// Copyright 2019 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package log

import (
	"os"
	"sync/atomic"

	"errors"

	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
	lumberjack "gopkg.in/natefinch/lumberjack.v2"
)

var _globalL, _globalP, _globalS atomic.Value

func init() {
	l, p := newStdLogger()
	_globalL.Store(l)
	_globalP.Store(p)

	s := _globalL.Load().(*zap.Logger).Sugar()
	_globalS.Store(s)
}

// InitLogger initializes a zap logger.
func InitLogger(cfg *Config, opts ...zap.Option) (*zap.Logger, *ZapProperties, error) {
	var output zapcore.WriteSyncer
	if len(cfg.File.Filename) > 0 {
		lg, err := initFileLog(&cfg.File)
		if err != nil {
			return nil, nil, err
		}
		output = zapcore.AddSync(lg)
	} else {
		stdOut, _, err := zap.Open([]string{"stdout"}...)
		if err != nil {
			return nil, nil, err
		}
		output = stdOut
	}
	return InitLoggerWithWriteSyncer(cfg, output, opts...)
}

// InitLoggerWithWriteSyncer initializes a zap logger with specified  write syncer.
func InitLoggerWithWriteSyncer(cfg *Config, output zapcore.WriteSyncer, opts ...zap.Option) (*zap.Logger, *ZapProperties, error) {
	level := zap.NewAtomicLevel()
	err := level.UnmarshalText([]byte(cfg.Level))
	if err != nil {
		return nil, nil, err
	}
	core := NewTextCore(newZapTextEncoder(cfg), output, level)
	opts = append(cfg.buildOptions(output), opts...)
	lg := zap.New(core, opts...)
	r := &ZapProperties{
		Core:   core,
		Syncer: output,
		Level:  level,
	}
	return lg, r, nil
}

// initFileLog initializes file based logging options.
func initFileLog(cfg *FileLogConfig) (*lumberjack.Logger, error) {
	if st, err := os.Stat(cfg.Filename); err == nil {
		if st.IsDir() {
			return nil, errors.New("can't use directory as log file name")
		}
	}
	if cfg.MaxSize == 0 {
		cfg.MaxSize = defaultLogMaxSize
	}

	// use lumberjack to logrotate
	return &lumberjack.Logger{
		Filename:   cfg.Filename,
		MaxSize:    cfg.MaxSize,
		MaxBackups: cfg.MaxBackups,
		MaxAge:     cfg.MaxDays,
		LocalTime:  true,
	}, nil
}

func newStdLogger() (*zap.Logger, *ZapProperties) {
	conf := &Config{Level: "debug", File: FileLogConfig{}}
	lg, r, _ := InitLogger(conf)
	return lg, r
}

// L returns the global Logger, which can be reconfigured with ReplaceGlobals.
// It's safe for concurrent use.
func L() *zap.Logger {
	return _globalL.Load().(*zap.Logger)
}

// S returns the global SugaredLogger, which can be reconfigured with
// ReplaceGlobals. It's safe for concurrent use.
func S() *zap.SugaredLogger {
	return _globalS.Load().(*zap.SugaredLogger)
}

// ReplaceGlobals replaces the global Logger and SugaredLogger.
// It's safe for concurrent use.
func ReplaceGlobals(logger *zap.Logger, props *ZapProperties) {
	_globalL.Store(logger)
	_globalS.Store(logger.Sugar())
	_globalP.Store(props)
}

// Sync flushes any buffered log entries.
func Sync() error {
	err := L().Sync()
	if err != nil {
		return err
	}
	return S().Sync()
}