writer.ts

// AUTO-GENERATED by scripts/generate-client-packages.ts — DO NOT EDIT.
// Edit scripts/client-codegen/template/writer.ts (+ versions.json) and run: npm run generate:clients

import type { FetchFn, WithId } from "./types.js";

/** Options for {@link FhirResourceWriter.create}. */
export interface CreateOptions {
  /**
   * FHIR conditional create — the `If-None-Exist` header, given as a search string
   * (e.g. `identifier=https://example.org/mrn|12345`).
   *
   * The server creates the resource only when that search matches nothing; on a match it returns
   * the existing resource instead of a duplicate. This is what makes a create idempotent, and so
   * what makes a write safe to retry: a provisioning job that runs twice produces one resource.
   *
   * Pass the raw search string, NOT url-encoded — this is a header, not a query string, and
   * encoding the `|` makes the search match nothing, which silently turns every retry into
   * another copy.
   */
  ifNoneExist?: string;
}

/**
 * Generic FHIR resource writer with create, update, delete and createOrUpdate (PUT).
 */
export class FhirResourceWriter<T extends fhir4.Resource> {
  private readonly fetchFn: FetchFn;

  constructor(
    public readonly baseUrl: string,
    public readonly resourceType: string,
    fetchFn?: FetchFn,
  ) {
    this.fetchFn = fetchFn ?? globalThis.fetch.bind(globalThis);
  }

  /**
   * Create a new resource (POST).
   *
   * With {@link CreateOptions.ifNoneExist} this is a conditional create: `201` for a resource that
   * was created, `200` for one that already matched. Both resolve to the resource; check
   * `meta.versionId` or search first if the caller needs to tell them apart.
   */
  async create(resource: T, options?: CreateOptions): Promise<WithId<T>> {
    const url = `${this.baseUrl}/${this.resourceType}`;
    const headers: Record<string, string> = {
      "Content-Type": "application/fhir+json",
      Accept: "application/fhir+json",
    };
    if (options?.ifNoneExist) headers["If-None-Exist"] = options.ifNoneExist;

    const res = await this.fetchFn(url, {
      method: "POST",
      headers,
      body: JSON.stringify(resource),
    });
    if (!res.ok) throw new Error(`POST ${this.resourceType}: ${res.status} ${res.statusText}`);
    return (await this.resourceFromResponse(res)) as WithId<T>;
  }

  /** Update an existing resource (PUT with ID). */
  async update(resource: WithId<T>): Promise<WithId<T>> {
    const url = `${this.baseUrl}/${this.resourceType}/${encodeURIComponent(resource.id)}`;
    const res = await this.fetchFn(url, {
      method: "PUT",
      headers: { "Content-Type": "application/fhir+json", Accept: "application/fhir+json" },
      body: JSON.stringify(resource),
    });
    if (!res.ok) throw new Error(`PUT ${this.resourceType}/${resource.id}: ${res.status} ${res.statusText}`);
    return (await res.json()) as WithId<T>;
  }

  /** Delete a resource by ID. */
  async delete(id: string): Promise<void> {
    const url = `${this.baseUrl}/${this.resourceType}/${encodeURIComponent(id)}`;
    const res = await this.fetchFn(url, {
      method: "DELETE",
      headers: { Accept: "application/fhir+json" },
    });
    if (!res.ok) throw new Error(`DELETE ${this.resourceType}/${id}: ${res.status} ${res.statusText}`);
  }

  /** Create-or-update via conditional PUT. */
  async createOrUpdate(resource: WithId<T>): Promise<WithId<T>> {
    return this.update(resource);
  }

  /**
   * The resource a write responded with, falling back to the `Location` header.
   *
   * A conditional create that MATCHES is allowed to answer `200` with no body — the server has
   * nothing new to report — and the id then exists only in `Location`. Parsing the body alone
   * would throw there, which would make the idempotent path the one that fails.
   */
  private async resourceFromResponse(res: Response): Promise<fhir4.Resource> {
    const text = await res.text();
    if (text.trim()) return JSON.parse(text) as fhir4.Resource;

    const location = res.headers?.get("Location") ?? res.headers?.get("Content-Location") ?? "";
    // `[base/]Type/<id>[/_history/<v>]` — take the segment after the resource type.
    const id = new RegExp(`${this.resourceType}/([^/?]+)`).exec(location)?.[1];
    if (!id) {
      throw new Error(`POST ${this.resourceType}: response carried neither a body nor a Location`);
    }
    return { resourceType: this.resourceType, id } as fhir4.Resource;
  }
}