#!/usr/bin/env python3

import traceback
import os
from sys import exit, stdout
from os.path import join as pathjoin
from os.path import exists, getsize
from common.cgi import parse_qs, parse_auth, start_response
from common.datadb import DATADB_ROOT, DATADB_DIR_TIMESTAMP_FORMAT
from datetime import datetime


def get_backup_dir(backup_name):
    """
    Get the absolute local path to a backup or raise an exception if none exists. When getting a backup, sort folder
    names (they're timestamps) and return newest.
    :returns: str absolute path to backup seq /0/
    """
    backups_dir = pathjoin(DATADB_ROOT, backup_name, 'data')

    if not exists(backups_dir):
        raise Exception("Backup does not exist")

    dirs = sorted([datetime.strptime(d, DATADB_DIR_TIMESTAMP_FORMAT) for d in os.listdir(backups_dir)])

    return os.path.join(backups_dir, dirs[-1].strftime(DATADB_DIR_TIMESTAMP_FORMAT), 'data')


def handle_head(backup_name):
    try:
        # backup_path = get_backup_dir(backup_name)
        # TODO appropriate content-length for HEAD
        start_response(extra_headers=['Content-length: 0'])
    except:
        start_response(status_code=("404", "Not Found",), extra_headers=['Content-length: 0'])
    exit(0)


def handle_get_rsync(backup_name):
    """
    Prints the absolute path an rsync backup should pull from
    """
    backup_path = get_backup_dir(backup_name)

    start_response()
    print(backup_path + '/')


def handle_get_archive(backup_name):
    """
    Returns .tar.gz data to the browser
    """
    backup_path = pathjoin(get_backup_dir(backup_name), 'backup.tar.gz')

    with open(backup_path, 'rb') as f:
        start_response(content_type="application/x-gzip",
                       extra_headers=["Content-length: %s" % getsize(backup_path),
                                      "Content-Disposition: attachment; filename=\"backup.tar.gz\""])
        while True:
            data = f.read(8192)
            if not data:
                break
            stdout.buffer.write(data)
    exit(0)


def handle_req():
    """
    Parse http query parameters and act accordingly.
    """
    params = parse_qs()

    for param_name in ["proto", "name"]:
        if param_name not in params:
            raise Exception("Missing parameter: %s" % param_name)

    if os.environ['REQUEST_METHOD'] == "GET" and params["proto"] == "rsync":
        # Should return absolute local path to latest backup dir
        handle_get_rsync(params["name"])

    elif os.environ['REQUEST_METHOD'] == "GET" and params["proto"] == "archive":
        # Should respond by transferring tar.gz data
        handle_get_archive(params["name"])

    elif os.environ['REQUEST_METHOD'] == "HEAD":
        # Respond with 200 or 404 depending if backup exists
        # TODO: deeper inspection so the headers can be flushed out
        handle_head(params["name"])

    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)