package main

import "strconv"

// packetFixed computes the minimum complete packet size. The first XML byte
// occupies byte 1; the implicit sequence/length header follows that byte.
func packetFixed(m *Module, n *Node, reply bool) (int, error) {
	off := 1
	if n.Attr["no-sequence-number"] == "true" {
		off = 1
	}
	for _, f := range n.Children {
		if f.Kind == "doc" {
			continue
		}
		size := 0
		switch f.Kind {
		case "pad":
			if a := f.Attr["align"]; a != "" {
				align, _ := strconv.Atoi(a)
				size = (-off) & (align - 1)
			} else {
				size, _ = strconv.Atoi(f.Attr["bytes"])
			}
		case "field", "exprfield":
			typ, err := lookup(m, f.Attr["type"])
			if err != nil {
				return 0, err
			}
			size = typ.Size
		case "list":
			if len(f.Children) == 1 && f.Children[0].Kind == "value" {
				count, _ := strconv.Atoi(f.Children[0].Text)
				typ, err := lookup(m, f.Attr["type"])
				if err != nil {
					return 0, err
				}
				size = count * typ.Size
			} else {
				goto done
			}
		default:
			return 0, f.fail("unsupported packet member %s", f.Kind)
		}
		off += size
		if off == 2 && n.Attr["no-sequence-number"] != "true" {
			if reply {
				off = 8
			} else {
				off = 4
			}
		}
	}
done:
	if off < 32 {
		off = 32
	}
	return off, nil
}
func packetSizeChecks(m *Module) error {
	for _, n := range m.Root.Children {
		if n.Kind == "event" || n.Kind == "eventcopy" {
			size := 32
			if n.Kind == "event" {
				var err error
				size, err = packetFixed(m, n, false)
				if err != nil {
					return err
				}
			}
			if size != 32 {
				return n.fail("event fixed size %d, expected 32", size)
			}
			m.SizeChecks = append(m.SizeChecks, sizeCheck("event "+n.Attr["name"], size, 32))
		}
		if n.Kind == "request" {
			for _, r := range n.Children {
				if r.Kind != "reply" {
					continue
				}
				size, err := packetFixed(m, r, true)
				if err != nil {
					return err
				}
				expected := 32
				if m.Header == "xproto" {
					switch n.Attr["name"] {
					case "QueryKeymap":
						expected = 40
					case "GetKeyboardControl":
						expected = 52
					case "GetWindowAttributes":
						expected = 44
					case "QueryFont", "ListFontsWithInfo":
						expected = 60
					}
				}
				m.SizeChecks = append(m.SizeChecks, sizeCheck("reply "+n.Attr["name"], size, expected))
			}
		}
	}
	return nil
}