feat(commands): Enable @file processing in TOML commands (#6716)

packages/core/src/utils/partUtils.ts

@@ -8,6 +8,7 @@ import type {
   GenerateContentResponse,
   PartListUnion,
   Part,
+  PartUnion,
 } from '@google/genai';
 
 /**
@@ -87,3 +88,82 @@ export function getResponseText(
   }
   return null;
 }
+
+/**
+ * Asynchronously maps over a PartListUnion, applying a transformation function
+ * to the text content of each text-based part.
+ *
+ * @param parts The PartListUnion to process.
+ * @param transform A function that takes a string of text and returns a Promise
+ *   resolving to an array of new PartUnions.
+ * @returns A Promise that resolves to a new array of PartUnions with the
+ *   transformations applied.
+ */
+export async function flatMapTextParts(
+  parts: PartListUnion,
+  transform: (text: string) => Promise<PartUnion[]>,
+): Promise<PartUnion[]> {
+  const result: PartUnion[] = [];
+  const partArray = Array.isArray(parts)
+    ? parts
+    : typeof parts === 'string'
+      ? [{ text: parts }]
+      : [parts];
+
+  for (const part of partArray) {
+    let textToProcess: string | undefined;
+    if (typeof part === 'string') {
+      textToProcess = part;
+    } else if ('text' in part) {
+      textToProcess = part.text;
+    }
+
+    if (textToProcess !== undefined) {
+      const transformedParts = await transform(textToProcess);
+      result.push(...transformedParts);
+    } else {
+      // Pass through non-text parts unmodified.
+      result.push(part);
+    }
+  }
+  return result;
+}
+
+/**
+ * Appends a string of text to the last text part of a prompt, or adds a new
+ * text part if the last part is not a text part.
+ *
+ * @param prompt The prompt to modify.
+ * @param textToAppend The text to append to the prompt.
+ * @param separator The separator to add between existing text and the new text.
+ * @returns The modified prompt.
+ */
+export function appendToLastTextPart(
+  prompt: PartUnion[],
+  textToAppend: string,
+  separator = '\n\n',
+): PartUnion[] {
+  if (!textToAppend) {
+    return prompt;
+  }
+
+  if (prompt.length === 0) {
+    return [{ text: textToAppend }];
+  }
+
+  const newPrompt = [...prompt];
+  const lastPart = newPrompt.at(-1);
+
+  if (typeof lastPart === 'string') {
+    newPrompt[newPrompt.length - 1] = `${lastPart}${separator}${textToAppend}`;
+  } else if (lastPart && 'text' in lastPart) {
+    newPrompt[newPrompt.length - 1] = {
+      ...lastPart,
+      text: `${lastPart.text}${separator}${textToAppend}`,
+    };
+  } else {
+    newPrompt.push({ text: `${separator}${textToAppend}` });
+  }
+
+  return newPrompt;
+}