Add help to command line arguments

downloader.pas

@@ -1,6 +1,6 @@
 program downloader;
 
-uses fphttpclient, base64, opensslsockets, fpjson, jsonparser, SysUtils, process, Classes, libtar, CustApp;
+uses fphttpclient, base64, opensslsockets, fpjson, jsonparser, SysUtils, process, Classes, libtar, CustApp, Math;
 
 var
   gameId: Integer;
@@ -140,10 +140,55 @@ begin
   end;
 end;
 
+procedure displayHelp;
+const
+  optionFlags: TStringArray = (
+                '-h, --help',
+                '-g, --gameid <game id>',
+                '-u, --username <username>',
+                '-p, --password <password>');
+  optionDescriptions: TStringArray = (
+                       'Display help.',
+                       'Sets the game id. This is required.',
+                       'Sets the username for authentication.',
+                       'Sets the password for authentication.');
+
+var
+  i, lenFlag, lenDesc, maxLenFlag, maxLenDesc, minLenFlag, minLenDesc: Integer;
+
+begin
+  maxLenFlag := 0;
+  maxLenDesc := 0;
+  minLenFlag := 1000;
+  minLenDesc := 1000;
+  for i := 0 to Length(optionFlags)-1 do
+  begin
+    minLenFlag := Min(minLenFlag, Length(optionFlags[i]));
+    maxLenFlag := Max(maxLenFlag, Length(optionFlags[i]));
+    minLenDesc := Min(minLenDesc, Length(optionDescriptions[i]));
+    maxLenDesc := Max(maxLenDesc, Length(optionDescriptions[i]));
+  end;
+  WriteLn('Usage: downloader.exe [options]');
+  WriteLn;
+  WriteLn('Options:');
+  for i := 0 to Length(optionFLags)-1 do
+  begin
+    lenFlag := Length(optionFLags[i]);
+    lenDesc := Length(optionDescriptions[i]);
+    Write(optionFlags[i]:(lenFlag+2));
+    WriteLn(optionDescriptions[i]:(lenDesc+maxLenFlag-lenFlag+2))
+  end;
+end;
+
 begin
   app := TCustomApplication.Create(nil);
-  errorMsg := app.checkOptions('g:u:p:', 'gameid: username: password:');
+  errorMsg := app.checkOptions('hg:u:p:', 'help gameid: username: password:');
-  if (errorMsg = '') then
+  if (errorMsg <> '') or app.HasOption('h', 'help') then
+  begin
+    WriteLn(errorMsg);
+    displayHelp;
+  end
+  else
   begin
     if app.HasOption('g', 'gameid') then
     begin
@@ -172,10 +217,6 @@ begin
     begin
       WriteLn('No game id was given');
     end;
-  end
-  else
-  begin
-    WriteLn(errorMsg);
   end;
 end.