#!/usr/bin/env python
# Copyright 2019 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import json
import os
import shutil
import sys

SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
FUCHSIA_ROOT = os.path.dirname(  # $root
    os.path.dirname(             # build
        SCRIPT_DIR))                 # zircon
ZIRCON_PUBLIC = os.path.join(FUCHSIA_ROOT, 'zircon', 'public')
TEMPLATE_FILE = os.path.join(SCRIPT_DIR, 'template.gn')

PUBLIC_DIRS = set([
    'banjo',
    'fidl',
    'lib',
    'tool',
])


def main():
    with open(sys.argv[1]) as f:
        legacy_dirs = json.load(f)
    dirs = {}
    for dir in legacy_dirs:
        top_dir = os.path.dirname(dir)
        dirs[top_dir] = dirs.get(top_dir, []) + [os.path.basename(dir)]
    assert set(dirs.keys()) == PUBLIC_DIRS, (
        "%r from JSON should match %r" % (set(dirs.keys()), PUBLIC_DIRS))
    template_stat = os.lstat(TEMPLATE_FILE)
    for top_dir, subdirs in dirs.iteritems():
        top_dir = os.path.join(ZIRCON_PUBLIC, top_dir)
        subdirs = set(subdirs)
        if not os.path.exists(top_dir):
            os.mkdir(top_dir)
        else:
            # Go over the existing contents of the directory.
            for existing in os.listdir(top_dir):
                existing_dir = os.path.join(top_dir, existing)
                build_file = os.path.join(existing_dir, 'BUILD.gn')
                if os.path.isdir(existing_dir):
                    if existing in subdirs:
                        # An existing directory might already have the link.
                        # If the link doesn't exist or doesn't match, make it.
                        if not os.path.exists(build_file):
                            os.link(TEMPLATE_FILE, build_file)
                        elif not os.path.samestat(os.lstat(build_file),
                                                  template_stat):
                            os.remove(build_file)
                            os.link(TEMPLATE_FILE, build_file)
                        subdirs.remove(existing)
                    else:
                        # A stale directory that shouldn't exist any more.
                        shutil.rmtree(existing_dir)
                else:
                    # A stray file in one of the controlled directories.
                    os.remove(existing_dir)
        # Make and populate any directories that don't exist yet.
        for subdir in subdirs:
            subdir = os.path.join(top_dir, subdir)
            os.mkdir(subdir)
            os.link(TEMPLATE_FILE, os.path.join(subdir, 'BUILD.gn'))
    return 0


if __name__ == '__main__':
    sys.exit(main())