Added error handling for missing data files

README.md

@@ -6,7 +6,7 @@ This is a single command line application for all puzzles written in [FreePascal
 
 ## Puzzle Input
 
-This project does not contain the puzzle or example inputs as per the [copyright notice of Advent of Code](https://adventofcode.com/about).
+This project does not contain the puzzle or example inputs as per the [copyright notice of Advent of Code](https://adventofcode.com/about). In order to run the compiled application, the puzzle inputs have to be downloaded from the [Advent of Code 2023](https://adventofcode.com/2023/) puzzle pages, and placed as text files into the `bin\data` directory. The application will output an error with details, if it cannot find an input file.
 
 ## Day 1: Trebuchet?!
 

USolver.pas

@@ -69,6 +69,7 @@ type
     procedure ProcessData(const ASolver: ISolver);
     procedure Run(const ASolver: ISolver);
     procedure RunAndFree(const ASolver: ISolver);
+    function GetDataFileName(const ASolver: ISolver): string;
   end;
 
 implementation
@@ -105,7 +106,7 @@ var
 begin
   ASolver.Init;
 
-  AssignFile(data, ConcatPaths([FRelativeDataPath, ASolver.DataFileName]));
+  AssignFile(data, GetDataFileName(ASolver));
   try
     reset(data);
     while (not EOF(data)) do
@@ -121,12 +122,22 @@ begin
 end;
 
 procedure TSolverEngine.Run(const ASolver: ISolver);
+var
+  fileName: string;
 begin
   WriteLn;
   WriteLn('--- ', ASolver.PuzzleName, ' ---');
-  ProcessData(ASolver);
-  WriteLn('Part 1: ', ASolver.ResultPart1);
-  WriteLn('Part 2: ', ASolver.ResultPart2);
+  fileName := GetDataFileName(ASolver);
+  if FileExists(fileName) then
+  begin
+    ProcessData(ASolver);
+    WriteLn('Part 1: ', ASolver.ResultPart1);
+    WriteLn('Part 2: ', ASolver.ResultPart2);
+  end
+  else begin
+    WriteLn('Cannot find puzzle input file ''', ExpandFileName(fileName), '''.');
+    WriteLn('Please download the file content from https://adventofcode.com/2023/');
+  end;
 end;
 
 procedure TSolverEngine.RunAndFree(const ASolver: ISolver);
@@ -135,5 +146,10 @@ begin
   ASolver.Free;
 end;
 
+function TSolverEngine.GetDataFileName(const ASolver: ISolver): string;
+begin
+  Result := ConcatPaths([FRelativeDataPath, ASolver.DataFileName]);
+end;
+
 end.
 

tests/UBaseTestCases.pas

@@ -72,9 +72,15 @@ end;
 { TEngineBaseTest }
 
 procedure TEngineBaseTest.Setup;
+var
+  fileName: string;
 begin
   inherited Setup;
   FEngine := TSolverEngine.Create(GetDataPath);
+  fileName := FEngine.GetDataFileName(FSolver);
+  AssertTrue('Cannot find puzzle input file ''' + ExpandFileName(fileName) + '''. '
+    + 'Please download the file from https://adventofcode.com/2023/',
+    FileExists(fileName));
   FEngine.ProcessData(FSolver);
 end;