From 47d0f971fcf64d1bb036f0081d2ff209ec5007ee Mon Sep 17 00:00:00 2001
From: Jari Vetoniemi <jari.vetoniemi@indooratlas.com>
Date: Thu, 17 Feb 2022 05:31:06 +0900
Subject: initial commit

---
 src/pagination.rs | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 src/pagination.rs

(limited to 'src/pagination.rs')

diff --git a/src/pagination.rs b/src/pagination.rs
new file mode 100644
index 0000000..961b079
--- /dev/null
+++ b/src/pagination.rs
@@ -0,0 +1,103 @@
+use diesel::prelude::*;
+use diesel::query_builder::*;
+use diesel::query_dsl::methods::LoadQuery;
+use diesel::sql_types::BigInt;
+use diesel::sqlite::Sqlite;
+use rocket::serde::Serialize;
+
+pub trait SortingAndPaging: Sized {
+    fn paginate(self, page: i64) -> SortedAndPaginated<Self>;
+}
+
+impl<T> SortingAndPaging for T {
+    fn paginate(self, page: i64) -> SortedAndPaginated<Self> {
+        SortedAndPaginated {
+            query: self,
+            sort_by: "".to_string(),
+            sort_direction: "".to_string(),
+            per_page: 100,
+            page,
+        }
+    }
+}
+
+#[derive(Serialize)]
+#[serde(crate = "rocket::serde")]
+pub struct Page<T> {
+    pub data: Vec<T>,
+    pub page_num: i64,
+    pub page_size: i64,
+    pub total_elements: i64,
+}
+
+impl<T> Page<T> {
+    pub fn new(data: Vec<T>, page_num: i64, page_size: i64, total_elements: i64) -> Page<T> {
+        Page {
+            data,
+            page_num,
+            page_size,
+            total_elements,
+        }
+    }
+}
+
+#[derive(Debug, Clone, QueryId)]
+pub struct SortedAndPaginated<T> {
+    query: T,
+    sort_by: String,
+    sort_direction: String,
+    page: i64,
+    per_page: i64,
+}
+
+impl<T> SortedAndPaginated<T> {
+    pub fn per_page(self, per_page: i64) -> Self {
+        SortedAndPaginated { per_page, ..self }
+    }
+
+    pub fn sort(self, sort_by: String, sort_direction: String) -> Self {
+        SortedAndPaginated {
+            sort_by,
+            sort_direction,
+            ..self
+        }
+    }
+
+    pub fn load_and_count_items<U>(self, conn: &SqliteConnection) -> QueryResult<Page<U>>
+    where
+        Self: LoadQuery<SqliteConnection, (U, i64)>,
+    {
+        let page = self.page;
+        let per_page = self.per_page;
+        let results = self.load::<(U, i64)>(conn)?;
+        let total = results.get(0).map(|x| x.1).unwrap_or(0);
+        let records = results.into_iter().map(|x| x.0).collect();
+        Ok(Page::new(records, page, per_page, total))
+    }
+}
+
+impl<T: Query> Query for SortedAndPaginated<T> {
+    type SqlType = (T::SqlType, BigInt);
+}
+
+impl<T> RunQueryDsl<SqliteConnection> for SortedAndPaginated<T> {}
+
+impl<T> QueryFragment<Sqlite> for SortedAndPaginated<T>
+where
+    T: QueryFragment<Sqlite>,
+{
+    fn walk_ast(&self, mut out: AstPass<Sqlite>) -> QueryResult<()> {
+        out.push_sql("SELECT *, COUNT(*) OVER () FROM (");
+        self.query.walk_ast(out.reborrow())?;
+        out.push_sql(") t ");
+        if &self.sort_by.as_str().len() > &0 {
+            out.push_sql(format!(" ORDER BY {} {}", &self.sort_by, &self.sort_direction).as_str());
+        }
+        out.push_sql(" LIMIT ");
+        out.push_bind_param::<BigInt, _>(&self.per_page)?;
+        out.push_sql(" OFFSET ");
+        let offset = (self.page - 1) * self.per_page;
+        out.push_bind_param::<BigInt, _>(&offset)?;
+        Ok(())
+    }
+}
-- 
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