install.py

#!/usr/bin/env python

import argparse
import os.path
import sys
import yaml


def create_derived_file(src, subs, comment_delim=None, dry_run=False):
    derived_path = "%s.sub" % src
    print("Creating %s from %s:" % (derived_path, src))
    with open(src, 'r') as f_src:
        contents = f_src.read()
    for (to_replace, replace_with) in subs.items():
        to_replace_str = "@@%s@@" % to_replace
        print("- Substituting in %s: %s -> %s"
              % (derived_path, to_replace_str, replace_with))
        if to_replace_str not in contents:
            print("-- Warning: %s not found in %s" % (to_replace_str, src))
        contents = contents.replace(to_replace_str, replace_with)
    with open(derived_path, 'w') as f_derived:
        if comment_delim:
            preamble = ("%s This file has been autogenerated from %s\n\n" %
                        (comment_delim, os.path.realpath(src)))
            f_derived.writelines(preamble)
        f_derived.writelines(contents)
    return derived_path


def prompt_for_missing_subs(template, subs):
    result = {}
    print("Prompting for substitutions for %s..." % template)
    for sub in subs:
        if isinstance(sub, dict):
            result.update(sub)
        else:
            sub_with = raw_input("- Please provide %s: " % sub)
            result[sub] = sub_with
    return result


def install_symlink(link_to, link_from, force=False, dry_run=False):
    print("Installing symlink: %s -> %s" % (link_from, link_to))

    link_to = os.path.abspath(link_to)
    link_from = os.path.expanduser(link_from)
    link_from = os.path.normpath(link_from)

    # Quietly skip if link already valid
    if os.path.islink(link_from) and os.path.realpath(link_from) == link_to:
        return

    if os.path.lexists(link_from):
        if not force:
            print("- Skipping (exists)")
            return
        os.unlink(link_from)

    link_from_dir = os.path.dirname(link_from)
    if link_from_dir and not os.path.exists(link_from_dir):
        print("- Creating directory: %s" % link_from_dir)
        if not dry_run:
            os.makedirs(link_from_dir)

    print("- Creating link: %s -> %s" % (link_from, link_to))
    if not dry_run:
        os.symlink(link_to, link_from)


def parse_args_or_exit(argv=None):
    parser = argparse.ArgumentParser(description="Install all symlinks")
    parser.add_argument("--config", required=True, type=argparse.FileType('r'),
                        help="Path to config YAML")
    parser.add_argument("--force", action="store_true",
                        help="Force overwrite of existing files or links")
    parser.add_argument("--dry-run", action="store_true",
                        help="Don't do anything, just print")
    return parser.parse_args(argv)


def main(argv):
    args = parse_args_or_exit(argv)
    install = yaml.load(args.config)
    for (link_from, config) in install.items():
        if isinstance(config, str):
            link_to = config
        else:
            template = config["template"]
            subs = prompt_for_missing_subs(template, config.get("subs", []))
            comment_delim = config.get("comment_delim", None)
            link_to = create_derived_file(template, subs, comment_delim,
                                          args.dry_run)
        install_symlink(link_to, link_from, args.force, args.dry_run)


if __name__ == "__main__":
    main(sys.argv[1:])