/*
Copyright IBM Corp. 2017 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 flogging

import (
	"io"
	"os"
	"regexp"
	"strings"
	"sync"

	"github.com/op/go-logging"
)

const (
	pkgLogID      = "flogging"
	defaultFormat = "%{color}%{time:2006-01-02 15:04:05.000 MST} [%{module}] %{shortfunc} -> %{level:.4s} %{id:03x}%{color:reset} %{message}"
	defaultLevel  = logging.INFO
)

var (
	logger *logging.Logger

	defaultOutput *os.File

	modules          map[string]string // Holds the map of all modules and their respective log level
	peerStartModules map[string]string

	lock sync.RWMutex
	once sync.Once
)

func init() {
	logger = logging.MustGetLogger(pkgLogID)
	Reset()
	initgrpclogger()
}

// Reset sets to logging to the defaults defined in this package.
func Reset() {
	modules = make(map[string]string)
	lock = sync.RWMutex{}

	defaultOutput = os.Stderr
	InitBackend(SetFormat(defaultFormat), defaultOutput)
	InitFromSpec("")
}

// SetFormat sets the logging format.
func SetFormat(formatSpec string) logging.Formatter {
	if formatSpec == "" {
		formatSpec = defaultFormat
	}
	return logging.MustStringFormatter(formatSpec)
}

// InitBackend sets up the logging backend based on
// the provided logging formatter and I/O writer.
func InitBackend(formatter logging.Formatter, output io.Writer) {
	backend := logging.NewLogBackend(output, "", 0)
	backendFormatter := logging.NewBackendFormatter(backend, formatter)
	logging.SetBackend(backendFormatter).SetLevel(defaultLevel, "")
}

// DefaultLevel returns the fallback value for loggers to use if parsing fails.
func DefaultLevel() string {
	return defaultLevel.String()
}

// GetModuleLevel gets the current logging level for the specified module.
func GetModuleLevel(module string) string {
	// logging.GetLevel() returns the logging level for the module, if defined.
	// Otherwise, it returns the default logging level, as set by
	// `flogging/logging.go`.
	level := logging.GetLevel(module).String()
	return level
}

// SetModuleLevel sets the logging level for the modules that match the supplied
// regular expression. Can be used to dynamically change the log level for the
// module.
func SetModuleLevel(moduleRegExp string, level string) (string, error) {
	return setModuleLevel(moduleRegExp, level, true, false)
}

func setModuleLevel(moduleRegExp string, level string, isRegExp bool, revert bool) (string, error) {
	var re *regexp.Regexp
	logLevel, err := logging.LogLevel(level)
	if err != nil {
		logger.Warningf("Invalid logging level '%s' - ignored", level)
	} else {
		if !isRegExp || revert {
			logging.SetLevel(logLevel, moduleRegExp)
			logger.Debugf("Module '%s' logger enabled for log level '%s'", moduleRegExp, level)
		} else {
			re, err = regexp.Compile(moduleRegExp)
			if err != nil {
				logger.Warningf("Invalid regular expression: %s", moduleRegExp)
				return "", err
			}
			lock.Lock()
			defer lock.Unlock()
			for module := range modules {
				if re.MatchString(module) {
					logging.SetLevel(logging.Level(logLevel), module)
					modules[module] = logLevel.String()
					logger.Debugf("Module '%s' logger enabled for log level '%s'", module, logLevel)
				}
			}
		}
	}
	return logLevel.String(), err
}

// MustGetLogger is used in place of `logging.MustGetLogger` to allow us to
// store a map of all modules and submodules that have loggers in the system.
func MustGetLogger(module string) *logging.Logger {
	l := logging.MustGetLogger(module)
	lock.Lock()
	defer lock.Unlock()
	modules[module] = GetModuleLevel(module)
	return l
}

// InitFromSpec initializes the logging based on the supplied spec. It is
// exposed externally so that consumers of the flogging package may parse their
// own logging specification. The logging specification has the following form:
//		[<module>[,<module>...]=]<level>[:[<module>[,<module>...]=]<level>...]
func InitFromSpec(spec string) string {
	levelAll := defaultLevel
	var err error

	if spec != "" {
		fields := strings.Split(spec, ":")
		for _, field := range fields {
			split := strings.Split(field, "=")
			switch len(split) {
			case 1:
				if levelAll, err = logging.LogLevel(field); err != nil {
					logger.Warningf("Logging level '%s' not recognized, defaulting to '%s': %s", field, defaultLevel, err)
					levelAll = defaultLevel // need to reset cause original value was overwritten
				}
			case 2:
				// <module>[,<module>...]=<level>
				levelSingle, err := logging.LogLevel(split[1])
				if err != nil {
					logger.Warningf("Invalid logging level in '%s' ignored", field)
					continue
				}

				if split[0] == "" {
					logger.Warningf("Invalid logging override specification '%s' ignored - no module specified", field)
				} else {
					modules := strings.Split(split[0], ",")
					for _, module := range modules {
						logger.Debugf("Setting logging level for module '%s' to '%s'", module, levelSingle)
						logging.SetLevel(levelSingle, module)
					}
				}
			default:
				logger.Warningf("Invalid logging override '%s' ignored - missing ':'?", field)
			}
		}
	}

	logging.SetLevel(levelAll, "") // set the logging level for all modules

	// iterate through modules to reload their level in the modules map based on
	// the new default level
	for k := range modules {
		MustGetLogger(k)
	}
	// register flogging logger in the modules map
	MustGetLogger(pkgLogID)

	return levelAll.String()
}

// SetPeerStartupModulesMap saves the modules and their log levels.
// this function should only be called at the end of peer startup.
func SetPeerStartupModulesMap() {
	lock.Lock()
	defer lock.Unlock()

	once.Do(func() {
		peerStartModules = make(map[string]string)
		for k, v := range modules {
			peerStartModules[k] = v
		}
	})
}

// GetPeerStartupLevel returns the peer startup level for the specified module.
// It will return an empty string if the input parameter is empty or the module
// is not found
func GetPeerStartupLevel(module string) string {
	if module != "" {
		if level, ok := peerStartModules[module]; ok {
			return level
		}
	}

	return ""
}

// RevertToPeerStartupLevels reverts the log levels for all modules to the level
// defined at the end of peer startup.
func RevertToPeerStartupLevels() error {
	lock.RLock()
	defer lock.RUnlock()
	for key := range peerStartModules {
		_, err := setModuleLevel(key, peerStartModules[key], false, true)
		if err != nil {
			return err
		}
	}
	logger.Info("Log levels reverted to the levels defined at the end of peer startup")
	return nil
}