Convert a pawn promotion from algebraic to ICCF numeric notation

Question

Input

A single string, which contains no whitespace, as a command-line argument.

Output

If the string is not a valid algebraic notation pawn promotion, produce no output and exit. If the string is a valid pawn promotion, convert it to ICCF numeric notation and print the result, followed by a newline.

A valid algebraic notation pawn promotion consists of:

• A letter from a to h indicating the pawn's departure column (known as a "file" in chess);
• Optionally, "x" followed by the file of the pawn's arrival square if it has captured a piece in promoting;
• "1" or "8" depending on which side promoted; and
• "=" followed by one of "Q", "R", "B", "N" to indicate the chosen piece;
• Optionally, "+" to indicate the move was a check or "#" to indicate the move was a checkmate.

An valid ICCF numeric notation pawn promotion consists of:

• Two digits indicating the coordinates of the square from which the pawn departed (the files are numbered and not lettered as in algebraic notation);
• One digit indicating the file on which the pawn arrived, in case it has captured a piece while promoting (this does not officially comply with the standard, but I prefer keeping all moves as 4 digits for simplicity); and
• One digit to indicate the chosen piece: 1 for queen, 2 for rook, 3 for bishop, 4 for knight.

Examples

e1=Q   => 5251
cxd8=B => 3743
axh8=R => no output (a-pawns cannot capture on h-file)
h8=N+  => 8784

Answer 1

JavaScript (ES6), 166 bytes

s=>(g=n=>parseInt(m[n][0],19)-9,m=s.match(/^([a-h]x)?([a-h][18]=[QRBN])[+#]?$/))?m[1]&&g(2)+~g(0)&&g(0)+~g(2)?'':''+g(0)+(m[2][1]-1|2)+g(2)+" QRBN".search(m[2][3]):''

The validation makes this horribly long. Without validation, it's only 108 bytes:

s=>s.replace(/(.x)?(..=.).*/,([a],_,[c,d,,f])=>g(a)+(d-1|2)+g(c)+" QRBN".search(f),g=f=>parseInt(f,19)-9+'')