1 files changed, 74 insertions, 0 deletions
diff --git a/node_modules/doiuse/lib/stream/SourceMapTransform.js b/node_modules/doiuse/lib/stream/SourceMapTransform.js
new file mode 100644
index 00000000..6295b1d3
--- /dev/null
+++ b/node_modules/doiuse/lib/stream/SourceMapTransform.js
@@ -0,0 +1,74 @@
+/* eslint-disable no-underscore-dangle */
+import { Transform } from 'node:stream';
+
+const NEW_LINE_CHAR = '\n'.codePointAt(0);
+
+/**
+ * @typedef {Object} SourceMapTransformation
+ * @prop {number} line
+ * @prop {number} column
+ * @prop {string} content
+ */
+
+export default class SourceMapTransform extends Transform {
+  constructor() {
+    super({ objectMode: true });
+  }
+
+  /**
+   * @type {?{location:[number,number], buffers: Buffer[]}}
+   * buffer for the current incoming rule.
+   */
+  #current = null;
+
+  /** track depth to handle rules nested in at-rules. */
+  #depth = 0;
+
+  /** track this and pass it downstream for source mapping. */
+  #line = 1;
+
+  /** track this and pass it downstream for source mapping. */
+  #column = 1;
+
+  /**
+   * @param {[string,Buffer]} chunk
+   * @param {any} encoding
+   * @param {Function} callback
+   */
+  _transform([type, buf], encoding, callback) {
+    if ((type === 'rule_start' || type === 'atrule_start')) {
+      this.#depth += 1;
+    }
+    if (this.#depth > 0 && !this.#current) {
+      this.#current = { location: [this.#line, this.#column], buffers: [] };
+    }
+    if (type === 'rule_end' || type === 'atrule_end') {
+      this.#depth -= 1;
+    }
+
+    if (this.#current) {
+      this.#current.buffers.push(buf);
+      if (this.#depth === 0) {
+        // Push rule
+        this.push({
+          line: this.#current.location[0],
+          column: this.#current.location[1],
+          content: Buffer.concat(this.#current.buffers).toString(),
+        });
+        this.#current = null;
+      }
+    }
+
+    // Update position
+    for (const char of buf) {
+      if (char === NEW_LINE_CHAR) {
+        this.#line += 1;
+        this.#column = 1;
+      } else {
+        this.#column += 1;
+      }
+    }
+
+    callback();
+  }
+}