Allow to keep query params in paginate

Fix #349

src/routes/search.rs

@@ -29,13 +29,11 @@ pub struct SearchQuery {
 macro_rules! param_to_query {
     ( $query:ident, $parsed_query:ident; normal: $($field:ident),*; date: $($date:ident),*) => {
         $(
-            if let Some(ref field) = $query.$field {
-                let mut rest = field.as_str();
-                while !rest.is_empty() {
-                    let (token, r) = Query::get_first_token(rest);
-                    rest = r;
-                    $parsed_query.$field(token, None);
-                }
+            let mut rest = $query.$field.as_ref().map(String::as_str).unwrap_or_default();
+            while !rest.is_empty() {
+                let (token, r) = Query::get_first_token(rest);
+                rest = r;
+                $parsed_query.$field(token, None);
             }
         )*
         $(

src/template_utils.rs

@@ -75,18 +75,36 @@ pub fn tabs(links: &[(&str, &str, bool)]) -> Html<String> {
 }
 
 pub fn paginate(catalog: &Catalog, page: i32, total: i32) -> Html<String> {
+    paginate_param(catalog, page, total, None)
+}
+pub fn paginate_param(catalog: &Catalog, page: i32, total: i32, param: Option<String>) -> Html<String> {
     let mut res = String::new();
+    let param = param.map(|mut p| {p.push('&'); p}).unwrap_or_default();
     res.push_str(r#"<div class="pagination">"#);
     if page != 1 {
-        res.push_str(format!(r#"<a href="?page={}">{}</a>"#, page - 1, catalog.gettext("Previous page")).as_str());
+        res.push_str(format!(r#"<a href="?{}page={}">{}</a>"#, param, page - 1, catalog.gettext("Previous page")).as_str());
     }
     if page < total {
-        res.push_str(format!(r#"<a href="?page={}">{}</a>"#, page + 1, catalog.gettext("Next page")).as_str());
+        res.push_str(format!(r#"<a href="?{}page={}">{}</a>"#, param, page + 1, catalog.gettext("Next page")).as_str());
     }
     res.push_str("</div>");
     Html(res)
 }
 
+pub fn encode_query_param(param: &str) -> String {
+    param.chars().map(|c| match c {
+        '+' => Ok("%2B"),
+        ' ' => Err('+'),
+        c   => Err(c),
+    }).fold(String::new(), |mut s,r| {
+        match r {
+            Ok(r) => s.push_str(r),
+            Err(r) => s.push(r),
+        };
+        s
+    })
+}
+
 #[macro_export]
 macro_rules! icon {
     ($name:expr) => {

templates/search/result.rs.html

@@ -23,5 +23,5 @@
             }
         </div>
     }
-    @paginate(ctx.1, page, n_pages)
+    @paginate_param(ctx.1, page, n_pages, Some(format!("q={}", encode_query_param(query_str))))
 })