// Copyright (C) 2019-2020 Zilliz. All rights reserved.
//
// 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 timerecord

import (
	"context"
	"fmt"
	"time"

	"github.com/milvus-io/milvus/internal/log"
	"go.opentelemetry.io/otel/trace"
	"go.uber.org/zap"
)

// TimeRecorder provides methods to record time duration
type TimeRecorder struct {
	header string
	start  time.Time
	last   time.Time
}

// NewTimeRecorder creates a new TimeRecorder
func NewTimeRecorder(header string) *TimeRecorder {
	return &TimeRecorder{
		header: header,
		start:  time.Now(),
		last:   time.Now(),
	}
}

// NewTimeRecorderWithCtx creates a new TimeRecorder with context's traceID,
func NewTimeRecorderWithTrace(ctx context.Context, header string) *TimeRecorder {
	traceID := trace.SpanFromContext(ctx).SpanContext().TraceID()
	return &TimeRecorder{
		header: fmt.Sprintf("%s(%s)", header, traceID),
		start:  time.Now(),
		last:   time.Now(),
	}
}

// RecordSpan returns the duration from last record
func (tr *TimeRecorder) RecordSpan() time.Duration {
	curr := time.Now()
	span := curr.Sub(tr.last)
	tr.last = curr
	return span
}

// ElapseSpan returns the duration from the beginning
func (tr *TimeRecorder) ElapseSpan() time.Duration {
	curr := time.Now()
	span := curr.Sub(tr.start)
	tr.last = curr
	return span
}

// Record calculates the time span from previous Record call
func (tr *TimeRecorder) Record(msg string) time.Duration {
	span := tr.RecordSpan()
	tr.printTimeRecord(context.TODO(), msg, span)
	return span
}

func (tr *TimeRecorder) CtxRecord(ctx context.Context, msg string) time.Duration {
	span := tr.RecordSpan()
	tr.printTimeRecord(ctx, msg, span)
	return span
}

// Elapse calculates the time span from the beginning of this TimeRecorder
func (tr *TimeRecorder) Elapse(msg string) time.Duration {
	span := tr.ElapseSpan()
	tr.printTimeRecord(context.TODO(), msg, span)
	return span
}

func (tr *TimeRecorder) CtxElapse(ctx context.Context, msg string) time.Duration {
	span := tr.ElapseSpan()
	tr.printTimeRecord(ctx, msg, span)
	return span
}

func (tr *TimeRecorder) printTimeRecord(ctx context.Context, msg string, span time.Duration) {
	ts := trace.SpanFromContext(ctx)
	ts.AddEvent(fmt.Sprintf("%s, cost %s", msg, span.String()))
	log.Ctx(ctx).WithOptions(zap.AddCallerSkip(2)).
		Debug(fmt.Sprintf("tr/%s", tr.header),
			zap.String("msg", msg),
			zap.Duration("duration", span),
		)
}

// LongTermChecker checks we receive at least one msg in d duration. If not, checker
// will print a warn message.
type LongTermChecker struct {
	d    time.Duration
	t    *time.Ticker
	ch   chan struct{}
	warn string
	name string
}

// NewLongTermChecker creates a long term checker specified name, checking interval and warning string to print
func NewLongTermChecker(ctx context.Context, name string, d time.Duration, warn string) *LongTermChecker {
	c := &LongTermChecker{
		name: name,
		d:    d,
		warn: warn,
		ch:   make(chan struct{}),
	}
	return c
}

// Start starts the check process
func (c *LongTermChecker) Start() {
	c.t = time.NewTicker(c.d)
	go func() {
		for {
			select {
			case <-c.ch:
				log.Warn(fmt.Sprintf("long term checker [%s] shutdown", c.name))
				return
			case <-c.t.C:
				log.Warn(c.warn)
			}
		}
	}()
}

// Check resets the time ticker
func (c *LongTermChecker) Check() {
	c.t.Reset(c.d)
}

// Stop stops the checker
func (c *LongTermChecker) Stop() {
	c.t.Stop()
	close(c.ch)
}
