require "util"

local p = Proto("rxhdr", "Hardware RX header")

-- based off <https://www.problemkaputt.de/gbatek.htm#dswifihardwareheaders>

p.fields.unknown = ProtoField.bytes("rxhdr.unknown", "Unknown")

p.fields.flags = ProtoField.new("Flags", "rxhdr.flags", ftypes.BYTES)
p.fields.flag_type = ProtoField.uint16("rxhdr.flags.type", "Frame type", base.DEC, nil, bits(0, 4))
p.fields.flag_more = ProtoField.bool("rxhdr.flags.more", "More fragments", base.DEC, nil, bits(8))

p.fields.new = ProtoField.bool("rxhdr.new", "New frame")
p.fields.magic = ProtoField.bytes("rxhdr.magic", "Magic")
p.fields.channel = ProtoField.uint8("rxhdr.channel", "802.11 channel")

p.fields.rate = ProtoField.uint16("rxhdr.rate", "Transfer rate", base.HEX, {
	[0x0a] = "1 Mbit/s",
	[0x14] = "2 Mbit/s",
})
p.fields.length = ProtoField.uint16("rxhdr.len", "Remaining message length")

local ieee_dissector = Dissector.get("ieee")

function p.dissector(buffer, pinfo, tree)
	local header_size = 12
	-- check buffer size
	if buffer:len() < header_size then return 0 end

	local subtree = tree:add(p, buffer(0, header_size), string.format("%s: %d bytes", p.description, header_size))

	local flags_tree = subtree:add(p.fields.flags, buffer(0x00, 2))
		flags_tree:add_le(p.fields.flag_type, buffer(0x00, 2))
		flags_tree:add_le(p.fields.flag_more, buffer(0x00, 2))

	subtree:add(p.fields.unknown, buffer(0x02, 2))
	subtree:add(p.fields.unknown, buffer(0x04, 2))

	subtree:add_le(p.fields.rate, buffer(0x06, 2))
	subtree:add_le(p.fields.length, buffer(0x08, 2))
	local length = buffer(0x08, 2):le_uint()

	-- pretty wireshark shit
	pinfo.cols.protocol = p.name

	ieee_dissector:call(buffer(header_size, length):tvb(), pinfo, tree)

	return header_size
end