Make interfaces for compress/decompress more clear.

- Separate responsibilities for transforming JSON-LD <=> CBOR
  abstract form from serializing / deserializing it.

lib/Compressor.js

@@ -1,27 +1,15 @@
 /*!
  * Copyright (c) 2021-2024 Digital Bazaar, Inc. All rights reserved.
  */
-import * as cborg from 'cborg';
-import {CborldEncoder} from './codecs/CborldEncoder.js';
 import {ContextEncoder} from './codecs/ContextEncoder.js';
 import {ContextProcessor} from './ContextProcessor.js';
-import {inspect} from './util.js';
 import {KEYWORDS_TABLE} from './tables.js';
 import {Transformer} from './Transformer.js';
 import {ValueEncoder} from './codecs/ValueEncoder.js';
 
 const CONTEXT_TERM_ID = KEYWORDS_TABLE.get('@context');
 const CONTEXT_TERM_ID_PLURAL = CONTEXT_TERM_ID + 1;
 
-// override cborg object encoder to use cborld encoders
-const typeEncoders = {
-  Object(obj) {
-    if(obj instanceof CborldEncoder) {
-      return obj.encode({obj});
-    }
-  }
-};
-
 export class Compressor {
   /**
    * Creates a new Compressor for generating compressed CBOR-LD from a
@@ -54,23 +42,13 @@ export class Compressor {
    * @param {object} options - The options to use.
    * @param {object} options.jsonldDocument - The JSON-LD Document to convert
    *   to CBOR-LD bytes.
-   * @param {diagnosticFunction} [options.diagnose] - A function that, if
-   *   provided, is called with diagnostic information.
    *
-   * @returns {Promise<Uint8Array>} - The compressed CBOR-LD bytes.
+   * @returns {Map|Array} - The transform map(s) to produce CBOR-LD bytes.
    */
-  async compress({jsonldDocument, diagnose} = {}) {
+  async compress({jsonldDocument} = {}) {
+    // FIXME: remove unused reset feature
     this.transformer.reset();
 
-    const transformMaps = await this._createTransformMaps({jsonldDocument});
-    if(diagnose) {
-      diagnose('Diagnostic CBOR-LD compression transform map(s):');
-      diagnose(inspect(transformMaps, {depth: null, colors: true}));
-    }
-    return cborg.encode(transformMaps, {typeEncoders});
-  }
-
-  async _createTransformMaps({jsonldDocument}) {
     // handle single or multiple JSON-LD docs
     const transformMaps = [];
     const isArray = Array.isArray(jsonldDocument);

lib/Decompressor.js

@@ -1,12 +1,10 @@
 /*!
  * Copyright (c) 2021-2024 Digital Bazaar, Inc. All rights reserved.
  */
-import * as cborg from 'cborg';
 import {KEYWORDS_TABLE, reverseMap} from './tables.js';
 import {CborldError} from './CborldError.js';
 import {ContextDecoder} from './codecs/ContextDecoder.js';
 import {ContextProcessor} from './ContextProcessor.js';
-import {inspect} from './util.js';
 import {Transformer} from './Transformer.js';
 import {ValueDecoder} from './codecs/ValueDecoder.js';
 
@@ -55,23 +53,15 @@ export class Decompressor {
    * Decompresses the given CBOR-LD byte array to a JSON-LD document.
    *
    * @param {object} options - The options to use.
-   * @param {Uint8Array} options.compressedBytes - The CBOR-LD compressed
-   *   bytes that follow the compressed CBOR-LD CBOR tag.
-   * @param {diagnosticFunction} [options.diagnose] - A function that, if
-   *   provided, is called with diagnostic information.
+   * @param {Map|Array} options.transformMap - The transform map(s) to
+   *   convert CBOR-LD to JSON-LD.
    *
    * @returns {Promise<object>} - The JSON-LD document.
    */
-  async decompress({compressedBytes, diagnose} = {}) {
+  async decompress({transformMap} = {}) {
+    // FIXME: remove unused reset feature
     this.transformer.reset();
 
