/*
 *  Copyright (c) 2019 AT&T Intellectual Property.
 *  Copyright (c) 2018-2019 Nokia.
 *
 *  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.
 *
 * This source code is part of the near-RT RIC (RAN Intelligent Controller)
 * platform project (RICP).
 */

// Package golog implements a simple structured logging with MDC (Mapped Diagnostics Context) support.
package golog

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"sync"
	"time"
)

// Level is a type define for the logging level.
type Level int

const (
	// ERR is an error level log entry.
	ERR Level = 1
	// WARN is a warning level log entry.
	WARN Level = 2
	// INFO is an info level log entry.
	INFO Level = 3
	// DEBUG is a debug level log entry.
	DEBUG Level = 4
)

// MdcLogger is the logger instance, created with InitLogger() function.
type MdcLogger struct {
	proc   string
	writer io.Writer
	mdc    map[string]string
	mutex  sync.Mutex
	level  Level
}

type logEntry struct {
	Ts   int64             `json:"ts"`
	Crit string            `json:"crit"`
	Id   string            `json:"id"`
	Mdc  map[string]string `json:"mdc"`
	Msg  string            `json:"msg"`
}

func levelString(level Level) string {
	switch level {
	case ERR:
		return "ERROR"
	case WARN:
		return "WARNING"
	case INFO:
		return "INFO"
	case DEBUG:
		return "DEBUG"
	default:
		return ""
	}
}

func getTime() int64 {
	ns := time.Time.UnixNano(time.Now())
	return ns / int64(time.Millisecond)
}

func (l *MdcLogger) formatLog(level Level, msg string) ([]byte, error) {
	log := logEntry{getTime(), levelString(level), l.proc, l.mdc, msg}
	buf := bytes.NewBuffer(nil)
	encoder := json.NewEncoder(buf)
	encoder.SetEscapeHTML(false)
	err := encoder.Encode(log)
	return buf.Bytes(), err
}

func initLogger(proc string, writer io.Writer) (*MdcLogger, error) {
	return &MdcLogger{proc: proc, writer: writer, mdc: make(map[string]string), level: DEBUG}, nil
}

// InitLogger is the init routine which returns a new logger instance.
// The program identity is given as a parameter. The identity
// is added to every log writing.
// The function returns a new instance or an error.
func InitLogger(proc string) (*MdcLogger, error) {
	return initLogger(proc, os.Stdout)
}

// Log is the basic logging function to write a log message with
// the given level
func (l *MdcLogger) Log(level Level, formatMsg string, a ...interface{}) {
	l.mutex.Lock()
	defer l.mutex.Unlock()
	if l.level < level {
		return
	}
	log, err := l.formatLog(level, fmt.Sprintf(formatMsg, a...))
	if err == nil {
		l.writer.Write(log)
	}
}

// Error is the "error" level logging function.
func (l *MdcLogger) Error(formatMsg string, a ...interface{}) {
	l.Log(ERR, formatMsg, a...)
}

// Warning is the "warning" level logging function.
func (l *MdcLogger) Warning(formatMsg string, a ...interface{}) {
	l.Log(WARN, formatMsg, a...)
}

// Info is the "info" level logging function.
func (l *MdcLogger) Info(formatMsg string, a ...interface{}) {
	l.Log(INFO, formatMsg, a...)
}

// Debug is the "debug" level logging function.
func (l *MdcLogger) Debug(formatMsg string, a ...interface{}) {
	l.Log(DEBUG, formatMsg, a...)
}

// LevelSet sets the current logging level.
// Log writings with less significant level are discarded.
func (l *MdcLogger) LevelSet(level Level) {
	l.level = level
}

// LevelGet returns the current logging level.
func (l *MdcLogger) LevelGet() Level {
	return l.level
}

// MdcAdd adds a new MDC key value pair to the logger.
func (l *MdcLogger) MdcAdd(key string, value string) {
	l.mutex.Lock()
	defer l.mutex.Unlock()
	l.mdc[key] = value
}

// MdcRemove removes an MDC key from the logger.
func (l *MdcLogger) MdcRemove(key string) {
	l.mutex.Lock()
	defer l.mutex.Unlock()
	delete(l.mdc, key)
}

// MdcGet gets the value of an MDC from the logger.
// The function returns the value string and a boolean
// which tells if the key was found or not.
func (l *MdcLogger) MdcGet(key string) (string, bool) {
	l.mutex.Lock()
	defer l.mutex.Unlock()
	val, ok := l.mdc[key]
	return val, ok
}

// MdcClean removes all MDC keys from the logger.
func (l *MdcLogger) MdcClean() {
	l.mutex.Lock()
	defer l.mutex.Unlock()
	l.mdc = make(map[string]string)
}