diff.rs

extern crate alloc;

use alloc::string::{String, ToString};
use core::ffi::c_int;

use powersync_sqlite_nostd as sqlite;
use powersync_sqlite_nostd::{Connection, Context, Value};
use sqlite::ResultCode;

use crate::constants::SUBTYPE_JSON;
use crate::create_sqlite_text_fn;
use crate::error::PowerSyncError;
use powersync_sqlite_nostd::bindings::SQLITE_RESULT_SUBTYPE;
use serde_json as json;

fn powersync_diff_impl(
    ctx: *mut sqlite::context,
    args: &[*mut sqlite::value],
) -> Result<String, PowerSyncError> {
    let data_old = args[0].text();
    let data_new = args[1].text();

    ctx.result_subtype(SUBTYPE_JSON);
    diff_objects(data_old, data_new)
}

pub fn diff_objects(data_old: &str, data_new: &str) -> Result<String, PowerSyncError> {
    let v_new: json::Value = json::from_str(data_new).map_err(PowerSyncError::as_argument_error)?;
    let v_old: json::Value = json::from_str(data_old).map_err(PowerSyncError::as_argument_error)?;

    if let (json::Value::Object(mut left), json::Value::Object(mut right)) = (v_new, v_old) {
        // Remove all null values
        right.retain(|_, v| !v.is_null());
        left.retain(|_, v| !v.is_null());

        if right.len() == 0 {
            // Simple case
            return Ok(json::Value::Object(left).to_string());
        }

        // Add missing nulls to left
        for key in right.keys() {
            if !left.contains_key(key) {
                left.insert(key.clone(), json::Value::Null);
            }
        }

        left.retain(|key, value| {
            let r = right.get(key);
            if let Some(r) = r {
                // Check if value is different
                value != r
            } else {
                // Value not present in right
                true
            }
        });

        Ok(json::Value::Object(left).to_string())
    } else {
        return Err(PowerSyncError::argument_error("expected two JSON objects"));
    }
}

create_sqlite_text_fn!(powersync_diff, powersync_diff_impl, "powersync_diff");

pub fn register(db: *mut sqlite::sqlite3) -> Result<(), ResultCode> {
    db.create_function_v2(
        "powersync_diff",
        2,
        sqlite::UTF8 | sqlite::DETERMINISTIC | SQLITE_RESULT_SUBTYPE,
        None,
        Some(powersync_diff),
        None,
        None,
        None,
    )?;

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn basic_diff_test() {
        assert_eq!(diff_objects("{}", "{}").unwrap(), "{}");
        assert_eq!(diff_objects(r#"{"a": null}"#, "{}").unwrap(), "{}");
        assert_eq!(diff_objects(r#"{}"#, r#"{"a": null}"#).unwrap(), "{}");
        assert_eq!(
            diff_objects(r#"{"b": 1}"#, r#"{"a": null, "b": 1}"#).unwrap(),
            "{}"
        );
        assert_eq!(
            diff_objects(r#"{"b": 1}"#, r#"{"a": null, "b": 2}"#).unwrap(),
            r#"{"b":2}"#
        );
        assert_eq!(
            diff_objects(r#"{"a": 0, "b": 1}"#, r#"{"a": null, "b": 2}"#).unwrap(),
            r#"{"a":null,"b":2}"#
        );
        assert_eq!(
            diff_objects(r#"{"a": 1}"#, r#"{"a": null}"#).unwrap(),
            r#"{"a":null}"#
        );
        assert_eq!(
            diff_objects(r#"{"a": 1}"#, r#"{}"#).unwrap(),
            r#"{"a":null}"#
        );
        assert_eq!(
            diff_objects(r#"{"a": 1}"#, r#"{"a": 2}"#).unwrap(),
            r#"{"a":2}"#
        );
        assert_eq!(
            diff_objects(r#"{"a": 1}"#, r#"{"a": "1"}"#).unwrap(),
            r#"{"a":"1"}"#
        );
        assert_eq!(
            diff_objects(r#"{"a": 1}"#, r#"{"a": 1.0}"#).unwrap(),
            r#"{"a":1.0}"#
        );
        assert_eq!(
            diff_objects(r#"{"a": 1.00}"#, r#"{"a": 1.0}"#).unwrap(),
            r#"{}"#
        );
        assert_eq!(
            diff_objects(r#"{}"#, r#"{"a": 1.0}"#).unwrap(),
            r#"{"a":1.0}"#
        );
        assert_eq!(
            diff_objects(r#"{}"#, r#"{"a": [1,2,3]}"#).unwrap(),
            r#"{"a":[1,2,3]}"#
        );
        assert_eq!(
            diff_objects(r#"{"a": 1}"#, r#"{"a": [1,2,3]}"#).unwrap(),
            r#"{"a":[1,2,3]}"#
        );
    }
}