package log

import (
	"errors"
	zp "go.uber.org/zap"
	zc "go.uber.org/zap/zapcore"
	"runtime"
	"strings"
	"fmt"
)

const (
	// DebugLevel logs a message at debug level
	DebugLevel = iota
	// InfoLevel logs a message at info level
	InfoLevel
	// WarnLevel logs a message at warning level
	WarnLevel
	// ErrorLevel logs a message at error level
	ErrorLevel
	// PanicLevel logs a message, then panics.
	PanicLevel
	// FatalLevel logs a message, then calls os.Exit(1).
	FatalLevel
)

// CONSOLE formats the log for the console, mostly used during development
const CONSOLE = "console"
// JSON formats the log using json format, mostly used by an automated logging system consumption
const JSON = "json"

// Logger represents an abstract logging interface.  Any logging implementation used
// will need to abide by this interface
type Logger interface {
	Debug(...interface{})
	Debugln(...interface{})
	Debugf(string, ...interface{})
	Debugw(string, Fields)

	Info(...interface{})
	Infoln(...interface{})
	Infof(string, ...interface{})
	Infow(string, Fields)

	Warn(...interface{})
	Warnln(...interface{})
	Warnf(string, ...interface{})
	Warnw(string, Fields)

	Error(...interface{})
	Errorln(...interface{})
	Errorf(string, ...interface{})
	Errorw(string, Fields)

	Fatal(...interface{})
	Fatalln(...interface{})
	Fatalf(string, ...interface{})
	Fatalw(string, Fields)

	With(Fields) Logger
}

// Fields is used as key-value pairs for structural logging
type Fields map[string]interface{}

var defaultLogger *logger

type logger struct {
	log    *zp.SugaredLogger
	parent *zp.Logger
}

func parseLevel(l int) zp.AtomicLevel {
	switch l {
	case DebugLevel:
		return zp.NewAtomicLevelAt(zc.DebugLevel)
	case InfoLevel:
		return zp.NewAtomicLevelAt(zc.InfoLevel)
	case WarnLevel:
		return zp.NewAtomicLevelAt(zc.WarnLevel)
	case ErrorLevel:
		return zp.NewAtomicLevelAt(zc.ErrorLevel)
	case PanicLevel:
		return zp.NewAtomicLevelAt(zc.PanicLevel)
	case FatalLevel:
		return zp.NewAtomicLevelAt(zc.FatalLevel)
	}
	return zp.NewAtomicLevelAt(zc.ErrorLevel)
}

func getDefaultConfig(outputType string, level int, defaultFields Fields) zp.Config {
	return zp.Config{
		Level:            parseLevel(level),
		Encoding:         outputType,
		Development:      true,
		OutputPaths:      []string{"stdout"},
		ErrorOutputPaths: []string{"stderr"},
		InitialFields:    defaultFields,
		EncoderConfig: zc.EncoderConfig{
			LevelKey:       "level",
			MessageKey:     "msg",
			TimeKey:        "ts",
			StacktraceKey:  "stacktrace",
			LineEnding:     zc.DefaultLineEnding,
			EncodeLevel:    zc.LowercaseLevelEncoder,
			EncodeTime:     zc.ISO8601TimeEncoder,
			EncodeDuration: zc.SecondsDurationEncoder,
			EncodeCaller:   zc.ShortCallerEncoder,
		},
	}
}

// SetLogger needs to be invoked before the logger API can be invoked.  This function
// initialize the default logger (zap's sugaredlogger)
func SetLogger(outputType string, level int, defaultFields Fields) (Logger, error) {

	// Build a custom config using zap
	cfg := getDefaultConfig(outputType, level, defaultFields)

	l, err := cfg.Build()
	if err != nil {
		return nil, err
	}

	defaultLogger = &logger{
		log:    l.Sugar(),
		parent: l,
	}

	return defaultLogger, nil
}

// CleanUp flushed any buffered log entries. Applications should take care to call
// CleanUp before exiting.
func CleanUp() error {
	if defaultLogger != nil {
		if defaultLogger.parent != nil {
			if err := defaultLogger.parent.Sync(); err != nil {
				return err
			}
		}
	}
	return nil
}

