mesh2-json-transaction-building-and-modular-serialization-layers.md

About transaction building with JSON

The goal is to pass a JSON object to the Rust code, which will build a transaction and return the serialized transaction in hex format. This is used between Mesh and the Rust code.

Instead of build transactions directly with cardano-serialization-lib, we build the whisky package that wraps the cardano-serialization-lib package. Doing so, this allow us to create useful functions that can be used in the Rust code base.

Then, we create a JSON parser in Rust that can parse JSON objects and build transactions with the whisky package.

Example

Example of a txBody in JSON format:

{
  inputs: [
    {
      type: "PubKey",
      txIn: {
        txHash:
          "1662c4b349907e4d92e0995fd9dcdc9a4489f7dff4f5cce6b4b3901de479308c",
        txIndex: 14,
        amount: [
          {
            unit: "lovelace",
            quantity: "774643176",
          },
        ],
        address:
          "addr_test1qq0yavv5uve45rwvfaw96qynrqt8ckpmkwcg08vlwxxdncxk82f5wz75mzaesmqzl79xqsmedwgucwtuav5str6untqqmykcpn",
      },
    },
  ],
  outputs: [
    {
      address:
        "addr_test1qq0yavv5uve45rwvfaw96qynrqt8ckpmkwcg08vlwxxdncxk82f5wz75mzaesmqzl79xqsmedwgucwtuav5str6untqqmykcpn",
      amount: [
        {
          unit: "lovelace",
          quantity: "1231231",
        },
      ],
    },
  ],
  extraInputs: [
    {
      input: {
        outputIndex: 14,
        txHash:
          "1662c4b349907e4d92e0995fd9dcdc9a4489f7dff4f5cce6b4b3901de479308c",
      },
      output: {
        address:
          "addr_test1qq0yavv5uve45rwvfaw96qynrqt8ckpmkwcg08vlwxxdncxk82f5wz75mzaesmqzl79xqsmedwgucwtuav5str6untqqmykcpn",
        amount: [
          {
            unit: "lovelace",
            quantity: "774643176",
          },
        ],
      },
    },
    {
      input: {
        outputIndex: 54,
        txHash:
          "43cdd76f2b74d31e56813276b695b64fe91daac195ac37ac3b4a4b44b405f3bf",
      },
      output: {
        address:
          "addr_test1qq0yavv5uve45rwvfaw96qynrqt8ckpmkwcg08vlwxxdncxk82f5wz75mzaesmqzl79xqsmedwgucwtuav5str6untqqmykcpn",
        amount: [
          {
            unit: "lovelace",
            quantity: "390216112",
          },
        ],
      },
    },
  ],
  selectionThreshold: 5000000,
  collaterals: [],
  requiredSignatures: [],
  referenceInputs: [],
  mints: [],
  changeAddress:
    "addr_test1qq0yavv5uve45rwvfaw96qynrqt8ckpmkwcg08vlwxxdncxk82f5wz75mzaesmqzl79xqsmedwgucwtuav5str6untqqmykcpn",
  metadata: [],
  validityRange: {},
  certificates: [],
  withdrawals: [],
  signingKey: [],
}

Together with the protocol params in JSON format, is then passed to the js_serialize_tx_body function in the sidan-csl-rs package (the WASM of the core logic of whisky package).

In Rust, parse the JSON, build the transaction and return the serialized transaction in hex format:

const txHex = serializer.js_serialize_tx_body(txBodyJson, params);
// txHex = 84a300818258201662c4b349907e4d92e0995fd9dcdc9a4489f7dff4f5cce6b4b3901de479308c0e0182825839001e4eb194e3335a0dcc4f5c5d009318167c583bb3b0879d9f718cd9e0d63a93470bd4d8bb986c02ff8a6043796b91cc397ceb29058f5c9ac01a0012c97f825839001e4eb194e3335a0dcc4f5c5d009318167c583bb3b0879d9f718cd9e0d63a93470bd4d8bb986c02ff8a6043796b91cc397ceb29058f5c9ac01a2e16c3f4021a00029075a0f5f6

About Mesh v2

Mesh v2 focused on modularizing the serialization layers and provide various developer facing packages:

• @meshsdk/core (typescript):
  • for all JS frontend frameworks
  • rely on cardano-sdk and stricahq packages to parse CBOR and build transactions.
• @meshsdk/core-csl (webassembly):
  • for JS backends
  • wraps the sidan-csl-rs package which is a WASM of whisky
  • provide useful functions to build transactions and parse CBOR objects in Rust
  • exposes the functions to JavaScript, building transactions via JSON objects
• whisky (Rust):
  • wraps the cardano-serialization-lib package
  • provide useful functions to build transactions and parse CBOR objects in Rust
  • think of Mesh written in Rust
  • we can test CSL completeness, and build helpers that CSL is missing

All 3 packages have very similar functions. With Mesh providing multiple wallets and aceess to community projects service providers, while the Rust package is focused on building transactions and parsing CBOR objects.