# GetJournalEntryBySource

## Overview

GetJournalEntryBySource retrieves the original journal entry produced by a source document. Reversal entries are excluded so callers can pass the returned entry to reverseJournalEntry.

## Business Rules

- Source document type and source document ID are required
- Only an original entry with `reversalOfId = null` is returned
- Returns null when the source document produced no journal entry

## Process Flow

```mermaid
flowchart LR
    A[Receive source document type and ID] --> B[Read original JournalEntry]
    B --> C[Return journal entry or null]
```

## External Dependencies

- None

## Error Scenarios

- None

## Test Cases

- returns the original journal entry for a source document
- returns null when the source document produced no journal entry