From 350cde2324cf4bc9df6c4bcecf638b8208495b64 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@mit.edu>
Date: Thu, 25 Apr 2013 17:03:10 -0400
Subject: Forum: Move asker into its own datatype

---
 forum/asker.ur  | 26 ++++++++++++++++++++++++++
 forum/asker.urs | 17 +++++++++++++++++
 forum/forum.ur  | 19 +++++--------------
 forum/lib.urp   |  2 ++
 4 files changed, 50 insertions(+), 14 deletions(-)
 create mode 100644 forum/asker.ur
 create mode 100644 forum/asker.urs

diff --git a/forum/asker.ur b/forum/asker.ur
new file mode 100644
index 0000000..947f20c
--- /dev/null
+++ b/forum/asker.ur
@@ -0,0 +1,26 @@
+type asker = option string
+
+val eq_asker = Option.eq
+
+val show_asker =
+    mkShow (
+        fn nameOpt =>
+	    case nameOpt of
+        	None => "Anonymous"
+              | Some nam => nam
+    )
+
+val read_asker =
+    let fun parse text =
+	    case text of
+		"Anonymous" => None
+	      | nam => Some nam
+    in
+	mkRead parse (compose Some parse)
+    end
+
+val sql_asker = sql_option_prim
+
+val anonymous = None
+
+val namedAsker = Some
diff --git a/forum/asker.urs b/forum/asker.urs
new file mode 100644
index 0000000..99be711
--- /dev/null
+++ b/forum/asker.urs
@@ -0,0 +1,17 @@
+type asker
+
+val anonymous : asker
+val namedAsker : string -> asker
+
+
+(********************************* Instances *********************************)
+
+val eq_asker : eq asker
+
+val show_asker : show asker
+
+(* 'read' producing an 'asker' is guaranteed to never fail, so you can use
+'readError' with impunity. *)
+val read_asker : read asker
+
+val sql_asker : sql_injectable asker
diff --git a/forum/forum.ur b/forum/forum.ur
index 9556068..2dbfcb0 100644
--- a/forum/forum.ur
+++ b/forum/forum.ur
@@ -21,30 +21,21 @@ functor Make(Template : sig
 end) = struct
 
 open Styles
+open Asker
 
 table question : { Id : int,
 		   Title : string,
 		   Body : string,
-		   Asker : option string (* 'None' if anonymous *)
+		   Asker : asker
 		 } PRIMARY KEY Id
 sequence questionIdS
 
-fun showAskerOpt (askerOpt : option string) : string =
-    case askerOpt of
-	None => "Anonymous"
-      | Some nam => nam
-
-fun readAskerOpt (text : string) : option string =
-    case text of
-	"Anonymous" => None
-      | nam => Some nam
-
 (* Grabs real name out of MIT certificate. *)
 val getName = getenv (blessEnvVar "SSL_CLIENT_S_DN_CN")
 
 fun prettyPrintQuestion row : xbody =
     <xml>
-      <p>{[row.Question.Title]}: {[row.Question.Body]} (asked by {[showAskerOpt row.Question.Asker]})</p>
+      <p>{[row.Question.Title]}: {[row.Question.Body]} (asked by {[row.Question.Asker]})</p>
     </xml>
 
 fun main () : transaction page =
@@ -61,7 +52,7 @@ fun main () : transaction page =
 	      <textarea {#Body} rows=12 cols=80 /><br />
 	      Asking as:
 	        <select {#Asker}>
-		  <option>{[showAskerOpt askerOpt]}</option>
+		  <option>{[askerOpt]}</option>
 		  <option>Anonymous</option>
 		</select>
 	      <submit action={ask} value="Ask" />
@@ -73,7 +64,7 @@ fun main () : transaction page =
 and ask submission =
     id <- nextval questionIdS;
     dml (INSERT INTO question (Id, Title, Body, Asker)
-	 VALUES ({[id]}, {[submission.Title]}, {[submission.Body]}, {[readAskerOpt submission.Asker]}));
+	 VALUES ({[id]}, {[submission.Title]}, {[submission.Body]}, {[readError submission.Asker]}));
     main ()
 
 end
diff --git a/forum/lib.urp b/forum/lib.urp
index 8f0ef71..dd3456d 100644
--- a/forum/lib.urp
+++ b/forum/lib.urp
@@ -1,4 +1,6 @@
 allow env SSL_CLIENT_S_DN_CN
 
+$/option
 ../styles
+asker
 forum
-- 
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