Add list option to scripts/codecs.py and restructure script with …

…subcommands.

scripts/codecs.py

@@ -1,9 +1,14 @@
+#!/usr/bin/env python3
+# TO-DO Add license notice
 """
 Encodes/decodes data fed from the command line with PyPDF codecs.
+
+Although PyPDF4 mandates Python 2 support as well, only Python 3 is supported
+by this script.
 """
 import argparse
+from sys import path, stderr
 
-from sys import argv, path, stderr
 from os.path import abspath, dirname, join, pardir
 
 PROJECT_ROOT = abspath(
@@ -13,64 +18,80 @@
 
 from pypdf4.filters import *
 
-__version__ = "0.1.0"
+__version__ = "0.2.0"
 CODECS = {
     "flate": FlateCodec, "asciihex": ASCIIHexCodec, "lzw": LZWCodec,
     "ascii85": ASCII85Codec, "dct": DCTCodec, "jpx": JPXCodec,
     "ccittfax": CCITTFaxCodec
 }
-# TO-DO Add a list command
-ENCODE, DECODE = ("encode", "decode")
-ACTIONS = (ENCODE, DECODE)
+
+ENCODE, DECODE, LIST = ("encode", "decode", "list")
+CODEC_ACTIONS = (ENCODE, DECODE)
+VIEW_ACTIONS = (LIST, )
 
 
 def main():
+    """
+    :return: exit status of program (``0`` with no errors, ``1`` with a generic
+        error).
+    """
     parser = argparse.ArgumentParser(
         description="Encodes/decodes some data fed in with PyPDF codecs",
         epilog="Version %s" % __version__
     )
-
-    # When not specified, the default action= keyword is "store"
-    parser.add_argument(
-        "action", choices=ACTIONS, help="The action to perform"
+    subparsers = parser.add_subparsers(title="Commands", dest="action")
+    codecParser = subparsers.add_parser(
+        ENCODE, aliases=(DECODE, ), help="Encode/decode data"
     )
-    parser.add_argument("data", help="Data to either encode or decode")
+    listParser = subparsers.add_parser(LIST, help="List available codecs")
+
+    subparsers.required = True
     parser.add_argument(
-        "-f", "--file", dest="isfile", action="store_const", const=True,
-        help="Whether the argument provided to DATA should be interpreted as a"
-        " file path"
+        "-v", "--version", action="version", version="%(prog)s " + __version__
     )
-    parser.add_argument(
+
+    codecParser.add_argument("data", help="Data to either encode or decode")
+    # TO-DO Add chained list of encoders/decoders support (like
+    # ASCIIHexDecode(LZWDecode(data))).
+    codecParser.add_argument(
         "-c", "--codec", choices=CODECS.keys(), required=True,
         help="The codec to encode/decode with"
     )
-    parser.add_argument(
-        "-v", "--version", action="version", version="%(prog)s " + __version__
+    codecParser.add_argument(
+        "-f", "--file", dest="isfile", action="store_const", const=True,
+        help="Whether the argument provided to DATA should be interpreted as a"
+             " file path"
     )
 
     args = parser.parse_args()
-    codec = CODECS[args.codec]
-
-    if args.isfile:
-        try:
-            with open(args.data, "rb") as infile:
-                data = infile.read()
-        except IOError as e:
-            print(e, file=stderr)
-            exit(1)
-    else:
-        data = args.data.encode("LATIN1")
 
     # TO-DO If the output is in bytes form, strip the b'' characters from the
     # output
-    if args.action == ENCODE:
-        print(codec.encode(data))
-    elif args.action == DECODE:
-        print(codec.decode(data))
+    if args.action in CODEC_ACTIONS:
+        codec = CODECS[args.codec]
+
+        if args.isfile:
+            try:
+                with open(args.data, "rb") as infile:
+                    data = infile.read()
+            except IOError as e:
+                print(e, file=stderr)
+                return 1
+        else:
+            data = args.data.encode("LATIN1")
+
+        if args.action == ENCODE:
+            print(codec.encode(data))
+        elif args.action == DECODE:
+            print(codec.decode(data))
+    elif args.action == LIST:
+        print("Available codecs:", *CODECS.keys(), sep="\n\t")
     else:
-        print("Unsupported action %s" % args.action, file=stderr)
-        exit(1)
+        print("Unrecognized action", args.action, file=stderr)
+        return 1
+
+    return 0
 
 
 if __name__ == "__main__":
-    main()
+    exit(main())