package iana

import (
	"fmt"
	"strings"

	"github.com/u-root/u-root/pkg/uio"
)

// Arch encodes an architecture type per RFC 4578, Section 2.1.
type Arch uint16

// See RFC 4578.
const (
	INTEL_X86PC       Arch = 0
	NEC_PC98          Arch = 1
	EFI_ITANIUM       Arch = 2
	DEC_ALPHA         Arch = 3
	ARC_X86           Arch = 4
	INTEL_LEAN_CLIENT Arch = 5
	EFI_IA32          Arch = 6
	EFI_BC            Arch = 7
	EFI_XSCALE        Arch = 8
	EFI_X86_64        Arch = 9
)

// archTypeToStringMap maps an Arch to a mnemonic name
var archTypeToStringMap = map[Arch]string{
	INTEL_X86PC:       "Intel x86PC",
	NEC_PC98:          "NEC/PC98",
	EFI_ITANIUM:       "EFI Itanium",
	DEC_ALPHA:         "DEC Alpha",
	ARC_X86:           "Arc x86",
	INTEL_LEAN_CLIENT: "Intel Lean Client",
	EFI_IA32:          "EFI IA32",
	EFI_BC:            "EFI BC",
	EFI_XSCALE:        "EFI Xscale",
	EFI_X86_64:        "EFI x86-64",
}

// String returns a mnemonic name for a given architecture type.
func (a Arch) String() string {
	if at := archTypeToStringMap[a]; at != "" {
		return at
	}
	return "unknown"
}

// Archs represents multiple Arch values.
type Archs []Arch

// ToBytes returns the serialized option defined by RFC 4578 (DHCPv4) and RFC
// 5970 (DHCPv6) as the Client System Architecture Option.
func (a Archs) ToBytes() []byte {
	buf := uio.NewBigEndianBuffer(nil)
	for _, at := range a {
		buf.Write16(uint16(at))
	}
	return buf.Data()
}

// String returns the list of archs in a human-readable manner.
func (a Archs) String() string {
	s := make([]string, 0, len(a))
	for _, arch := range a {
		s = append(s, arch.String())
	}
	return strings.Join(s, ", ")
}

// FromBytes parses a DHCP list of architecture types as defined by RFC 4578
// and RFC 5970.
func (a *Archs) FromBytes(data []byte) error {
	buf := uio.NewBigEndianBuffer(data)
	if buf.Len() == 0 {
		return fmt.Errorf("must have at least one archtype if option is present")
	}

	*a = make([]Arch, 0, buf.Len()/2)
	for buf.Has(2) {
		*a = append(*a, Arch(buf.Read16()))
	}
	return buf.FinError()
}