filesync.py

__author__ = 'katharine'

import os.path
import errno


class FileSync(object):
    def __init__(self, root_dir):
        assert isinstance(root_dir, basestring)
        self.root_dir = root_dir

    def apply_patches(self, patch_sequence):
        # TODO: optimisations, if we care.
        # We can keep the files in memory
        # A sequence of patches probably all apply to the same file. We can optimise around this.
        # But does it matter?

        # The patches should arrive in order.
        patches = sorted(patch_sequence, key=lambda x: x['sequence'])

        for patch in patches:
            abs_path = self.abs_path(patch['filename'])

            with open(abs_path) as f:
                lines = [x.decode('utf-8') for x in f.readlines()]
                start = patch['start']
                end = patch['end']

                # Including everything up to the start line
                content = lines[:start['line']]
                # Merge the start line, replacement, and end line into a single line
                merged_line = ''
                if len(lines) > start['line']:
                    merged_line += lines[start['line']][:start['ch']]
                merged_line += "\n".join(patch['text'])
                if len(lines) > end['line']:
                    merged_line += lines[end['line']][end['ch']:]
                content.append(merged_line)
                # Add the lines from the end through to the end.
                if len(lines) > end['line'] + 1:
                    content.extend(lines[end['line'] + 1:])

            # Writeback.
            with open(abs_path, 'w') as f:
                f.writelines([x.encode('utf-8') for x in content])

    def create_file(self, path, content):
        path = self.abs_path(path)
        dir_name = os.path.dirname(path)
        try:
            os.makedirs(dir_name)
        except OSError as e:
            if e.errno == errno.EEXIST and os.path.isdir(dir_name):
                pass
            else:
                raise
        with open(path, 'w') as f:
            f.write(content)

    def rename_file(self, path, new_path):
        path = self.abs_path(path)
        new_path = self.abs_path(new_path)
        if os.path.exists(new_path):
            raise Exception("Cannot rename file, path already exists")
        os.rename(path, new_path)

    def delete_file(self, path):
        path = self.abs_path(path)
        os.unlink(path)

    def abs_path(self, path):
        abs_path = os.path.normpath(os.path.join(self.root_dir, path))
        if not abs_path.startswith(self.root_dir):
            raise Exception("Bad path")
        return abs_path