feat: Convert data from ResourceStore based on preferences

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

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+import { Representation } from '../../../../src/ldp/representation/Representation';
+import { RepresentationPreferences } from '../../../../src/ldp/representation/RepresentationPreferences';
+import { ResourceIdentifier } from '../../../../src/ldp/representation/ResourceIdentifier';
+import { checkRequest, matchingTypes } from '../../../../src/storage/conversion/ConversionUtil';
+
+describe('A ConversionUtil', (): void => {
+  const identifier: ResourceIdentifier = { path: 'path' };
+
+  describe('#checkRequest', (): void => {
+    it('requires an input type.', async(): Promise<void> => {
+      const representation = { metadata: {}} as Representation;
+      const preferences: RepresentationPreferences = {};
+      expect((): any => checkRequest({ identifier, representation, preferences }, [ '*/*' ], [ '*/*' ]))
+        .toThrow('Input type required for conversion.');
+    });
+
+    it('requires a matching input type.', async(): Promise<void> => {
+      const representation = { metadata: { contentType: 'a/x' }} as Representation;
+      const preferences: RepresentationPreferences = { type: [{ value: 'b/x', weight: 1 }]};
+      expect((): any => checkRequest({ identifier, representation, preferences }, [ 'c/x' ], [ '*/*' ]))
+        .toThrow('Can only convert from c/x to */*.');
+    });
+
+    it('requires a matching output type.', async(): Promise<void> => {
+      const representation = { metadata: { contentType: 'a/x' }} as Representation;
+      const preferences: RepresentationPreferences = { type: [{ value: 'b/x', weight: 1 }]};
+      expect((): any => checkRequest({ identifier, representation, preferences }, [ '*/*' ], [ 'c/x' ]))
+        .toThrow('Can only convert from */* to c/x.');
+    });
+
+    it('succeeds with a valid input and output type.', async(): Promise<void> => {
+      const representation = { metadata: { contentType: 'a/x' }} as Representation;
+      const preferences: RepresentationPreferences = { type: [{ value: 'b/x', weight: 1 }]};
+      expect(checkRequest({ identifier, representation, preferences }, [ '*/*' ], [ '*/*' ]))
+        .toBeUndefined();
+    });
+  });
+
+  describe('#matchingTypes', (): void => {
+    it('requires type preferences.', async(): Promise<void> => {
+      const preferences: RepresentationPreferences = {};
+      expect((): any => matchingTypes(preferences, [ '*/*' ]))
+        .toThrow('Output type required for conversion.');
+    });
+
+    it('returns matching types if weight > 0.', async(): Promise<void> => {
+      const preferences: RepresentationPreferences = { type:
+          [{ value: 'a/x', weight: 1 }, { value: 'b/x', weight: 0.5 }, { value: 'c/x', weight: 0 }]};
+      expect(matchingTypes(preferences, [ 'b/x', 'c/x' ])).toEqual([{ value: 'b/x', weight: 0.5 }]);
+    });
+  });
+});

test/unit/storage/conversion/QuadToTurtleConverter.test.ts

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+import arrayifyStream from 'arrayify-stream';
+import { QuadToTurtleConverter } from '../../../../src/storage/conversion/QuadToTurtleConverter';
+import { Readable } from 'stream';
+import { Representation } from '../../../../src/ldp/representation/Representation';
+import { RepresentationPreferences } from '../../../../src/ldp/representation/RepresentationPreferences';
+import { ResourceIdentifier } from '../../../../src/ldp/representation/ResourceIdentifier';
+import streamifyArray from 'streamify-array';
+import { CONTENT_TYPE_QUADS, DATA_TYPE_BINARY } from '../../../../src/util/ContentTypes';
+import { namedNode, triple } from '@rdfjs/data-model';
+
+describe('A QuadToTurtleConverter', (): void => {
+  const converter = new QuadToTurtleConverter();
+  const identifier: ResourceIdentifier = { path: 'path' };
+
+  it('can handle quad to turtle conversions.', async(): Promise<void> => {
+    const representation = { metadata: { contentType: CONTENT_TYPE_QUADS }} as Representation;
+    const preferences: RepresentationPreferences = { type: [{ value: 'text/turtle', weight: 1 }]};
+    await expect(converter.canHandle({ identifier, representation, preferences })).resolves.toBeUndefined();
+  });
+
+  it('converts quads to turtle.', async(): Promise<void> => {
+    const representation = {
+      data: streamifyArray([ triple(
+        namedNode('http://test.com/s'),
+        namedNode('http://test.com/p'),
+        namedNode('http://test.com/o'),
+      ) ]),
+      metadata: { contentType: CONTENT_TYPE_QUADS },
+    } as Representation;
+    const preferences: RepresentationPreferences = { type: [{ value: 'text/turtle', weight: 1 }]};
+    const result = await converter.handle({ identifier, representation, preferences });
+    expect(result).toEqual({
+      data: expect.any(Readable),
+      dataType: DATA_TYPE_BINARY,
+      metadata: {
+        contentType: 'text/turtle',
+      },
+    });
+    await expect(arrayifyStream(result.data)).resolves.toContain(
+      '<http://test.com/s> <http://test.com/p> <http://test.com/o>',
+    );
+  });
+});

