auto join on invite

fixes #3

this adds m.room.member to the StateFilter and introduces the function
Join-MatrixRoom
it also introduces an additional hook in Invoke-MatrixSync

bot.ps1

@@ -11,6 +11,7 @@ param (
     [securestring]
     $AccessToken
 )
+$ErrorActionPreference = 'Stop'
 
 $account_data_type_prefix = 'de.lubiland.pingposh.'
 $account_data_types = @{
@@ -180,7 +181,7 @@ function Join-Pong {
         FormattedBody = $formatted_body
     }
 }
-function Open-Event {
+function Open-JoinEvent {
     param (
         [Parameter(Mandatory=$true)]
         $Event,
@@ -201,6 +202,31 @@ function Open-Event {
         Send-Pong -RoomId $RoomId @bodies -OriginHomeServer $origin_homeserver -Duration $difference.TotalMilliseconds -PingEventId $Event.event_id
     }
 }
+function Join-MatrixRoom {
+    param (
+        [Parameter(Mandatory=$true)]
+        $RoomId
+    )
+
+    $uri = '{0}/_matrix/client/r0/rooms/{1}/join' -f $HomeServer,$RoomId
+
+    $header_splat = @{
+        Authentication = 'Bearer'
+        Token = $AccessToken
+        ContentType = 'application/json'
+    }
+    $http_splat = @{
+        Uri = $uri
+        Method = 'Post'
+    }
+
+    $response = Invoke-RestMethod @header_splat @http_splat
+    if($response.room_id) {
+        Write-Host ('Joined room {0}' -f $RoomId)
+    } else {
+        Write-Error ('Error joining room {0}: {1}' -f $RoomId,$response.error)
+    }
+}
 function Get-MatrixAccountData {
     param (
         [Parameter(Mandatory=$true)]
@@ -298,7 +324,16 @@ function Invoke-MatrixSync {
     foreach($room_id in $room_ids) {
         $events = $response.rooms.join.$room_id.timeline.events
         foreach($event in $events) {
-            Open-Event -Event $event -RoomId $room_id
+            Open-JoinEvent -Event $event -RoomId $room_id
+        }
+    }
+
+    #.PSObject.Properties because the rooms under .invite are [NoteProperty]
+    $room_ids = $response.rooms.invite.PSObject.Properties.Name
+    foreach($room_id in $room_ids) {
+        $invites = $response.rooms.invite.$room_id.invite_state.events | Where-Object {$_.content.join_rule -eq 'invite'}
+        foreach($invite in $invites) {
+            Join-MatrixRoom -RoomId $room_id
         }
     }
 
@@ -332,12 +367,13 @@ function Get-MatrixFilterId {
 function Get-FilterId {
     $filter = @{
         event_fields = @(
-            #all fields used in Open-Event
+            #all fields used in Open-JoinEvent
             'event_id'
             'sender'
             'origin_server_ts'
             'content.msgtype'
             'content.body'
+            #'content.membership' #invites only
         )
         presence = @{
             #we don't use presence information
@@ -353,8 +389,11 @@ function Get-FilterId {
                 types = @('invalid')
             }
             state = @{
-                #we don't use room state
-                types = @('invalid')
+                types = @(
+                    #to receive invites
+                    'm.room.member'
+                )
+                lazy_load_members = $true
             }
             timeline = @{
                 #exclude ourself