fix(resp-tranformer) handle already existing headers

Now add will only add header/json if it does not exist, config `append` added to support adding new value to existing header/json. If header does not exist, a new one will be added. config `replace added to replace the value of existing header/json with new value

kong-0.5.4-1.rockspec

@@ -167,8 +167,8 @@ build = {
     ["kong.plugins.request-transformer.schema"] = "kong/plugins/request-transformer/schema.lua",
 
     ["kong.plugins.response-transformer.handler"] = "kong/plugins/response-transformer/handler.lua",
-    ["kong.plugins.response-transformer.body_filter"] = "kong/plugins/response-transformer/body_filter.lua",
-    ["kong.plugins.response-transformer.header_filter"] = "kong/plugins/response-transformer/header_filter.lua",
+    ["kong.plugins.response-transformer.body_transformer"] = "kong/plugins/response-transformer/body_transformer.lua",
+    ["kong.plugins.response-transformer.header_transformer"] = "kong/plugins/response-transformer/header_transformer.lua",
     ["kong.plugins.response-transformer.schema"] = "kong/plugins/response-transformer/schema.lua",
 
     ["kong.plugins.cors.handler"] = "kong/plugins/cors/handler.lua",

kong/plugins/response-transformer/body_transformer.lua

@@ -0,0 +1,93 @@
+local stringy = require "stringy"
+local cjson = require "cjson"
+
+local table_insert = table.insert
+local pcall = pcall
+local string_find = string.find
+local unpack = unpack
+local type = type
+
+local _M = {}
+
+local function read_json_body(body)
+  if body then
+    local status, res = pcall(cjson.decode, body)
+    if status then
+      return res
+    end
+  end
+end
+
+local function append_value(current_value, value)
+  local current_value_type = type(current_value)
+
+  if current_value_type  == "string" then
+    return {current_value, value}
+  elseif current_value_type  == "table" then
+    table_insert(current_value, value)
+    return current_value  
+  else
+    return {value} 
+  end
+end
+
+local function iter(config_array)
+  return function(config_array, i, previous_name, previous_value)
+    i = i + 1
+    local current_pair = config_array[i]
+    if current_pair == nil then -- n + 1
+      return nil
+    end
+    local current_name, current_value = unpack(stringy.split(current_pair, ":"))
+    return i, current_name, current_value  
+  end, config_array, 0
+end
+
+function _M.is_json_body(content_type)
+  return content_type and string_find(content_type:lower(), "application/json", nil, true)
+end
+
+function _M.transform_json_body(conf, buffered_data)
+  local json_body = read_json_body(buffered_data)
+  if json_body == nil then return end
+
+  -- remove key:value to body
+  for _, name in iter(conf.remove.json) do
+    json_body[name] = nil
+  end
+
+  -- replace  key:value to body
+  for _, name, value in iter(conf.replace.json) do
+    local v = cjson.encode(value)
+    if stringy.startswith(v, "\"") and stringy.endswith(v, "\"") then
+      v = v:sub(2, v:len() - 1):gsub("\\\"", "\"") -- To prevent having double encoded quotes
+    end
+    if json_body[name] then
+      json_body[name] = v
+    end
+  end
+
+  -- add new key:value to body    
+  for _, name, value in iter(conf.add.json) do
+    local v = cjson.encode(value)
+    if stringy.startswith(v, "\"") and stringy.endswith(v, "\"") then
+      v = v:sub(2, v:len() - 1):gsub("\\\"", "\"") -- To prevent having double encoded quotes
+    end
+    if not json_body[name] then
+      json_body[name] = v
+    end
+  end
+
+  -- append new key:value or value to existing key    
+  for _, name, value in iter(conf.append.json) do
+    local v = cjson.encode(value)
+    if stringy.startswith(v, "\"") and stringy.endswith(v, "\"") then
+      v = v:sub(2, v:len() - 1):gsub("\\\"", "\"") -- To prevent having double encoded quotes
+    end
+    json_body[name] = append_value(json_body[name],v)
+  end
+
+  return cjson.encode(json_body) 
+end
+
+return _M

kong/plugins/response-transformer/handler.lua

@@ -1,21 +1,35 @@
 local BasePlugin = require "kong.plugins.base_plugin"
-local body_filter = require "kong.plugins.response-transformer.body_filter"
-local header_filter = require "kong.plugins.response-transformer.header_filter"
+local body_filter = require "kong.plugins.response-transformer.body_transformer"
+local header_filter = require "kong.plugins.response-transformer.header_transformer"
 
 local ResponseTransformerHandler = BasePlugin:extend()
 
 function ResponseTransformerHandler:new()
   ResponseTransformerHandler.super.new(self, "response-transformer")
 end
 
