WASM Client Features

[jsdanielh]

• A way to pass configuration to it on launch
  • Supply configuration information from JS #1341
• Proper client library/bundle
• A way to access the actual hostname or IP addresses of connected peers, for our world map.
  • Access to network peer information (IP, type, etc.) #357
  • Add a way to access peer information #1344
• Access to PrivateKey, PublicKey, Commitments, SerialBuffer, etc. Sign a transaction with my PrivateKey
  • Wasm-JS interactivity, first steps #1349
  • Wasm-JS interactivity, part two: staking roundtrip #1350
  • Event listeners/callbacks
    • WASM Client: Convert subscriptions to listeners #1363
    • Serialize blocks to JS as objects #1410
  • HTLC signing support
    • HTLCs are technically supported. They can be created, just have to be signed manually, as the sign() method does not support it.
  • Multisig primitives
    • Documented in the last check box.
• Method to tell client to reconnect after all peers lost, or it tries reconnecting itself
  • Implement listener for offline/online events in the web-client, add fixes and documentation #1357
• Query tx history by address
  • Create the TransactionsProof request #1346
  • Expose getTransactionsByAddress to JS #1356
  • Array of plain JS transaction objects from getTransactionsByAddress #1385
  • Transaction history optimizations #1386
  • Transaction inclusion proofs enhancements  #1401
• Query balances for addresses
  • Create the accounts proof request #1408
  • Change read interface for the staking contract and remove database dependency from account crate #1462
• Subscribe to tx events/logs for addresses
  • Tx events subscription #1437
• Compatibility with 1.0 client
  • Add client.waitForConsensusEstablished() #1418
  • Use 1.0 arguments for getTransactionsByAddress: (address, sinceBlockHeight, knownTransactionDetails, limit)
    • Adapt arguments of getTransactionsByAddress to be 1.0-compatible #1430
  • Return PlainTransactionDetails from tx sending methods #1425
    • also adds getTransactionReceiptsByAddress(address, limit)
  • Accept Transaction | PlainTransaction | string for sendTransaction
  • getTransaction(hash, blockHash, blockHeight)
  • getTransactionReceipt(hash)
  • getTransactionReceiptsByHashes(hashes)
• multisig support
  • Will not be addressed in this issue and tracking of this will continue in Add multisig support for the web client #1578.

[sisou]

So I just tested disconnection/reconnection behavior. Detection of network loss takes around 10-12 seconds (all peers leave and consensus is marked as "lost" when the number of peers drop under the configured minimum). However, when network is reconnected, the client does not start reconnecting by itself. So we need a way to tell it to start connecting again. Or we need to kill it and start a new client, but the first option would be better.

[sisou]

As for the export of further primitives and structs, we will run into various problems with Rust things that wasm-bindgen does not (yet) support:

• It cannot generate bindings for trait implementations, so e.g. the from_hex method of PrivateKey is not supported
• It cannot generate/convert pub const properties in implementations, so e.g. the SIZE constant on PrivateKey is not supported, preventing the whole impl bock from getting generated.

I think exposing these extra classes to JS would require proxying them by structs that wasm-bindgen understands.

Related wasm-bindgen issue and incomplete draft PR for trait impls.

[sisou]

Proxying the structs we want to expose could look like this: eee2035. This creates a class PrivateKey in JS with the methods static fromHex(hex: string): PrivateKey and toHex(): string.

Doing this for all classes we want to expose and their APIs will be a lot of work though.

[sisou]

I extended the proof-of-concept for the proxied structs in 64714ad. One thing to note is that every struct that is passed to JS is pushed onto the WASM stack, and only removed when its free() method is called, which cannot be called automatically by JS on garbage collection, if I understood that correctly. So all created objects will leak memory if not explicitly freed by userland code.

This is a problem when for example accessing a public or private key on a keypair, as that will create a new copy of that object on the stack.

[sisou]

Good news! wasm-bindgen actually supports automatic freeing of the rust struct when the Javascript reference is dereferenced (i.e. garbage collected). wasm-pack also merged support for it, but has not released a new version with it. It can however be enabled by an environment flag:
rustwasm/wasm-pack#937 (comment)

Enabling this feature requires support for WeakRefs in browsers, but support is pretty good and only getting better: https://caniuse.com/mdn-javascript_builtins_weakref

So I'd say let's enable that and pass structs to JS to our heart's content! 👌

[jsdanielh]

All items are now addressed with the exception of multisig which will be tracked in a different issue as documented in the issue description.