264 lines
9.6 KiB
Python
264 lines
9.6 KiB
Python
"""
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This module interfaces the Wayback Machine's CDX server API.
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The module has WaybackMachineCDXServerAPI which should be used by the users of
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this module to consume the CDX server API.
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WaybackMachineCDXServerAPI has a snapshot method that yields the snapshots, and
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the snapshots are yielded as instances of the CDXSnapshot class.
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"""
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from typing import Dict, Generator, List, Optional, cast
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from .cdx_snapshot import CDXSnapshot
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from .cdx_utils import (
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check_collapses,
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check_filters,
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check_match_type,
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full_url,
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get_response,
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get_total_pages,
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)
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from .exceptions import WaybackError
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from .utils import DEFAULT_USER_AGENT
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class WaybackMachineCDXServerAPI:
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"""
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Class that interfaces the CDX server API of the Wayback Machine.
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snapshot() returns a generator that can be iterated upon by the end-user,
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the generator returns the snapshots/entries as instance of CDXSnapshot to
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make the usage easy, just use '.' to get any attribute as the attributes are
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accessible via a dot ".".
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"""
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# start_timestamp: from, can not use from as it's a keyword
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# end_timestamp: to, not using to as can not use from
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def __init__(
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self,
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url: str,
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user_agent: str = DEFAULT_USER_AGENT,
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start_timestamp: Optional[str] = None,
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end_timestamp: Optional[str] = None,
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filters: Optional[List[str]] = None,
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match_type: Optional[str] = None,
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gzip: Optional[str] = None,
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collapses: Optional[List[str]] = None,
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limit: Optional[str] = None,
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max_tries: int = 3,
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) -> None:
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self.url = str(url).strip().replace(" ", "%20")
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self.user_agent = user_agent
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self.start_timestamp = None if start_timestamp is None else str(start_timestamp)
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self.end_timestamp = None if end_timestamp is None else str(end_timestamp)
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self.filters = [] if filters is None else filters
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check_filters(self.filters)
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self.match_type = None if match_type is None else str(match_type).strip()
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check_match_type(self.match_type, self.url)
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self.gzip = gzip
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self.collapses = [] if collapses is None else collapses
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check_collapses(self.collapses)
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self.limit = 5000 if limit is None else limit
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self.max_tries = max_tries
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self.last_api_request_url: Optional[str] = None
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self.use_page = False
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self.endpoint = "https://web.archive.org/cdx/search/cdx"
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def cdx_api_manager(
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self, payload: Dict[str, str], headers: Dict[str, str], use_page: bool = False
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) -> Generator[str, None, None]:
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"""
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Manages the API calls for the instance, it automatically selects the best
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parameters by looking as the query of the end-user. For bigger queries
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automatically use the CDX pagination API and for smaller queries use the
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normal API.
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CDX Server API is a complex API and to make it easy for the end user to
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consume it the CDX manager(this method) handles the selection of the
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API output, whether to use the pagination API or not.
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For doing large/bulk queries, the use of the Pagination API is
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recommended by the Wayback Machine authors. And it determines if the
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query would be large or not by using the showNumPages=true parameter,
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this tells the number of pages of CDX DATA that the pagination API
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will return.
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If the number of page is less than 2 we use the normal non-pagination
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API as the pagination API is known to lag and for big queries it should
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not matter but for queries where the number of pages are less this
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method chooses accuracy over the pagination API.
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"""
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# number of pages that will returned by the pagination API.
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# get_total_pages adds the showNumPages=true param to pagination API
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# requests.
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# This is a special query that will return a single number indicating
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# the number of pages.
