package main

import (
	"crypto/sha256"
	"fmt"
	"sort"
	"strings"
)

const crockfordAlphabet = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"

func buildDeviceID(publicKey []byte) string {
	material := append([]byte("dcauth.device.v1"), publicKey...)
	sum := sha256.Sum256(material)
	return formatCode("D1", sum[:])
}

func buildMachineCode() (string, error) {
	components, err := collectHardwareComponents()
	if err != nil {
		return "", err
	}
	keys := make([]string, 0, len(components))
	for key := range components {
		keys = append(keys, key)
	}
	sort.Strings(keys)

	parts := []string{"dcauth.machine.v1"}
	for _, key := range keys {
		parts = append(parts, key+"="+components[key])
	}
	sum := sha256.Sum256([]byte(strings.Join(parts, "\n")))
	return formatCode("M1", sum[:]), nil
}

func formatCode(prefix string, data []byte) string {
	encoded := base32Crockford(data)
	if len(encoded) > 20 {
		encoded = encoded[:20]
	}
	groups := make([]string, 0, 5)
	for len(encoded) > 0 {
		size := 4
		if len(encoded) < size {
			size = len(encoded)
		}
		groups = append(groups, encoded[:size])
		encoded = encoded[size:]
	}
	return prefix + "-" + strings.Join(groups, "-")
}

func base32Crockford(data []byte) string {
	var builder strings.Builder
	var buffer uint32
	var bits uint
	for _, value := range data {
		buffer = (buffer << 8) | uint32(value)
		bits += 8
		for bits >= 5 {
			bits -= 5
			builder.WriteByte(crockfordAlphabet[(buffer>>bits)&31])
		}
	}
	if bits > 0 {
		builder.WriteByte(crockfordAlphabet[(buffer<<(5-bits))&31])
	}
	return builder.String()
}

func normalizeComponent(value string) string {
	normalized := strings.ToUpper(strings.TrimSpace(value))
	normalized = strings.Join(strings.Fields(normalized), "")
	switch normalized {
	case "", "0", "NONE", "N/A", "NA", "UNKNOWN", "DEFAULTSTRING",
		"TOBEFILLEDBYO.E.M.", "TOBEFILLEDBYOEM", "SYSTEMSERIALNUMBER",
		"00000000-0000-0000-0000-000000000000":
		return ""
	}
	return normalized
}

func ensureNotEmpty(components map[string]string) error {
	if len(components) == 0 {
		return fmt.Errorf("无法读取本机硬件信息，请联系管理员")
	}
	return nil
}