package dnsmasq

import (
	"fmt"
	"os"
	"text/template"
)

// ConfDataHost describes a host which can be resolved by dnsmasq.
type ConfDataHost struct {
	Name string
	IP   string
}

// ConfData describes all the data needed to populate a dnsmasq.conf file.
type ConfData struct {
	Resolvers []string
	Domain    string
	IP        string
	Hosts     []ConfDataHost
}

var confTpl = template.Must(template.New("").Parse(`
port=53

bind-interfaces
listen-address={{ .IP }}

no-resolv
no-hosts

user=
group=

{{- $domain := .Domain -}}

{{- range .Hosts }}
address=/{{ .Name }}.hosts.{{ $domain }}/{{ .IP }}
{{ end -}}

{{- range .Resolvers }}
server={{ . }}
{{ end -}}
`))

// WriteConfFile renders a dnsmasq.conf using the given data to a new
// file at the given path.
func WriteConfFile(path string, data ConfData) error {

	file, err := os.OpenFile(
		path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0640,
	)

	if err != nil {
		return fmt.Errorf("creating file: %w", err)
	}

	defer file.Close()

	if err := confTpl.Execute(file, data); err != nil {
		return fmt.Errorf("rendering template to file: %w", err)
	}

	return nil
}