#!/usr/bin/env python
import os
import sys


def cheat_directories():
    "Assembles a list of directories containing cheatsheets."
    default_directories = [os.path.expanduser('~/.cheat')]
    try:
        import cheatsheets
        default_directories.append(cheatsheets.cheat_dir)
    except ImportError:
        pass

    default = [default_dir for default_dir in default_directories
               if os.path.isdir(default_dir)]

    if 'CHEATPATH' in os.environ and os.environ['CHEATPATH']:
        return [path for path in os.environ['CHEATPATH'].split(os.pathsep)
                if os.path.isdir(path)] + default
    else:
        return default


def cheat_files(cheat_directories):
    "Assembles a dictionary of cheatsheets found in the above directories."
    cheats = {}
    for cheat_dir in reversed(cheat_directories):
        cheats.update(dict([(cheat, cheat_dir)
                            for cheat in os.listdir(cheat_dir)
                            if not cheat.startswith('.')]))
    return cheats


def main():
    # assemble a keyphrase out of all params passed to the script
    keyphrase = ' '.join(sys.argv[1:])
    cheat_dirs = cheat_directories()

    # verify that we have at least one cheat directory
    if not cheat_dirs:
        print >> sys.stderr, ('The ~/.cheat dir does not exist or the '
                              'CHEATPATH var is not set.')
        exit()

    # list the files in the ~/.cheat directory
    cheatsheets = cheat_files(cheat_dirs)

    # print help if requested
    if keyphrase.lower() in ['', 'cheat', 'help', '-h', '-help', '--help']:
        print "Usage: cheat [keyphrase]\n"
        print "Available keyphrases:"
        max_command = max([len(x) for x in cheatsheets.keys()]) + 3
        print '\n'.join(sorted(['%s [%s]' % (key.ljust(max_command), value)
                                for key, value in cheatsheets.items()]))
        exit()

    # print the cheatsheet if it exists
    if keyphrase in cheatsheets:
        filename = os.path.join(cheatsheets[keyphrase], keyphrase)
        with open(filename, 'r') as cheatsheet:
            print cheatsheet.read()

    # if it does not, say so
    else:
        print 'No cheatsheet found for %s.' % keyphrase


if __name__ == '__main__':
    main()