program Schachdomino;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils;

const BOARD_SIZE = 8;

type TBoard = Array[1..BOARD_SIZE,1..BOARD_SIZE] of Integer;
type TResult = record
  possible:Boolean;
  field:TBoard;
  tryCount:Integer;
end;

const
  sLineBreak = {$IFDEF LINUX} AnsiChar(#10) {$ENDIF}
               {$IFDEF MSWINDOWS} AnsiString(#13#10) {$ENDIF};


var LogFile:TextFile;

// Write a board to console and log file
procedure WriteBoard(field:TBoard);
var
  S1: String;
  C1: Integer;
  C2: Integer;
begin
  S1:='[';
  for C2 := 1 to BOARD_SIZE do begin
    S1:=S1 + sLineBreak;
    for C1 := 1 to BOARD_SIZE do begin
      S1:=S1 + Format('%2d',[field[C1,C2]])+ ', ';
    end;
  end;
  S1:=S1 + ']';
  Writeln(S1);
  Writeln(logFile,S1);
end;

// Write placing a brick at a given position and check if it is still possible
// to fill the remaining free space of the board
function tryBrick(posX,posY:Integer; field:TBoard; TryCount:Integer; BrickNum:Integer):TResult;
var
  nextBrickX: Integer;
  nextBrickY: Integer;
  newField: TBoard;
  resultRight: TResult;
  resultBot: TResult;
  rightPossible: Boolean;
  botPossible: Boolean;
begin
  if (posX=BOARD_SIZE) and (posY=BOARD_SIZE) then begin
    result.possible:=True;
    result.field:=field;
    result.tryCount:=TryCount+1;
    Exit;
  end;

  if posX = BOARD_SIZE then begin
    nextBrickX:=1;
    nextBrickY:=posY+1;
  end else begin
    nextBrickX:=posX+1;
    nextBrickY:=posY;
  end;

  Result.possible:=false;
  Result.tryCount:=TryCount;

  if field[posX,posY]<>0 then begin
    Result:=tryBrick(nextBrickX,nextBrickY,field,TryCount,BrickNum);
    Exit;
  end else begin
    //rechts
    rightPossible:=((posX+2<=BOARD_SIZE-1) or ((posY<=BOARD_SIZE-1) and (posX+2<=BOARD_SIZE)))
      and (field[posX+1,posY]=0)
      and (field[posX+2,posY]=0);
    if rightPossible then begin
      newField:=field;
      newField[posX,posY]:=BrickNum;
      newField[posX+1,posY]:=BrickNum;
      newField[posX+2,posY]:=BrickNum;
      resultRight:=tryBrick(nextBrickX,nextBrickY,newField,Result.tryCount,BrickNum+1);
      Result.tryCount:=resultRight.tryCount;
      if resultRight.possible then begin
        Result:=resultRight;
        Exit;
      end
    end;

    //unten
    botPossible:=((posY+2<=BOARD_SIZE-1) or ((posX<=BOARD_SIZE-1) and (posY+2<=BOARD_SIZE)))
      {and (field[posX,posY+1]=0)  //always true
      and (field[posX,posY+2]=0)};
    if botPossible then begin
      newField:=field;
      newField[posX,posY]:=BrickNum;
      newField[posX,posY+1]:=BrickNum;
      newField[posX,posY+2]:=BrickNum;
      resultBot:=tryBrick(nextBrickX,nextBrickY,newField,Result.tryCount,BrickNum+1);
      Result.tryCount:=resultBot.tryCount;
      Result.possible:=resultBot.possible;
      if resultBot.possible then begin
        Result:=resultBot;
        Exit;
      end
    end;
  end;

  if not rightPossible and not botPossible then begin
    result.tryCount:=result.tryCount+1;
    Writeln('Try No. ' + IntToStr(result.TryCount) + ':');
    Writeln(logFile, 'Try No. ' + IntToStr(result.TryCount) + ':');
    WriteBoard(field);
  end;
end;

// Write a result to console and log file
procedure WriteResult(result:TResult);
var
  C1: Integer;
  C2: Integer;
  S1: string;
begin
  if result.possible then begin
    Writeln('It is possible to fill this board.');
    Writeln(LogFile, 'It is possible to fill this board.');
    Writeln('This is the result:');
    Writeln(LogFile, 'This is the result:');
    WriteBoard(result.field);
  end else begin
    Writeln('It is not possible to fill this board.');
    Writeln(LogFile, 'It is not possible to fill this board.');
  end;
  Writeln('Program finished after '+IntToStr(result.tryCount) + ' tries. A log has been written to log.txt');
  Writeln(LogFile, 'Program finished after '+IntToStr(result.tryCount) + ' tries. A log has been written to log.txt');
  ReadLn;
end;


// main program
var
  Field: TBoard;
  result:TResult;
begin
  AssignFile(logFile, 'log.txt');
  ReWrite(logFile);

  result := tryBrick(1,1,Field,0,1);
  WriteResult(result);

  CloseFile(logFile);
end.