Function createGeneration

packages/ai-svelte/src/create-generation.svelte.ts:112–234

(
  options: Omit<CreateGenerationOptions<TInput, TResult>, 'onResult'> & {
    onResult?: (result: TResult) => TTransformed
  },
)

// default, leaving the parameter `any` — a hard error under `strict`. See
// issue #848.
export function createGeneration<
  TInput extends Record<string, any>,
  TResult,
  TTransformed = void,
>(
  options: Omit<CreateGenerationOptions<TInput, TResult>, 'onResult'> & {
    onResult?: (result: TResult) => TTransformed
  },
): CreateGenerationReturn<
  InferGenerationOutputFromReturn<TResult, TTransformed>
> {
  type TOutput = InferGenerationOutputFromReturn<TResult, TTransformed>
  const clientId =
    options.id || `gen-${Date.now()}-${Math.random().toString(36).substring(7)}`

  // Create reactive state using Svelte 5 runes
  let result = $state<TOutput | null>(null)
  let isLoading = $state(false)
  let error = $state<Error | undefined>(undefined)
  let status = $state<GenerationClientState>('idle')

  // `body` uses a conditional spread because `GenerationClientOptions.body`
  // is declared `body?: Record<string, any>` (absent vs. present) under
  // `exactOptionalPropertyTypes`. Assigning `undefined` directly would be
  // rejected — the optional caller `options.body` may be undefined, in which
  // case we want the key to be absent.
  const clientOptions: GenerationClientOptions<TInput, TResult, TOutput> = {
    id: clientId,
    body: options.body,
    devtoolsBridgeFactory: createGenerationDevtoolsBridge,
    devtools: {
      ...options.devtools,
      framework: 'svelte',
      hookName: 'createGeneration',
    },
    // The transform's raw return type (`TTransformed`) and the stored output
    // (`TOutput`, with null/void/undefined stripped) are identical at runtime;
    // the cast bridges the relationship that the conditional type hides.
    onResult: ((r: TResult) => options.onResult?.(r)) as (
      result: TResult,
    ) => TOutput | null | void,
    onError: (e: Error) => options.onError?.(e),
    onProgress: (p: number, m?: string) => options.onProgress?.(p, m),
    onChunk: (c: StreamChunk) => options.onChunk?.(c),
    onResultChange: (r: TOutput | null) => {
      result = r
    },
    onLoadingChange: (l: boolean) => {
      isLoading = l
    },
    onErrorChange: (e: Error | undefined) => {
      error = e
    },
    onStatusChange: (s: GenerationClientState) => {
      status = s
    },
  }