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total_pages = get_total_pages(self.url, self.user_agent)
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if use_page is True and total_pages >= 2:
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blank_pages = 0
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for i in range(total_pages):
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payload["page"] = str(i)
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url = full_url(self.endpoint, params=payload)
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res = get_response(url, headers=headers)
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if isinstance(res, Exception):
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raise res
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self.last_api_request_url = url
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text = res.text
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if len(text) == 0:
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blank_pages += 1
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if blank_pages >= 2:
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break
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yield text
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else:
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payload["showResumeKey"] = "true"
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payload["limit"] = str(self.limit)
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resume_key = None
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more = True
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while more:
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if resume_key:
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payload["resumeKey"] = resume_key
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url = full_url(self.endpoint, params=payload)
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res = get_response(url, headers=headers)
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if isinstance(res, Exception):
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raise res
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self.last_api_request_url = url
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text = res.text.strip()
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lines = text.splitlines()
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more = False
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if len(lines) >= 3:
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second_last_line = lines[-2]
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if len(second_last_line) == 0:
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resume_key = lines[-1].strip()
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text = text.replace(resume_key, "", 1).strip()
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more = True
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yield text
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def add_payload(self, payload: Dict[str, str]) -> None:
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"""
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Adds the payload to the payload dictionary.
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"""
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if self.start_timestamp:
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payload["from"] = self.start_timestamp
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if self.end_timestamp:
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payload["to"] = self.end_timestamp
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if self.gzip is None:
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payload["gzip"] = "false"
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if self.match_type:
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payload["matchType"] = self.match_type
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if self.filters and len(self.filters) > 0:
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for i, _filter in enumerate(self.filters):
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payload["filter" + str(i)] = _filter
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if self.collapses and len(self.collapses) > 0:
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for i, collapse in enumerate(self.collapses):
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payload["collapse" + str(i)] = collapse
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# Don't need to return anything as it's dictionary.
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payload["url"] = self.url
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def snapshots(self) -> Generator[CDXSnapshot, None, None]:
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"""
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This function yields the CDX data lines as snapshots.
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As it is a generator it exhaustible, the reason that this is
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a generator and not a list are:
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a) CDX server API can return millions of entries for a query and list
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is not suitable for such cases.
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b) Preventing memory usage issues, as told before this method may yield
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millions of records for some queries and your system may not have enough
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memory for such a big list. Also Remember this if outputing to Jupyter
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Notebooks.
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The objects yielded by this method are instance of CDXSnapshot class,
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you can access the attributes of the entries as the attribute of the instance
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itself.
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"""
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payload: Dict[str, str] = {}
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headers = {"User-Agent": self.user_agent}
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self.add_payload(payload)
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if not self.start_timestamp or self.end_timestamp:
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self.use_page = True
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if self.collapses != []:
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self.use_page = False
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entries = self.cdx_api_manager(payload, headers, use_page=self.use_page)
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for entry in entries:
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if entry.isspace() or len(entry) <= 1 or not entry:
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continue
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# each line is a snapshot aka entry of the CDX server API.
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# We are able to split the page by lines because it only
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# splits the lines on a sinlge page and not all the entries
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# at once, thus there should be no issues of too much memory usage.
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snapshot_list = entry.split("\n")
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for snapshot in snapshot_list:
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# 14 + 32 == 46 ( timestamp + digest ), ignore the invalid entries.
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# they are invalid if their length is smaller than sum of length
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# of a standard wayback_timestamp and standard digest of an entry.
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if len(snapshot) < 46:
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continue
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properties: Dict[str, Optional[str]] = {
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"urlkey": None,
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"timestamp": None,
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"original": None,
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"mimetype": None,
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"statuscode": None,
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"digest": None,
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"length": None,
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}
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property_value = snapshot.split(" ")
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total_property_values = len(property_value)
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warranted_total_property_values = len(properties)
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if total_property_values != warranted_total_property_values:
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raise WaybackError(
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f"Snapshot returned by CDX API has {total_property_values} prop"
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f"erties instead of expected {warranted_total_property_values} "
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f"properties.\nProblematic Snapshot: {snapshot}"
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)
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(
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properties["urlkey"],
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properties["timestamp"],
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properties["original"],
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properties["mimetype"],
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properties["statuscode"],
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properties["digest"],
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properties["length"],
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) = property_value
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yield CDXSnapshot(cast(Dict[str, str], properties))
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