package main

// NetworkManager's word on each link's names: `nmcli device show`, read in its terse form. A link
// NetworkManager does not manage — a tunnel a VPN client raised with `ip`, the mesh's own — is not in it,
// and the links verb says the link without what the manager does not know.

import (
	"context"
	"strings"
)

func managerDNS(ctx context.Context) (map[string]LinkDNS, error) {
	out, err := execRunner(ctx, "nmcli", "-t", "-f", "GENERAL.DEVICE,GENERAL.STATE,IP4.DNS,IP6.DNS,IP4.DOMAIN,IP6.DOMAIN",
		"device", "show")
	if err != nil {
		return nil, err
	}
	return parseNmcli(out), nil
}

// parseNmcli reads `nmcli -t device show`: blocks of KEY:value lines, one block per device.
func parseNmcli(out string) map[string]LinkDNS {
	links := map[string]LinkDNS{}
	device := ""
	var cur LinkDNS
	flush := func() {
		if device != "" && (len(cur.Servers) > 0 || len(cur.Domains) > 0) {
			cur.Manager = "NetworkManager"
			links[device] = cur
		}
		device, cur = "", LinkDNS{}
	}
	for _, line := range strings.Split(out, "\n") {
		key, value, ok := strings.Cut(strings.TrimSpace(line), ":")
		if !ok {
			continue
		}
		switch {
		case key == "GENERAL.DEVICE":
			flush()
			device = value
		case key == "GENERAL.STATE":
			cur.State = value
		case strings.HasPrefix(key, "IP4.DNS"), strings.HasPrefix(key, "IP6.DNS"):
			cur.Servers = append(cur.Servers, value)
		case strings.HasPrefix(key, "IP4.DOMAIN"), strings.HasPrefix(key, "IP6.DOMAIN"):
			cur.Domains = append(cur.Domains, value)
		}
	}
	flush()
	return links
}