--[[

    Description: 
        Provides interoperability for Microsoft Lync 

        Handle Below Scenarios 
        
        1. Add user=phone for all outbound Invite messages because it is          
           mandatory for Lync

        2. Change the CT=Line values to 1000 , Moderate bandwidth in all 
           outgoing  messages from CUCM to Lync
           
        3. There is Remote ringback hear issue
           There is ssue with PRACK enabled on CUCM and media bypass enabled on  
           Lync. Enabling media bypass on Lync allows the rtp from lync 
           endpoint to flow through CUCM directly instead of flowing through 
           mediation server. The problem with PRACK enabled is that Lync end  
           point is now not able to answer the incoming call.Looking into the 
           traces, it appears that even though Lync sent updated connection  
           information in 183 w/sdp, the call manager is still sending rtp to the 
           mediation server which seems to be incorrect" So In this scenario  
           CUCM expects 180 Ringing not 183 Session progress.
           So added the Script to convert 183 Session Progress to 180 Ringing.
        
        4. There is incoming Invite from Lync and in From Header there is 
           "user=phone" which cause CUCM to send malformed data in to 
           different layers which cause call failure.So this is work around for that 
           scenario.
           
        5. Script modify the AS header which from outgoing messages because call forward 
           fails due to bandwith negotiation value is A=64 is not supported
           
        6. Script convert the History info to diversion Header since call forward to unity
           is not supported. 
           
        7. Transfer Scenario: Referred-By in Incoming Invite is converted to Diversion Header.
            
           
                                   
    Script Parameters:

    Release: 9.1(2) , 10.0.(1) 

    Copyright (c) 2009-2011 Cisco Systems, Inc. All rights reserved.
    All rights reserved.
--]]

M = {}

M.allowHeaders = {"History-Info"}

-- trace.enable()

local function modify_CT_bandwidth(msg)
    local sdp = msg:getSdp()
    if sdp
    then
        local b_CT_line = sdp:getLine("b=CT","64")
        if not b_CT_line
        then
            local b_CT_line = sdp:getLine("b=CT","0")
            if not b_CT_line
            then 
                return
            end
            b_CT_line = b_CT_line:gsub("0", "1000")
            sdp = sdp:modifyLine("b=CT", "0", b_CT_line)
            msg:setSdp(sdp)
            return
        end   
        b_CT_line = b_CT_line:gsub("64", "1000")
        sdp = sdp:modifyLine("b=CT", "64", b_CT_line)
        msg:setSdp(sdp)
    end
end

local function remove_AS_bandwidth(msg)
    local sdp = msg:getSdp()
    if sdp
    then
	local b_AS_line = sdp:getLine("b=AS","64")
        if b_AS_line
        then
            sdp = sdp:removeLine("b=AS", "64")
            msg:setSdp(sdp)
        end
    end
end

local function process_outbound_request(msg)

    local method, ruri, ver = msg:getRequestLine()

    if string.find(ruri, "@")
    then
        local uri = ruri .. ";user=phone"
        msg:setRequestUri(uri)
    end
   
    modify_CT_bandwidth(msg)
    remove_AS_bandwidth(msg)

end

local function process_outbound_message(msg)
    modify_CT_bandwidth(msg)
    remove_AS_bandwidth(msg)
end


local function process_inbound_progress(msg)

    msg:setResponseCode(180, "Ringing")

    local req = msg:getHeader("Require")    
    local reqHeader = req 
    if req
    then
        msg:removeHeader("Require")
    end
    
    local rseq = msg:getHeader("Rseq")    
    local rseqPresnt = rseq    
    if rseq
    then 
        seqVal = msg:getHeaderValues("Rseq")
        msg:removeHeader("Rseq")
    end
    
    local sdp = msg:getSdp()
    if sdp
    then
        msg:removeUnreliableSdp()
    end

    if reqHeader
    then
        msg:addHeader("Require", "100rel")
    end

    if rseqPresnt
    then
       msg:addHeader("RSeq",seqVal[1])
    end
end

-- Future reference for changing cause values in divertion header scenario
-- local HiCauseToDiversion = { }
-- HiCauseToDiversion["302"] = "unconditional"
-- HiCauseToDiversion["486"] = "user-busy"
-- HiCauseToDiversion["408"] = "no-answer"
-- HiCauseToDiversion["480"] = "deflection"
-- HiCauseToDiversion["487"] = "deflection"
-- HiCauseToDiversion["503"] = "unavailable"
-- HiCauseToDiversion["404"] = "unknown"

function convertHIToDiversion(msg)
    local historyInfos = msg:getHeaderValues("History-Info")

    for i, hi in ipairs(historyInfos)
    do
        hi = string.gsub(hi, "%%3B", ";")
        hi = string.gsub(hi, "%%3D", "=")
        hi = string.gsub(hi, "%%22", "\"")
        hi = string.gsub(hi, "%%20", " ")

        -- MS format: <sip:+19728522619@med02.lynclabsj.local;user=phone>;index=1;ms-retarget-reason=forwarding

        local uri, index, reason = string.match(hi, "<(sip:.*@.*)>;index=(.*)reason=(.*)")

        trace.format("hi: uri '%s', reason '%s'", uri or "nil", reason or "nil")


        if uri
        then
            local diversion = string.format("<%s>", uri)
            if reason
            then            
                diversion = string.format("<%s>;reason=\"unconditional\"", uri)
            end
            msg:addHeader("Diversion", diversion)
        end
    end
end

function convertReferredByToDiversion(msg)

    local refInfo = msg:getHeader("Referred-By")
    if refInfo
    then
        local diversion = string.format("%s;reason=\"unconditional\"", refInfo)
        msg:addHeader("Diversion", diversion)
    end

end 

local function replaceHistoryHeader(msg)

    local hist = msg:getHeader("History-Info")

    if hist
    then
        convertHIToDiversion(msg)
    
        local di  = msg:getHeader("Diversion")

        if di
        then
            msg:removeHeader("History-Info")
        end 
    end 
  
end

local function replaceReferredByHeader(msg)

    local refby = msg:getHeader("Referred-By")
    if refby 
    then
        convertReferredByToDiversion(msg)
    end

end

local function modifyUserFrom(msg)
-- get a data from "From" header and replace 
    local removeUser= ""
    local value = msg:getHeader("From")

    if value
    then
        value = value:gsub(";user=phone", removeUser)
        if value
        then
            msg:modifyHeader("From", value)
        end
    end
end

local function process_inbound_request(msg)      
    modifyUserFrom(msg)    
    replaceHistoryHeader(msg)
    replaceReferredByHeader(msg)
end               



M.outbound_INVITE          = process_outbound_request
M.outbound_ACK             = process_outbound_message
M.outbound_200_INVITE      = process_outbound_message
M.outbound_18X_INVITE      = process_outbound_message

M.inbound_183_INVITE       = process_inbound_progress
M.inbound_INVITE           = process_inbound_request

return M