#!/usr/bin/env python3

import os,sys,cgi
import traceback
from os import mkdir,rename,unlink
from os.path import exists
from os.path import join as pathjoin
from common.cgi import parse_qs,parse_auth,start_response
from common.datadb import DATADB_ROOT,DATADB_TMP
from shutil import rmtree
from subprocess import Popen,PIPE
from time import time


def rotate_backups(backup_dir, sync_prev=False, max_backups=5):
    """
    In the backup dir, cascade backups. (/1/ becomes /2/, /0/ becomes /1/, etc)
    :param backup_dir: absolute path to dir containing the numbered dirs we will be rotating
    :param sync_prev: if true, the previous backup's content will be copied to the newly create backup dir (0)
    :param max_backups: Max number of dirs to keep
    :returns: Full path of new data dir
    """
    
    # Path to this profile's backup data dir
    #profile_base_path = pathjoin(DATADB_ROOT, backupName, 'data')
    
    dirs = os.listdir(backup_dir)
    
    if len(dirs) > 0:
        # If there are some dirs, rotate them
        # Assume all items are dirs and all dirs are named numerically
        dirs = sorted([int(d) for d in dirs])
        dirs.reverse() # we now have [5, 4, 3, 2, 1, 0]
        
        for item in dirs:
            if (item+1) >= max_backups:
                rmtree(pathjoin(backup_dir, str(item)))
                continue
            
            # Rotate each backup once
            rename(
                pathjoin(backup_dir, str(item)), 
                pathjoin(backup_dir, str(item+1))
            )
    
    # Create the new backup dir
    new_backup_path = pathjoin(backup_dir, "0")
    mkdir(new_backup_path)
    mkdir(pathjoin(new_backup_path, "data"))
    
    prev_backup_path = pathjoin(backup_dir, "1")
    
    if sync_prev and exists(prev_backup_path):
        # if we're using rsync let's cp -r the previous backup to the empty new dir. 
        # this should save some network time rsyncing later
        #copytree(prev_backup_path, new_backup_path)
        cp = Popen(['rsync', '-avr', '--one-file-system', prev_backup_path+'/data/', new_backup_path+'/data/'],
                   stdout=PIPE, stderr=PIPE)
        cp.communicate()
        
    return new_backup_path+'/data/'


def prepare_backup_dirs(backupName, sync_prev=False, max_backups=5):
    """
    Check and create dirs where backups under this name will go
    :param backupName: name of backup profile
    :param sync_prev: if true, the previous backup's content will be copied to the newly create backup dir (0)
    :returns: absolute path to newly created backup dir (0)
    """
    #print("prepare_backup(%s, %s)" % (backupName, proto))
    
    # Ensure the following dir exists: <DATADB_ROOT>/<backup_name>/data/0/
    backup_base_path = pathjoin(DATADB_ROOT, backupName)
    if not exists(backup_base_path):
        mkdir(backup_base_path)
    
    backup_data_path = pathjoin(backup_base_path, 'data')
    if not exists(backup_data_path):
        mkdir(backup_data_path)
    
    # Should always return bkname/data/0/data/
    new_path = rotate_backups(backup_data_path, sync_prev=sync_prev, max_backups=max_backups)
    
    return new_path


def handle_get_rsync(backupName, max_backups):
    """
    Prepare for an rsync backup transfer. Prints path to screen after preparing it.
    :param backupName: name of backup profile
    """
    # Prepare new dir
    new_target_dir = prepare_backup_dirs(backupName, sync_prev=True, max_backups=max_backups)
    
    # Print absolute path to screen. datadb client will use this path as the rsync dest
    start_response()
    print(new_target_dir)
    
    exit(0)


def handle_put_archive(backupName, fileStream, max_backups):
    """
    Prepare and accept a new archive backup - a single tar.gz archive.
    :param backupName: profile the new file will be added to
    :param fileStream: file-like object to read archive data from, to disk
    """
    
    # Temp file we will store data in as it is uploaded
    tmp_fname = pathjoin(DATADB_TMP, "%s.tar.gz" % time())
    
    # Track uploaded data size
    bk_size = 0
    with open(tmp_fname, 'wb') as f:
        while True:
            data = fileStream.read(8192)
            if not data:
                break
            bk_size += len(data)
            f.write(data)
    
    # No data = assume something failed
    if bk_size == 0:
        unlink(tmp_fname)
        raise Exception("No file uploaded...")
    
    new_target_dir = prepare_backup_dirs(backupName, max_backups=max_backups)
    
    # Move backup into place
    rename(tmp_fname, pathjoin(new_target_dir, 'backup.tar.gz'))
    
    # Done
    start_response() # send 200 response code
    exit(0)


def handle_req():
    """
    Parse http query parameters and act accordingly.
    """
    params = parse_qs()
    
    for param_name in ["proto", "name"]:
        if not param_name in params:
            raise Exception("Missing parameter: %s" % param_name)
    
    max_backups = int(params["keep"]) if "keep" in params else 5
    assert max_backups > 0, "Must keep at least one backup"
    
    if os.environ['REQUEST_METHOD'] == "GET" and params["proto"] == "rsync":
        # Rsync is always GET
        handle_get_rsync(params["name"], max_backups)
    
    elif os.environ['REQUEST_METHOD'] == "PUT" and params["proto"] == "archive":
        # Archive mode PUTs a file
        handle_put_archive(params["name"], sys.stdin.buffer, max_backups)
    
    else:
        raise Exception("Invalid request. Params: %s" % params)


if __name__ == "__main__":
    try:
        handle_req()
    except Exception as e:
        start_response(status_code=("500", "Internal server error"))
        
        tb = traceback.format_exc()
        print(tb)