// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Functions to start services needed by the Vanadium playground.
// These should never trigger program exit.
// TODO(ivanpi): Use the modules library to start the services instead.

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"os/exec"
	"regexp"
	"time"

	"v.io/x/playground/lib"
	"v.io/x/ref"
)

var (
	proxyName = "proxy"
)

// TODO(ivanpi): this is all implemented in veyron/lib/modules/core, you
// may be able to use that directly.

func makeServiceCmd(progName string, args ...string) (*exec.Cmd, error) {
	return makeCmd(fmt.Sprintf("<%v>", progName), true, progName, progName, args...)
}

// startMount starts a mounttabled process, and sets the V23_NAMESPACE env
// variable to the mounttable's location.  We run one mounttabled process for
// the entire environment.
func startMount(timeLimit time.Duration) (proc *os.Process, err error) {
	cmd, err := makeServiceCmd("mounttabled", "-v23.tcp.address=127.0.0.1:0")
	if err != nil {
		return nil, err
	}
	matches, err := startAndWaitFor(cmd, timeLimit, regexp.MustCompile("NAME=(.*)"))
	if err != nil {
		return nil, fmt.Errorf("Error starting mounttabled: %v", err)
	}
	endpoint := matches[1]
	if endpoint == "" {
		return nil, fmt.Errorf("Failed to get mounttable endpoint")
	}
	return cmd.Process, os.Setenv(ref.EnvNamespacePrefix, endpoint)
}

// startProxy starts a proxyd process.  We run one proxyd process for the
// entire environment.
func startProxy(timeLimit time.Duration) (proc *os.Process, err error) {
	cmd, err := makeServiceCmd(
		"xproxyd",
		"-log_dir=/tmp/logs",
		"-name="+proxyName,
		"-access-list", fmt.Sprintf("{\"In\":[\"%v\"]}", identityProvider),
		"-v23.tcp.address=127.0.0.1:0")
	if err != nil {
		return nil, err
	}
	if _, err := startAndWaitFor(cmd, timeLimit, regexp.MustCompile("NAME=(.*)")); err != nil {
		return nil, fmt.Errorf("Error starting proxy: %v", err)
	}
	return cmd.Process, nil
}

// Helper function to start a command and wait for output.  Arguments are a cmd
// to run, a timeout, and a regexp.  The slice of strings matched by the regexp
// is returned.
// TODO(nlacasse): Consider standardizing how services log when they start
// listening, and their endpoints (if any).  Then this could become a common
// util function.
func startAndWaitFor(cmd *exec.Cmd, timeout time.Duration, outputRegexp *regexp.Regexp) ([]string, error) {
	reader, writer := io.Pipe()
	cmd.Stdout.(*lib.MultiWriter).Add(writer)
	if err := cmd.Start(); err != nil {
		return nil, err
	}

	ch := make(chan []string)
	go (func() {
		scanner := bufio.NewScanner(reader)
		for scanner.Scan() {
			line := scanner.Text()
			if matches := outputRegexp.FindStringSubmatch(line); matches != nil {
				ch <- matches
			}
		}
		close(ch)
	})()
	select {
	case <-time.After(timeout):
		return nil, fmt.Errorf("Timeout starting service: %v", cmd.Path)
	case matches := <-ch:
		return matches, nil
	}
}