feat(core): added custom PlutusData serialization classes

packages/core/src/Serialization/PlutusData/ConstrPlutusData.ts

@@ -0,0 +1,136 @@
+import { CborReader, CborWriter } from '../CBOR';
+import { HexBlob } from '@cardano-sdk/util';
+import { PlutusList } from './PlutusList';
+import { hexToBytes } from '../../util/misc';
+
+const GENERAL_FORM_TAG = 102n;
+const ALTERNATIVE_TAG_OFFSET = 7n;
+
+/**
+ * The main datatype `Constr` represents the nth constructor
+ * along with its arguments.
+ *
+ * Remark: We don't directly serialize the alternative in the tag,
+ * instead the scheme is:
+ *
+ * - Alternatives 0-6 -> tags 121-127, followed by the arguments in a list.
+ * - Alternatives 7-127 -> tags 1280-1400, followed by the arguments in a list.
+ * - Any alternatives, including those that don't fit in the above -> tag 102 followed by a list containing
+ * an unsigned integer for the actual alternative, and then the arguments in a (nested!) list.
+ */
+export class ConstrPlutusData {
+  private readonly _alternative: bigint = 0n;
+  private readonly _data = new PlutusList();
+
+  /**
+   * Initializes a new instance of the ConstrPlutusData class.
+   *
+   * @param alternative Get the Constr alternative. The alternative represents the nth
+   * constructor of a 'Sum Type'.
+   * @param data Gets the list of arguments of the 'Sum Type' as a 'PlutusList'.
+   */
+  constructor(alternative: bigint, data: PlutusList) {
+    this._alternative = alternative;
+    this._data = data;
+  }
+
+  /**
+   * Serializes this ConstrPlutusData instance into its CBOR representation as a Uint8Array.
+   *
+   * @returns The CBOR representation of this instance as a Uint8Array.
+   */
+  toCbor(): HexBlob {
+    const writer = new CborWriter();
+    const compactTag = ConstrPlutusData.alternativeToCompactCborTag(this._alternative);
+
+    writer.writeTag(Number(compactTag));
+
+    if (compactTag !== GENERAL_FORM_TAG) {
+      writer.writeEncodedValue(hexToBytes(this._data.toCbor()));
+    } else {
+      writer.writeStartArray(2);
+      writer.writeInt(this._alternative);
+      writer.writeEncodedValue(hexToBytes(this._data.toCbor()));
+    }
+
+    return HexBlob.fromBytes(writer.encode());
+  }
+
+  /**
+   * Deserializes a ConstrPlutusData instance from its CBOR representation.
+   *
+   * @param cbor The CBOR representation of this instance as a Uint8Array.
+   * @returns A ConstrPlutusData instance.
+   */
+  static fromCbor(cbor: HexBlob): ConstrPlutusData {
+    const reader = new CborReader(cbor);
+
+    const tag = reader.readTag();
+
+    if (tag === Number(GENERAL_FORM_TAG)) {
+      reader.readStartArray();
+
+      const alternative = reader.readInt();
+      const data = reader.readEncodedValue();
+      const plutusList = PlutusList.fromCbor(HexBlob.fromBytes(data));
+
+      reader.readEndArray();
+
+      return new ConstrPlutusData(alternative, plutusList);
+    }
+
+    const alternative = ConstrPlutusData.compactCborTagToAlternative(BigInt(tag));
+    const data = reader.readEncodedValue();
+    const plutusList = PlutusList.fromCbor(HexBlob.fromBytes(data));
+
+    return new ConstrPlutusData(alternative, plutusList);
+  }
+
+  /**
+   * Gets the ConstrPlutusData alternative. The alternative represents the nth
+   * constructor of a 'Sum Type'.
+   *
+   * @returns The alternative constructor of the 'Sum Type'.
+   */
+  getAlternative(): bigint {
+    return this._alternative;
+  }
+
+  /**
+   * The list of arguments of the 'Sum Type' as a 'PlutusList'.
+   *
+   * @returns The list of arguments.
+   */
+  getData(): PlutusList {
+    return this._data;
+  }
+
+  // Mapping functions to and from alternative to and from CBOR tags.
+  // See https://github.com/input-output-hk/plutus/blob/1f31e640e8a258185db01fa899da63f9018c0e85/plutus-core/plutus-core/src/PlutusCore/Data.hs#L69-L72
+
+  /**
+   * Converts a CBOR compact tag to a Constr alternative.
+   *
+   * @param tag The tag to be converted.
+   * @returns The Constr alternative.
+   */
+  private static compactCborTagToAlternative(tag: bigint): bigint {
+    if (tag >= 121n && tag <= 127) return tag - 121n;
+    if (tag >= 1280n && tag <= 1400) return tag - 1280n + ALTERNATIVE_TAG_OFFSET;
+
+    return GENERAL_FORM_TAG;
+  }
+
+  /**
+   * Converts the constructor alternative to its CBOR compact tag.
+   *
+   * @param alternative The Constr alternative to be converted.
+   * @returns The compact CBOR tag.
+   */
+  private static alternativeToCompactCborTag(alternative: bigint): bigint {
+    if (alternative <= 6n) return 121n + alternative;
+    if (alternative >= 7n && alternative <= 127n) return 1280n - ALTERNATIVE_TAG_OFFSET + alternative;
+
+    return GENERAL_FORM_TAG;
+  }
+}