/*
Copyright 2021 Alibaba Group Holding Limited.

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.
*/

package control

import (
	"errors"
	"fmt"
	"strings"

	"github.com/go-logr/logr"
	"sigs.k8s.io/controller-runtime/pkg/reconcile"

	"gitee.com/eezz10001/polardbx-operator/pkg/debug"
)

type Executor interface {
	Execute(rc ReconcileContext, task *Task) (reconcile.Result, error)
}

type executor struct {
	logger logr.Logger
	flow   innerFlow
	tracer *tracer
	debug  bool
}

func (e *executor) isDebugEnabled() bool {
	return debug.IsDebugEnabled() || e.debug
}

func (e *executor) handlePanic(r interface{}) error {
	var err error

	// Extract error from panic
	switch r.(type) {
	case error:
		err = r.(error)
	case string:
		err = fmt.Errorf(r.(string))
	default:
		err = fmt.Errorf("%+v", r)
	}
	e.logger.Error(err, "Panic detected, recovered and return error")

	return err
}

func (e *executor) prepare(rc ReconcileContext, step Step, log logr.Logger) {
	name := step.Name()

	log = log.WithValues("action", name, "step", e.tracer.currentStepIndex())
	e.flow.SetLoggerFunc(func() logr.Logger {
		return log
	})

	if e.isDebugEnabled() || rc.Debug() {
		log.WithName("trace").Info("BEGIN")
	}
}

func (e *executor) done(rc ReconcileContext, err error, deferred bool, last bool) {
	e.tracer.markStepDone()

	if e.isDebugEnabled() || rc.Debug() {
		log := e.flow.Logger().WithName("trace")
		if err != nil {
			log.Info("ERROR", "err", err.Error())
		} else if last {
			log.Info("COMPLETE")
		} else if deferred {
			log.Info("CONTINUE [DEFER]")
		} else if e.flow.BreakLoop() {
			log.Info("BREAK")
		} else {
			log.Info("CONTINUE")
		}
	}
}

func (e *executor) execute(rc ReconcileContext, step Step, log logr.Logger, deferred bool, last bool) (result reconcile.Result, err error) {
	e.prepare(rc, step, log)

	defer e.done(rc, err, deferred, last)

	return step.Execute(rc, e.flow)
}

func (e *executor) executeDeferredSteps(rc ReconcileContext, task *Task) error {
	log := e.logger.WithValues("defer_exec", true)

	errs := make([]string, 0)
	for task.hasNextDeferredStep() {
		step := task.nextDeferredStep()
		_, err := e.execute(rc, step, log, true, !task.hasNextDeferredStep())

		// Never breaks the reconciliation flow, each deferred step will be executed.
		if err != nil {
			// e.logger.Error(err, "Err detected in deferred action.")
			errs = append(errs, err.Error())
		}
	}

	if len(errs) > 0 {
		return errors.New("Err in deferred actions: " + strings.Join(errs, ", "))
	}
	return nil
}

func (e *executor) Execute(rc ReconcileContext, task *Task) (result reconcile.Result, err error) {
	// Handle panic.
	defer func() {
		if r := recover(); r != nil {
			err = e.handlePanic(r)
		}
	}()

	// Handle force requeue after.
	defer func() {
		forceRequeueAfter := rc.ForceRequeueAfter()
		if forceRequeueAfter > 0 {
			if err != nil {
				// Reset error (should have been logged by flow.Error()).
				err = nil
				result = reconcile.Result{RequeueAfter: forceRequeueAfter}
			} else {
				// Set the requeue after if not set or larger than the task's.
				if result.RequeueAfter == 0 || result.RequeueAfter > forceRequeueAfter {
					result.RequeueAfter = forceRequeueAfter
				}
			}
		}
	}()

	// Handle deferred actions.
	defer func() {
		err1 := e.executeDeferredSteps(rc, task)
		if err1 != nil {
			err = err1
		}
	}()

	// Execute steps.
	for task.hasNextStep() {
		step := task.nextStep()
		result, err = e.execute(rc, step, e.logger, false, !task.hasNextStep() && !task.hasNextDeferredStep())
		if e.flow.BreakLoop() {
			return
		}
	}

	return
}

type ExecutorOption func(e *executor)

func Debug(e *executor) {
	e.debug = true
}

func NewExecutor(logger logr.Logger, opts ...ExecutorOption) Executor {
	tracer := newTracer()

	exec := &executor{
		logger: logger.WithValues("trace", tracer.id),
		tracer: tracer,
	}

	exec.flow = newFlow(func() logr.Logger {
		return exec.logger
	})

	for _, opt := range opts {
		opt(exec)
	}

	return exec
}