From 78c4b98ffab0915f8d457572509de3ea465a0269 Mon Sep 17 00:00:00 2001
From: Alex Rudenko <OrKoN@users.noreply.github.com>
Date: Fri, 18 Nov 2022 10:54:16 +0100
Subject: [PATCH] feat: parse source map (#386)

This PR adds a helper for parsing a source map
from a recording.
---
 src/main.ts            |  7 ++++++-
 src/stringify.ts       | 24 ++++++++++++++++++++++--
 test/stringify.test.ts | 12 +++++++++++-
 3 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/src/main.ts b/src/main.ts
index a1527bfc..ca0fb0b8 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -21,7 +21,12 @@ export * from './Schema.js';
 export * as Schema from './Schema.js';
 export * from './SchemaUtils.js';
 export { StringifyExtension } from './StringifyExtension.js';
-export { stringify, stringifyStep, StringifyOptions } from './stringify.js';
+export {
+  stringify,
+  stringifyStep,
+  StringifyOptions,
+  parseSourceMap,
+} from './stringify.js';
 export { LineWriter } from './LineWriter.js';
 export { RunnerExtension } from './RunnerExtension.js';
 export { createRunner, Runner } from './Runner.js';
diff --git a/src/stringify.ts b/src/stringify.ts
index ae349d4c..300a7944 100644
--- a/src/stringify.ts
+++ b/src/stringify.ts
@@ -27,6 +27,13 @@ export interface StringifyOptions {
   indentation?: string;
 }
 
+const SOURCE_MAP_PREFIX = '//# recorderSourceMap=';
+
+/**
+ * The format is [version, [lineNo, length], [lineNo, length] ... [lineNo, length]].
+ */
+export type SourceMap = Array<number>;
+
 /**
  * Stringifes an entire recording. The following hooks are invoked with the `flow` parameter containing the entire flow:
  * - `beforeAllSteps` (once)
@@ -47,7 +54,6 @@ export async function stringify(
 
   await ext.beforeAllSteps?.(out, flow);
 
-  // version, [lineNo, length], [lineNo, length] ...
   const sourceMap: Array<number> = [1];
   for (const step of flow.steps) {
     const firstLine = out.getSize();
@@ -59,7 +65,7 @@ export async function stringify(
   }
   await ext.afterAllSteps?.(out, flow);
 
-  out.appendLine('//# recorderSourceMap=' + vlq.encode(sourceMap));
+  out.appendLine(SOURCE_MAP_PREFIX + vlq.encode(sourceMap));
 
   return out.toString();
 }
@@ -92,3 +98,17 @@ export async function stringifyStep(
 
   return out.toString();
 }
+
+/**
+ * Extracts a source map from a text.
+ */
+export function parseSourceMap(text: string): SourceMap | undefined {
+  const lines = text.split('\n');
+  for (let i = lines.length - 1; i >= 0; i--) {
+    const line = lines[i] as string;
+    if (line.trim().startsWith(SOURCE_MAP_PREFIX)) {
+      return vlq.decode(line.trim().substring(SOURCE_MAP_PREFIX.length));
+    }
+  }
+  return;
+}
diff --git a/test/stringify.test.ts b/test/stringify.test.ts
index 2bcd9828..989904c3 100644
--- a/test/stringify.test.ts
+++ b/test/stringify.test.ts
@@ -14,7 +14,7 @@
     limitations under the License.
  */
 
-import { stringify } from '../src/stringify.js';
+import { parseSourceMap, stringify } from '../src/stringify.js';
 import { assert } from 'chai';
 import { StringifyExtension } from '../src/StringifyExtension.js';
 import { Step, StepType, UserFlow } from '../src/Schema.js';
@@ -275,4 +275,14 @@ describe('stringify', () => {
       vlq.decode(sourceMapLine?.split('//# recorderSourceMap=').pop() as string)
     );
   });
+
+  it('should parse a source map', async () => {
+    const sourceMap = parseSourceMap(`
+      test
+      test
+      test
+      //# recorderSourceMap=CCG
+    `);
+    assert.deepStrictEqual(sourceMap, [1, 1, 3]);
+  });
 });