<?php

function mattermost_send($server, $token, $channel_id, $msg, $fields = [])
{
  $url = "$server/api/v4/posts";

  $headers = [
    'Content-Type: application/json',
    'Authorization: Bearer ' . $token
  ];

  $fields['channel_id'] = $channel_id;
  $fields['message'] = $msg;

  $ch = curl_init($url);

  curl_setopt($ch, CURLOPT_POST, true);
  curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
  curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

  $result = curl_exec($ch);
  $status = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  curl_close($ch);

  if($status != 201)
    throw new Exception("Post failed with status: " . $status .", result: " . var_export($result, true));

  return json_decode($result, true);
}

function mattermost_send_file($server, $token, $channel_id, $title, $filepath, $mime = 'application/octet-stream', $post_fields = [])
{
  $url = "$server/api/v4/files";

  $headers = [
    'Content-Type: multipart/form-data',
    'Authorization: Bearer ' . $token
  ];

  $cfile = new \CURLFile(realpath($filepath), $mime, basename($filepath));

  $upload_fields = [
    'channel_id' => $channel_id,
    'files'      => $cfile
  ];

  $ch = curl_init($url);
  curl_setopt($ch, CURLOPT_POST, true);
  curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $upload_fields);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_VERBOSE, true);
  curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);

  $result = curl_exec($ch);
  $status = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  curl_close($ch);

  if($status != 201)
    throw new Exception("File failed with status: " . $status .", result: " . var_export($result, true));

  $result = json_decode($result, true);
  $file_id = $result['file_infos'][0]['id'];

  $post_fields['file_ids'] = array($file_id);
  return mattermost_send($server, $token, $channel_id, $title, $post_fields);
}

function mattermost_send_thread_with_replies($server, $token, $channel_id, $msg, array $replies, $fields = [])
{
  $mm_orig_resp = mattermost_send($server, $token, $channel_id, $msg, $fields);

  $root_key = 'id';
  if(!isset($mm_orig_resp[$root_key]))
  {
    echo "Failed to post to Mattermost: response contains no '$root_key' value to post thread replies:\n".json_encode($mm_orig_resp, JSON_PRETTY_PRINT)."\n"; 
    return null;
  }

  $root_id = $mm_orig_resp[$root_key];
  $fields['root_id'] = $root_id;

  foreach($replies as $reply)
    mattermost_send($server, $token, $channel_id, $reply, $fields); 

  return $root_id;
}