#!/usr/bin/env python

# Copyright 2011 GRNET S.A. All rights reserved.
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# without modification, are permitted provided that the following
# conditions are met:
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#   1. Redistributions of source code must retain the above
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#      disclaimer.
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#   2. Redistributions in binary form must reproduce the above
#      copyright notice, this list of conditions and the following
#      disclaimer in the documentation and/or other materials
#      provided with the distribution.
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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import os
import sqlite3
import sys

from cStringIO import StringIO
from hashlib import md5

from lib.client import Pithos_Client, Fault


SQL_CREATE_TABLE = '''CREATE TABLE IF NOT EXISTS files (
                        path TEXT PRIMARY KEY, hash TEXT)'''


class LocalState(object):
    def __init__(self):
        dbpath = os.path.expanduser('~/.psyncdb')
        self.conn = sqlite3.connect(dbpath)
        self.conn.execute(SQL_CREATE_TABLE)
        self.conn.commit()
    
    def get(self, path):
        sql = 'SELECT hash FROM files WHERE path = ?'
        ret = self.conn.execute(sql, (path,)).fetchone()
        return ret[0] if ret else ''
    
    def put(self, path, hash):
        sql = 'INSERT OR REPLACE INTO files VALUES (?, ?)'
        self.conn.execute(sql, (path, hash))
        self.conn.commit()


class CurrentState(object):
    def __init__(self, dir):
        self.dir = dir
    
    def list(self):
        return os.listdir(self.dir)
        
    def get(self, path):
        fullpath = os.path.join(self.dir, path)
        if os.path.exists(fullpath):
            with open(fullpath) as f:
                data = f.read()
                return md5(data).hexdigest()
        else:
            return ''

    def read(self, path):
        fullpath = os.path.join(self.dir, path)
        if not os.path.exists(fullpath):
            return None
        with open(fullpath) as f:
            return f.read()
    
    def write(self, path, data):
        fullpath = os.path.join(self.dir, path)
        if data is None:
            os.remove(fullpath)
        else:
            with open(fullpath, 'w') as f:
                f.write(data)
    
    def resolve_conflict(self, path):
        fullpath = os.path.join(self.dir, path)
        os.rename(fullpath, fullpath + '.local')


class RemoteState(object):
    def __init__(self):
        host = os.environ['PITHOS_SERVER']
        user = os.environ['PITHOS_USER']
        token = os.environ['PITHOS_AUTH']
        self.container = 'pithos'
        self.client = Pithos_Client(host, token, user)

    def list(self):
        return self.client.list_objects(self.container)
        
    def get(self, path):
        try:
            meta = self.client.retrieve_object_metadata(self.container, path)
        except Fault:
            return ''
        return meta['etag']
    
    def read(self, path):
        try:
            return self.client.retrieve_object(self.container, path)
        except Fault:
            return None
    
    def write(self, path, data):
        if data is None:
            self.client.delete_object(self.container, path)
        else:
            f = StringIO(data)
            self.client.create_object(self.container, path, f=f)


def sync(path, lstate, cstate, rstate):
    s0 = lstate.get(path)
    s1 = cstate.get(path)
    s = rstate.get(path)

    if s1 == s0:
        # No local changes
        if s != s0:
            data = rstate.read(path)
            cstate.write(path, data)
            assert cstate.get(path) == s
            lstate.put(path, s)
        return
    
    if s == s0:
        # No remote changes
        if s1 != s0:
            data = cstate.read(path)
            rstate.write(path, data)
            assert rstate.get(path) == s1
            lstate.put(path, s1)
        return
    
    # At this point both local and remote states have changes since last sync

    if s1 == s:
        # We were lucky, both had the same change
        lstate.put(path, s)
    else:
        # Conflict, try to resolve it
        cstate.resolve_conflict(path)
        data = rstate.read(path)
        cstate.write(path, data)
        assert cstate.get(path) == s
        lstate.put(path, s)


def main():
    if len(sys.argv) != 2:
        print 'syntax: %s <dir>' % sys.argv[0]
        sys.exit(1)
    
    lstate = LocalState()
    cstate = CurrentState(sys.argv[1])
    rstate = RemoteState()

    local_files = set(cstate.list())
    remote_files = set(rstate.list())

    for path in local_files | remote_files:
        sync(path, lstate, cstate, rstate)


if __name__ == '__main__':
    main()