chore(http): unify the pagination of the index and documents route behind a common type

meilisearch-http/src/routes/mod.rs

@@ -3,6 +3,7 @@ use std::str::FromStr;
 use actix_web::{web, HttpResponse};
 use log::debug;
 use serde::{Deserialize, Serialize};
+
 use time::OffsetDateTime;
 
 use meilisearch_error::ResponseError;
@@ -58,6 +59,86 @@ pub fn fold_star_or<T>(content: impl IntoIterator<Item = StarOr<T>>) -> Option<V
         .collect()
 }
 
+const PAGINATION_DEFAULT_LIMIT: fn() -> usize = || 20;
+
+#[derive(Debug, Clone, Copy, Deserialize)]
+#[serde(rename_all = "camelCase", deny_unknown_fields)]
+pub struct Pagination {
+    #[serde(default)]
+    pub offset: usize,
+    #[serde(default = "PAGINATION_DEFAULT_LIMIT")]
+    pub limit: usize,
+}
+
+#[derive(Debug, Clone, Serialize)]
+pub struct PaginationView<T> {
+    pub results: Vec<T>,
+    pub offset: usize,
+    pub limit: usize,
+    pub total: usize,
+}
+
+impl Pagination {
+    /// Given the full data to paginate, returns the selected section.
+    pub fn auto_paginate_sized<T>(
+        self,
+        content: impl IntoIterator<Item = T> + ExactSizeIterator,
+    ) -> PaginationView<T>
+    where
+        T: Serialize,
+    {
+        let total = content.len();
+        let content: Vec<_> = content
+            .into_iter()
+            .skip(self.offset)
+            .take(self.limit)
+            .collect();
+        self.format_with(total, content)
+    }
+
+    /// Given an iterator and the total number of elements, returns the selected section.
+    pub fn auto_paginate_unsized<T>(
+        self,
+        total: usize,
+        content: impl IntoIterator<Item = T>,
+    ) -> PaginationView<T>
+    where
+        T: Serialize,
+    {
+        let content: Vec<_> = content
+            .into_iter()
+            .skip(self.offset)
+            .take(self.limit)
+            .collect();
+        self.format_with(total, content)
+    }
+
+    /// Given the data already paginated + the total number of elements, it stores
+    /// everything in a [PaginationResult].
+    pub fn format_with<T>(self, total: usize, results: Vec<T>) -> PaginationView<T>
+    where
+        T: Serialize,
+    {
+        PaginationView {
+            results,
+            offset: self.offset,
+            limit: self.limit,
+            total,
+        }
+    }
+}
+
+impl<T> PaginationView<T> {
+    pub fn new(offset: usize, limit: usize, total: usize, results: Vec<T>) -> Self {
+        Self {
+            offset,
+            limit,
+            results,
+            total,
+        }
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[allow(clippy::large_enum_variant)]
 #[serde(tag = "name")]