optimize startup and filter events

next_batch now is saved to account_data and retreived on the first start,
so we don't get already processed events during startup

additionally there now is a huge filter, which extracts only the
events+fields we really need. this prevents problems like e.g. account_data
feedback loops uneccessary syncs because ephemeral events

bot.ps1

@@ -5,13 +5,19 @@ param (
 
     [Parameter(Mandatory=$true)]
     [string]
-    $User,
+    $UserId,
 
     [Parameter(Mandatory=$true)]
     [securestring]
     $AccessToken
 )
 
+$account_data_type_prefix = 'de.lubiland.pingposh.'
+$account_data_types = @{
+    next_batch = $account_data_type_prefix+'next_batch'
+}
+
+
 function Send-MatrixEvent {
     param (
         [Parameter(Mandatory=$true)]
@@ -174,7 +180,7 @@ function Join-Pong {
         FormattedBody = $formatted_body
     }
 }
-function Open-MatrixEvent {
+function Open-Event {
     param (
         [Parameter(Mandatory=$true)]
         $Event,
@@ -195,11 +201,75 @@ function Open-MatrixEvent {
         Send-Pong -RoomId $RoomId @bodies -OriginHomeServer $origin_homeserver -Duration $difference.TotalMilliseconds -PingEventId $Event.event_id
     }
 }
-function Start-MatrixSync {
+function Get-MatrixAccountData {
+    param (
+        [Parameter(Mandatory=$true)]
+        [string]
+        $Type
+    )
+
+    $uri = '{0}/_matrix/client/r0/user/{1}/account_data/{2}' -f $HomeServer,$UserId,$Type
+
+    $header_splat = @{
+        Authentication = 'Bearer'
+        Token = $AccessToken
+        ContentType = 'application/json'
+    }
+    $http_splat = @{
+        Uri = $uri
+        Method = 'Get'
+    }
+
+    $response = Invoke-RestMethod @header_splat @http_splat
+    return $response
+}
+function Set-MatrixAccountData {
+    param (
+        [Parameter(Mandatory=$true)]
+        [string]
+        $Type,
+
+        [Parameter(Mandatory=$true)]
+        [System.Object]
+        $Content
+    )
+
+    $uri = '{0}/_matrix/client/r0/user/{1}/account_data/{2}' -f $HomeServer,$UserId,$Type
+
+    $header_splat = @{
+        Authentication = 'Bearer'
+        Token = $AccessToken
+        ContentType = 'application/json'
+    }
+    $http_splat = @{
+        Uri = $uri
+        Method = 'Put'
+        Body = $Content | ConvertTo-Json -Compress
+    }
+
+    Invoke-RestMethod @header_splat @http_splat | Out-Null
+}
+function Get-NextBatchToken {
+    $account_data = Get-MatrixAccountData -Type $account_data_types.next_batch
+    return $account_data.next_batch
+}
+function Set-NextBatchToken {
+    param (
+        [Parameter(Mandatory=$true)]
+        [string]
+        $Token
+    )
+
+    Set-MatrixAccountData -Type $account_data_types.next_batch -Content @{next_batch = $Token}
+}
+function Invoke-MatrixSync {
     param (
         [string]
         $Token,
 
+        [string]
+        $FilterId,
+
         [int]
         $Timeout = 30000
     )
@@ -208,6 +278,9 @@ function Start-MatrixSync {
     if($Token) {
         $uri += '&since={0}' -f $Token
     }
+    if($FilterId) {
+        $uri += '&filter={0}' -f $FilterId
+    }
 
     $header_splat = @{
         Authentication = 'Bearer'
@@ -225,17 +298,105 @@ function Start-MatrixSync {
     foreach($room_id in $room_ids) {
         $events = $response.rooms.join.$room_id.timeline.events
         foreach($event in $events) {
-            Open-MatrixEvent -Event $event -RoomId $room_id
+            Open-Event -Event $event -RoomId $room_id
         }
     }
 
-    Write-Output $response.next_batch
+    return $response.next_batch
+}
+function Get-MatrixFilterId {
+    param (
+        [System.Object]
+        $Filter
+    )
+
+    $uri = '{0}/_matrix/client/r0/user/{1}/filter' -f $HomeServer,$UserId
+
+    $header_splat = @{
+        Authentication = 'Bearer'
+        Token = $AccessToken
+        ContentType = 'application/json'
+    }
+    $http_splat = @{
+        Uri = $uri
+        Method = 'Post'
+        #a filter can be up to 3 layers deep according to spec
+        #https://matrix.org/docs/spec/client_server/r0.6.0#filtering
+        Body = $Filter | ConvertTo-Json -Compress -Depth 3
+    }
+
+    $response = Invoke-RestMethod @header_splat @http_splat
+
+    return $response.filter_id
+}
+function Get-FilterId {
+    $filter = @{
+        event_fields = @(
+            #all fields used in Open-Event
+            'event_id'
+            'sender'
+            'origin_server_ts'
+            'content.msgtype'
+            'content.body'
+        )
+        presence = @{
+            #we don't use presence information
+            types = @('invalid')
+        }
+        account_data = @{
+            #we only retrieve account_data via the account_data api endpoint
+            types = @('invalid')
+        }
+        room = @{
+            ephemeral = @{
+                #we don't use ephemeral events like typing or read receipts
+                types = @('invalid')
+            }
+            state = @{
+                #we don't use room state
+                types = @('invalid')
+            }
+            timeline = @{
+                #exclude ourself
+                not_senders = @(
+                    $UserId
+                )
+                types = @(
+                    #to receive !ping commands
+                    'm.room.message'
+                )
+            }
+            account_data = @{
+                #we don't use room specific account_data
+                types = @('invalid')
+            }
+        }
+    }
+
+    $filter_id = Get-MatrixFilterId -Filter $filter
+    return $filter_id
+}
+function Start-MatrixSync {
+    #get last used next_batch from account_data
+    $token = Get-NextBatchToken
+
+    #get /sync filter
+    $filter_id = Get-FilterId
+
+    Try {
+        #try first sync with the old token
+        $token = Invoke-MatrixSync -Token $token -FilterId $filter_id
+    } Catch {
+        #if it fails start a fresh sync reset $token
+        $token = $null
+    }
+
+    while($true) {
+        #use $token of the previous sync
+        Set-NextBatchToken -Token $token
+        $token = Invoke-MatrixSync -Token $token -FilterId $filter_id
+    }
 }
 
 
-#start sync loop
+Start-MatrixSync
-while($true) {
-    #use the token of the last sync
-    #initial token is $null
-    $token = Start-MatrixSync -Token $token
-}