// Adapted from https://github.com/canjs/can-ndjson-stream/blob/master/can-ndjson-stream.js
// Did not use the package because it had a useless dependency on can-namespace which was unlicensed

// The MIT License (MIT)
//
// Copyright 2017 Justin Meyer (justinbmeyer@gmail.com), Fang Lu
// (cc2lufang@gmail.com), Siyao Wu (wusiyao@umich.edu), Shang Jiang
// (mrjiangshang@gmail.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

export default function ndjsonStream(stream: ReadableStream) {
  // For cancellation
  let is_reader: ReadableStreamDefaultReader | undefined = undefined;
  let cancellationRequest = false;
  return new ReadableStream({
    start: (controller) => {
      const reader = stream.getReader();
      is_reader = reader;
      const decoder = new TextDecoder();
      let data_buf = "";

      reader.read().then(function processResult(result) {
        if (result.done) {
          if (cancellationRequest) {
            // Immediately exit
            return;
          }

          data_buf = data_buf.trim();
          if (data_buf.length !== 0) {
            try {
              const data_l = JSON.parse(data_buf);
              controller.enqueue(data_l);
            } catch (e) {
              controller.error(e);
              return;
            }
          }
          controller.close();
          return;
        }

        const data = decoder.decode(result.value, { stream: true });
        data_buf += data;
        const lines = data_buf.split("\n");
        for (let i = 0; i < lines.length - 1; ++i) {
          const l = lines[i].trim();
          if (l.length > 0) {
            try {
              const data_line = JSON.parse(l);
              controller.enqueue(data_line);
            } catch (e) {
              controller.error(e);
              cancellationRequest = true;
              reader.cancel();
              return;
            }
          }
        }
        data_buf = lines[lines.length - 1];

        return reader.read().then(processResult);
      });
    },

    cancel: (reason) => {
      console.log("Cancel registered due to ", reason);
      cancellationRequest = true;
      is_reader.cancel();
    },
  });
}