import hashlib
import io
from pathlib import Path
import tempfile
import unittest
from unittest.mock import patch
from urllib.error import HTTPError,URLError

from paper_atlas.io.http import fetch


class Response(io.BytesIO):
    def __init__(self,body,expected=None):
        super().__init__(body);self.status=200;self.headers={'Content-Length':str(expected if expected is not None else len(body))}


class FetchTests(unittest.TestCase):
    def test_transient_connection_failure_is_retried(self):
        with tempfile.TemporaryDirectory() as tmp,patch('paper_atlas.io.http.time.sleep'),patch('paper_atlas.io.http.urllib.request.urlopen',side_effect=[URLError(ConnectionResetError('reset')),Response(b'complete')]) as network:
            self.assertEqual(fetch('https://example.org/metadata',tmp),b'complete')
            self.assertEqual(network.call_count,2)

    def test_truncated_response_is_not_cached_as_complete(self):
        with tempfile.TemporaryDirectory() as tmp,patch('paper_atlas.io.http.time.sleep'),patch('paper_atlas.io.http.urllib.request.urlopen',side_effect=[Response(b'bad',expected=8),Response(b'complete')]):
            self.assertEqual(fetch('https://example.org/metadata',tmp),b'complete')
            path=Path(tmp)/hashlib.sha256(b'https://example.org/metadata').hexdigest()
            self.assertEqual(path.read_bytes(),b'complete')

    def test_forbidden_response_is_not_retried_or_bypassed(self):
        body=io.BytesIO(b'Forbidden');error=HTTPError('https://example.org/metadata',403,'Forbidden',{},body)
        with tempfile.TemporaryDirectory() as tmp,patch('paper_atlas.io.http.time.sleep'),patch('paper_atlas.io.http.urllib.request.urlopen',side_effect=error) as network:
            with self.assertRaises(HTTPError):fetch('https://example.org/metadata',tmp)
            self.assertEqual(network.call_count,1)
            self.assertTrue(body.closed)

    def test_transport_retries_are_bounded(self):
        with tempfile.TemporaryDirectory() as tmp,patch('paper_atlas.io.http.time.sleep'),patch('paper_atlas.io.http.urllib.request.urlopen',side_effect=ConnectionResetError('reset')) as network:
            with self.assertRaises(ConnectionResetError):fetch('https://example.org/metadata',tmp)
            self.assertEqual(network.call_count,3)

    def test_cached_response_still_obeys_the_size_limit(self):
        with tempfile.TemporaryDirectory() as tmp,patch('paper_atlas.io.http.urllib.request.urlopen') as network:
            path=Path(tmp)/hashlib.sha256(b'https://example.org/metadata').hexdigest();path.write_bytes(b'too large')
            with self.assertRaisesRegex(RuntimeError,'exceeds byte limit'):
                fetch('https://example.org/metadata',tmp,limit=2)
            network.assert_not_called()


if __name__=='__main__':unittest.main()