// GetLogger returned the default logger.  If SetLogger was not previously invoked then
// this method will return an error
func GetLogger() (Logger, error) {
	if defaultLogger == nil {
		return nil, errors.New("Uninitialized-logger")
	}
	return defaultLogger, nil
}

func extractFileNameAndLineNumber(skipLevel int) (string, int) {
	_, file, line, ok := runtime.Caller(skipLevel)
	var key string
	if !ok {
		key = "<???>"
		line = 1
	} else {
		slash := strings.LastIndex(file, "/")
		key = file[slash+1:]
	}
	return key, line
}

// sourced adds a source field to the logger that contains
// the file name and line where the logging happened.
func (l *logger) sourced() *zp.SugaredLogger {
	key, line := extractFileNameAndLineNumber(3)
	if strings.HasSuffix(key, "log.go") || strings.HasSuffix(key, "proc.go") {
		// Go to a lower level
		key, line = extractFileNameAndLineNumber(2)
	}
	if !strings.HasSuffix(key, ".go") {
		// Go to a higher level
		key, line = extractFileNameAndLineNumber(4)
	}

	return l.log.With("caller", fmt.Sprintf("%s:%d", key, line))
}

//func serializeMap(fields Fields) []interface{} {
//	data := make([]interface{}, len(fields)*2+2)
//	i := 0
//	for k, v := range fields {
//		data[i] = k
//		data[i+1] = v
//		i = i + 2
//	}
//	key, line := extractFileNameAndLineNumber(3)
//	data[i] = "caller"
//	data[i+1] = fmt.Sprintf("%s:%d", key, line)
//
//	return data
//}

func serializeMap(fields Fields) []interface{} {
	data := make([]interface{}, len(fields)*2)
	i := 0
	for k, v := range fields {
		data[i] = k
		data[i+1] = v
		i = i + 2
	}
	return data
}

// With returns a logger initialized with the key-value pairs
func (l logger) With(keysAndValues Fields) Logger {
	return logger{log: l.log.With(serializeMap(keysAndValues)...), parent: l.parent}
}

// Debug logs a message at level Debug on the standard logger.
func (l logger) Debug(args ...interface{}) {
	l.log.Debug(args...)
}

// Debugln logs a message at level Debug on the standard logger with a line feed. Default in any case.
func (l logger) Debugln(args ...interface{}) {
	l.log.Debug(args...)
}

// Debugw logs a message at level Debug on the standard logger.
func (l logger) Debugf(format string, args ...interface{}) {
	l.log.Debugf(format, args...)
}

// Debugw logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func (l logger) Debugw(msg string, keysAndValues Fields) {
	l.log.Debugw(msg, serializeMap(keysAndValues)...)
}

// Info logs a message at level Info on the standard logger.
func (l logger) Info(args ...interface{}) {
	l.log.Info(args...)
}

// Infoln logs a message at level Info on the standard logger with a line feed. Default in any case.
func (l logger) Infoln(args ...interface{}) {
	l.log.Info(args...)
	//msg := fmt.Sprintln(args...)
	//l.sourced().Info(msg[:len(msg)-1])
}

// Infof logs a message at level Info on the standard logger.
func (l logger) Infof(format string, args ...interface{}) {
	l.log.Infof(format, args...)
}

// Infow logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func (l logger) Infow(msg string, keysAndValues Fields) {
	l.log.Infow(msg, serializeMap(keysAndValues)...)
}

// Warn logs a message at level Warn on the standard logger.
func (l logger) Warn(args ...interface{}) {
	l.log.Warn(args...)
}

// Warnln logs a message at level Warn on the standard logger with a line feed. Default in any case.
func (l logger) Warnln(args ...interface{}) {
	l.log.Warn(args...)
}

// Warnf logs a message at level Warn on the standard logger.
func (l logger) Warnf(format string, args ...interface{}) {
	l.log.Warnf(format, args...)
}

// Warnw logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func (l logger) Warnw(msg string, keysAndValues Fields) {
	l.log.Warnw(msg, serializeMap(keysAndValues)...)
}

// Error logs a message at level Error on the standard logger.
func (l logger) Error(args ...interface{}) {
	l.log.Error(args...)
}

// Errorln logs a message at level Error on the standard logger with a line feed. Default in any case.
func (l logger) Errorln(args ...interface{}) {
	l.log.Error(args...)
}

// Errorf logs a message at level Error on the standard logger.
func (l logger) Errorf(format string, args ...interface{}) {
	l.log.Errorf(format, args...)
}

