// Same compilation mechanism as stan-playground: POST the program to the
// compilation server, then download the compiled artifact. The server
// (stan-wasm-wasi) produces a pure-WASI command module at
// /download/{model_id}/main.wasm, runnable on wasm-exec workers.

export const DEFAULT_WASI_SERVER_URL = "https://stan-wasm-wasi.fly.dev";

const compileStanProgram = async (
  serverUrl: string,
  stanProgram: string,
  onStatus: (s: string) => void,
): Promise<{ artifactUrl?: string }> => {
  try {
    onStatus("compiling...");

    const compileURL = `${serverUrl}/compile`;
    const runCompile = await fetch(compileURL, {
      method: "POST",
      headers: {
        "Content-Type": "text/plain",
        Authorization: "Bearer 1234",
      },
      body: stanProgram,
    });
    if (!runCompile.ok) {
      onStatus(`failed to compile: ${await messageOrStatus(runCompile)}`);
      return {};
    }
    const compileResp = await runCompile.json();
    const artifactUrl = `${serverUrl}/download/${compileResp.model_id}/main.wasm`;

    // download to make sure it is there
    onStatus("checking download of main.wasm");
    const downloadCheck = await fetch(artifactUrl, { method: "HEAD" });
    if (!downloadCheck.ok) {
      onStatus(
        `failed to download main.wasm: ${await messageOrStatus(downloadCheck)}`,
      );
      return {};
    }

    onStatus("compiled");
    return { artifactUrl };
  } catch (e) {
    onStatus(`failed to compile: ${e}`);
    return {};
  }
};

const messageOrStatus = async (response: Response) => {
  try {
    const j = await response.json();
    return j?.message ?? response.statusText;
  } catch {
    return response.statusText;
  }
};

export default compileStanProgram;