-- Written by Eitam Doodai
-- trivial postdissector example
-- declare some Fields to be read
full_uri_from_request = Field.new("http.request.full_uri")

-- declare our (pseudo) protocol
http_query_params_proto = Proto("http.query_parameters","HTTP Query Parameters Postdissector")

-- create the fields for our "protocol"
query_param1 = ProtoField.string("http.query_parameters.param1","PARAM1")
query_param2 = ProtoField.string("http.query_parameters.param2","PARAM2")
query_param3 = ProtoField.string("http.query_parameters.param3","PARAM3")

-- add the field to the protocol
http_query_params_proto.fields = {query_param1}
http_query_params_proto.fields = {query_param2}
http_query_params_proto.fields = {query_param3}

-- Add prefs
local p1 = http_query_params_proto.prefs
p1.value1 = Pref.string ("Param1 Value", "123", "Param key to extract")
p1.value2 = Pref.string ("Param2 Value", "456", "Param key to extract")
p1.value3 = Pref.string ("Param3 Value", "789", "Param key to extract")

-- create a function to "postdissect" each frame
function http_query_params_proto.dissector(buffer,pinfo,tree)
    -- obtain the current values the protocol fields
    local full_uri_value = full_uri_from_request()
    if full_uri_value then
        local value = tostring(full_uri_value)
        local subtree = tree:add(http_query_params_proto,"Query Param1")
        local subtree = tree:add(http_query_params_proto,"Query Param2")
        local subtree = tree:add(http_query_params_proto,"Query Param3")
        _, _, query_param1_str = string.find(value,p1.value1 .. "=([^&]+)")
        _, _, query_param2_str = string.find(value,p1.value2 .. "=([^&]+)")
        _, _, query_param3_str = string.find(value,p1.value3 .. "=([^&]+)")
        if query_param1_str then
            subtree:add(query_param1,query_param1_str)
        end

        if query_param2_str then
            subtree:add(query_param2,query_param2_str)
        end
        if query_param3_str then
            subtree:add(query_param3,query_param3_str)
        end
    end
end

-- register our protocol as a postdissector
register_postdissector(http_query_params_proto)