open Base
let symbols = Map.of_alist_exn (module String) [
    "R0",     0;
    "R1",     1;
    "R2",     2;
    "R3",     3;
    "R4",     4;
    "R5",     5;
    "R6",     6;
    "R7",     7;
    "R8",     8;
    "R9",     9;
    "R10",    10;
    "R11",    11;
    "R12",    12;
    "R13",    13;
    "R14",    14;
    "R15",    15;
    "SP",     0;
    "LCL",    1;
    "ARG",    2;
    "THIS",   3;
    "THAT",   4;
    "SCREEN", 16384;
    "KBD",    24576;
  ]

let comp c =
  match c with
  | "0"   -> "0101010"
  | "1"   -> "0111111"
  | "-1"  -> "0111010"
  | "D"   -> "0001100"
  | "A"   -> "0110000"
  | "M"   -> "1110000"
  | "!D"  -> "0001101"
  | "!A"  -> "0110001"
  | "!M"  -> "1110001"
  | "-D"  -> "0001111"
  | "-A"  -> "0110011"
  | "-M"  -> "1110011"
  | "D+1" -> "0011111"
  | "A+1" -> "0110111"
  | "M+1" -> "1110111"
  | "D-1" -> "0001110"
  | "A-1" -> "0110010"
  | "M-1" -> "1110010"
  | "D+A" -> "0000010"
  | "D+M" -> "1000010"
  | "D-A" -> "0010011"
  | "D-M" -> "1010011"
  | "A-D" -> "0000111"
  | "M-D" -> "1000111"
  | "D&A" -> "0000000"
  | "D&M" -> "1000000"
  | "D|A" -> "0010101"
  | "D|M" -> "1010101"
  | _ -> failwith "Unknown COMP Instruction"
;;

let dest d =
  match d with
  | ""    -> "000"
  | "M"   -> "001"
  | "D"   -> "010"
  | "MD"  -> "011"
  | "A"   -> "100"
  | "AM"  -> "101"
  | "AD"  -> "110"
  | "ADM" -> "111"
  | _ -> failwith "Unknown DEST Instruction"
;;

let jump j =
  match j with
  | ""    -> "000"
  | "JGT" -> "001"
  | "JEQ" -> "010"
  | "JGE" -> "011"
  | "JLT" -> "100"
  | "JNE" -> "101"
  | "JLE" -> "110"
  | "JMP" -> "111"
  | _ -> failwith "Unknown JUMP Instruction"
;;