Refactor handling of pagination query arguments

src/main.rs

@@ -16,6 +16,7 @@ extern crate percent_encoding;
 extern crate pulldown_cmark;
 extern crate r2d2;
 extern crate r2d2_diesel;
+extern crate serde;
 extern crate serde_json;
 extern crate serde_urlencoded;
 extern crate slug;

src/resources/changes_resource.rs

@@ -9,14 +9,16 @@ use site::Layout;
 use state::State;
 use web::{Resource, ResponseFuture};
 
+use super::pagination::Pagination;
+
 pub struct ChangesResource {
     state: State,
     before: Option<i32>,
 }
 
 impl ChangesResource {
-    pub fn new(state: State, before: Option<i32>) -> Self {
-        Self { state, before }
+    pub fn new(state: State, pagination: Pagination<i32>) -> Self {
+        Self { state, before: match pagination { Pagination::Before(x) => Some(x), _ => None } }
     }
 }
 

src/resources/mod.rs

@@ -1,3 +1,5 @@
+pub mod pagination;
+
 mod article_redirect_resource;
 mod article_resource;
 mod changes_resource;

src/resources/pagination.rs

@@ -0,0 +1,29 @@
+use serde;
+use serde_urlencoded;
+
+#[derive(Deserialize)]
+struct PaginationStruct<T> {
+    after: Option<T>,
+    before: Option<T>,
+}
+
+pub enum Pagination<T> {
+    After(T),
+    Before(T),
+    None,
+}
+
+impl<T> PaginationStruct<T> {
+    fn into_enum(self) -> Pagination<T> {
+        match (self.after, self.before) {
+            (Some(x), _) => Pagination::After(x),
+            (None, Some(x)) => Pagination::Before(x),
+            _ => Pagination::None,
+        }
+    }
+}
+
+pub fn from_str<'a, T: serde::Deserialize<'a>>(s: &'a str) -> Result<Pagination<T>, serde::de::value::Error> {
+    let pagination: PaginationStruct<T> = serde_urlencoded::from_str(s)?;
+    Ok(pagination.into_enum())
+}

src/wiki_lookup.rs

@@ -2,10 +2,9 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 use std::str::Utf8Error;
 
-use futures::{Future, finished, failed};
+use futures::{Future, finished, failed, done};
 use futures::future::FutureResult;
 use percent_encoding::percent_decode;
-use serde_urlencoded;
 use slug::slugify;
 
 use resources::*;
@@ -84,17 +83,12 @@ impl WikiLookup {
             ("_assets", Some(asset)) =>
                 Box::new(asset_lookup(asset)),
             ("_changes", None) => {
-                #[derive(Deserialize)]
-                struct Query {
-                    before: Option<i32>,
-                }
-
-                let query: Query = match serde_urlencoded::from_str(query.unwrap_or("")) {
-                    Ok(x) => x,
-                    Err(x) => return Box::new(failed(x.into())),
-                };
-
-                Box::new(finished(Some(Box::new(ChangesResource::new(self.state.clone(), query.before)) as BoxResource)))
+                Box::new(done(
+                    pagination::from_str(query.unwrap_or("")).map_err(Into::into)
+                    .and_then(|pagination| Ok(Some(
+                        Box::new(ChangesResource::new(self.state.clone(), pagination)) as BoxResource
+                    )))
+                ))
             },
             ("_new", None) =>
                 Box::new(finished(Some(Box::new(NewArticleResource::new(self.state.clone(), None)) as BoxResource))),