-- Wireshark Dissector for LG LAF protocol
-- Tested with Wireshark 2.0
--
-- Place it in ~/.config/wireshark/plugins/
-- (or ~/.wireshark/plugins/ if ~/.wireshark/ exists)
--
-- Alternatively start with: wireshark -X lua_script:path/to/lglaf.lua

local lglaf = Proto("lglaf", "LG LAF")

local usb_transfer_type = Field.new("usb.transfer_type")
local usb_endpoint = Field.new("usb.endpoint_number")

lglaf.fields.cmd = ProtoField.string("lglaf.command", "Command")
lglaf.fields.arg1 = ProtoField.uint32("lglaf.arg1", "Argument 1", base.HEX_DEC)
lglaf.fields.arg2 = ProtoField.uint32("lglaf.arg2", "Argument 2", base.HEX_DEC)
lglaf.fields.arg3 = ProtoField.uint32("lglaf.arg3", "Argument 3", base.HEX_DEC)
lglaf.fields.arg4 = ProtoField.uint32("lglaf.arg4", "Argument 4", base.HEX_DEC)
lglaf.fields.len = ProtoField.uint32("lglaf.len", "Body length")
lglaf.fields.crc = ProtoField.uint32("lglaf.crc", "CRC", base.HEX)
lglaf.fields.cmd_inv = ProtoField.bytes("lglaf.command_inv", "Command (inverted)")
lglaf.fields.body = ProtoField.bytes("lglaf.body", "Body")
lglaf.fields.body_str = ProtoField.string("lglaf.body_str", "Body (text)")

function dissect_tx(tvb, pinfo, tree)
    local i
    local offset = 0
    for i = 1, 2 do
        tree:add_le(lglaf.fields.opts, tvb(offset, 4))
        offset = offset + 4
    end
    return offset
end

function lglaf.dissector(tvb, pinfo, tree)
    local offset
    local transfer_type = usb_transfer_type().value
    local endpoint = usb_endpoint().value

    -- Process only bulk packets from (EP 5) and to the device (EP 3)
    if not ((endpoint == 0x85 or endpoint == 3) and transfer_type == 3) then
        return 0
    end

    pinfo.cols.protocol = lglaf.name

    local lglaf_tree = tree:add(lglaf, tvb())
    if tvb(0, 4):le_uint() ~= bit.bnot(tvb(0x1c, 4):le_uint()) then
        pinfo.cols.info:set("Continuation")
        return
    end

    local next_offset = 0
    function add_dword(field)
        next_offset = next_offset + 4
        field_tvb = tvb(next_offset - 4, 4)
        lglaf_tree:add_le(field, field_tvb)
        return field_tvb
    end
    add_dword(lglaf.fields.cmd)
    local v_args = {
        add_dword(lglaf.fields.arg1),
        add_dword(lglaf.fields.arg2),
        add_dword(lglaf.fields.arg3),
        add_dword(lglaf.fields.arg4),
    }
    local v_len = add_dword(lglaf.fields.len)
    add_dword(lglaf.fields.crc)
    add_dword(lglaf.fields.cmd_inv)

    pinfo.cols.info:set(tvb(0, 4):string() .. "(")
    for i, arg in ipairs(v_args) do
        if i > 1 then
            pinfo.cols.info:append(",");
        end
        pinfo.cols.info:append(arg:le_uint())
    end
    pinfo.cols.info:append(")")

    -- TODO desegmentation support
    local body_len = v_len:le_uint()
    if body_len > 0 then
        local body_tvb = tvb(next_offset, body_len)
        lglaf_tree:add(lglaf.fields.body, body_tvb)
        lglaf_tree:add(lglaf.fields.body_str, body_tvb)

        local body_summary = body_tvb:string()
        body_summary = string.gsub(body_summary, "\n", "\\n")
        if #body_summary > 50 then
            body_summary = string.sub(body_summary, 1, 80) .. "…"
        end
        pinfo.cols.info:append(" [" .. body_len ..  "] " .. body_summary)
    end
end

function lglaf.init()
    local usb_product = DissectorTable.get("usb.product");
    usb_product:add(0x1004633e, lglaf)
end