-- Copyright (c) 2016 IBM. All rights reserved.
--
--   Permission is hereby granted, free of charge, to any person obtaining a
--   copy of this software and associated documentation files (the "Software"),
--   to deal in the Software without restriction, including without limitation
--   the rights to use, copy, modify, merge, publish, distribute, sublicense,
--   and/or sell copies of the Software, and to permit persons to whom the
--   Software is furnished to do so, subject to the following conditions:
--
--   The above copyright notice and this permission notice shall be included in
--   all copies or substantial portions of the Software.
--
--   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
--   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
--   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
--   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
--   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
--   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
--   DEALINGS IN THE SOFTWARE.

--- @module oauth
-- A module to check with an oauth provider and reject an api call with a bad oauth token
-- @author David Green (greend), Alex Song (songs)


local utils = require "lib/utils"
local request = require "lib/request"
local redis = require "lib/redis"
local cjson = require "cjson"

local REDIS_HOST = os.getenv("REDIS_HOST")
local REDIS_PORT = os.getenv("REDIS_PORT")
local REDIS_PASS = os.getenv("REDIS_PASS")

-- Process the security object
-- @param securityObj security object from nginx conf file
-- @return oauthId oauth identification
local _M = {}

function process(securityObj)
  local red = redis.init(REDIS_HOST, REDIS_PORT, REDIS_PASS, 1000)
  local result = processWithRedis(red, securityObj)
  redis.close(red)
  return result
end

function processWithRedis(red, securityObj)
 
  local headerName = utils.concatStrings({'http_', 'x-facebook-app-token'}):gsub("-", "_")
  local facebookAppToken = ngx.var[headerName]
 
  local accessToken = ngx.var['http_Authorization']
  if accessToken == nil then
    request.err(401, "No Authorization header provided")
  end
  accessToken = string.gsub(accessToken, '^Bearer%s', '')
  local token = {}
  local key = utils.concatStrings({"oauth:providers:", securityObj.provider, ":tokens:", accessToken})
  -- If we haven't cached the token go to the oauth provider
  if redis.exists(red, key) == 1 then
    return cjson.decode(redis.get(red, key))
  end
 
  if securityObj.provider == 'facebook' or securityObj.provider == 'fake_facebook' then
    if redis.exists(red, utils.concatStrings({key, facebookAppToken})) == 1  then
      return cjson.decode(redis.get(red, utils.concatStrings({key, facebookAppToken})))
    end
  end
 
  local token = exchange(accessToken, securityObj.provider)
  if token == nil then
    request.err(401, 'Token didn\'t work or provider doesn\'t support OpenID connect. ')
    return nil
  end
 
  if token.error ~= nil then
    request.err(401, 'Token didn\'t work or provider doesn\'t support OpenID connect. ')
    return nil
  end

  if securityObj.provider == 'facebook' or securityObj.provider == 'fake_facebook' then
    key = utils.concatStrings({key, facebookAppToken})
  end
 
  redis.set(red, key, cjson.encode(token))

  if token.expires ~= nil then
    redis.expire(red, key, token.expires)
  end
  return token
end

--- Exchange tokens with an oauth provider. Loads a provider based on configuration in the nginx.conf
-- @param token the accessToken passed in the authorization header of the routing request
-- @param provider the name of the provider we will load from a file. Currently supported google/github/facebook
-- @return the json object recieved from exchanging tokens with the provider
  function exchange(token, provider)
    -- exchange tokens with the provider
    local loaded, provider = pcall(require, utils.concatStrings({'oauth/', provider}))
  
    if not loaded then
      request.err(500, 'Error loading OAuth provider authentication module')
      return
    end
    local token = provider(token)
    -- cache the token
    return token
end

_M.process = process
_M.processWithRedis = processWithRedis
return _M