-    // decoded output could be one or more transform maps
-    const transformMap = cborg.decode(compressedBytes, {useMaps: true});
-    if(diagnose) {
-      diagnose('Diagnostic CBOR-LD decompression transform map(s):');
-      diagnose(inspect(transformMap, {depth: null, colors: true}));
-    }
-
     // handle single or multiple JSON-LD docs
     const results = [];
     const isArray = Array.isArray(transformMap);

lib/decode.js

@@ -56,20 +56,27 @@ export async function decode({
   }
   const {suffix, isLegacy} = _getSuffix({cborldBytes});
   const isCompressed = _checkCompressionMode({cborldBytes, isLegacy});
+  if(!isCompressed) {
+    return cborg.decode(suffix, {useMaps: false});
+  }
+
+  // decoded output should be one or more transform maps
+  // FIXME: `transformMap` is an abstract representation of CBOR-LD, might
+  // be good to rename it
+  const transformMap = cborg.decode(suffix, {useMaps: true});
+  if(diagnose) {
+    diagnose('Diagnostic CBOR-LD decompression transform map(s):');
+    diagnose(inspect(transformMap, {depth: null, colors: true}));
+  }
 
+  // decompress CBOR-LD => JSON-LD
   const decompressor = _createDecompressor({
     isLegacy,
     documentLoader,
     typeTable,
     appContextMap
   });
-
-  if(!isCompressed) {
-    return cborg.decode(suffix, {useMaps: false});
-  }
-
-  const result = await decompressor.decompress(
-    {compressedBytes: suffix, diagnose});
+  const result = await decompressor.decompress({transformMap});
 
   if(diagnose) {
     diagnose('Diagnostic JSON-LD result:');

lib/encode.js

@@ -3,11 +3,21 @@
  */
 import * as cborg from 'cborg';
 import * as varint from 'varint';
+import {CborldEncoder} from './codecs/CborldEncoder.js';
 import {CborldError} from './CborldError.js';
 import {Compressor} from './Compressor.js';
 import {createLegacyTypeTable} from './tables.js';
 import {inspect} from './util.js';
 
+// override cborg object encoder to use cborld encoders
+const typeEncoders = {
+  Object(obj) {
+    if(obj instanceof CborldEncoder) {
+      return obj.encode({obj});
+    }
+  }
+};
+
 /**
  * Encodes a given JSON-LD document into a CBOR-LD byte array.
  *
@@ -79,22 +89,31 @@ export async function encode({
     }
   }
 
-  const prefix = _getPrefix({isLegacy, compressionMode, registryEntryId});
-  const compressor = _createCompressor({
-    isLegacy,
-    appContextMap,
-    documentLoader,
-    typeTable
-  });
+  // compute CBOR-LD suffix
   let suffix;
   if(compressionMode === 0 || registryEntryId === 0) {
-    // handle uncompressed CBOR-LD
+    // output uncompressed CBOR-LD
     suffix = cborg.encode(jsonldDocument);
   } else {
-    suffix = await compressor.compress({jsonldDocument, diagnose});
+    // compress JSON-LD => CBOR-LD
+    const compressor = _createCompressor({
+      isLegacy,
+      appContextMap,
+      documentLoader,
+      typeTable
+    });
+    // FIXME: `transformMap` is an abstract representation of CBOR-LD, might
+    // be good to rename it
+    const transformMap = await compressor.compress({jsonldDocument});
+    if(diagnose) {
+      diagnose('Diagnostic CBOR-LD compression transform map(s):');
+      diagnose(inspect(transformMap, {depth: null, colors: true}));
+    }
+    suffix = cborg.encode(transformMap, {typeEncoders});
   }
 
   // concatenate prefix and suffix
+  const prefix = _getPrefix({isLegacy, compressionMode, registryEntryId});
   const length = prefix.length + suffix.length;
   const bytes = new Uint8Array(length);
   bytes.set(prefix);