package tunnel

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"strings"
)

// Endpoints represents the endpoints listed in the API service directory.
// Ideally the Relay URL is discoverable and will provide the authn endpoint,
// which will provide the tunnel endpoint. However, for the sake of testing,
// these things may happen out-of-order.
type Endpoints struct {
	ToS          string   `json:"terms_of_service"`
	APIHost      string   `json:"api_host"`
	Tunnel       Endpoint `json:"tunnel"`
	Authenticate Endpoint `json:"authn"`
	/*
		{
			"terms_of_service": ":hostname/tos/",
			"api_host": ":hostname/api",
			"pair_request": {
				"method": "POST",
				"pathname": "api/telebit.app/pair_request"
			}
		}
	*/
}

// Endpoint represents a URL Request
type Endpoint struct {
	URL      string `json:"-"`
	Method   string `json:"method"`
	Scheme   string `json:"scheme"`
	Host     string `json:"host"`
	Pathname string `json:"pathname"`
}

// Discover checks the .well-known directory for service endpoints
func Discover(relay string) (*Endpoints, error) {
	directives := &Endpoints{}
	relayURL, err := url.Parse(relay)
	if nil != err {
		fmt.Fprintf(os.Stderr, "Error: invalid Tunnel Relay URL %q: %s\n", relay, err)
		os.Exit(1)
	}
	if "ws" != relayURL.Scheme[:2] {

		if '/' != relayURL.Path[len(relayURL.Path)-1] {
			relayURL.Path += "/"
		}
		resp, err := http.Get(relayURL.String() + ".well-known/telebit.app/index.json")
		if nil != err {
			fmt.Fprintf(os.Stderr, "Error: invalid Tunnel Relay URL %q: %s\n", relay, err)
			os.Exit(1)
		}
		b, err := ioutil.ReadAll(resp.Body)
		resp.Body.Close()
		if nil != err {
			return nil, err
		}
		body := strings.Replace(string(b), ":hostname", relayURL.Host, -1)
		err = json.Unmarshal([]byte(body), directives)
		if nil != err {
			return nil, err
		}

		directives.Tunnel.URL = endpointToURLString(directives.APIHost, directives.Tunnel)

	} else {

		directives.Tunnel.URL = relayURL.String()
		directives.APIHost = relayURL.Host

	}

	directives.Authenticate.URL = endpointToURLString(directives.APIHost, directives.Authenticate)

	return directives, nil
}

func endpointToURLString(apiHost string, endpoint Endpoint) string {
	pathname := endpoint.Pathname
	if "" == pathname {
		return ""
	}

	host := endpoint.Host
	if "" == host {
		host = apiHost
	}

	scheme := endpoint.Scheme
	if "" == scheme {
		scheme = "https:"
	}

	return fmt.Sprintf("%s//%s/%s", scheme, host, pathname)
}