fix(nep): truncate editor state (aws#7256)

## Problem
We introduced `editorState` in data instrumentation launch. The service
has a requirement of 40k character limit for the `text` field.

## Solution
Implement a check on text length. If the text length exceeds 40k
characters, section 20k max characters from the left and right side of
current cursor position, so the final text is always less than 40k.

validated prod endpoint inline working for files > 40k characters.
Example request id: `57bbbe65-fbe7-47fc-81c4-c65262f47ce8`

---

- Treat all work as PUBLIC. Private `feature/x` branches will not be
squash-merged at release time.
- Your code changes must meet the guidelines in
[CONTRIBUTING.md](https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#guidelines).
- License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

Author: tomcat323

packages/amazonq/.changes/next-release/Bug Fix-75375702-36b5-4e89-af57-4afe983a7238.json

@@ -0,0 +1,4 @@
+{
+	"type": "Bug Fix",
+	"description": "Avoid inline completion 'Improperly formed request' errors when file is too large"
+}

packages/core/src/codewhisperer/models/constants.ts

@@ -87,6 +87,9 @@ export const lineBreakWin = '\r\n'
 export const supplementalContextTimeoutInMs = 100
 
 export const supplementalContextMaxTotalLength = 20480
+
+export const editorStateMaxLength = 40000
+
 /**
  * Ux of recommendations
  */

packages/core/src/codewhisperer/util/editorContext.ts

@@ -8,10 +8,11 @@ import * as codewhispererClient from '../client/codewhisperer'
 import * as path from 'path'
 import * as CodeWhispererConstants from '../models/constants'
 import { getTabSizeSetting } from '../../shared/utilities/editorUtilities'
+import { truncate } from '../../shared/utilities/textUtilities'
 import { getLogger } from '../../shared/logger/logger'
 import { runtimeLanguageContext } from './runtimeLanguageContext'
 import { fetchSupplementalContext } from './supplementalContext/supplementalContextUtil'
-import { supplementalContextTimeoutInMs } from '../models/constants'
+import { editorStateMaxLength, supplementalContextTimeoutInMs } from '../models/constants'
 import { getSelectedCustomization } from './customizationUtil'
 import { selectFrom } from '../../shared/utilities/tsUtils'
 import { checkLeftContextKeywordsForJson } from './commonUtil'
@@ -216,13 +217,29 @@ export function getTabSize(): number {
 
 export function getEditorState(editor: vscode.TextEditor, fileContext: codewhispererClient.FileContext): any {
     try {
+        const cursorPosition = editor.selection.active
+        const cursorOffset = editor.document.offsetAt(cursorPosition)
+        const documentText = editor.document.getText()
+
+        // Truncate if document content is too large (defined in constants.ts)
+        let fileText = documentText
+        if (documentText.length > editorStateMaxLength) {
+            const halfLength = Math.floor(editorStateMaxLength / 2)
+
+            // Use truncate function to get the text around the cursor position
+            const leftPart = truncate(documentText.substring(0, cursorOffset), -halfLength, '')
+            const rightPart = truncate(documentText.substring(cursorOffset), halfLength, '')
+
+            fileText = leftPart + rightPart
+        }
+
         return {
             document: {
                 programmingLanguage: {
                     languageName: fileContext.programmingLanguage.languageName,
                 },
                 relativeFilePath: fileContext.filename,
-                text: editor.document.getText(),
+                text: fileText,
             },
             cursorState: {
                 position: {