BaseContext: Shared Hydration Context

Goal: Extract a shared BaseContext type from hatk so hydrators work with both feed and XRPC contexts without manual field spreading or as any casts.

Problem: HydrateContext and XrpcContext share 90% of their fields (db, lookup, count, getRecords, labels, blobUrl, viewer). Hydrators that need to work with both must manually spread every field and cast. Adding getRecords to XrpcContext required touching four construction sites.

Design

BaseContext

Shared interface in hydrate.ts. Provides data access tools any hydrator needs.

export interface BaseContext {
  viewer: { did: string; handle?: string } | null
  db: { query: (sql: string, params?: unknown[]) => Promise<unknown[]> }
  getRecords: <R = unknown>(collection: string, uris: string[]) => Promise<Map<string, Row<R>>>
  lookup: <R = unknown>(collection: string, field: string, values: string[]) => Promise<Map<string, Row<R>>>
  count: (collection: string, field: string, values: string[]) => Promise<Map<string, number>>
  labels: (uris: string[]) => Promise<Map<string, unknown[]>>
  blobUrl: (did: string, ref: unknown, preset?: 'avatar' | 'banner' | 'feed_thumbnail' | 'feed_fullsize') => string | undefined
}

buildBaseContext(viewer) constructs one. No items parameter — items are always a separate argument.

XrpcContext extends BaseContext

Adds XRPC-specific fields: params, cursor, limit, search, resolve, exists, packCursor, unpackCursor, isTakendown, filterTakendownDids, db.run. Context construction in xrpc.ts and opengraph.ts reuses buildBaseContext and extends.

Feed hydrate signature

Changes from (ctx: HydrateContext<T>) => Promise<View[]> to (ctx: BaseContext, items: Row<T>[]) => Promise<View[]>. HydrateContext is removed entirely.

Hydrator reuse

XRPC handlers pass ctx directly to hydrators since XrpcContext extends BaseContext:

// Before
const galleries = await hydrateGalleries({
  items: result.records, viewer: ctx.viewer, db: ctx.db,
  getRecords: ctx.getRecords, lookup: ctx.lookup, count: ctx.count,
  labels: ctx.labels, blobUrl: ctx.blobUrl,
} as any);

// After
const galleries = await hydrateGalleries(ctx, result.records);

Files to change

hatk framework:

hydrate.ts — Add BaseContext, remove HydrateContext, buildBaseContext
xrpc.ts — XrpcContext extends BaseContext, reuse buildBaseContext
opengraph.ts — Reuse buildBaseContext
feeds.ts — Hydrate signature, executeFeed, exports
cli.ts — Codegen: BaseContext imports/exports, defineFeed overloads

Template projects:

server/feeds/_hydrate.ts — Accept (ctx: BaseContext, items: Row<T>[])
server/feeds/*.ts — Pass (ctx, items) to hydrate
server/xrpc/*.ts — Pass ctx directly to hydrators

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