add sort param support in CDX API class (#156)

see https://nla.github.io/outbackcdx/api.html#operation/query

sort takes string input which must be one of the follwoing:
- default
- closest
- reverse

This commit shall help in closing issue at #155

tests/test_cdx_utils.py

@@ -6,6 +6,7 @@
     check_collapses,
     check_filters,
     check_match_type,
+    check_sort,
     full_url,
     get_response,
     get_total_pages,
@@ -101,3 +102,12 @@ def test_check_match_type() -> None:
 
     with pytest.raises(WaybackError):
         check_match_type("not a valid type", "url")
+
+
+def test_check_sort() -> None:
+    assert check_sort("default")
+    assert check_sort("closest")
+    assert check_sort("reverse")
+
+    with pytest.raises(WaybackError):
+        assert check_sort("random crap")

waybackpy/cdx_api.py

@@ -16,6 +16,7 @@
     check_collapses,
     check_filters,
     check_match_type,
+    check_sort,
     full_url,
     get_response,
     get_total_pages,
@@ -44,6 +45,7 @@ def __init__(
         end_timestamp: Optional[str] = None,
         filters: Optional[List[str]] = None,
         match_type: Optional[str] = None,
+        sort: Optional[str] = None,
         gzip: Optional[str] = None,
         collapses: Optional[List[str]] = None,
         limit: Optional[str] = None,
@@ -57,6 +59,8 @@ def __init__(
         check_filters(self.filters)
         self.match_type = None if match_type is None else str(match_type).strip()
         check_match_type(self.match_type, self.url)
+        self.sort = None if sort is None else str(sort).strip()
+        check_sort(self.sort)
         self.gzip = gzip
         self.collapses = [] if collapses is None else collapses
         check_collapses(self.collapses)
@@ -165,6 +169,9 @@ def add_payload(self, payload: Dict[str, str]) -> None:
         if self.match_type:
             payload["matchType"] = self.match_type
 
+        if self.sort:
+            payload["sort"] = self.sort
+
         if self.filters and len(self.filters) > 0:
             for i, _filter in enumerate(self.filters):
                 payload["filter" + str(i)] = _filter

waybackpy/cdx_utils.py

@@ -151,3 +151,24 @@ def check_match_type(match_type: Optional[str], url: str) -> bool:
         raise WaybackError(exc_message)
 
     return True
+
+
+def check_sort(sort: Optional[str]) -> bool:
+    """
+    Check that the sort argument passed by the end-user is valid.
+    If not valid then raise WaybackError.
+    """
+
+    legal_sort = ["default", "closest", "reverse"]
+
+    if not sort:
+        return True
+
+    if sort not in legal_sort:
+        exc_message = (
+            f"{sort} is not an allowed argument for sort.\n"
+            "Use one from 'default', 'closest' or 'reverse'"
+        )
+        raise WaybackError(exc_message)
+
+    return True