package cudy

import (
	"net"
	"net/netip"
	"sort"
	"strconv"
	"strings"

	"golang.org/x/net/html"
)

func parseClients(data []byte) ([]Client, error) {
	doc, err := html.Parse(strings.NewReader(string(data)))
	if err != nil {
		return nil, ErrRead
	}
	clients := []Client{}
	var table *html.Node
	walk(doc, func(n *html.Node) {
		if n.Data == "th" && nodeText(n) == "IP / MAC Address" {
			for parent := n.Parent; parent != nil; parent = parent.Parent {
				if parent.Data == "table" {
					table = parent
					break
				}
			}
		}
	})
	if table == nil {
		return nil, ErrRead
	}
	invalid := false
	seen := map[string]bool{}
	walk(table, func(row *html.Node) {
		if row.Type != html.ElementNode {
			return
		}
		if row.Data != "tr" {
			return
		}
		hasData := false
		for child := row.FirstChild; child != nil; child = child.NextSibling {
			hasData = hasData || child.Data == "td"
		}
		if !hasData {
			return
		}
		if !strings.HasPrefix(attr(row, "id"), "cbi-table-") {
			invalid = true
			return
		}
		fields := map[string]*html.Node{}
		prefix := attr(row, "id") + "-"
		walk(row, func(n *html.Node) {
			if n.Data == "div" && strings.HasPrefix(attr(n, "id"), prefix) {
				fields[strings.TrimPrefix(attr(n, "id"), prefix)] = n
			}
		})
		var band string
		wired := false
		if hostname := fields["hostname"]; hostname != nil {
			walk(hostname, func(n *html.Node) {
				if n.Data == "span" {
					label := nodeText(n)
					wired = wired || label == "Ethernet"
					if label == "2.4G WiFi" {
						band = "2.4 GHz"
					}
					if label == "5G WiFi" {
						band = "5 GHz"
					}
				}
			})
		}
		// shortcut: stock TR3000 2.5.27 DOM and two bands; update parser fixtures for other firmware.
		if band == "" {
			if !wired {
				invalid = true
			}
			return
		}
		client := Client{Band: band}
		if field := fields["ipmac"]; field != nil {
			walk(field, func(n *html.Node) {
				if n.Data != "p" || client.MAC != "" {
					return
				}
				for _, value := range strings.Fields(nodeText(n)) {
					if ip, e := netip.ParseAddr(value); e == nil {
						client.IP = ip.String()
					}
					if mac, e := net.ParseMAC(value); e == nil && len(mac) == 6 {
						client.MAC = strings.ToUpper(mac.String())
					}
				}
			})
		}
		if field := fields["signal"]; field != nil {
			walk(field, func(n *html.Node) {
				if n.Data == "p" && client.Signal == nil {
					parts := strings.Fields(nodeText(n))
					if len(parts) == 2 && parts[1] == "dBm" {
						if value, e := strconv.Atoi(parts[0]); e == nil && value >= -120 && value <= 0 {
							client.Signal = &value
						}
					}
				}
			})
		}
		if client.MAC == "" || seen[client.MAC] {
			invalid = true
			return
		}
		seen[client.MAC] = true
		clients = append(clients, client)
	})
	if invalid || len(clients) > 1024 {
		return nil, ErrRead
	}
	sort.Slice(clients, func(i, j int) bool { return clients[i].MAC < clients[j].MAC })
	return clients, nil
}