Update architecture documentation

* Update architecture documentation

docs/client-architecture.md

@@ -46,6 +46,9 @@ The diagrams below show the high level process flow and decision making when run
 ### Processing a potentially changed local item
 ![applyPotentiallyChangedItem](./puml/applyPotentiallyChangedItem.png)
 
+### Download a file
+![downloadFile](./puml/downloadFile.png)
+
 ### Determining if an 'item' is syncronised between Microsoft OneDrive and the local file system
 ![Item Sync Determination](./puml/is_item_in_sync.png)
 
@@ -93,7 +96,7 @@ Due to this factor, when using `--resync` the online source is always going to b
 
 ## Client Functional Component Architecture Relationships
 
-The diagram below shows the functional relationship of application code components, and how these relate to each relevant code module within this application:
+The diagram below shows the main functional relationship of application code components, and how these relate to each relevant code module within this application:
 
 ![Functional Code Components](./puml/code_functional_component_relationships.png)
 

docs/puml/downloadFile.puml

@@ -0,0 +1,63 @@
+@startuml
+start
+
+partition "Download File" {
+
+  :Get item specifics from JSON;
+  :Calculate item's path;
+  
+  if (Is item malware?) then (yes)
+      :Log malware detected;
+      stop
+  else (no)
+      :Check for file size in JSON;
+      if (File size missing) then (yes)
+          :Log error;
+          stop
+      endif
+      
+      :Configure hashes for comparison;
+      if (Hashes missing) then (yes)
+          :Log error;
+          stop
+      endif
+      
+      if (Does file exist locally?) then (yes)
+          :Check DB for item;
+          if (DB hash match?) then (no)
+              :Log modification; Perform safe backup;
+              note left: Local data loss prevention
+          endif
+      endif
+      
+      :Check local disk space;
+      if (Insufficient space?) then (yes)
+          :Log insufficient space;
+          stop
+      else (no)
+          if (Dry run?) then (yes)
+              :Fake download process;
+          else (no)
+              :Attempt to download file;
+              if (Download exception occurs?) then (yes)
+                  :Handle exceptions; Retry download or log error;
+              endif
+              
+              if (File downloaded successfully?) then (yes)
+                  :Validate download;
+                  if (Validation passes?) then (yes)
+                      :Log success; Update DB;
+                  else (no)
+                      :Log validation failure; Remove file;
+                  endif
+              else (no)
+                  :Log download failed;
+              endif
+          endif
+      endif
+  endif
+
+}
+
+stop
+@enduml

docs/puml/main_activity_flows.puml

@@ -9,7 +9,7 @@ note right: Query Microsoft OneDrive /delta API
 :Receive JSON responses;
 
 :Process JSON Responses;
-partition "Process JSON Responses" {
+partition "Process /delta JSON Responses" {
     while (for each JSON response) is (yes)
         :Determine if JSON is 'root'\nor 'deleted' item;
         if ('root' or 'deleted') then (yes)
@@ -30,7 +30,6 @@ partition "Process JSON Responses" {
                 :Discard JSON;
             else (no)
                 :Process JSON (create dir/download file);
-                
                 if (Is the 'JSON' item in the local cache) then (yes)
                   :Process JSON as a potentially changed local item;
                   note left: Run 'applyPotentiallyChangedItem' function
@@ -38,25 +37,28 @@ partition "Process JSON Responses" {
                   :Process JSON as potentially new local item;
                   note right:  Run 'applyPotentiallyNewLocalItem' function
                 endif
-                
                 :Process objects in download queue;
+                :Download File;
+                note left: Download file from Microsoft OneDrive (Multi Threaded Download)
                 :Save in local database cache;
             endif
         endif
     endwhile
 }
 
-:Process local cache database\nto check local data integrity and for differences;
-if (difference found) then (yes)
-    :Upload file/folder change including deletion;
-    note right: Upload to Microsoft OneDrive
-    :Receive response with item metadata;
-    :Save response to local cache database;
-else (no)
-endif
+partition "Perform data integrity check based on local cache database" {
+  :Process local cache database\nto check local data integrity and for differences;
+  if (difference found) then (yes)
+      :Upload file/folder change including deletion;
+      note right: Upload local change to Microsoft OneDrive
+      :Receive response with item metadata;
+      :Save response to local cache database;
+  else (no)
+  endif
+}
 
-:Scan local filesystem\nfor new files/folders;
 partition "Local Filesystem Scanning" {
+  :Scan local filesystem\nfor new files/folders;
     while (for each new item) is (yes)
         :Check item against 'Client Side Filtering' rules;
         if (item passes filtering) then (yes)
@@ -70,9 +72,10 @@ partition "Local Filesystem Scanning" {
     endwhile
 }
 
-:Query /delta link for true-up;
-note right: Final Data True-Up
-:Process further online JSON changes if required;
-
+partition "Final True-Up" {
+  :Query /delta link for true-up;
+  note right: Final Data True-Up
+  :Process further online JSON changes if required;
+}
 stop
 @enduml