Creating a Lua wrapper for Google Gmail API integration

Other Questions Gmail
1

Building a Gmail API Client in Lua

I’m developing a Lua application that needs to work with the Gmail API. I prefer to write my own client library rather than relying on available options.

Here’s what I aim to accomplish:

local gmail_client = require('my_gmail_lib')

function setup_connection()
    local client = gmail_client.new({
        api_key = "your_api_key_here",
        auth_token = "oauth_token"
    })
    return client
end

function fetch_messages(client)
    local inbox = client:get_mailbox('inbox')
    for _, msg in ipairs(inbox.messages) do
        print(msg.subject)
    end
end

I’m looking for advice on effectively managing OAuth authentication and making HTTP calls to Google’s REST services. What would be the best way to organize this library? Are there any particular Lua HTTP libraries or JSON tools you recommend?

Any suggestions for implementing the key features would be greatly appreciated.

2

I’ve used Gmail API in production, so here’s what I learned the hard way: build solid error handling and retry logic from day one. Google’s servers throw random 503s and timeouts all the time. For HTTP, lua-http works great if you need HTTP/2, but lua-socket handles basic stuff fine. Here’s what caught me off guard - Gmail sends huge JSON responses by default. Use field selection to grab only what you need, or you’ll waste bandwidth and slow everything down. Batch your requests too, especially for bulk operations like marking messages read. Individual API calls burn through your quota fast. One more thing - users can revoke access anytime, so your refresh tokens will suddenly fail. Plan for graceful degradation when that happens.

3

I built something similar last year. For API calls, lua-resty-http works great with OpenResty - otherwise use lua-socket with SSL support for HTTPS. With OAuth, store refresh tokens securely and auto-renew them before making requests. Gmail API’s message formatting is weird - the payload structure gets deeply nested depending on message type. I split my library into separate modules: auth, message handling, and API calls. Made debugging way easier. Also heads up - Google’s rate limits are per user per second, so you’ll need request queuing if you’re handling multiple accounts.

4

totally! oauth can be tricky. i recommend using luasec for secure calls and cjson for json parsing. also, make sure to implement token refreshing since they do expire. oh, and keep an eye on your request limits or google will throttle ya.