(*
 * dodge
 * You are in a 30 x 15 square. There are 6 attackers, one tank,
 * and you. If you hit one of the attackers (or the tank), you
 * are destroyed. If two attackers hit each other, they are randomly
 * put somewhere else. If an attacker hits the tank, then the
 * attacker is destroyed. As an added bonus, there are 15 mines
 * in the square (and the border of the square). If you hit a mine
 * you are destroyed. If an attacker hits a mine, then the attacker
 * is destroyed. Your object is to destroy the 6 attackers.
 *
 * You can move by:
 *     812
 *     703
 *     654
 *
 * Note that 0 leaves you in the same place. A move of 9 will put you
 * in some random place on the square (even on a mine)
 *)

program dodge(input, output);

const
   numattackers = 6;   (* number of attackers *)
   length       = 30;  (* length of playing field *)
   width        = 15;  (* width of playing field *)
   numines      = 15;  (* number of mines *)
   ninemax      = 2;   (* number of times the 9 escape can be used *)

type
   (* what can be at a location *)
   what = (me,attacker,tank,mine,nothing);

   xindex = 0..length;
   yindex = 0..width;

   (* directions something can move *)
   direction = (stay,n,ne,e,se,s,sw,w,nw,nowhere);

   (* the location of an object *)
   loc = record
      xcord : xindex;
      ycord : yindex
   end;

var
   (* the playing field *)
   square : array[1..width,1..length] of what;

   tankloc: loc;
   myloc  : loc;
   atack  : array[1..numattackers] of loc;

   ch     : char;
   left   : 0..numattackers;
   nines  : 0..ninemax;
   saydir : direction;

procedure saywhat;
begin
   write('x = ',myloc.xcord,', y = ',myloc.ycord,', dir = ');
   case saydir of
      n    : writeln('n');
      s    : writeln('s');
      e    : writeln('e');
      w    : writeln('w');
      ne   : writeln('ne');
      nw   : writeln('nw');
      se   : writeln('se');
      sw   : writeln('sw');
      stay : writeln('stay');
      nowhere: writeln('nothing');
   end;
end;


(*
 * makeboard
 * creates the board and place every thing in at random places
 *)

procedure makeboard;

var
   placed : integer;
   xloc   : xindex;
   yloc   : yindex;
   i,j    : integer;

begin
   nines := ninemax;
   for i := 1 to width do
      for j := 1 to length do
         square[i][j] := nothing;
   left := numattackers;

   for i := 1 to length do
   begin
      square[1][i] := mine;
      square[width][i] := mine
   end;

   for i := 1 to width do
   begin
      square[i][1] := mine;
      square[i][length] := mine
   end;

   placed := 0;
   while placed < numines do
   begin
      xloc := 1 + random(length);
      yloc := 1 + random(width);
      if square[yloc][xloc] = nothing then
         begin
            square[yloc][xloc] := mine;
            placed := placed + 1
         end
   end;

   placed := 1;

   while placed <= numattackers do
   begin
      xloc := 1 + random(length);
      yloc := 1 + random(width);
      if square[yloc][xloc] = nothing then
      begin
         square[yloc][xloc] := attacker;
         atack[placed].xcord := xloc;
         atack[placed].ycord := yloc;
         placed := placed + 1
      end
   end;

   while square[yloc][xloc] <> nothing do
   begin
      xloc := 1 + random(length);
      yloc := 1 + random(width)
   end;
   square[yloc][xloc] := tank;
   tankloc.xcord := xloc;
   tankloc.ycord := yloc;

   while square[yloc][xloc] <> nothing do
   begin
      xloc := 1 + random(length);
      yloc := 1 + random(width)
   end;
   square[yloc][xloc] := me;
   myloc.xcord := xloc;
   myloc.ycord := yloc;
end;

(*
 * print
 * print out the field
 *)

procedure print;

var
   i : xindex;
   j : yindex;

begin
   for j := 1 to width do
   begin
      for i := 1 to length do
         case square[j][i] of
            me : write('*');
            tank : write('T');
            attacker : write('$');
            mine : write('X');
            nothing : write(' ')
         end;
      writeln
   end
end;

(*
 * move
 * attempt to move something from curx,cury in the direction
 * indicated. returns what was on the location.
 *)

function move(var curx:xindex;var cury:yindex;where:direction): what;

begin
   case where of
     n   : cury := cury - 1;
     stay: ;
     s   : cury := cury + 1;
     w   : curx := curx - 1;
     e   : curx := curx + 1;
     nw  : begin
              curx := curx - 1;
              cury := cury - 1
           end;
     sw  : begin
              curx := curx - 1;
              cury := cury + 1
           end;
     ne  : begin
              curx := curx + 1;
              cury := cury - 1
           end;
     se  : begin
              curx := curx + 1;
              cury := cury + 1
           end
  end;

  move := square[cury][curx]
end;

(*
 * ask
 * ask the user where he wants to go, then attempt to go there.
 * returns what the player lands on.
 *)

function ask:what;

var
   command:array['0'..'9'] of direction;
   dir    : direction;
   ch     : char;

begin
   (* init the commands *)
   dir := stay;
   for ch := '0' to '9' do
   begin
      command[ch] := dir;
      dir := succ(dir)
   end;

   write('Direction? ');
   readln(ch);
   if not (ch in ['0'..'9']) or ((ch = '9') and (nines = 0)) then
   begin
      writeln('How is that? ');
      ask := ask
   end

   else
   begin
      square[myloc.ycord][myloc.xcord] := nothing;
      (* on a command of '9', relocate yourself randomly *)
      if ch = '9' then
      begin
         nines := nines - 1;
         myloc.ycord := 1 + random(width);
         myloc.xcord := 1 + random(length);
         ch := '0'
      end;
      saydir := command[ch];
      ask := move(myloc.xcord,myloc.ycord,command[ch]);
      square[myloc.ycord][myloc.xcord] := me
   end
end;

