Added argparse support

README.md

@@ -2,19 +2,38 @@
 
 This script will convert the dsv save from drastic emulator to a melonDS save file
 
-How this works ?
+### How to use
+
+You need python 3 installed.  
+Specify the input save file
+
+```bash
+./dr2mds.py "Pokemon Black.dsv"
+```
+
+This will make a "Pokemon Black.sav" file as output
+You can also specify the output like
+
+```bash
+./dr2mds.py "Pokemon Black.dsv" -o "PKMN.sav"
+```
+
+### How this works ?
+
+MelonDS determines the type of save using exact byte count in the save file
 
-MelonDS determines save type using exact byte count in the save file
 Which needs to be a power of 2 as mentioned [here](http://melonds.kuribo64.net/faq.php).  
-This script calculates the closest power of 2 to the save file and removes the padding
+In _Importing a savefile from another emulator_ part under _How to_ section
 
-This can be easily done manually by removing the padding using a hex editor.
+This script calculates the closest power of 2 to the save file and removes the padding.
-Or using dd like this
+
+### Other ways of doing this
+
+This can be done manually by removing the padding using a hex editor.
+Or using dd like this (on linux/macos)
 
 ```bash
 dd if=Pokemon.dsv of=Pokemon.sav bs=1 count=524288
 ```
 
 This will make a 4KiB EEPROM save from drastic to melonDS save.
-
-I will add argparse later.

dr2mds.py

@@ -1,21 +1,67 @@
 #!/usr/bin/python3
 
 from math import log
+import errno
+import argparse
+import sys
 import os
 
-DRASTIC_SAVE="Pokemon Black.dsv"
+sys.tracebacklimit = 0
-MELONDS_SAVE="Pokemon Black.sav"
 
-def st_size(path):
-    return os.stat(path).st_size
 
 def closest2pow(n):
+    # int always returns the floor of the float
+    # log(n)/log(2) gives log base 2 of n
     return 2**int(log(n) / log(2))
 
-def drastic2melonds(infile,outfile):
-    with open(infile,"rb") as inf, open(outfile,"wb") as ouf:
 
-        ouf.write(inf.read(closest2pow(st_size(infile))))
+def drastic2melonds(infile, outfile):
+    with open(infile, "rb") as inf, open(outfile, "wb") as ouf:
+        in_bytes = os.stat(infile).st_size
+        out_bytes = closest2pow(in_bytes)
+        print(f"Reading {in_bytes} bytes from {infile}", file=sys.stderr)
+        print(f"Writing {out_bytes} bytes to {outfile}", file=sys.stderr)
+        ouf.write(inf.read(out_bytes))
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "-o",
+        "--output",
+        help="Specify the output file")
+    parser.add_argument(
+        "-f",
+        "--force",
+        help="Overwrite the output file if it exists",
+        action="store_true")  # This stores false by default unless -f is given
+
+    parser.add_argument(
+        "file", help="The drastic save file")
+    if len(sys.argv) == 1:
+        parser.print_help(sys.stderr)
+        sys.exit(0)
+
+    args = parser.parse_args()
+
+    if not os.path.isfile(args.file):
+        parser.print_usage()
+        raise FileNotFoundError(
+            errno.ENOENT, os.strerror(errno.ENOENT), args.file)
+
+    if not args.output:
+        args.output = os.path.splitext(args.file)[0] + ".sav"
+
+    if os.path.isfile(args.output):
+        if args.force:
+            print(f"Overwriting file {args.output}", file=sys.stderr)
+            drastic2melonds(args.file, args.output)
+        else:
+            print(f"Output file {args.output} already exists "
+                  "pass -f/--force flag to overwrite the file", file=sys.stderr)
+    else:
+        drastic2melonds(args.file, args.output)
+
 
 if __name__ == "__main__":
-    drastic2melonds(DRASTIC_SAVE,MELONDS_SAVE)
+    main()