+function ResponseTransformerHandler:access(conf)
+  ResponseTransformerHandler.super.access(self)
+  ngx.ctx.buffer = ""
+end
+
 function ResponseTransformerHandler:header_filter(conf)
   ResponseTransformerHandler.super.header_filter(self)
-  header_filter.execute(conf)
+  header_filter.transform_headers(conf, ngx.header)
 end
 
 function ResponseTransformerHandler:body_filter(conf)
   ResponseTransformerHandler.super.body_filter(self)
-  body_filter.execute(conf)
+  if body_filter.is_json_body(ngx.header["content-type"]) then
+    local chunk, eof = ngx.arg[1], ngx.arg[2]
+    if eof then
+      local body = body_filter.transform_json_body(conf, ngx.ctx.buffer)
+      ngx.arg[1] = body
+    else
+      ngx.ctx.buffer = ngx.ctx.buffer..chunk
+      ngx.arg[1] = nil
+    end  
+  end  
 end
 
 ResponseTransformerHandler.PRIORITY = 800

kong/plugins/response-transformer/header_transformer.lua

@@ -0,0 +1,77 @@
+local stringy = require "stringy"
+
+local table_insert = table.insert
+local unpack = unpack
+local type = type
+local string_find = string.find
+
+local _M = {}
+
+local function iter(config_array)
+  return function(config_array, i, previous_header_name, previous_header_value)
+    i = i + 1
+    local header_to_test = config_array[i]
+    if header_to_test == nil then -- n + 1
+      return nil
+    end
+    local header_to_test_name, header_to_test_value = unpack(stringy.split(header_to_test, ":"))
+    return i, header_to_test_name, header_to_test_value  
+  end, config_array, 0
+end
+
+local function append_value(current_value, value)
+  local current_value_type = type(current_value)
+
+  if current_value_type == "string" then
+    return {current_value, value}
+  elseif current_value_type == "table" then
+    table_insert(current_value, value)
+    return current_value  
+  else
+    return {value} 
+  end
+end
+
+local function is_json_body(content_type)
+  return content_type and string_find(content_type:lower(), "application/json", nil, true)
+end
+
+---
+--   # Example:
+--   ngx.headers = header_filter.transform_headers(conf, ngx.headers)
+-- We run transformations in following order: remove, replace, add, append. 
+-- @param[type=table] conf Plugin configuration.
+-- @param[type=table] ngx_headers Table of headers, that should be `ngx.headers`
+-- @return table A table containing the new headers.
+function _M.transform_headers(conf, ngx_headers)
+  -- remove headers
+  for _, header_name, header_value in iter(conf.remove.headers) do
+      ngx_headers[header_name] = nil
+  end
+
+  -- replace headers
+  for _, header_name, header_value in iter(conf.replace.headers) do
+    if ngx_headers[header_name] ~= nil then
+      ngx_headers[header_name] = header_value
+    end
+  end
+
+  -- add headers
+  for _, header_name, header_value in iter(conf.add.headers) do
+    if ngx_headers[header_name] == nil then
+      ngx_headers[header_name] = header_value
+    end
+  end
+
+  -- append headers
+  for _, header_name, header_value in iter(conf.append.headers) do
+    ngx_headers[header_name] = append_value(ngx_headers[header_name], header_value)
+  end
+
+  -- Removing the content-length header because the body is going to change
+  if conf.add.json and is_json_body(ngx_headers["content-type"]) then
+    ngx_headers["content-length"] = nil
+  end
+end
+
+return _M