feat(pagination): add paginate function to calculate offset, limit, a…

…nd total pages in `get_table` handler (#26)

* feat(pagination): add paginate function to calculate offset, limit, and total pages in `get_table` handler

* move more work into the `Pagination` struct

---------

Co-authored-by: Jacob Heider <[email protected]>

api/src/handlers.rs

@@ -5,12 +5,12 @@ use tokio_postgres::error::SqlState;
 use uuid::Uuid;
 
 use crate::app_state::AppState;
-use crate::utils::{get_column_names, rows_to_json};
+use crate::utils::{get_column_names, rows_to_json, Pagination};
 
 #[derive(Deserialize)]
-struct PaginationParams {
-    page: Option<i64>,
-    limit: Option<i64>,
+pub struct PaginationParams {
+    pub page: Option<i64>,
+    pub limit: Option<i64>,
 }
 
 #[derive(Serialize)]
@@ -59,29 +59,27 @@ pub async fn get_table(
         }));
     }
 
-    let page = query.page.unwrap_or(1).max(1);
-    let limit = query.limit.unwrap_or(200).clamp(1, 1000);
-    let offset = (page - 1) * limit;
-
     let count_query = format!("SELECT COUNT(*) FROM {}", table);
-    let data_query = format!("SELECT * FROM {} LIMIT $1 OFFSET $2", table);
-
     match data.pool.get().await {
         Ok(client) => match client.query_one(&count_query, &[]).await {
             Ok(count_row) => {
                 let total_count: i64 = count_row.get(0);
-                let total_pages = (total_count as f64 / limit as f64).ceil() as i64;
+                let pagination = Pagination::new(query, total_count);
 
-                match client.query(&data_query, &[&limit, &offset]).await {
+                let data_query = format!("SELECT * FROM {} LIMIT $1 OFFSET $2", table);
+                match client
+                    .query(&data_query, &[&pagination.limit, &pagination.offset])
+                    .await
+                {
                     Ok(rows) => {
                         let columns = get_column_names(&rows);
                         let data = rows_to_json(&rows);
                         let response = PaginatedResponse {
                             table,
                             total_count,
-                            page,
-                            limit,
-                            total_pages,
+                            page: pagination.page,
+                            limit: pagination.limit,
+                            total_pages: pagination.total_pages,
                             columns,
                             data,
                         };

api/src/utils.rs

@@ -1,8 +1,11 @@
+use actix_web::web::Query;
 use chrono::{DateTime, NaiveDate, NaiveDateTime, Utc};
 use serde_json::{json, Value};
 use tokio_postgres::{types::Type, Row};
 use uuid::Uuid;
 
+use crate::handlers::PaginationParams;
+
 pub fn get_column_names(rows: &[Row]) -> Vec<String> {
     if let Some(row) = rows.first() {
         row.columns()
@@ -55,3 +58,27 @@ pub fn rows_to_json(rows: &[Row]) -> Vec<Value> {
         })
         .collect()
 }
+
+pub struct Pagination {
+    pub page: i64,
+    pub limit: i64,
+    pub offset: i64,
+    pub total_pages: i64,
+}
+
+impl Pagination {
+    pub fn new(query: Query<PaginationParams>, total_count: i64) -> Self {
+        let limit = query.limit.unwrap_or(200).clamp(1, 1000);
+        let total_pages = (total_count as f64 / limit as f64).ceil() as i64;
+
+        let page = query.page.unwrap_or(1).clamp(1, total_pages);
+
+        let offset = (page - 1) * limit;
+        Self {
+            page,
+            limit,
+            offset,
+            total_pages,
+        }
+    }
+}