// Errorw logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func (l logger) Errorw(msg string, keysAndValues Fields) {
	l.log.Errorw(msg, serializeMap(keysAndValues)...)
}

// Fatal logs a message at level Fatal on the standard logger.
func (l logger) Fatal(args ...interface{}) {
	l.log.Fatal(args...)
}

// Fatalln logs a message at level Fatal on the standard logger with a line feed. Default in any case.
func (l logger) Fatalln(args ...interface{}) {
	l.log.Fatal(args...)
}

// Fatalf logs a message at level Fatal on the standard logger.
func (l logger) Fatalf(format string, args ...interface{}) {
	l.log.Fatalf(format, args...)
}

// Fatalw logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func (l logger) Fatalw(msg string, keysAndValues Fields) {
	l.log.Fatalw(msg, serializeMap(keysAndValues)...)
}

// With returns a logger initialized with the key-value pairs
func With(keysAndValues Fields) Logger {
	return logger{log: defaultLogger.sourced().With(serializeMap(keysAndValues)...), parent: defaultLogger.parent}
}

// Debug logs a message at level Debug on the standard logger.
func Debug(args ...interface{}) {
	defaultLogger.sourced().Debug(args...)
}

// Debugln logs a message at level Debug on the standard logger.
func Debugln(args ...interface{}) {
	defaultLogger.sourced().Debug(args...)
}

// Debugf logs a message at level Debug on the standard logger.
func Debugf(format string, args ...interface{}) {
	defaultLogger.sourced().Debugf(format, args...)
}

// Debugw logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func Debugw(msg string, keysAndValues Fields) {
	defaultLogger.sourced().Debugw(msg, serializeMap(keysAndValues)...)
}

// Info logs a message at level Info on the standard logger.
func Info(args ...interface{}) {
	defaultLogger.sourced().Info(args...)
}

// Infoln logs a message at level Info on the standard logger.
func Infoln(args ...interface{}) {
	defaultLogger.sourced().Info(args...)
}

// Infof logs a message at level Info on the standard logger.
func Infof(format string, args ...interface{}) {
	defaultLogger.sourced().Infof(format, args...)
}

//Infow logs a message with some additional context. The variadic key-value
//pairs are treated as they are in With.
func Infow(msg string, keysAndValues Fields) {
	defaultLogger.sourced().Infow(msg, serializeMap(keysAndValues)...)
}

// Warn logs a message at level Warn on the standard logger.
func Warn(args ...interface{}) {
	defaultLogger.sourced().Warn(args...)
}

// Warnln logs a message at level Warn on the standard logger.
func Warnln(args ...interface{}) {
	defaultLogger.sourced().Warn(args...)
}

// Warnf logs a message at level Warn on the standard logger.
func Warnf(format string, args ...interface{}) {
	defaultLogger.sourced().Warnf(format, args...)
}

// Warnw logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func Warnw(msg string, keysAndValues Fields) {
	defaultLogger.sourced().Warnw(msg, serializeMap(keysAndValues)...)
}

// Error logs a message at level Error on the standard logger.
func Error(args ...interface{}) {
	defaultLogger.sourced().Error(args...)
}

// Errorln logs a message at level Error on the standard logger.
func Errorln(args ...interface{}) {
	defaultLogger.sourced().Error(args...)
}

// Errorf logs a message at level Error on the standard logger.
func Errorf(format string, args ...interface{}) {
	defaultLogger.sourced().Errorf(format, args...)
}

// Errorw logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func Errorw(msg string, keysAndValues Fields) {
	defaultLogger.sourced().Errorw(msg, serializeMap(keysAndValues)...)
}

// Fatal logs a message at level Fatal on the standard logger.
func Fatal(args ...interface{}) {
	defaultLogger.sourced().Fatal(args...)
}

// Fatalln logs a message at level Fatal on the standard logger.
func Fatalln(args ...interface{}) {
	defaultLogger.sourced().Fatal(args...)
}

// Fatalf logs a message at level Fatal on the standard logger.
func Fatalf(format string, args ...interface{}) {
	defaultLogger.sourced().Fatalf(format, args...)
}

// Fatalw logs a message with some additional context. The variadic key-value
// pairs are treated as they are in With.
func Fatalw(msg string, keysAndValues Fields) {
	defaultLogger.sourced().Fatalw(msg, serializeMap(keysAndValues)...)
}