lambda_function.rb

require "uri"
require "net/http"
require "cgi"
require "json"

module SmalrubyScratchApiProxyTranslate
  ALLOW_ORIGINS = %w[
    https://smalruby.app
    https://smalruby.jp
    http://localhost:8601
  ]
  API_HOST = "https://translate-service.scratch.mit.edu"

  def self.lambda_handler(event:, context:)
    origin = event.dig("headers", "origin").to_s.strip
    headers = {
      "Access-Control-Allow-Origin": ALLOW_ORIGINS.include?(origin) ? origin : ALLOW_ORIGINS.first,
      "Access-Control-Allow-Headers": "Content-Type",
      "Access-Control-Allow-Methods": "OPTIONS,GET"
    }

    if event["httpMethod"] == "OPTIONS"
      return {
        statusCode: 200,
        headers:,
        body: JSON.generate(message: "OK")
      }
    end

    language = event.dig("queryStringParameters", "language").to_s.strip
    text = event.dig("queryStringParameters", "text").to_s

    if language.length == 0
      return {
        statusCode: 400,
        headers:,
        body: {
          code: "Bad Request",
          message: "invalid locale code"
        }.to_json
      }
    end

    query = {
      language:,
      text:
    }.map { |key, value|
      "#{CGI.escape(key.to_s)}=#{CGI.escape(value.to_s)}"
    }.join("&")
    api_uri = URI.join(API_HOST, "/translate?#{query}")
    res = Net::HTTP.get_response(api_uri)
    {
      statusCode: res.code,
      headers:,
      body: res.body.dup.force_encoding("utf-8")
    }
  end
end

# AWS Lambda entry point
unless ENV["CI"] == "true"
  def lambda_handler(event:, context:)
    SmalrubyScratchApiProxyTranslate.lambda_handler(event: event, context: context)
  end
end