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(* Forum -- forum subapp
Copyright (C) 2013 Benjamin Barenblat <bbaren@mit.edu>
This file is a part of 6.947.
6.947 is is free software: you can redistribute it and/or modify it under the
terms of the GNU Affero General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your option) any
later version.
6.947 is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU Affero General Public License for more
details.
You should have received a copy of the GNU Affero General Public License along
with 6.947. If not, see <http://www.gnu.org/licenses/>. *)
functor Make(Template : sig
val generic : option string -> xbody -> page
end) = struct
open Styles
style entryList
style entryMetadata
style entryTitle
style entryBody
style voting
table entry : { Id : int,
References : option int,
Class : EntryClass.entryClass,
Title : option string,
Body : string,
Author : Author.usernameOrAnonymous
} PRIMARY KEY Id
sequence entryIdS
table vote : { QuestionId : int,
Author : Author.username,
Value : Score.score
}
CONSTRAINT OneVotePerEntry UNIQUE (QuestionId, Author),
CONSTRAINT RefersToEntry FOREIGN KEY QuestionId REFERENCES entry(Id)
(* Like query1', but automatically dereferences the field *)
fun queryColumn [tab ::: Name] [field ::: Name] [state ::: Type]
(q : sql_query [] [] [tab = [field = state]] [])
(f : state -> state -> state)
(initial : state)
: transaction state =
query q (fn row state => return (f row.tab.field state)) initial
(* Sum all the votes on a single question. *)
fun getScore (questionId : int) : transaction Score.score =
queryColumn (SELECT Vote.Value FROM vote
WHERE Vote.QuestionId = {[questionId]})
Score.update
Score.undecided
fun recordVote (value : Score.score) (entryId : int) _formData : transaction page =
authorOpt <- Author.current;
(* If the user didn't exist, the user should not have been allowed to vote
in the first place. *)
let val author = Author.nameError authorOpt
in
dml (INSERT INTO vote (QuestionId, Author, Value)
VALUES ({[entryId]}, {[author]}, {[value]}));
detail entryId
end
and upvote entryId _formData = recordVote Score.insightful entryId _formData
(***************************** Single questions ******************************)
and detail (id : int) : transaction page =
authorOpt <- Author.current;
question <- oneRow1 (SELECT * FROM entry
WHERE Entry.Class = {[EntryClass.question]}
AND Entry.Id = {[id]});
score <- getScore id;
answerBlock <- queryX1' (SELECT * FROM entry
WHERE Entry.Class = {[EntryClass.answer]}
AND Entry.References = {[Some id]})
(fn answer =>
score <- getScore answer.Id;
return (
<xml><p>
{[answer.Body]}
<span class={entryMetadata}>—{[answer.Author]} ({[Score.withUnits score "point"]})</span>
</p></xml>));
return (
Template.generic (Some "Forum") <xml>
<div class={content}>
<h2>{[question.Title]}</h2>
<p>{[question.Body]}</p>
<p class={entryMetadata}>
Asked by {[question.Author]} ({[Score.withUnits score "point"]})
</p>
{Author.whenIdentified authorOpt
<xml>
<form class={voting}><submit action={upvote id} value="⬆" /></form>
</xml>}
<div>{answerBlock}</div>
<h3>Your answer</h3>
<form>
<textarea {#Body} class={entryBody} /><br />
Answering as:
<select {#Author}>
{Author.whenIdentified' authorOpt (fn u => <xml><option>{[u]}</option></xml>)}
<option>Anonymous</option>
</select>
<submit action={reply id} value="Answer" />
</form>
</div>
</xml>)
and reply qId submission =
id <- nextval entryIdS;
dml (INSERT INTO entry (Id, References, Class, Title, Body, Author)
VALUES ({[id]},
{[Some qId]},
{[EntryClass.answer]},
{[None]},
{[submission.Body]},
{[readError submission.Author]}));
detail qId
(**************************** Lists of questions *****************************)
fun prettyPrintQuestion entry : transaction xbody =
score <- getScore entry.Id;
return (
<xml><li>
<h3><a link={detail entry.Id}>{[entry.Title]}</a></h3>
{[entry.Body]}
<span class={entryMetadata}>Asked by {[entry.Author]} ({[Score.withUnits score "point"]})</span>
</li></xml>)
val allQuestions : transaction page =
questionsList <- queryX1' (SELECT * FROM entry
WHERE Entry.Class = {[EntryClass.question]}
ORDER BY Entry.Id DESC)
prettyPrintQuestion;
return (
Template.generic (Some "Forum – All questions") <xml>
<div class={content}>
<h2>All questions</h2>
<ul class={entryList}>
{questionsList}
</ul>
</div>
</xml>)
fun main () : transaction page =
newestQuestions <- queryX1' (SELECT * FROM entry
WHERE Entry.Class = {[EntryClass.question]}
ORDER BY Entry.Id DESC
LIMIT 5)
prettyPrintQuestion;
askerOpt <- Author.current;
return (
Template.generic (Some "Forum") <xml>
<div class={content}>
<h2>Latest questions</h2>
<ul class={entryList}>
{newestQuestions}
</ul>
<a link={allQuestions}>View all questions</a>
<h2>Ask a new question</h2>
<form>
<textbox {#Title} placeholder="Title" class={entryTitle} /><br />
<textarea {#Body} class={entryBody} /><br />
Asking as:
<select {#Author}>
{Author.whenIdentified' askerOpt (fn u =>
<xml><option>{[u]}</option></xml>)}
<option>Anonymous</option>
</select>
<submit action={ask} value="Ask" />
</form>
</div>
</xml>)
and ask submission =
id <- nextval entryIdS;
dml (INSERT INTO entry (Id, References, Class, Title, Body, Author)
VALUES ({[id]},
{[None]},
{[EntryClass.question]},
{[Some submission.Title]},
{[submission.Body]},
{[readError submission.Author]}));
main ()
end
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