Extract binary merging logic

backend/sync_lib/src/errors.rs

@@ -1,16 +1,29 @@
+use std::str::Utf8Error;
+
 use base64::DecodeError;
 use thiserror::Error;
 use wasm_bindgen::JsValue;
 
 #[derive(Error, Debug)]
 pub enum SyncLibError {
-    #[error("Base64 decoding error: {}", .reason)]
-    DecodingError { reason: String },
+    #[error("Base64 decoding error because of {}", .reason)]
+    Base64DecodingError { reason: String },
+
+    #[error("Bytes cannot be decoded as UTF-8 string because of {}", .reason)]
+    StringDecodingError { reason: String },
 }
 
 impl From<DecodeError> for SyncLibError {
     fn from(e: DecodeError) -> Self {
-        SyncLibError::DecodingError {
+        SyncLibError::Base64DecodingError {
+            reason: e.to_string(),
+        }
+    }
+}
+
+impl From<Utf8Error> for SyncLibError {
+    fn from(e: Utf8Error) -> Self {
+        SyncLibError::StringDecodingError {
             reason: e.to_string(),
         }
     }
@@ -18,7 +31,7 @@ impl From<DecodeError> for SyncLibError {
 
 impl From<std::string::FromUtf8Error> for SyncLibError {
     fn from(e: std::string::FromUtf8Error) -> Self {
-        SyncLibError::DecodingError {
+        SyncLibError::Base64DecodingError {
             reason: e.to_string(),
         }
     }

backend/sync_lib/src/lib.rs

@@ -1,3 +1,5 @@
+use core::str;
+
 use base64::{engine::general_purpose::STANDARD_NO_PAD, Engine as _};
 use errors::SyncLibError;
 use wasm_bindgen::prelude::*;
@@ -27,6 +29,20 @@ pub fn base64_to_string(input: &str) -> Result<String, SyncLibError> {
     String::from_utf8(bytes).map_err(SyncLibError::from)
 }
 
+#[wasm_bindgen]
+pub fn merge(parent: &[u8], left: &[u8], right: &[u8]) -> Result<Vec<u8>, SyncLibError> {
+    Ok(if is_binary(right) {
+        right.to_vec()
+    } else {
+        reconcile::reconcile(
+            str::from_utf8(parent).map_err(SyncLibError::from)?,
+            str::from_utf8(left).map_err(SyncLibError::from)?,
+            str::from_utf8(right).map_err(SyncLibError::from)?,
+        )
+        .into_bytes()
+    })
+}
+
 #[wasm_bindgen]
 pub fn is_binary(data: &[u8]) -> bool { data.iter().any(|&b| b == 0) }