Implementing Lua Extensions

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: example-lua-filter
spec:
  hosts:
  - httpbin.org
  http:
  - route:
    - destination:
        host: httpbin.org
        port:
          number: 8000
    filters:
    - name: istio.filters.http.lua
      typedConfig:
        "@type": type.googleapis.com/istio.filters.http.lua.Lua
        inlineCode: |
          function envoy_on_request(request_handle)
            request_handle:headers():add("X-Lua-Injected", "true")
          end

-- Example Lua filter script
function on_request(request)
  request:add_header("X-Processed-By", "Lua-Filter")
end

function on_response(response)
  response:add_header("X-Filtered-At", "Edge")
end

apiVersion: networking.istio.io/v1beta1
kind: EnvoyFilter
metadata:
  name: lua-filter
  namespace: istio-system
spec:
  priority: 100
  match:
    context: SIDECAR_INBOUND
    listener:
      portNumber: 80
  config:
    listener:
      filterChain:
        filters:
          - name: envoy.filters.http.lua
            typedConfig:
              $type: type.googleapis.com/envoy.extensions.filters.http.lua.v3.Lua
              inlineCode: |
                function envoy_on_request(request)
                  request:headers():add("X-Lua-Processed", "true")
                end

local headers = ngx.req.get_headers()
headers['X-Transformed'] = 'true'
ngx.req.set_headers(headers)

local uri = ngx.var.uri
ngx.var.uri = '/transformed' .. uri

local body = ngx.req.get_body_data()
if body then
    local newBody = string.gsub(body, 'old', 'new')
    ngx.req.set_body_data(newBody)
end

function response_transform(response)
    local new_response = string.gsub(response, "old_value", "new_value")
    return new_response
end

function response_transform(response)
    response_headers['X-Processed'] = 'true'
    return response
end

-- Initialize script
local myscript = require("my_script")

-- Define cleanup function
function cleanup()
    print("Cleaning up resources")
    collectgarbage("collect")
end

-- Use script
local result = myscript.handle_request()

-- Cleanup when done
cleanup()

function envoy_on_request(request_handle)
  -- Log request info
  print("Request method: " .. request_handle:getMethod())
  print("Request path: " .. request_handle:getPath())
  
  -- Set a debug header
  request_handle:headers():add("X-Debug", "enabled")
end

function envoy_on_request(request_handle)
  local headers = request_handle:headers()
  
  -- Add debug info to headers
  headers:add("X-Request-ID", "debug-" .. os.time())
  headers:add("X-Filter-Debug", "true")
  
  -- Log to console (if enabled)
  print("Processing request with ID: " .. headers:get("X-Request-ID"))
end

local count = 1000
local result = {}
local temp = {}

for i = 1, count do
    temp[i] = i * 2
end

for i = 1, count do
    result[i] = temp[i]
end

local success, result = pcall(function()
    local value = 10 / 0
    return value
end)

if not success then
    print("Error occurred: " .. result)
else
    print("Result: " <= result)
end

local function customErrorHandler(err)
    print("Custom error handler: " .. err)
    return "Handled gracefully"
end

local success, result = xpcall(function()
    error("Something went wrong")
end, customErrorHandler)

if success then
    print("Success: " .. result)
else
    print("Failed with error: " .. result)
end

-- test_extension.lua
local extension = require("my_extension")

-- Test function
assert(extension.add(2, 3) == 5)
print("Test passed: add function works")

-- Test with negative numbers
assert(extension.multiply(-2, 3) == -6)
print("Test passed: multiply function works")

-- test_my_extension.lua
local luaunit = require("luaunit")
local extension = require("my_extension")

TestExtension = {}

function TestExtension:test_add()
    luaunit.assertEquals(extension.add(2, 3), 5)
end

function TestExtension:test_multiply()
    luaunit.assertEquals(extension.multiply(-2, 3), -6)
end

os.exit(luaunit.run())

local headers = {
  ['X-Custom-Header'] = 'value'
}

for key, value in pairs(headers) do
  ngx.req.set_header(key, value)
end

local headers = {
  ['Content-Type'] = 'application/json'
}

for key, value in pairs(headers) do
  ngx.header[key] = value
end

-- Example of a Lua script that sanitizes input before processing
local function sanitize_input(input)
  if type(input) ~= "string" then
    return nil
  end
  -- Remove dangerous characters or patterns
  return input:gsub("[^%w%s%-_]", "")
end

local user_data = sanitize_input(request.header["user-id"])
if user_data then
  -- Process sanitized input
  response.body = "Processed: " .. user_data
else
  response.status = 400
end