package executor

import (
	pb "github.com/OliveTin/OliveTin/gen/grpc"
	acl "github.com/OliveTin/OliveTin/internal/acl"
	config "github.com/OliveTin/OliveTin/internal/config"
	log "github.com/sirupsen/logrus"

	"bytes"
	"context"
	"io"
	"os/exec"
	"runtime"
	"time"
)

// Executor represents a helper class for executing commands. It's main method
// is ExecRequest
type Executor struct {
	Logs map[string]*InternalLogEntry

	listeners []listener

	chainOfCommand []executorStepFunc
}

// ExecutionRequest is a request to execute an action. It's passed to an
// Executor. They're created from the grpcapi.
type ExecutionRequest struct {
	ActionName         string
	Arguments          map[string]string
	UUID               string
	Tags               []string
	action             *config.Action
	Cfg                *config.Config
	AuthenticatedUser  *acl.AuthenticatedUser
	logEntry           *InternalLogEntry
	finalParsedCommand string
	executor           *Executor
}

// InternalLogEntry objects are created by an Executor, and represent the final
// state of execution (even if the command is not executed). It's designed to be
// easily serializable.
type InternalLogEntry struct {
	DatetimeStarted    string
	DatetimeFinished   string
	Stdout             string
	Stderr             string
	StdoutBuffer       io.ReadCloser
	StderrBuffer       io.ReadCloser
	TimedOut           bool
	ExitCode           int32
	Tags               []string
	ExecutionStarted   bool
	ExecutionCompleted bool

	/*
		The following 3 properties are obviously on Action normally, but it's useful
		that logs are lightweight (so we don't need to have an action associated to
		logs, etc. Therefore, we duplicate those values here.
	*/
	ActionTitle string
	ActionIcon  string
	UUID        string
}

type executorStepFunc func(*ExecutionRequest) bool

// DefaultExecutor returns an Executor, with a sensible "chain of command" for
// executing actions.
func DefaultExecutor() *Executor {
	e := Executor{}
	e.Logs = make(map[string]*InternalLogEntry)

	e.chainOfCommand = []executorStepFunc{
		stepLogRequested,
		stepFindAction,
		stepACLCheck,
		stepParseArgs,
		stepLogStart,
		stepExec,
		stepNotifyListeners,
		stepLogFinish,
	}

	return &e
}

type listener interface {
	OnExecutionStarted(actionName string)
	OnExecutionFinished(logEntry *InternalLogEntry)
}

func (e *Executor) AddListener(m listener) {
	e.listeners = append(e.listeners, m)
}

// ExecRequest processes an ExecutionRequest
func (e *Executor) ExecRequest(req *ExecutionRequest) *pb.StartActionResponse {
	// req.UUID is now set by the client, so that they can track the request
	// from start to finish. This means that a malicious client could send
	// duplicate UUIDs (or just random strings), but this is the only way.
	req.executor = e
	req.logEntry = &InternalLogEntry{
		DatetimeStarted:    time.Now().Format("2006-01-02 15:04:05"),
		ActionTitle:        req.ActionName,
		UUID:               req.UUID,
		Stdout:             "",
		Stderr:             "",
		ExitCode:           -1337, // If an Action is not actually executed, this is the default exit code.
		ExecutionStarted:   false,
		ExecutionCompleted: false,
	}

	e.Logs[req.UUID] = req.logEntry

	for _, listener := range e.listeners {
		listener.OnExecutionStarted(req.ActionName)
	}

	go e.execChain(req)

	return &pb.StartActionResponse{
		ExecutionUuid: req.UUID,
	}
}

func (e *Executor) execChain(req *ExecutionRequest) {
	for _, step := range e.chainOfCommand {
		if !step(req) {
			break
		}
	}
}

func stepFindAction(req *ExecutionRequest) bool {
	actualAction := req.Cfg.FindAction(req.ActionName)

	if actualAction == nil {
		log.WithFields(log.Fields{
			"actionName": req.ActionName,
		}).Warnf("Action not found")

		req.logEntry.Stderr = "Action not found"

		return false
	}

	req.action = actualAction
	req.logEntry.ActionIcon = actualAction.Icon

	return true
}

func stepACLCheck(req *ExecutionRequest) bool {
	return acl.IsAllowedExec(req.Cfg, req.AuthenticatedUser, req.action)
}

func stepParseArgs(req *ExecutionRequest) bool {
	var err error

	req.finalParsedCommand, err = parseActionArguments(req.action.Shell, req.Arguments, req.action)

	if err != nil {
		req.logEntry.Stdout = err.Error()

		log.Warnf(err.Error())

		return false
	}

	return true
}

func stepLogRequested(req *ExecutionRequest) bool {
	log.WithFields(log.Fields{
		"actionTitle": req.ActionName,
	}).Infof("Action requested")

	return true
}

func stepLogStart(req *ExecutionRequest) bool {
	log.WithFields(log.Fields{
		"actionTitle": req.action.Title,
		"timeout":     req.action.Timeout,
	}).Infof("Action starting")

	return true
}

func stepLogFinish(req *ExecutionRequest) bool {
	log.WithFields(log.Fields{
		"actionTitle": req.action.Title,
		"stdout":      req.logEntry.Stdout,
		"stderr":      req.logEntry.Stderr,
		"timedOut":    req.logEntry.TimedOut,
		"exit":        req.logEntry.ExitCode,
	}).Infof("Action finished")

	return true
}

func stepNotifyListeners(req *ExecutionRequest) bool {
	for _, listener := range req.executor.listeners {
		listener.OnExecutionFinished(req.logEntry)
	}

	return true
}

func wrapCommandInShell(ctx context.Context, finalParsedCommand string) *exec.Cmd {
	if runtime.GOOS == "windows" {
		return exec.CommandContext(ctx, "cmd", "/C", finalParsedCommand)
	}

	return exec.CommandContext(ctx, "sh", "-c", finalParsedCommand)
}

func stepExec(req *ExecutionRequest) bool {
	ctx, cancel := context.WithTimeout(context.Background(), time.Duration(req.action.Timeout)*time.Second)
	defer cancel()

	var stdout bytes.Buffer
	var stderr bytes.Buffer

	cmd := wrapCommandInShell(ctx, req.finalParsedCommand)
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr
	req.logEntry.StdoutBuffer, _ = cmd.StdoutPipe()
	req.logEntry.StderrBuffer, _ = cmd.StderrPipe()

	req.logEntry.ExecutionStarted = true

	runerr := cmd.Start()

	cmd.Wait()

	// req.logEntry.Stdout = req.logEntry.StdoutBuffer.String()
	// req.logEntry.Stderr = req.logEntry.StderrBuffer.String()

	req.logEntry.ExecutionCompleted = true
	req.logEntry.ExitCode = int32(cmd.ProcessState.ExitCode())
	req.logEntry.Stdout = stdout.String()
	req.logEntry.Stderr = stderr.String()

	if runerr != nil {
		req.logEntry.Stderr = runerr.Error() + "\n\n" + req.logEntry.Stderr
	}

	if ctx.Err() == context.DeadlineExceeded {
		req.logEntry.TimedOut = true
	}

	req.logEntry.Tags = req.Tags
	req.logEntry.DatetimeFinished = time.Now().Format("2006-01-02 15:04:05")

	return true
}