edmv

#!/usr/bin/env python

# "editron move" -- rename or move files by editing filenames in your
# favorite text editron

# ------------------------------------------------------
# use with caution! this code is not sufficiently tested
# ------------------------------------------------------

# Author: David McClosky
# Homepage: http://zorglish.org
# Code: http://github.com/dmcc

# vi: syntax=python

# TODO: better assertions, assertion handling
#       spit it out if there are errors and describe what we already did
#       read options from .edmvrc?
#       make sure we never overwrite files
#       try to put temp dirs in the dir of the original files

import sys, os, os.path, shutil, tempfile

DEFAULT_EDITOR = "vim -gf '%s'"  # I'm a vim-guy, myself

def saferename(source, target):
    """Do a "mv -i" and make sure that we don't overwrite any files."""
    if os.path.exists(target):
        raise OSError("Target %r already exists." % target)
    else:
        shutil.move(source, target)

file_mapping = []  # we save this so we can gracefully handle errors

def unique(seq):
    """Removes duplicate elements from a sequence.  This function is
    not stable at all."""
    u = {}
    for x in seq:
        u[x] = 1
    return u.keys()

def has_no_duplicates(seq):
    """Returns whether a sequence has no duplicates."""
    uniq_version = unique(seq)
    # if there were duplicates, len(uniq_version) should be less than the
    # original
    return len(seq) == len(uniq_version)

def error(message):
    """Print a message and exit, printing a log of what we did and how to
    undo it."""
    # TODO: actually do the graceful exit and such
    print("Error:", message)
    if file_mapping:
        print("Mapping table:")
        for old, inter, new in file_mapping:
            print(repr(old), repr(inter), repr(new))
    else:
        print("No mapping table yet -- no changes were made.")
    sys.exit(1)

def editron_move(editron=DEFAULT_EDITOR, files_to_rename=None):
    old_list = files_to_rename or []  # TODO: warn when old_list is empty

    with tempfile.NamedTemporaryFile(mode="w",
                                     dir="/tmp",
                                     prefix="edmv") as filename_list:
        filename_list.write('\n'.join(old_list) + '\n')
        filename_list.flush()
        filename_list_file = filename_list.name

        # editron must have exactly one %s
        assert(editron.count('%s') == 1)
        try:
            command = editron % filename_list_file
        except TypeError:
            # we will get this if there are too many things to interpolate
            error("editor ('%s') should have exactly one thing to interpolate." %
                  command)

        print('run', command)
        os.system(command)

        with open(filename_list.name) as readable_filename_list:
            new_list = readable_filename_list.read().splitlines()

    for old, new in zip(old_list, new_list):
        print(f"{old} -> {new}")

    try:
        perform_rename(old_list, new_list)
    except AssertionError:
        error("Assertion error -- descriptions coming soon")

def perform_rename(old_list, new_list):
    global file_mapping

    assert has_no_duplicates(old_list)
    assert has_no_duplicates(new_list)

    # first, create a secure temporary directory
    temp_directory = tempfile.mkdtemp(prefix='edmv')

    def intermediate_name(old_name):
        return "%s/%d-%s" % (temp_directory, old_list.index(old_name), old_name)

    file_mapping = [(old, intermediate_name(old), new)
                    for old, new in zip(old_list, new_list)]

    # next, move every file to the temporary directory, giving it a unique
    # name -- list index is sufficient in this case
    for old, inter, new in file_mapping:
        print(f"rename {old!r} -> {inter!r}")
        shutil.move(old, inter)
    for old, inter, new in file_mapping:
        print(f"rename {inter!r} -> {new!r}")
        shutil.move(inter, new)

    # erase temporary directory -- everything should have been moved out of it
    # TODO: make sure it is empty
    os.removedirs(temp_directory)

if __name__ == "__main__":
    from optparse import OptionParser

    parser = OptionParser()
    parser.add_option("-e", "--editor",
                      dest="editor", default=DEFAULT_EDITOR,
                      help="Editron to use")

    (options, files) = parser.parse_args()
    editron_move(options.editor, files)