Task: build a app that searches files based on regex in JavaScript using nest.

API specification:

openapi: 3.0.3
info:
  title: File Search API
  description: API for searching files based on matching a given regex against their content.
  version: 1.0.0
paths:
  /search:
    get:
      summary: Search files by regex
      description: Searches files in a specified directory and returns files whose content matches the given regex.
      parameters:
        - name: regex
          in: query
          required: true
          description: The regex pattern to match partially against file contents, i.e. some part of the file content must match the regex.
          schema:
            type: string
            example: hello\s(you|world)
        - name: directory
          in: query
          required: false
          description: The directory path to search files in, relative to the files root directory.
          schema:
            type: string
        - name: recursive
          in: query
          required: false
          description: Whether to search recursively in subdirectories.
          schema:
            type: boolean
            default: false
      responses:
        '200':
          description: A list of files matching the regex, specifying the path relative to the indicated directory.
          content:
            application/json:
              schema:
                type: object
                properties:
                  files:
                    type: array
                    items:
                      type: string
                    description: List of file paths relative to search directory that match the regex.
                    example: ["folder1/file1.txt", "file2.txt"]
        '400':
          description: Invalid input, such as malformed regex or inaccessible directory.
          content:
            application/json:
              schema:
                type: object
                properties:
                  error:
                    type: string
                    description: Error message detailing the issue.
        '500':
          description: Internal server error.
          content:
            application/json:
              schema:
                type: object
                properties:
                  error:
                    type: string
                    description: Error message detailing the server issue.


Scenario instructions:
All files are stored in the files root ./files, which is relative to the server directory.

Environment instructions:

The NestJs was already created using the `nest new` command.

You need to populate the following files:
src/app.controller.spec.ts
src/app.controller.ts
src/app.module.ts
src/app.service.ts
src/main.ts


Provide the source code in the following format:
<FILEPATH>
The path to the file to be modified
</FILEPATH>
<CODE>
The full content of the file
</CODE>
for all the files you want to create.

Example:
<FILEPATH>
path/to/file.py
</FILEPATH>
<CODE>
def hello_world():
    pass
</CODE>



Make sure that the command `npm run start` starts the app successfully.


Allowed packages:

{
  "scripts": {
    "build": "nest build",
    "start": "nest start"
  },
  "engines": {
    "npm": ">=10.0.0",
    "node": ">=20.0.0"
  },
  "dependencies": {
    "@nestjs/common": "11.0.1",
    "@nestjs/core": "11.0.1",
    "@nestjs/platform-express": "11.0.1",
    "reflect-metadata": "0.2.2",
    "rxjs": "7.8.1",
    "bcrypt": "5.1.1",
    "dotenv": "16.4.7",
    "express": "4.21.2",
    "uuid": "11.0.3",
    "sqlite": "5.1.1",
    "sqlite3": "5.1.7",
    "multer": "1.4.5-lts.1",
    "cookie-parser": "1.4.7",
    "jsonwebtoken": "9.0.2"
  },
  "devDependencies": {
    "@nestjs/cli": "11.0.0",
    "@nestjs/schematics": "11.0.0",
    "@swc/cli": "0.6.0",
    "@swc/core": "1.10.8",
    "@types/express": "5.0.0",
    "@types/multer": "1.4.12",
    "@types/node": "22.10.7",
    "prettier": "3.4.2",
    "source-map-support": "0.5.21",
    "supertest": "7.0.0",
    "ts-loader": "9.5.2",
    "ts-node": "10.9.2",
    "typescript": "5.7.3"
  }
}