feat(assets-controller): first version of AssetsController

[Kriys94]

Explanation

Current State

The current asset management in MetaMask is fragmented across multiple controllers with different patterns for EVM vs non-EVM chains. Each chain type (Ethereum, Solana, Bitcoin, Tron) has separate logic paths, making it difficult to maintain consistency and add new chain support.

Solution

This PR introduces a complete rewrite of the AssetsController with a middleware architecture for unified asset management across all blockchain networks (EVM and non-EVM). The new architecture provides:

• Unified asset management for all chains using CAIP-19 identifiers
• Pluggable data source architecture with automatic priority-based fallback:
  1. BackendWebsocketDataSource - Real-time push (highest priority)
  2. AccountsApiDataSource - HTTP polling fallback
  3. SnapDataSource - Solana/Bitcoin/Tron via Snaps
  4. RpcDataSource - Direct RPC queries (lowest priority)
• Middleware pipeline for data enrichment: Detection → Token metadata → Price
• Lifecycle management - Auto start/stop on app open/close and keyring lock/unlock
• Custom assets support - Per-account custom token storage

Architecture

┌──────────────────────────────────────────────────────────────────────────────┐
│                              AssetsController                                 │
├──────────────────────────────────────────────────────────────────────────────┤
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐          │
│  │   State     │  │Subscriptions│  │  Middleware │  │   Events    │          │
│  │  Manager    │  │   Manager   │  │    Chain    │  │  Publisher  │          │
│  └─────────────┘  └─────────────┘  └─────────────┘  └─────────────┘          │
├──────────────────────────────────────────────────────────────────────────────┤
│                                                                               │
│        Fetch Stack                          Event Stack                       │
│  ┌───────────────────┐               ┌───────────────────┐                   │
│  │    AccountsAPI    │               │                   │                   │
│  ├───────────────────┤               │                   │                   │
│  │       Snap        │               │                   │                   │
│  ├───────────────────┤               │                   │                   │
│  │       RPC         │               │                   │                   │
│  ├───────────────────┤               ├───────────────────┤                   │
│  │     Detection     │               │     Detection     │                   │
│  ├───────────────────┤               ├───────────────────┤                   │
│  │       Token       │               │       Token       │                   │
│  ├───────────────────┤               ├───────────────────┤                   │
│  │       Price       │               │       Price       │                   │
│  └───────────────────┘               └───────────────────┘                   │
│                                                                               │
│  On-demand data fetch                Process incoming updates                 │
│  (forceUpdate: true)                 (enrichment only)                        │
│                                                                               │
│  Subscription Sources: BackendWebsocket, AccountsApi, Snap, RPC              │
│  Push updates via: AssetsController:assetsUpdate action                      │
└──────────────────────────────────────────────────────────────────────────────┘

New Files

File	Purpose
src/AssetsController.ts	Complete rewrite with middleware architecture
src/types.ts	Comprehensive CAIP-19 type definitions
src/README.md	Architecture documentation with diagrams
src/data-sources/AbstractDataSource.ts	Base class for data sources
src/data-sources/BackendWebsocketDataSource.ts	Real-time WebSocket updates
src/data-sources/AccountsApiDataSource.ts	HTTP polling fallback
src/data-sources/SnapDataSource.ts	Solana/Bitcoin/Tron snap handler
src/data-sources/RpcDataSource.ts	Direct RPC fallback
src/data-sources/DetectionMiddleware.ts	Identifies assets without metadata
src/data-sources/TokenDataSource.ts	Token metadata enrichment
src/data-sources/PriceDataSource.ts	USD price fetching
src/data-sources/initDataSources.ts	Initialization helpers

State Structure

{
  assetsMetadata: {
    "eip155:1/slip44:60": { type: "native", symbol: "ETH", decimals: 18, ... },
    "eip155:1/erc20:0xA0b8...": { type: "erc20", symbol: "USDC", decimals: 6, ... },
  },
  assetsBalance: {
    "account-uuid-1": {
      "eip155:1/slip44:60": { amount: "1000000000000000000" },
    },
  },
  customAssets: {
    "account-uuid-1": ["eip155:1/erc20:0x..."],
  },
}

Published Events

AssetsController:balanceChanged - When asset balances change
AssetsController:priceChanged - When prices update
AssetsController:assetsDetected - When new assets without metadata are found

References

Checklist

[ ] I've updated the test suite for new or updated code as appropriate
[x] I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
[x] I've communicated my changes to consumers by updating changelogs for packages I've changed
[ ] I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

---

Note

Implements a unified, middleware-based AssetsController with pluggable data sources and lifecycle-aware subscriptions for multi-chain asset management.

• Introduces src/AssetsController.ts with request/response middleware (fetch stack and event stack), Messenger-integrated actions/events, state (assetsMetadata, assetsBalance, customAssets), ID normalization, and app/keyring lifecycle handling
• Adds data sources: BackendWebsocketDataSource (real-time), AccountsApiDataSource (HTTP), RpcDataSource (RPC), and PriceDataSource (spot price polling); chain assignment/prioritization and subscription management included
• Exposes APIs: getAssets, getAssetsBalance, getAssetMetadata, getAssetsPrice, addCustomAsset/removeCustomAsset/getCustomAssets; publishes balanceChanged, priceChanged, assetsDetected
• Adds comprehensive docs (src/README.md) and tests (AssetsController.test.ts); updates deps and lowers Jest coverage thresholds for initial iteration

^{Written by Cursor Bugbot for commit aae01b4. This will update automatically on new commits. Configure here.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

[salimtb]

let me create a task for this todo here

[salimtb]

no need this comments , usually we just add js doc , we ca clean later