(*
 * moveall
 * moves all the attackers around, and the tank *)

procedure moveall;


var
   i   : 1..numattackers;   (* index used to run through all attackers *)

(*
 * which
 * given a loc, it decides which direction to go so as to come closer
 * to you. returns the direction.
 *)

function which(curr : loc):direction;

var
   xdir,
   ydir : direction;

begin
   xdir := stay;
   ydir := stay;

   if myloc.xcord > curr.xcord then
      xdir := e
   else
      if myloc.xcord < curr.xcord then
         xdir := w;

   if myloc.ycord > curr.ycord then
      ydir := s
   else
      if myloc.ycord < curr.ycord then
         ydir := n;

   if (xdir = stay) or (ydir = stay) then
   begin
      if xdir = stay then
         which := ydir
      else
         which := xdir
      end
   else
   begin
      case xdir of
         w: if ydir = n then
               which := nw
            else
               which := sw;
         e: if ydir = n then
               which := ne
            else
               which := se;
      end
   end
end;

(*
 * checkmove
 * checks to see what happens to an attacker when it is moved
 *)

procedure checkmove(i : integer; dir : what);

var
   remember,
   index     : 1..numattackers;

begin
   case dir of
      nothing : square[atack[i].ycord][atack[i].xcord] := attacker;

      tank    : begin
                   writeln('The tank just destroyed an attacker');
                   atack[i].xcord := 0;
                   left := left - 1
                end;
      me      : begin
                   writeln('You just died!!!');
                   myloc.xcord := 0
                end;
      attacker: begin
                   (* find out which attacker we hit *)

                   for index := 1 to numattackers do
                      if (atack[i].xcord = atack[index].xcord) and
                         (atack[i].ycord = atack[index].ycord) and
                         (i <> index) then
                            remember := index;
                   writeln('Two attackers just collided!');

                   (* remove it from the field *)
                   square[atack[remember].ycord][atack[remember].xcord] := nothing;

                   (* choose a random spot for the first attacker *)
                   atack[i].xcord := 1 + random(length);
                   atack[i].ycord := 1 + random(width);

                   (* move the attacker *)
                   checkmove(i,move(atack[i].xcord,atack[i].ycord,which(atack[i])));

                   (* repeat the same with the other attacker *)
                   atack[remember].xcord := 1 + random(length);
                   atack[remember].ycord := 1 + random(width);
                   checkmove(remember,move(atack[remember].xcord,
                             atack[remember].ycord,which(atack[remember])));
                end;
      mine    : begin
                   writeln('An attacker just hit a mine.');
                   atack[i].xcord := 0;
                   left := left - 1
                end
   end;
end;

begin
   (* for each attacker, if he is still alive, move him toward you *)

   for i := 1 to numattackers do
   begin
      if atack[i].xcord <> 0 then
      begin
         square[atack[i].ycord][atack[i].xcord] := nothing;
         checkmove(i,move(atack[i].xcord,atack[i].ycord,which(atack[i])))
      end
   end;

   (* move the tank, note that the tank will destroy anything in its way
    * (including mines) *)

   square[tankloc.ycord][tankloc.xcord] := nothing;

   case move(tankloc.xcord,tankloc.ycord,which(tankloc)) of
      attacker : begin
                    writeln('The tank just destroyed an attacker');
                    left := left - 1;
                    for i := 1 to numattackers do
                       if (atack[i].xcord = tankloc.xcord) and
                          (atack[i].ycord = tankloc.ycord) then
                             atack[i].xcord := 0
                 end;

      mine     : writeln('The tank just destroyed a mine');

      me       : begin
                    writeln('The tank just destroyed you');
                    myloc.xcord := 0
                 end;

      nothing  :

   end;
   square[tankloc.ycord][tankloc.xcord] := tank
end;

(*
 * inst
 * prints out the instructions
 *)

procedure inst;

begin
   writeln('     Dodge');
   writeln(' You are in a 30 x 15 square. There are ',numattackers:1,' attackers,');
   writeln(' one tank, and you. If you hit one of the attackers (or the tank)');
   writeln(' you are destroyed. If two attackers hit each other, they are');
   writeln(' randomly put somewhere else. If an attacker hits the tank, then');
   writeln(' the attacker is destroyed. As an added bonus, there are ',numines);
   writeln(' mines in the square (and the border of the square). If you hit');
   writeln(' a mine, you are destroyed. If an attacker hits a mine, then the');
   writeln(' attacker is destroyed. Your object is to destroy the attackers.');
   writeln;
   writeln(' You can move by:');
   writeln('     812');
   writeln('     703');
   writeln('     654');
   writeln(' Note that a 0 leaves you in the same place. A move of 9 will');
   writeln(' put you in some random place on the square (even on a mine).');
   writeln;
   readln(ch);
end;

(* dodge *)

begin
   write('Want instructions? ');
   readln(ch);
   if (ch = 'y') or (ch = 'Y') then
      inst;


   repeat
      randomize;

      makeboard;
      print;
      while (myloc.xcord <> 0) and (left > 0) do
      begin
         (* test to see if you killed yourself *)
         if ask <> nothing then
            myloc.xcord := 0
         else
         begin
            moveall;
            print
         end;
         writeln;
      end;

      if myloc.xcord = 0 then
         writeln('Well, you got yourself killed!!!')
      else
         writeln('Congratulations, you did it!!!');

      writeln;
      write('Want to try again? ');
      readln(ch)
   until (ch <> 'y') and (ch <> 'Y');

end.