Refactor render_body to handle each mime-type in a nested function

This replaces the giant elif cascade with a table lookup. It also allows
me to call one function from another.

mbox2web

@@ -83,22 +83,17 @@ def save_part(msg, disposition):
 partial_message_cache = {}
 
 def render_body(msg):
-    content_type = msg.get_content_type()
+    def render_text_plain(msg):
-    content_disposition = msg.get_content_disposition()
-    if content_disposition == "attachment":
-        # XXX - not sure, if we should just store all content-types. 
-        # We probably should clean up html. Alternatively we could just store
-        # all of them application/octet-stream, which browsers should download
-        # and not try to display.
-        bodyhtml = save_part(msg, content_disposition)
-
-    elif content_type == "text/plain":
         bodytmpl = jenv.get_template("body_text_plain.html")
         context = {
             "body": msg.get_payload(decode=True).decode(msg.get_charset() or "iso-8859-1")
         }
         bodyhtml = bodytmpl.render(context)
-    elif content_type == "multipart/mixed":
+    def render_multipart_mixed(msg):
+        parts = msg.get_payload()
+        if type(parts) == str:
+            # mislabelled, assume text/plain
+            raise NotImplementedError()
         partshtml = []
         for part in msg.get_payload():
             partshtml.append(render_body(part))
@@ -107,7 +102,7 @@ def render_body(msg):
             "parts": partshtml
         }
         bodyhtml = bodytmpl.render(context)
-    elif content_type == "multipart/digest":
+    def render_multipart_digest(msg):
         partshtml = []
         for part in msg.get_payload():
             partshtml.append(render_message(part))
@@ -116,7 +111,7 @@ def render_body(msg):
             "parts": partshtml
         }
         bodyhtml = bodytmpl.render(context)
-    elif content_type == "message/rfc822":
+    def render_message_rfc822(msg):
         partshtml = []
         for part in msg.get_payload():
             partshtml.append(render_message(part))
@@ -125,7 +120,7 @@ def render_body(msg):
             "parts": partshtml
         }
         bodyhtml = bodytmpl.render(context)
-    elif content_type == "text/html":
+    def render_text_html(msg):
         htmlpart = HTMLPart()
         htmlpart.feed(msg.get_payload(decode=True).decode(msg.get_charset() or "iso-8859-1"))
         bodytmpl = jenv.get_template("body_text_html.html")
@@ -133,7 +128,7 @@ def render_body(msg):
             "body": jinja2.Markup(htmlpart.as_string())
         }
         bodyhtml = bodytmpl.render(context)
-    elif content_type == "text/enriched":
+    def render_text_enriched(msg):
         payload = msg.get_payload(decode=True).decode(msg.get_charset() or "iso-8859-1")
         tepart = TextEnrichedPart(payload)
         bodytmpl = jenv.get_template("body_text_enriched.html")
@@ -141,7 +136,7 @@ def render_body(msg):
             "body": jinja2.Markup(tepart.as_string())
         }
         bodyhtml = bodytmpl.render(context)
-    elif content_type == "message/partial":
+    def render_message_partial(msg):
         # Default header for get_param is Content-Type
         whole_msg_id = msg.get_param("id")
         if not whole_msg_id in partial_message_cache:
@@ -167,10 +162,10 @@ def render_body(msg):
                         encode_message_id(whole_msg_id),
                         html.escape(whole_msg_id))
 
-    elif content_type == "application/octet-stream":
+    def render_application_octet_stream(msg):
         bodyhtml = save_part(msg, "attachment")
 
-    elif content_type == "multipart/signed":
+    def render_multipart_signed(msg):
         content, signature = msg.get_payload()
         with tempfile.NamedTemporaryFile(buffering=0) as content_fh:
             content_fh.write(content.as_bytes())
@@ -194,7 +189,7 @@ def render_body(msg):
         }
         bodyhtml = bodytmpl.render(context)
 
-    elif content_type == "application/pgp":
+    def render_application_pgp(msg):
         with tempfile.NamedTemporaryFile(buffering=0) as content_fh:
             content_fh.write(msg.get_payload(decode=True))
             r = subprocess.run(["gpg", "--decrypt", content_fh.name],
@@ -217,7 +212,7 @@ def render_body(msg):
         }
         bodyhtml = bodytmpl.render(context)
 
-    elif content_type == "multipart/alternative":
+    def render_multipart_alternative(msg):
         partshtml = []
         partstypes = []
         for part in msg.get_payload():
@@ -230,24 +225,24 @@ def render_body(msg):
         }
         bodyhtml = bodytmpl.render(context)
 
-    elif content_type == "application/x-unknown-content-type-scpfile":
+    def render_application_x_unknown_content_type_scpfile(msg):
         bodytmpl = jenv.get_template("body_application_x-unknown-content-type-scpfile.html")
         context = {
             "body": msg.get_payload(decode=True).decode(msg.get_charset() or "iso-8859-1")
         }
         bodyhtml = bodytmpl.render(context)
 
-    elif content_type == "application/pgp-signature":
+    def render_application_pgp_signature(msg):
         # A PGP signature outside of a multipart/signed - useless
         bodytmpl = jenv.get_template("body_application_pgp-signature.html")
         context = {
         }
         bodyhtml = bodytmpl.render(context)
 
-    elif content_type == "application/x-gzip":
+    def render_application_x_gzip(msg):
         bodyhtml = save_part(msg, "attachment")
 
-    elif content_type == "message/news":
+    def render_message_news(msg):
         partshtml = []
         for part in msg.get_payload():
             partshtml.append(render_message(part))
@@ -258,11 +253,37 @@ def render_body(msg):
         }
         bodyhtml = bodytmpl.render(context)
 
-    elif content_type == "image/gif":
+    def render_image_gif(msg):
         bodyhtml = save_part(msg, "inline")
 
+    renderers = {
+        "text/plain": render_text_plain,
+        "multipart/mixed": render_multipart_mixed,
+        "multipart/digest": render_multipart_digest,
+        "message/rfc822": render_message_rfc822,
+        "text/html": render_text_html,
+        "text/enriched": render_text_enriched,
+        "message/partial": render_message_partial,
+        "application/octet-stream": render_application_octet_stream,
+        "multipart/signed": render_multipart_signed,
+        "application/pgp": render_application_pgp,
+        "multipart/alternative": render_multipart_alternative,
+        "application/x-unknown-content-type-scpfile": render_application_x_unknown_content_type_scpfile,
+        "application/pgp-signature": render_application_pgp_signature,
+        "application/x-gzip": render_application_x_gzip,
+        "message/news": render_message_news,
+        "image/gif": render_image_gif,
+    }
+    content_type = msg.get_content_type()
+    content_disposition = msg.get_content_disposition()
+    if content_disposition == "attachment":
+        # XXX - not sure, if we should just store all content-types. 
+        # We probably should clean up html. Alternatively we could just store
+        # all of them application/octet-stream, which browsers should download
+        # and not try to display.
+        bodyhtml = save_part(msg, content_disposition)
     else:
-        raise RuntimeError("Content-type " + content_type + " not implemented yet")
+        bodyhtml = renderers[content_type](msg)
 
     return jinja2.Markup(bodyhtml)