@tanstack/ai/dist/esm/activities/chat/middleware/capabilities.js

Type-safe TypeScript AI SDK for streaming chat, tool calling, agents, structured outputs, and multimodal generation.

class CapabilityRegistry {
  provided = /* @__PURE__ */ new Set();
  onDuplicate;
  /** Register a callback fired when a handle is provided more than once. */
  setOnDuplicate(cb) {
    this.onDuplicate = cb;
  }
  /** Record that `handle` was provided; fire the duplicate callback on repeats. */
  markProvided(handle) {
    if (this.provided.has(handle)) this.onDuplicate?.(handle.capabilityName);
    this.provided.add(handle);
  }
  has(handle) {
    return this.provided.has(handle);
  }
}
function createCapability() {
  return (name) => {
    const values = /* @__PURE__ */ new WeakMap();
    function get(ctx, opts) {
      if (!values.has(ctx)) {
        if (opts?.optional) return void 0;
        throw new Error(
          `Capability "${name}" was requested but never provided. Ensure a middleware provides it in setup(), ordered before this consumer.`
        );
      }
      return values.get(ctx);
    }
    const provide = (ctx, value) => {
      values.set(ctx, value);
      ctx.capabilities.markProvided(handle);
    };
    const pair = [get, provide];
    const handle = Object.assign(pair, {
      capabilityName: name,
      has: (ctx) => values.has(ctx)
    });
    return handle;
  };
}
export {
  CapabilityRegistry,
  createCapability
};
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