from os import sys
from re import sub

if len(sys.argv) == 1:
    print("[PREPROCESSOR ERR] Filename not specified.")
    exit()
elif len(sys.argv) == 2:
    print("[PREPROCESSOR ERR] Output location not specified.")
    exit()

args = sys.argv[1:]
filename = args[0]
output_path = args[1]

sym_table = {}

with open(filename) as file:
    lines = file.read().split("\n")

    for i in range(len(lines)):
        if lines[i].find("DEF_SYMS") >= 0:
            line = lines[i][(lines[i].find("DEF_SYMS ") + len("DEF_SYMS ")):]
            curr_line = line.split(" ")
            curr_line = [e.split("=") for e in curr_line]

            try:
                for e in curr_line:
                    sym_table[e[0]] = e[1]
            except:
                print("[PREPROCESSOR ERR] DEF_SYMS directive must be formatted exactly like the following (_ = space) 'DEF_SYMS_<sym1>=<v1>_<sym2>=<v2>...'")
                break

        elif lines[i].find("END_SYMS") >= 0:
            line = lines[i][(lines[i].find("END_SYMS ") + len("END_SYMS ")):]
            curr_line = line.split(" ")

            try:
                for e in curr_line:
                    if e in sym_table.keys():
                        sym_table.pop(e)
                    else:
                        print("[PREPROCESSOR ERR] Cannot delete symbol: '" + e + "'")
                        break
            except:
                print("[PREPROCESSOR ERR] END_SYMS directive must be formatted exactly like the following (_ = space) 'END_SYMS_<sym1>_<sym2>..'")
                break

        elif lines[i].find("END_ALL_SYMS") >= 0:
            sym_table = {}

        else:
            for key, value in sorted(sym_table.items(), key=lambda x: len(x)):
                lines[i] = sub(r"\b" + key + r"\b", value, lines[i])

    output = "\n".join(lines)

    try:
        with open(output_path, "r") as out: # When you use 'with', Python closes the file handle automatically when finished
            if out.read() != "":
                if input(output_path + " is not empty. Are you sure you want to overwrite it? (y/n): ") != "y":
                    print("Cancelling preprocessing")
                else:
                    with open(output_path, "w+") as out:
                        out.write(output)
                        print("Successfully preprocessed", filename)
    except:
        with open(output_path, "w") as out:
            out.write(output)
            print("Successfully preprocessed", filename)