CommunitySolidServer/src/storage/patch/ConvertingPatcher.ts at main · ls-css/CommunitySolidServer · GitHub

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import { BasicRepresentation } from '../../http/representation/BasicRepresentation';

import type { Representation } from '../../http/representation/Representation';

import { getLoggerFor } from '../../logging/LogUtil';

import type { RepresentationConverter } from '../conversion/RepresentationConverter';

import type { RepresentationPatcherInput } from './RepresentationPatcher';

import { RepresentationPatcher } from './RepresentationPatcher';

/**

* A `ConvertingPatcher` converts a document to its `intermediateType`,

* sends the result to the wrapped patcher, and then converts back to its original type.

* No changes will take place if no `intermediateType` is provided.

* In case there is no resource yet and a new one needs to be created,

* the result of the wrapped patcher will be converted to the provided `defaultType`.

* In case no `defaultType` is provided, the patcher output will be returned directly.

export class ConvertingPatcher extends RepresentationPatcher<Representation> {

protected readonly logger = getLoggerFor(this);

private readonly patcher: RepresentationPatcher<Representation>;

private readonly converter: RepresentationConverter;

private readonly intermediateType?: string;

private readonly defaultType?: string;

/**

* @param patcher - Patcher that will be called with the Representation.

* @param converter - Converter that will be used to generate intermediate Representation.

* @param intermediateType - Content-type of the intermediate Representation if conversion is needed.

* @param defaultType - Content-type in case a new resource gets created and needs to be converted.

public constructor(

patcher: RepresentationPatcher<Representation>,

converter: RepresentationConverter,

intermediateType?: string,

defaultType?: string,

) {

super();

this.patcher = patcher;

this.converter = converter;

this.intermediateType = intermediateType;

this.defaultType = defaultType;

}

public async canHandle(input: RepresentationPatcherInput<Representation>): Promise<void> {

// Verify the converter can handle the input representation if needed

const { identifier, representation } = input;

let convertedPlaceholder = representation;

if (representation && this.intermediateType) {

const preferences = { type: { [this.intermediateType]: 1 }};

await this.converter.canHandle({ representation, identifier, preferences });

convertedPlaceholder = new BasicRepresentation([], representation.metadata, this.intermediateType);

}

// Verify the patcher can handle the (converted) representation

await this.patcher.canHandle({ ...input, representation: convertedPlaceholder });

}

public async handle(input: RepresentationPatcherInput<Representation>): Promise<Representation> {

const { identifier, representation } = input;

let outputType: string | undefined;

let converted = representation;

if (!representation) {

// If there is no representation the output will need to be converted to the default type

outputType = this.defaultType;

} else if (this.intermediateType) {

// Convert incoming representation to the requested type

outputType = representation.metadata.contentType;

const preferences = { type: { [this.intermediateType]: 1 }};

converted = await this.converter.handle({ representation, identifier, preferences });

}

// Call the wrapped patcher with the (potentially) converted representation

let result = await this.patcher.handle({ ...input, representation: converted });

// Convert the output back to its original type or the default type depending on what was set

if (outputType) {

const preferences = { type: { [outputType]: 1 }};

result = await this.converter.handle({ representation: result, identifier, preferences });

}

return result;

}

CommunitySolidServer/src/storage/patch/ConvertingPatcher.ts at main · ls-css/CommunitySolidServer · GitHub

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