/*
Copyright 2022 CAcert Inc.
SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// client simulator

package main

import (
	"fmt"
	"log"
	"os"
	"sync"
	"time"

	"github.com/justincpresley/go-cobs"
	"github.com/shamaton/msgpackgen/msgpack"

	"git.cacert.org/cacert-gosigner/pkg/messages"
)

const cobsDelimiter = 0x00

var cobsConfig = cobs.Config{SpecialByte: cobsDelimiter, Delimiter: true, EndingSave: true}

func main() {
	const (
		bufferSize   = 1024 * 1024
		readInterval = 50 * time.Millisecond
	)

	errors := make(chan error)

	errorLog := log.New(os.Stderr, "", log.LstdFlags)

	wg := sync.WaitGroup{}
	wg.Add(1)

	done := make(chan struct{})
	frame := make(chan []byte)

	go func(done chan struct{}) {
		buf := make([]byte, bufferSize)

		for {
			select {
			case <-done:
				wg.Done()

				return

			default:
				count, err := os.Stdin.Read(buf)
				if err != nil {
					errors <- err

					wg.Done()

					return
				}

				if count == 0 {
					time.Sleep(readInterval)

					continue
				}

				data := buf[:count]

				err = cobs.Verify(data, cobsConfig)
				if err != nil {
					errors <- err

					wg.Done()

					return
				}

				frame <- cobs.Decode(data, cobsConfig)
			}
		}
	}(done)

	err := writeTestCommands(frame, errorLog)
	if err != nil {
		errorLog.Printf("could not write test commands")
	}

	err = <-errors
	if err != nil {
		errorLog.Printf("error: %v", err)
	}

	wg.Wait()
}

func writeTestCommands(responses chan []byte, errorLog *log.Logger) error {
	messages.RegisterGeneratedResolver()

	commands := []messages.Command{
		{
			Code:      messages.CmdHealth,
			TimeStamp: time.Now().UTC(),
		},
	}

	for _, command := range commands {
		commandBytes, err := msgpack.Marshal(command)
		if err != nil {
			return fmt.Errorf("could not marshal command bytes: %w", err)
		}

		_, err = os.Stdout.Write(cobs.Encode(commandBytes, cobsConfig))
		if err != nil {
			return fmt.Errorf("write failed: %w", err)
		}

		responseBytes := <-responses

		var response messages.Response

		err = msgpack.Unmarshal(responseBytes, &response)
		if err != nil {
			return fmt.Errorf("could not unmarshal msgpack data: %w", err)
		}

		errorLog.Printf("received response: %+v", response)
	}

	return nil
}