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Feed Compiler ​

The FeedCompiler class is responsible for transforming feed definitions into executable relay requests. It handles the complex task of converting various feed types into optimized filters and relay selections.

Overview ​

typescript
class FeedCompiler {
  constructor(readonly options: FeedOptions)

  canCompile(feed: Feed): boolean
  compile(feed: Feed): Promise<RequestItem[]>
}

Feed Compilation Process ​

The compiler transforms feed definitions into RequestItem[], where each item contains:

typescript
type RequestItem = {
  relays?: string[]    // Specific relays to query
  filters?: Filter[]   // Nostr filters to apply
}

Examples ​

Basic Feed Compilation ​

typescript
const compiler = new FeedCompiler(options)

// Simple author feed
const feed = [FeedType.Author, "pubkey1", "pubkey2"]
const requests = await compiler.compile(feed)
// => [{ filters: [{ authors: ["pubkey1", "pubkey2"] }] }]

Complex Feed Compilation ​

typescript
// Complex feed with multiple operations
const feed = [
  FeedType.Intersection,
  [FeedType.Kind, 1],
  [
    FeedType.Union,
    [FeedType.Scope, Scope.Follows],
    [FeedType.List, { addresses: ["trending"] }]
  ]
]

const requests = await compiler.compile(feed)
// Compiles to optimized filters for relay queries

DVM Integration ​

typescript
const feed = [
  FeedType.DVM,
  {
    kind: 5300,
    mappings: [
      ["p", [FeedType.Author]],
      ["t", [FeedType.Tag, "#t"]]
    ]
  }
]

const requests = await compiler.compile(feed)
// Queries DVM and compiles resulting tags into feeds

Implementation Notes ​

Optimization Strategies ​

  1. Filter Merging: Similar filters are combined when possible

    typescript
    // Before: [{ authors: ["a"] }, { authors: ["b"] }]
// After: [{ authors: ["a", "b"] }]

  2. Relay Grouping: Requests are grouped by relay where possible

    typescript
    // Filters are organized by relay to minimize connections
filtersByRelay: Map<string, Filter[]>

  3. Deduplication: Duplicate values are removed using uniq

    typescript
    uniq(scopes.flatMap(this.options.getPubkeysForScope))

Error Handling ​

The compiler includes various safety checks:

typescript
canCompile(feed: Feed): boolean {
  // Checks if feed type is supported
  // Recursively checks sub-feeds
}