()).toThrow();
+    });
 
-  beforeEach(async(): Promise<void> => {
-    metadata = new RepresentationMetadata();
-    representation = { metadata } as Representation;
-  });
-
-  describe('#supportsConversion', (): void => {
     it('requires an input type.', async(): Promise<void> => {
-      const preferences: RepresentationPreferences = {};
-      expect((): any => supportsConversion({ identifier, representation, preferences },
-        { 'a/x': 1 },
-        { 'a/x': 1 }))
-        .toThrow('No content type indicated on request.');
+      expect((): any => supportsMediaTypeConversion(undefined, { 'b/x': 1 }, { 'a/x': 1 }, { 'a/x': 1 }))
+        .toThrow('Cannot convert from unknown to b/x, only from a/x to a/x.');
     });
 
     it('requires a matching input type.', async(): Promise<void> => {
-      metadata.contentType = 'a/x';
-      const preferences: RepresentationPreferences =
-        { type: { 'b/x': 1 }};
-      expect((): any => supportsConversion({ identifier, representation, preferences },
-        { 'c/x': 1 },
-        { 'a/x': 1 }))
-        .toThrow('Can only convert from c/x to a/x.');
+      expect((): any => supportsMediaTypeConversion('a/x', { 'b/x': 1 }, { 'c/x': 1 }, { 'a/x': 1 }))
+        .toThrow('Cannot convert from a/x to b/x, only from c/x to a/x.');
     });
 
     it('requires a matching output type.', async(): Promise<void> => {
-      metadata.contentType = 'a/x';
-      const preferences: RepresentationPreferences =
-        { type: { 'b/x': 1 }};
-      expect((): any => supportsConversion({ identifier, representation, preferences },
-        { 'a/x': 1 },
-        { 'c/x': 1 }))
-        .toThrow('Can only convert from a/x to c/x.');
+      expect((): any => supportsMediaTypeConversion('a/x', { 'b/x': 1 }, { 'a/x': 1 }, { 'c/x': 1 }))
+        .toThrow('Cannot convert from a/x to b/x, only from a/x to c/x.');
     });
 
     it('succeeds with a valid input and output type.', async(): Promise<void> => {
-      metadata.contentType = 'a/x';
-      const preferences: RepresentationPreferences =
-        { type: { 'b/x': 1 }};
-      expect(supportsConversion({ identifier, representation, preferences },
-        { 'a/x': 1 },
-        { 'b/x': 1 }))
+      expect(supportsMediaTypeConversion('a/x', { 'b/x': 1 }, { 'a/x': 1 }, { 'b/x': 1 }))
         .toBeUndefined();
     });
   });