-- 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
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--   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
--   DEALINGS IN THE SOFTWARE.

--- @module clientSecret

local _M = {}

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

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

local resty_sha256 = require "resty.sha256"
local resty_str = require "resty.string" 

function process(securityObj) 
  local tenant = ngx.var.tenant
  local gatewayPath = ngx.var.gatewayPath
  local apiId = ngx.var.apiId
  local scope = securityObj.scope

  local location = (securityObj.keyLocation == nil) and 'http_' or securityObj.keyLocation  
  if location == 'header' then
    location = 'http_'
  end
  
  local clientIdName = (securityObj.idFieldName == nil) and 'X-Client-ID' or securityObj.idFieldName
  
  local clientId = ngx.var[utils.concatStrings({location, clientIdName}):gsub("-", "_")]
  
  if not clientId then
    request.err(401, clientIdName .. " required")
  end

  local clientSecretName = (securityObj.secretFieldName == nil) and 'X-Client-Secret' or securityObj.secretFieldName 

  local clientSecret = ngx.var[utils.concatStrings({location, clientSecretName}):gsub("-","_")]
  if not clientSecret then
    request.err(401, clientSecretName .. " required")
  end
  
  local sha256 = resty_sha256:new() 
  sha256:update(clientSecret)  
  local digest = sha256:final()
  local result = validate(tenant, gatewayPath, apiId, scope, clientId, resty_str.to_hex(digest))
  if not result then
    request.err(401, "Secret mismatch or not subscribed to this api.")
  end

end

function validate(tenant, gatewayPath, apiId, scope, clientId, clientSecret)
  -- Open connection to redis or use one from connection pool
  local red = redis.init(REDIS_HOST, REDIS_PORT, REDIS_PASS, 1000)
  local k
  if scope == 'tenant' then
    k = utils.concatStrings({'subscriptions:tenant:', tenant})
  elseif scope == 'resource' then
    k = utils.concatStrings({'subscriptions:tenant:', tenant, ':resource:', gatewayPath})
  elseif scope == 'api' then
    k = utils.concatStrings({'subscriptions:tenant:', tenant, ':api:', apiId})
  end


  k = utils.concatStrings({k, ':clientsecret:', clientId, ':', clientSecret})
  local exists = red:exists(k)
  redis.close(red)
  return exists == 1
end

_M.process = process
return _M