Add OpaqueCursor #1040

Cargo.toml

@@ -53,6 +53,7 @@ serde_json = "1.0.64"
 static_assertions = "1.1.0"
 tempfile = "3.2.0"
 thiserror = "1.0.24"
+base64 = "0.13.0"
 
 # Feature optional dependencies
 bson = { version = "2.0.0", optional = true, features = ["chrono-0_4"] }

src/types/connection/cursor.rs

@@ -4,6 +4,8 @@ use std::{
     num::{ParseFloatError, ParseIntError},
 };
 
+use serde::{de::DeserializeOwned, Serialize};
+
 use crate::ID;
 
 /// Cursor type
@@ -104,3 +106,23 @@ impl CursorType for f32 {
         self.to_string()
     }
 }
+
+/// A opaque cursor that encode/decode the value to base64
+pub struct OpaqueCursor<T>(T);
+
+impl<T> CursorType for OpaqueCursor<T>
+where
+    T: Serialize + DeserializeOwned,
+{
+    type Error = Box<dyn std::error::Error + Send + Sync>;
+
+    fn decode_cursor(s: &str) -> Result<Self, Self::Error> {
+        let data = base64::decode_config(s, base64::URL_SAFE_NO_PAD)?;
+        Ok(Self(serde_json::from_slice(&data)?))
+    }
+
+    fn encode_cursor(&self) -> String {
+        let value = serde_json::to_vec(&self.0).unwrap_or_default();
+        base64::encode_config(value, base64::URL_SAFE_NO_PAD)
+    }
+}

src/types/connection/mod.rs

@@ -8,7 +8,7 @@ mod page_info;
 use std::{fmt::Display, future::Future};
 
 pub use connection_type::Connection;
-pub use cursor::CursorType;
+pub use cursor::{CursorType, OpaqueCursor};
 pub use edge::Edge;
 pub use page_info::PageInfo;