ch20: renamed directory

20-executors/getflags/flags2_common.py

@@ -0,0 +1,155 @@
+"""Utilities for second set of flag examples.
+"""
+
+import argparse
+import string
+import sys
+import time
+from collections import Counter
+from enum import Enum
+from pathlib import Path
+
+DownloadStatus = Enum('DownloadStatus', 'OK NOT_FOUND ERROR')
+
+POP20_CC = ('CN IN US ID BR PK NG BD RU JP '
+            'MX PH VN ET EG DE IR TR CD FR').split()
+
+DEFAULT_CONCUR_REQ = 1
+MAX_CONCUR_REQ = 1
+
+SERVERS = {
+    'REMOTE': 'https://www.fluentpython.com/data/flags',
+    'LOCAL':  'http://localhost:8000/flags',
+    'DELAY':  'http://localhost:8001/flags',
+    'ERROR':  'http://localhost:8002/flags',
+}
+DEFAULT_SERVER = 'LOCAL'
+
+DEST_DIR = Path('downloaded')
+COUNTRY_CODES_FILE = Path('country_codes.txt')
+
+
+def save_flag(img: bytes, filename: str) -> None:
+    (DEST_DIR / filename).write_bytes(img)
+
+
+def initial_report(cc_list: list[str],
+                   actual_req: int,
+                   server_label: str) -> None:
+    if len(cc_list) <= 10:
+        cc_msg = ', '.join(cc_list)
+    else:
+        cc_msg = f'from {cc_list[0]} to {cc_list[-1]}'
+    print(f'{server_label} site: {SERVERS[server_label]}')
+    plural = 's' if len(cc_list) != 1 else ''
+    print(f'Searching for {len(cc_list)} flag{plural}: {cc_msg}')
+    if actual_req == 1:
+        print('1 connection will be used.')
+    else:
+        print(f'{actual_req} concurrent connections will be used.')
+
+
+def final_report(cc_list: list[str],
+                 counter: Counter[DownloadStatus],
+                 start_time: float) -> None:
+    elapsed = time.perf_counter() - start_time
+    print('-' * 20)
+    plural = 's' if counter[DownloadStatus.OK] != 1 else ''
+    print(f'{counter[DownloadStatus.OK]:3} flag{plural} downloaded.')
+    if counter[DownloadStatus.NOT_FOUND]:
+        print(f'{counter[DownloadStatus.NOT_FOUND]:3} not found.')
+    if counter[DownloadStatus.ERROR]:
+        plural = 's' if counter[DownloadStatus.ERROR] != 1 else ''
+        print(f'{counter[DownloadStatus.ERROR]:3} error{plural}.')
+    print(f'Elapsed time: {elapsed:.2f}s')
+
+
+def expand_cc_args(every_cc: bool,
+                   all_cc: bool,
+                   cc_args: list[str],
+                   limit: int) -> list[str]:
+    codes: set[str] = set()
+    A_Z = string.ascii_uppercase
+    if every_cc:
+        codes.update(a+b for a in A_Z for b in A_Z)
+    elif all_cc:
+        text = COUNTRY_CODES_FILE.read_text()
+        codes.update(text.split())
+    else:
+        for cc in (c.upper() for c in cc_args):
+            if len(cc) == 1 and cc in A_Z:
+                codes.update(cc + c for c in A_Z)
+            elif len(cc) == 2 and all(c in A_Z for c in cc):
+                codes.add(cc)
+            else:
+                raise ValueError('*** Usage error: each CC argument '
+                                 'must be A to Z or AA to ZZ.')
+    return sorted(codes)[:limit]
+
+
+def process_args(default_concur_req):
+    server_options = ', '.join(sorted(SERVERS))
+    parser = argparse.ArgumentParser(
+        description='Download flags for country codes. '
+                    'Default: top 20 countries by population.')
+    parser.add_argument(
+        'cc', metavar='CC', nargs='*',
+        help='country code or 1st letter (eg. B for BA...BZ)')
+    parser.add_argument(
+        '-a', '--all', action='store_true',
+        help='get all available flags (AD to ZW)')
+    parser.add_argument(
+        '-e', '--every', action='store_true',
+        help='get flags for every possible code (AA...ZZ)')
+    parser.add_argument(
+        '-l', '--limit', metavar='N', type=int, help='limit to N first codes',
+        default=sys.maxsize)
+    parser.add_argument(
+        '-m', '--max_req', metavar='CONCURRENT', type=int,
+        default=default_concur_req,
+        help=f'maximum concurrent requests (default={default_concur_req})')
+    parser.add_argument(
+        '-s', '--server', metavar='LABEL', default=DEFAULT_SERVER,
+        help=f'Server to hit; one of {server_options} '
+             f'(default={DEFAULT_SERVER})')
+    parser.add_argument(
+        '-v', '--verbose', action='store_true',
+        help='output detailed progress info')
+    args = parser.parse_args()
+    if args.max_req < 1:
+        print('*** Usage error: --max_req CONCURRENT must be >= 1')
+        parser.print_usage()
+        # "standard" exit status codes:
+        # https://stackoverflow.com/questions/1101957/are-there-any-standard-exit-status-codes-in-linux/40484670#40484670
+        sys.exit(2)  # command line usage error
+    if args.limit < 1:
+        print('*** Usage error: --limit N must be >= 1')
+        parser.print_usage()
+        sys.exit(2)  # command line usage error
+    args.server = args.server.upper()
+    if args.server not in SERVERS:
+        print(f'*** Usage error: --server LABEL '
+              f'must be one of {server_options}')
+        parser.print_usage()
+        sys.exit(2)  # command line usage error
+    try:
+        cc_list = expand_cc_args(args.every, args.all, args.cc, args.limit)
+    except ValueError as exc:
+        print(exc.args[0])
+        parser.print_usage()
+        sys.exit(2)  # command line usage error
+
+    if not cc_list:
+        cc_list = sorted(POP20_CC)[:args.limit]
+    return args, cc_list
+
+
+def main(download_many, default_concur_req, max_concur_req):
+    args, cc_list = process_args(default_concur_req)
+    actual_req = min(args.max_req, max_concur_req, len(cc_list))
+    initial_report(cc_list, actual_req, args.server)
+    base_url = SERVERS[args.server]
+    DEST_DIR.mkdir(exist_ok=True)
+    t0 = time.perf_counter()
+    counter = download_many(cc_list, base_url, args.verbose, actual_req)
+    final_report(cc_list, counter, t0)