#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
This script is just a wrapper of the "aws s3api get-object" command to
download the spacenet dataset. It requires a configured AWS cli
see pages:
https://aws.amazon.com/public-datasets/spacenet/
http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-welcome.html
"""
from __future__ import print_function
import argparse
import os
import subprocess
from urlparse import urljoin


def download_file(s3_path, rooturl):
    """
    Downlad a single file from the s3://spacenet-dataset bucket. s3_path
    must be valid, a similar directory tree will be created locally. The
    manifest.txt file provides the list of paths. You can download it
    with the option: -p manifest.txt
    """
    # left and right strip some character of s3_path
    s3_path = s3_path.strip().lstrip('./')
    # s3_path is a file only if it contains a '.'
    if '.' not in s3_path:
        return
    # if a file already exists do nothing (no download)
    if os.path.isfile(s3_path):
        print('skip file: "{}", because it already exists'.format(s3_path))
        return
    # create the directory (and parents) for the new file
    try:
        dirname = os.path.dirname(s3_path)
        if dirname and not os.path.isdir(dirname):
            print('creating directory: {}'.format(dirname))
            os.makedirs(dirname)
    except Exception as e:
        print('Exception: {}'.format(e))
    # download the file with an 'aws s3api get-object' command
    try:
        print('downloading file: {} ...'.format(s3_path))
        # command = ['aws', 's3api', 'get-object',
        #     '--bucket', 'spacenet-dataset', '--request-payer', 'requester',
        #     '--key', s3_path, s3_path]
        command = ["axel", "-n", "10", urljoin(rooturl, s3_path), "--output", s3_path]
        subprocess.check_call(command)
    except Exception as e:
        print('Exception: {}'.format(e))


def download_selection(selection_file_path, rooturl):
    """
    Download files contained in a the selection_file, which must contain
    an s3 path on each line (as in the manifest file), for example:
    ./manifest.txt
    ./AOI_1_Rio/srcData/mosaic_8band/013022223121.tif
    """
    with open(selection_file_path, 'r') as selection_file:
        for s3_path in selection_file:
            download_file(s3_path, rooturl)


def main(args):
    """
    Parse the arguments, and call a download function
    usage: spacenet_download.py [-h] [-p PATH | -s SELECTION]

    optional arguments:
      -h, --help            show this help message and exit
      -p PATH, --path PATH  a single s3 path to be downloaded
      -s SELECTION, --selection SELECTION
                            path to a selection file. All s3 paths written in this
                            file will be downloaded
    """
    parser = argparse.ArgumentParser()
    group = parser.add_mutually_exclusive_group()
    group.add_argument("-p", "--path",
                       help="a single s3 path to be downloaded")
    group.add_argument("-s", "--selection",
                       help="path to a selection file. All s3 paths written in this " +
                       "file will be downloaded")
    group.add_argument("-r", "--rooturl",
                       help="url of the file to be download" +
                       "file will be downloaded")
    args = parser.parse_args()
    if not args.rooturl:
        parser.error("-r is mandatory")
    if args.path:
        download_file(args.path, args.rooturl)
    elif args.selection:
        download_selection(args.selection, args.rooturl)
    else:
        parser.error('Use the -p or -s option, for example: -p manifest.txt')
    return 0

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