====== Matrix On The Command Line  ======
===== Documentation =====
  * https://matrix.org/docs/api/client-server/#/
  * https://matrix.org/docs/spec/
===== Getting your access token =====
  * Using Riot (that's whats running on https://matrix.glasgow.social) - Click on your profile name at the top left corner and select ''Settings''
  * Click ''Help & About'' from the list then scroll down to the 'Advanced' section.
  * You should see the bottom line that reads ''Access Token <click to reveal>''
  * Copy and paste that into the example below

===== Getting a room ID =====
  * Click on the three dots at the edge of a room name and click ''Settings''
  * Choose ''Advanced'' to see the ''Internal Room ID''
  * #opensource on the server is ''!uVhYeryxRiaOwTlATT:glasgow.social''

===== Posting messages to a room =====
It can be very simple to post a message to a room on Matrix (note: you have to be a member of the room).
==== Via bash/curl ====
This script requires ''jq'', the command line JSON processor.
<code bash>
sudo apt install jq
</code>

<file bash post_to_matrix.sh>
#!/bin/bash
# Usage:
# echo "Hello world" | ./post_to_matrix.sh
msgtype=m.text
homeserver=glasgow.social
room=!BOrDFgeDdZZbUvfjjs:glasgow.social
access_token=put_your_user_access_token_here

curl -XPOST -d "$( jq -Rsc --arg msgtype "$msgtype" '{$msgtype, body:.}')" "https://$homeserver/_matrix/client/r0/rooms/$room/send/m.room.message?access_token=$access_token"
</file>

==== PHP example using Curl ====
<file php post_to_matrix.php>
<?php
$msgtype = "m.text";
$homeserver = "glasgow.social";
$room = "!BOrDFgeDdZZbUvfjjs:glasgow.social";
$access_token="put_your_user_access_token_here"
$url = "https://$homeserver/_matrix/client/r0/rooms/$room/send/m.room.message?access_token=$access_token";

$msg = "Hello world";

$payload = json_encode(array("msgtype"=>$msgtype, "body"=>$msg));

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
$response = curl_exec($ch);

?>
</file>

===== Listening to rooms =====
This is pretty straightforward.  This is just how to see messages that are posted, but if you explore what is returned then you can see all sorts of things too (like joins, images, likes, invites etc).  I run something like this on a terminal so I can see what's going on in all my rooms at a glance.  Very cool.

<code bash get_messages.sh>
#!/bin/bash
# Usage:
# ./get_messages.sh
msgtype=m.text
homeserver=glasgow.social
room=room_id_here
access_token=your_access_token_here
from=start_point_goes_here

curl -XGET "https://$homeserver/_matrix/client/r0/rooms/$room/messages?access_token=$access_token&from=$from"
</code>

<code php ListenToMatrix.php>
<?php
$homeserver = "glasgow.social";
$access_token = "access_token_goes_here";

// this is so you can start and stop the program, and it'll continue where it left off
$tracking_file "/tmp/listen_matrix.json";

while(true) {
$since = file_get_contents($tracking_file);
$messages = get_new_events($since);
if(!empty($messages['rooms']['join'] and is_array($messages['rooms']['join']))) {
   foreach($messages['rooms']['join'] as $room_id=>$data) {
      foreach($data['timeline']['events'] as $event_id=>$event) {
         if($event['type'] == "m.room.message") {
            $sender = $event['sender'];
            $content = "not text";
            if($event['content']['msgtype'] == "m.text")
               $content = $event['content']['body'];
            echo "$sender $room_id $content\n";
         }
      }
   }
}
$new_tracking_data = $messages['next_batch'];
file_put_contents($tracking_file, $new_tracking_data);
}

function get_new_events($since) {
   global $homeserver,$access_token;
   // timeout means the server will wait and only respond after 30 seconds, 
   // however if a message is returned before that time, it will return immediately
   $url = "https://$homeserver/_matrix/client/r0/sync?access_token=$access_token&timeout=30000";
   if(!empty($since))
      $url .= "&since=$since";
   $data = json_decode(file_get_contents($url), true);
   return $data;
}


?>
</code>

You can follow one particular room just using GET requests, by doing something like this:

<code php>
function get_new_events($room) {
   $homeserver = "glasgow.social";
   $access_token = "access_token_goes_here"
   $url = "https://$homeserver/_matrix/client/r0/rooms/$room/messages?access_token=$access_token&from=$tracking_id";
   $data = json_decode(file_get_contents($url), true);
   return $data;
}
</code>

===== Matrix Bot =====
The basis of my bot's interaction with Matrix is bascially the above code.  Replace the echo line with with whatever you want to do (in my case, I look up a list of rules [i.e. pairs of regexes and their response functions] I use in IRC from a database and act accordingly). 

