Http Client in Lua

Here’s an idiomatic Lua example demonstrating the concept of an HTTP client:

-- Import the required library
local http = require("socket.http")
local ltn12 = require("ltn12")

-- Function to make an HTTP GET request
local function httpGet(url)
  local response = {}
  local body = {}
  
  -- Make the HTTP request
  local request, code, responseHeaders = http.request{
    url = url,
    method = "GET",
    sink = ltn12.sink.table(body)
  }
  
  if code ~= 200 then
    error("HTTP request failed with status code: " .. code)
  end
  
  -- Combine the response parts
  response.body = table.concat(body)
  response.headers = responseHeaders
  response.code = code
  
  return response
end

-- Main function
local function main()
  local url = "https://example.com"
  local response = httpGet(url)
  
  -- Print the HTTP response status
  print("Response status: " .. response.code)
  
  -- Print the first 5 lines of the response body
  for line in response.body:gmatch("[^\r\n]+") do
    print(line)
    if line:find("</head>") then
      break
    end
  end
end

-- Run the main function
main()

This Lua script demonstrates how to create a simple HTTP client using the luasocket library. Here’s a breakdown of the code:

1. We import the required libraries: socket.http for making HTTP requests and ltn12 for handling input/output operations.

2. The httpGet function is defined to make an HTTP GET request. It uses the http.request method to send the request and collect the response.

3. In the main function, we specify a URL to request and call the httpGet function.

4. We print the response status code and the first few lines of the response body, similar to the original example.

To run this script, you’ll need to have Lua and the luasocket library installed. You can install luasocket using LuaRocks:

$ luarocks install luasocket

Then, save the script as http_client.lua and run it:

$ lua http_client.lua

This example demonstrates how to make HTTP requests in Lua, handle responses, and process the received data. It’s a simpler implementation compared to the Go example, as Lua doesn’t have built-in HTTP client functionality and relies on external libraries.

Note that error handling in this example is basic. In a production environment, you’d want to implement more robust error handling and possibly add support for other HTTP methods, request headers, and more advanced features.