fixed position command bug

src/main.zig

@@ -53,7 +53,7 @@ fn uciPos(str: []const u8, alloc: std.mem.Allocator) *types.game {
     if (std.mem.eql(u8, tok, "fen")) return fenGame(str[pos..], alloc);
     if (std.mem.eql(u8, tok, "startpos")) {
         var game = fenGame("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1", alloc);
-        game = mov.playMoves(game, str[pos..]);
+        game = mov.playMoves(game, str[(pos)..]);
         return game;
     }
     return fenGame("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1", alloc); //this should be an error
@@ -95,7 +95,7 @@ fn uciGo(game: *types.game, alloc: std.mem.Allocator) []u8 {
     const str = alloc.alloc(u8, 5) catch unreachable;
     mov.knightMove(game, &moves);
     if (moves.capacity == 0) {
-        @memcpy(str.ptr, "err");
+        @memcpy(str.ptr, "0000");
         return str;
     }
     mov.moveTypeToStr(moves.items[0], str);

src/move.zig

@@ -25,6 +25,8 @@ pub fn playMoves(game: *types.game, str: []const u8) *types.game {
     if (str.len < 4) return game;
     var splitItr = std.mem.splitSequence(u8, str, " ");
     while (splitItr.next()) |moveString| {
+        if (moveString.len < 4 or moveString[0] > 'h')
+            continue;
         var move: types.move = .{ .To = 0, .From = 0, .Promo = 0 };
         if (moveString.len < 4) continue;
         move.From = (moveString[0] - 'a') + (moveString[1] - '1') * 8;
@@ -81,8 +83,28 @@ pub fn knightMove(g: *types.game, arr: *std.ArrayList(types.move)) void {
 }
 
 fn knightCalc(index: u8) u64 {
-    _ = index;
+    var moves: u64 = 0;
-    return @as(u64,1)<<32;
+    const offsets = [_]i8{ 17, -17, 15, -15, 10, -10, 6, -6 };
+    var cnt: u8 = undefined;
+    for (offsets) |off| {
+        if (off > 0) {
+            cnt = index + @abs(off);
+        } else if (index > @abs(off)) { //Icky bad that zig makes me do
+            cnt = index - @abs(off);
+        }
+        const fromFile: i32 = index % 8;
+        const toFile: i32 = cnt % 8;
+        const fromRank: i32 = index / 8;
+        const toRank: i32 = cnt / 8;
+
+        const fileDiff = @abs(fromFile - toFile);
+        const rankDiff = @abs(fromRank - toRank);
+        if (!((fileDiff == 1 and rankDiff == 2) or
+            (fileDiff == 2 and rankDiff == 1)) or cnt > 63)
+            continue;
+        moves = moves | @as(u64, 1) << @truncate(cnt);
+    }
+    return moves;
 }
 
 fn bitboardToMoves(start: u8, moves: u64, arr: *std.ArrayList(types.move)) void {