docs: use html for notebook download links (#1976)

.docs/conf.py

@@ -23,15 +23,8 @@
 # -- determine if running on readthedocs ------------------------------------
 on_rtd = os.environ.get("READTHEDOCS") == "True"
 
-# -- determine if this version is a release candidate
-with open("../README.md") as f:
-    lines = f.readlines()
-rc_text = ""
-for line in lines:
-    if line.startswith("### Version"):
-        if "release candidate" in line:
-            rc_text = "release candidate"
-        break
+# -- determine if this is a development or release version ------------------
+branch_or_version = __version__ if "dev" not in __version__ else "develop"
 
 # -- get authors
 with open("../CITATION.cff") as f:
@@ -45,8 +38,6 @@
     for line in lines:
         if line.startswith("**Documentation for version"):
             line = f"**Documentation for version {__version__}"
-            if rc_text != "":
-                line += f" --- {rc_text}"
             line += "**\n"
         f.write(line)
 
@@ -272,6 +263,35 @@
 nbsphinx_prolog = (
     r"""
 {% set docname = env.doc2path(env.docname, base=None) %}
+
+.. raw:: html
+
+    <div class="admonition note">
+      This page was generated from
+      <a class="reference external" href="https://github.com/modflowpy/flopy/blob/"""
+    + branch_or_version
+    + r"""/.docs/Notebooks/{{ env.docname.split('/')|last|e + '.py' }}">{{ env.docname.split('/')|last|e + '.py' }}</a>.
+      It's also available as a <a href="{{ env.docname.split('/')|last|e + '.ipynb' }}" class="reference download internal" download>notebook</a>.
+      <script>
+        if (document.location.host) {
+          let nbviewer_link = document.createElement('a');
+          nbviewer_link.setAttribute('href',
+            'https://nbviewer.org/url' +
+            (window.location.protocol == 'https:' ? 's/' : '/') +
+            window.location.host +
+            window.location.pathname.slice(0, -4) +
+            'ipynb');
+          nbviewer_link.innerHTML = 'View in <em>nbviewer</em>';
+          nbviewer_link.innerHTML = 'Or view it on <em>nbviewer</em>';
+          nbviewer_link.classList.add('reference');
+          nbviewer_link.classList.add('external');
+          document.currentScript.replaceWith(nbviewer_link, '.');
+        }
+      </script>
+    </div>
 """
-    + Path("prolog.rst").read_text()
 )
+
+# Import Matplotlib to avoid this message in notebooks:
+# "Matplotlib is building the font cache; this may take a moment."
+import matplotlib.pyplot