Create Signposting from RO-Crate (#2)

* improvate jsonld parsing to be compatible with ro-crate

* refactoring

* example with RO-Crate

* bump version

---------

Co-authored-by: Daniel Bauer <daniel.bauer@senckenberg.de>

django_signposting/utils.py

@@ -1,5 +1,10 @@
+import json
 from django.http import HttpResponse
-from signposting import Signpost
+from rdflib import Graph
+from signposting import Signpost, LinkRel
+import re
+
+from django_signposting import sparql
 
 
 def add_signposts(response: HttpResponse, *args: Signpost):
@@ -15,3 +20,67 @@ def add_signposts(response: HttpResponse, *args: Signpost):
     for signpost in args:
         if signpost not in response._signposts:
             response._signposts.append(signpost)
+
+
+def select_url(elements: tuple[str, ...]) -> str | None:
+    def is_url(url: str) -> bool:
+        url_pattern = re.compile(
+            r"^(https?|ftp)://"  # protocol
+            r"(?:(?:[a-zA-Z0-9-_]+\.)?[a-zA-Z0-9-]+\.[a-zA-Z]{2,6})"  # domain
+            r"(?::\d{1,5})?"  # optional port
+            r"(?:/.*)?$"  # path
+        )
+        return bool(url_pattern.match(url))
+
+    for elem in elements[::-1]:
+        if is_url(str(elem)):
+            return str(elem)
+    return None
+
+
+def jsonld_to_signposts(jsonld: dict) -> []:
+    signposts = []
+    # TODO use jsonld context in query as prefix
+    g = Graph().parse(data=json.dumps(jsonld), format="json-ld")
+
+    rootElement = next(iter(sparql.root_element_query(g)), None)
+    if rootElement:
+        rootElement = rootElement[0]
+    else:
+        print("No root element found")
+        return {}
+    types = sparql.type_query(g, rootElement)
+    for type in types:
+        signposts.append(Signpost(LinkRel.type, str(type[0])))
+
+    authors = sparql.author_query(g, rootElement)
+    for author in authors:
+        author = select_url(author)
+        if author:
+            signposts.append(Signpost(LinkRel.author, author))
+
+    license = next(iter(sparql.license_query(g, rootElement)), [])
+    license = select_url(license)
+    if license:
+        signposts.append(Signpost(LinkRel.license, license))
+
+    citations = sparql.cite_query(g, rootElement)
+    for citation in citations:
+        citation = select_url(citation)
+        if citation:
+            signposts.append(Signpost(LinkRel.cite_as, citation))
+
+    sameas = sparql.sameas_query(g, rootElement)
+    for sa in sameas:
+        sa_media_type = sa[-1]
+        sa = select_url(sa[:-1])
+        if sa:
+            signposts.append(Signpost(LinkRel.describedby, sa, sa_media_type))
+
+    items = sparql.item_query(g, rootElement)
+    for item in items:
+        item_media_type = item[-1]
+        item = select_url(item[:-1])
+        if item:
+            signposts.append(Signpost(LinkRel.item, item, item_media_type))
+    return signposts