Function diff_arrays

nodedb/src/event/field_diff.rs:240–275

Diff two JSON arrays element-by-element. For short arrays or same-length arrays, diffs per index. For length changes, emits ArrayInsert/ArrayRemove for trailing elements.

(
    diffs: &mut Vec<FieldDiff>,
    prefix: &str,
    old_arr: &[serde_json::Value],
    new_arr: &[serde_json::Value],
)

/// For short arrays or same-length arrays, diffs per index.
/// For length changes, emits ArrayInsert/ArrayRemove for trailing elements.
fn diff_arrays(
    diffs: &mut Vec<FieldDiff>,
    prefix: &str,
    old_arr: &[serde_json::Value],
    new_arr: &[serde_json::Value],
) {
    let min_len = old_arr.len().min(new_arr.len());

    // Compare overlapping elements.
    for i in 0..min_len {
        let path = format!("{prefix}[{i}]");
        diff_values(diffs, &path, &old_arr[i], &new_arr[i]);
    }

    // Elements removed from old (old is longer).
    for (i, item) in old_arr.iter().enumerate().skip(min_len) {
        let path = format!("{prefix}[{i}]");
        diffs.push(FieldDiff {
            field: path,
            op: DiffOp::ArrayRemove,
            old_value: Some(item.clone()),
            new_value: None,
        });
    }

    // Elements added in new (new is longer).
    for (i, item) in new_arr.iter().enumerate().skip(min_len) {
        let path = format!("{prefix}[{i}]");
        diffs.push(FieldDiff {
            field: path,
            op: DiffOp::ArrayInsert,
            old_value: None,
            new_value: Some(item.clone()),
        });
    }
}

/// Diff two strings, producing TextInsert/TextDelete for simple edits
/// or Modified for complex changes.