import { Buffer } from "buffer";

import { HTTPRequest } from "./types";
import { buildPointerInfo, PointerInfo } from "./pointers";
import { bodyToBuffer, getAuthHeader } from "./util";

interface LFSInfoResponse {
  objects: {
    actions?: {
      upload: {
        href: string;
        header?: Record<string, string>;
      };
      verify?: {
        href: string;
        header?: Record<string, string>;
      };
    };
  }[];
}

function isValidLFSInfoResponseData(
  val: Record<string, any>
): val is LFSInfoResponse {
  const obj = val.objects?.[0];
  return obj && (!obj.actions || obj.actions.upload.href.trim !== undefined);
}

/**
 * Given a blob, uploads the blob to LFS server and returns a PointerInfo,
 * which the caller can then combine with object path into a Pointer
 * and commit in place of the original Git blob.
 */
export default async function uploadBlob(
  { http: { request }, headers = {}, url, auth }: HTTPRequest,
  content: Buffer
): Promise<PointerInfo> {
  const info = await buildPointerInfo(content);

  const authHeaders: Record<string, string> = auth ? getAuthHeader(auth) : {};

  // Request LFS transfer

  const lfsInfoRequestData = {
    operation: "upload",
    transfers: ["basic"],
    objects: [info],
  };

  const { body: lfsInfoBody } = await request({
    url: `${url}/info/lfs/objects/batch`,
    method: "POST",
    headers: {
      // Github LFS doesn’t seem to accept this UA
      // 'User-Agent': `git/isomorphic-git@${git.version()}`,
      ...headers,
      ...authHeaders,
      Accept: "application/vnd.git-lfs+json",
      "Content-Type": "application/vnd.git-lfs+json",
    },
    body: [Buffer.from(JSON.stringify(lfsInfoRequestData))],
  });

  const lfsInfoResponseRaw = (await bodyToBuffer(lfsInfoBody)).toString();
  let lfsInfoResponseData: any;
  try {
    lfsInfoResponseData = JSON.parse(lfsInfoResponseRaw);
  } catch (e) {
    throw new Error(
      `Unexpected structure received from LFS server: unable to parse JSON ${lfsInfoResponseRaw}`
    );
  }

  if (isValidLFSInfoResponseData(lfsInfoResponseData)) {
    // Upload the actual blob

    const actions = lfsInfoResponseData.objects[0].actions;

    if (!actions) {
      // Presume LFS already has the blob. Don’t fail loudly.
      return info;
    } else {
      const uploadAction = actions.upload;
      const lfsObjectUploadURL = uploadAction.href;
      const lfsObjectUploadHeaders = uploadAction.header ?? {};

      const dlHeaders = {
        ...headers,
        ...authHeaders,
        ...lfsObjectUploadHeaders,
      };

      const resp = await request({
        url: lfsObjectUploadURL,
        method: "PUT",
        headers: dlHeaders,
        body: [content],
      });

      if (resp.statusCode === 200) {
        const verifyAction = actions.verify;

        // Upload verification was requested. Do that

        if (verifyAction) {
          const verificationResp = await request({
            url: verifyAction.href,
            method: "POST",
            headers: {
              // Isomorphic Git’s UA header is considered invalid
              // and missing UA header causes an error in this case;
              // cURL is considered valid, so…
              "User-Agent": `curl/7.54`,
              // TODO: Generalize UA header handling
              // - Leave UA header twiddling to callers?
              // - Figure out which LFS implementation wants which UA header?
              ...(verifyAction.header ?? {}),
            },
            body: [Buffer.from(JSON.stringify(info))],
          });

          if (verificationResp.statusCode === 200) {
            return info;
          } else {
            throw new Error(
              `Upload might have been unsuccessful, verification action yielded HTTP ${verificationResp.statusCode}`
            );
          }
        } else {
          return info;
        }
      } else {
        throw new Error(
          `Upload might have been unsuccessful, upload action yielded HTTP ${resp.statusCode}`
        );
      }
    }
  } else {
    throw new Error(
      "Unexpected JSON structure received for LFS upload request"
    );
  }
}