===== Posting images to a room =====
Media must first be uploaded to your homeserver, then you can send a new message, as above, using the ''m.image'' event type.  Here is an example in PHP that works as a 'copy' command.
<code php matrix_cp.php>
#!/usr/bin/php
# Usage example: matrix_cp /tmp/test.jpg glasgow
# this will send the test.jpg to the glasgow room
# this also supports remote URLs
<?php
$usage = "Usage: ".$argv[0]." filename room_name alt_text[optional]\n";
$filename = "";
$room_name = "#pythia";
$alt_text = "Image attachment";
$homeserver = "glasgow.social";
$access_token = "access_token_goes_here"
// I have a lookup list of friendly room names to full IDs here
$channels["glasgow"] = "!BOrDFgeDdZZbUvfjjs:glasgow.social";

if(!empty($argv[2]))
   $room_name = $argv[2];
if(!empty($argv[3]))
   $alt_text = $argv[3];

$room = $channels[$room_name];
if(empty($room))
   die($room_name." not in room list");

if(empty($argv[1]))
   die("Filename is required. $usage");

$filename = $argv[1];
$image_data = file_get_contents($filename);

// this whole temporary file saving is all done to support mime_type lookups for remote URLs
$tmp_filename = "/tmp/".md5($argv[0].time());

if(empty($image_data))
   die("Unable to read file location");
file_put_contents($tmp_filename, $image_data);
$mime_type = mime_content_type($tmp_filename);

$url = "https://$homeserver/_matrix/media/r0/upload?access_token=$access_token";
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: $mime_type"));
curl_setopt($ch, CURLOPT_POSTFIELDS, $image_data);
$response = curl_exec($ch);

if(!empty($response_json['content_uri'])) {
      $url = "https://$homeserver/_matrix/client/r0/rooms/$room/send/m.room.message?access_token=$access_token";
      $msgtype = "m.image";
      $mxc_url = $response_json['content_uri'];
      $ch = curl_init($url);
      $payload = json_encode(array("msgtype"=>$msgtype, "body"=>$alt_text, "url"=>$mxc_url));
      curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
      curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
      $response = curl_exec($ch);
      // SUCCESS.  No output.
   } else {
      echo "Error uploading $filename. ";
      echo implode(" : ", $response_json)."\n";
   }
</code>

You can copy this file to your bin directory and use it on the command line with:

<code bash>
matrix_cp /tmp/example.jpg glasgow "This is an example image"
</code>

====== Setting up a Matrix Server =====
The most feature rich server for Matrix is the Matrix.org Foundation's own [[https://github.com/matrix-org/synapse/|Synapse server]].

You can read installation instructions here: https://github.com/matrix-org/synapse/blob/master/INSTALL.md

The basic steps for a Debian/Ubuntu machine are:

<code bash>
sudo apt-get install build-essential python3-dev libffi-dev python3-pip python3-setuptools sqlite3 libssl-dev virtualenv libjpeg-dev libxslt1-dev
</code>

<code bash>
sudo apt install -y lsb-release wget apt-transport-https
sudo wget -O /usr/share/keyrings/matrix-org-archive-keyring.gpg https://packages.matrix.org/debian/matrix-org-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/matrix-org-archive-keyring.gpg] https://packages.matrix.org/debian/ $(lsb_release -cs) main" |
    sudo tee /etc/apt/sources.list.d/matrix-org.list
sudo apt update
sudo apt install matrix-synapse-py3
</code>

Then just edit your ''/etc/matrix-synapse/homeserver.yaml'' file and set your SSL certifcate, host name and port.