test/unit/storage/conversion/TurtleToQuadConverter.test.ts

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+import arrayifyStream from 'arrayify-stream';
+import { Readable } from 'stream';
+import { Representation } from '../../../../src/ldp/representation/Representation';
+import { RepresentationPreferences } from '../../../../src/ldp/representation/RepresentationPreferences';
+import { ResourceIdentifier } from '../../../../src/ldp/representation/ResourceIdentifier';
+import streamifyArray from 'streamify-array';
+import { TurtleToQuadConverter } from '../../../../src/storage/conversion/TurtleToQuadConverter';
+import { UnsupportedHttpError } from '../../../../src/util/errors/UnsupportedHttpError';
+import { CONTENT_TYPE_QUADS, DATA_TYPE_QUAD } from '../../../../src/util/ContentTypes';
+import { namedNode, triple } from '@rdfjs/data-model';
+
+describe('A TurtleToQuadConverter', (): void => {
+  const converter = new TurtleToQuadConverter();
+  const identifier: ResourceIdentifier = { path: 'path' };
+
+  it('can handle turtle to quad conversions.', async(): Promise<void> => {
+    const representation = { metadata: { contentType: 'text/turtle' }} as Representation;
+    const preferences: RepresentationPreferences = { type: [{ value: CONTENT_TYPE_QUADS, weight: 1 }]};
+    await expect(converter.canHandle({ identifier, representation, preferences })).resolves.toBeUndefined();
+  });
+
+  it('converts turtle to quads.', async(): Promise<void> => {
+    const representation = {
+      data: streamifyArray([ '<http://test.com/s> <http://test.com/p> <http://test.com/o>.' ]),
+      metadata: { contentType: 'text/turtle' },
+    } as Representation;
+    const preferences: RepresentationPreferences = { type: [{ value: CONTENT_TYPE_QUADS, weight: 1 }]};
+    const result = await converter.handle({ identifier, representation, preferences });
+    expect(result).toEqual({
+      data: expect.any(Readable),
+      dataType: DATA_TYPE_QUAD,
+      metadata: {
+        contentType: CONTENT_TYPE_QUADS,
+      },
+    });
+    await expect(arrayifyStream(result.data)).resolves.toEqualRdfQuadArray([ triple(
+      namedNode('http://test.com/s'),
+      namedNode('http://test.com/p'),
+      namedNode('http://test.com/o'),
+    ) ]);
+  });
+
+  it('throws an UnsupportedHttpError on invalid triple data.', async(): Promise<void> => {
+    const representation = {
+      data: streamifyArray([ '<http://test.com/s> <http://test.com/p> <http://test.co' ]),
+      metadata: { contentType: 'text/turtle' },
+    } as Representation;
+    const preferences: RepresentationPreferences = { type: [{ value: CONTENT_TYPE_QUADS, weight: 1 }]};
+    const result = await converter.handle({ identifier, representation, preferences });
+    expect(result).toEqual({
+      data: expect.any(Readable),
+      dataType: DATA_TYPE_QUAD,
+      metadata: {
+        contentType: CONTENT_TYPE_QUADS,
+      },
+    });
+    await expect(arrayifyStream(result.data)).rejects.toThrow(UnsupportedHttpError);
+  });
+});