package synthetic

import (
	"fmt"
	"github.com/coredns/caddy"
	"github.com/coredns/coredns/core/dnsserver"
	"github.com/coredns/coredns/plugin"
	"net"
	"strconv"
	"strings"
)

// syntheticConfig holds the configuration options for the synthetic plugin.
type syntheticConfig struct {
	net     []*net.IPNet
	forward string
	ttl     uint32
	prefix  string
}

// init registers this plugin.
func init() { plugin.Register("synthetic", setup) }

// setup is the function that gets called when the config parser see the token "synthetic".
func setup(c *caddy.Controller) error {
	var config syntheticConfig

	// Parse the configuration file
	for c.Next() {
		for c.NextBlock() {
			switch v := c.Val(); v {

			// Configuration for forward lookup zones for which to do resolution
			case "net":
				args := c.RemainingArgs()
				for _, arg := range args {
					_, cidr, err := net.ParseCIDR(arg)
					if err == nil {
						config.net = append(config.net, cidr)
					} else {
						return fmt.Errorf("synthetic: invalid reverse lookup cidr: %v", arg)
					}
				}

			// Configuration for reverse lookup zones for the forward lookup zone name
			case "forward":
				args := c.RemainingArgs()
				for _, arg := range args {
					config.forward = arg
				}

			// Configuration for the TTL value
			case "ttl":
				args := c.RemainingArgs()
				for _, arg := range args {
					ttl64, err := strconv.ParseUint(arg, 10, 32)
					if err != nil {
						return fmt.Errorf("synthetic: invalid ttl value: %v", arg)
					}
					config.ttl = uint32(ttl64)
				}

				// configuration for the prefix value (defaults to `ip`)
			case "prefix":
				args := c.RemainingArgs()
				for _, arg := range args {
					config.prefix = arg
				}

			default:
				return c.Errf("unknown property '%s'", v)
			}
		}
	}

	if config.prefix == "" {
		config.prefix = "ip"
	}
	if !strings.HasSuffix(config.prefix, "-") {
		config.prefix = config.prefix + "-"
	}

	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
		return synthetic{Next: next, Config: config}
	})

	return nil
}