Change: add documentation

README.md

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+# Fastify Server Documentation
 
+## Overview
+This documentation provides explanation of a ambrodeo server implementation. The server is designed to handle user authentication, file uploads, and various API endpoints to manage users, messages, likes. It also includes OpenAPI documentation using Swagger.
+
+---
+
+## Table of Contents
+1. [Environment Variables](#environment-variables)
+2. [Initialization](#initialization)
+3. [Middleware and Hooks](#middleware-and-hooks)
+4. [Routes](#routes)
+    - [GET /](#get-)
+    - [POST /upload](#post-upload)
+    - [POST /api/user](#post-apiuser)
+    - [POST /api/message](#post-apimessage)
+    - [POST /api/like](#post-apilike)
+    - [GET /api/user](#get-apiuser)
+    - [GET /api/messages](#get-apimessages)
+    - [GET /api/token](#get-apitoken)
+    - [GET /api/likes](#get-apilikes)
+    - [GET /api/secret](#get-apisecret)
+5. [Utility Functions](#utility-functions)
+6. [Error Handling](#error-handling)
+
+---
+
+## Environment Variables
+The application relies on the following environment variables, fetched using `getEnv`:
+- `HOST`: Host address of the server.
+- `PORT`: Port number for the server.
+- `DATABASE_URL`: MongoDB connection URL.
+- `SUBGRAPHS_ENDPOINT`: GraphQL endpoint for querying tokens.
+- `UPLOAD_DIR`: Directory for uploaded files.
+
+---
+
+## Initialization
+The server is initialized using `initFastify()`. It registers plugins for:
+- **Swagger**: For OpenAPI documentation.
+- **MongoDB**: To interact with a MongoDB database.
+- **Multipart**: To handle file uploads.
+
+An OpenAPI specification is loaded from the `docs` YAML file.
+
+---
+
+## Middleware and Hooks
+### Pre-handler Hook
+- Validates requests with `POST` methods by checking for an `address` and `signature` in headers.
+- Verifies the signature using `ethers.verifyMessage`.
+- Responds with appropriate error codes for invalid or missing credentials.
+
+---
+
+## Routes
+
+### GET /
+**Description**: Basic health check endpoint.
+- **Response**: Empty object `{}`.
+
+### POST /upload
+**Description**: Handles file uploads.
+- **Headers**: Requires `address`.
+- **Process**:
+  - Ensures a directory exists for the uploaded file.
+  - Saves the file in the appropriate path.
+- **Response**: Success or error message.
+
+### POST /api/user
+**Description**: Adds or updates user details.
+- **Headers**: Requires `address`.
+- **Body**:
+  - `userName`: User's name.
+  - `image`: Profile image URL.
+- **Response**: Empty on success or error message.
+
+### POST /api/message
+**Description**: Adds a message associated with a token.
+- **Headers**: Requires `address`.
+- **Body**:
+  - `tokenAddress`: Address of the token.
+  - `message`: Message content.
+- **Response**: Empty on success or error message.
+
+### POST /api/like
+**Description**: Adds or deletes a like for a token.
+- **Headers**: Requires `address`.
+- **Body**:
+  - `tokenAddress`: Address of the token.
+  - `like`: Boolean indicating whether to add or remove the like.
+- **Response**: Empty on success or error message.
+
+### GET /api/user
+**Description**: Fetches details of a user.
+- **Headers**: Requires `address`.
+- **Response**: User object or error message.
+
+### GET /api/messages
+**Description**: Retrieves messages for a token.
+- **Query Parameters**:
+  - `tokenAddress`: Token address to fetch messages for.
+  - `skip`: Number of records to skip.
+  - `limit`: Maximum number of records to fetch.
+- **Response**: List of messages or error message.
+
+### GET /api/token
+**Description**: Retrieves details of a token.
+- **Query Parameters**:
+  - `tokenAddress`: Token address to fetch.
+- **Response**: Token object or error message.
+
+### GET /api/likes
+**Description**: Retrieves likes for a user.
+- **Headers**: Requires `address`.
+- **Query Parameters**:
+  - `skip`: Number of records to skip.
+  - `limit`: Maximum number of records to fetch.
+- **Response**: List of likes or error message.
+
+### GET /api/secret
+**Description**: Generates and retrieves a secret for an address.
+- **Headers**: Requires `address`.
+- **Response**: Secret string or error message.
+
+---
+
+## Utility Functions
+
+### checkTokenExist
+**Purpose**: Checks if a token exists in the database or the subgraph.
+- **Parameters**:
+  - `request`: FastifyRequest.
+  - `tokenAddress`: Token address to verify.
+- **Process**:
+  - Searches the database for the token.
+  - Queries the subgraph if not found.
+  - Updates the database if the token exists in the subgraph.
+- **Returns**: `true` if token exists, `false` otherwise.
+
+---
+
+## Error Handling
+The server employs consistent error handling with meaningful status codes and messages:
+- **400 Bad Request**: For missing or invalid parameters.
+- **401 Unauthorized**: For invalid signatures.
+- **404 Not Found**: For non-existent tokens.
+- **500 Internal Server Error**: For unexpected errors.