/*
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 (
	"context"
	"crypto/rand"
	"fmt"
	"io"
	"os"
	"time"

	"github.com/shamaton/msgpackgen/msgpack"
	"github.com/sirupsen/logrus"

	"git.cacert.org/cacert-gosigner/pkg/protocol"

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

type TestCommandGenerator struct {
	logger   *logrus.Logger
	commands chan *protocol.Command
}

func (g *TestCommandGenerator) GenerateCommands(ctx context.Context) error {
	var (
		announce *messages.CommandAnnounce
		err      error
	)

	// write some leading garbage to test signer robustness
	_, _ = io.CopyN(os.Stdout, rand.Reader, 50) //nolint:gomnd

	announce, err = messages.BuildCommandAnnounce(messages.CmdHealth)
	if err != nil {
		return fmt.Errorf("build command announce failed: %w", err)
	}

	g.commands <- &protocol.Command{Announce: announce, Command: &messages.HealthCommand{}}

	const (
		healthInterval = 5 * time.Second
		crlInterval    = 15 * time.Minute
		startPause     = 3 * time.Second
	)

	g.logger.Info("start generating commands")

	time.Sleep(startPause)

	announce, err = messages.BuildCommandAnnounce(messages.CmdFetchCRL)
	if err != nil {
		return fmt.Errorf("build command announce failed: %w", err)
	}

	g.commands <- &protocol.Command{
		Announce: announce,
		Command:  &messages.FetchCRLCommand{IssuerID: "sub-ecc_person_2022"},
	}

	healthTimer := time.NewTimer(healthInterval)
	crlTimer := time.NewTimer(crlInterval)

	for {
		select {
		case <-ctx.Done():
			_ = healthTimer.Stop()

			g.logger.Info("stopped health check loop")

			_ = crlTimer.Stop()

			g.logger.Info("stopped CRL fetch loop")

			return nil
		case <-healthTimer.C:
			announce, err = messages.BuildCommandAnnounce(messages.CmdHealth)
			if err != nil {
				return fmt.Errorf("build command announce failed: %w", err)
			}

			g.commands <- &protocol.Command{
				Announce: announce,
				Command:  &messages.HealthCommand{},
			}

			healthTimer.Reset(healthInterval)
		case <-crlTimer.C:
			g.commands <- &protocol.Command{
				Announce: announce,
				Command:  &messages.FetchCRLCommand{IssuerID: "sub-ecc_person_2022"},
			}
		}
	}
}

type clientSimulator struct {
	clientHandler    protocol.ClientHandler
	framesIn         chan []byte
	framesOut        chan []byte
	framer           protocol.Framer
	commandGenerator *TestCommandGenerator
	logger           *logrus.Logger
}

const (
	responseAnnounceTimeout = 30 * time.Second
	responseDataTimeout     = 2 * time.Second
)

func (c *clientSimulator) Run(ctx context.Context) error {
	framerErrors := make(chan error)
	protocolErrors := make(chan error)
	generatorErrors := make(chan error)

	go func() {
		err := c.framer.ReadFrames(os.Stdin, c.framesIn)

		framerErrors <- err
	}()

	go func() {
		err := c.framer.WriteFrames(os.Stdout, c.framesOut)

		framerErrors <- err
	}()

	go func() {
		clientProtocol := protocol.NewClient(c.clientHandler, c.commandGenerator.commands, c.framesIn, c.framesOut, c.logger)

		err := clientProtocol.Handle()

		protocolErrors <- err
	}()

	go func() {
		err := c.commandGenerator.GenerateCommands(ctx)

		generatorErrors <- err
	}()

	for {
		select {
		case <-ctx.Done():
			return nil
		case err := <-framerErrors:
			if err != nil {
				return fmt.Errorf("error from framer: %w", err)
			}

			return nil
		case err := <-generatorErrors:
			if err != nil {
				return fmt.Errorf("error from command generator: %w", err)
			}

			return nil
		case err := <-protocolErrors:
			if err != nil {
				return fmt.Errorf("error from protocol handler: %w", err)
			}

			return nil
		}
	}
}

type ClientHandler struct {
	logger *logrus.Logger
}

func (c ClientHandler) Send(command *protocol.Command, out chan []byte) error {
	var (
		frame []byte
		err   error
	)

	frame, err = msgpack.Marshal(command.Announce)
	if err != nil {
		return fmt.Errorf("could not marshal command annoucement: %w", err)
	}

	c.logger.WithField("announcement", command.Announce).Info("write command announcement")

	c.logger.Trace("writing command announcement")

	out <- frame

	frame, err = msgpack.Marshal(command.Command)
	if err != nil {
		return fmt.Errorf("could not marshal command data: %w", err)
	}

	c.logger.WithField("command", command.Command).Info("write command data")

	out <- frame

	return nil
}

func (c ClientHandler) ResponseAnnounce(in chan []byte) (*protocol.Response, error) {
	response := &protocol.Response{}

	var announce messages.ResponseAnnounce

	select {
	case frame := <-in:
		if err := msgpack.Unmarshal(frame, &announce); err != nil {
			return nil, fmt.Errorf("could not unmarshal response announcement: %w", err)
		}

		response.Announce = &announce

		c.logger.WithField("announcement", response.Announce).Debug("received response announcement")

		return response, nil
	case <-time.After(responseAnnounceTimeout):
		return nil, protocol.ErrResponseAnnounceTimeoutExpired
	}
}

func (c ClientHandler) ResponseData(in chan []byte, response *protocol.Response) error {
	select {
	case frame := <-in:
		switch response.Announce.Code {
		case messages.RespHealth:
			var resp messages.HealthResponse
			if err := msgpack.Unmarshal(frame, &resp); err != nil {
				return fmt.Errorf("could not unmarshal health response data: %w", err)
			}

			response.Response = &resp
		case messages.RespFetchCRL:
			var resp messages.FetchCRLResponse
			if err := msgpack.Unmarshal(frame, &resp); err != nil {
				return fmt.Errorf("could not unmarshal fetch CRL response data: %w", err)
			}

			response.Response = &resp
		default:
			return fmt.Errorf("unhandled response code %s", response.Announce.Code)
		}
	case <-time.After(responseDataTimeout):
		return protocol.ErrResponseDataTimeoutExpired
	}

	return nil
}

func (c ClientHandler) HandleResponse(response *protocol.Response) error {
	c.logger.WithField("response", response.Announce).Info("handled response")
	c.logger.WithField("response", response).Debug("full response")

	return nil
}

func newClientHandler(logger *logrus.Logger) *ClientHandler {
	return &ClientHandler{logger: logger}
}

func main() {
	logger := logrus.New()
	logger.SetOutput(os.Stderr)
	logger.SetLevel(logrus.DebugLevel)

	messages.RegisterGeneratedResolver()

	sim := &clientSimulator{
		commandGenerator: &TestCommandGenerator{
			logger:   logger,
			commands: make(chan *protocol.Command),
		},
		logger:        logger,
		framesIn:      make(chan []byte),
		framesOut:     make(chan []byte),
		framer:        protocol.NewCOBSFramer(logger),
		clientHandler: newClientHandler(logger),
	}

	err := sim.Run(context.Background())
	if err != nil {
		logger.WithError(err).Error("simulator returned an error")
	}
}