package gologger
  
  import (

  	"bytes"
  	"encoding/json"

  	"fmt"

  	"net/http"

  	"net/http/httputil"

  	"os"

  	"path/filepath"

  	"runtime"

  	"strings"

  	"sync"

  	"time"

  )

  const dateTimeFormat = "2006-01-02 15:04:05"

  // Block ...

  const (
  	MaxLogSize5MB   int64 = 5 * 1024 * 1024
  	MaxLogSize1MB   int64 = 1 * 1024 * 1024
  	MaxLogSize500KB int64 = 500 * 1024
  	MaxLogSize100KB int64 = 100 * 1024
  	MaxLogSize512B  int64 = 512
  )

  // Logger ...

  type Logger struct {

  	mu         *sync.Mutex
  	outputFile *os.File

  	outputFileName string

  	fullName       string

  	maxFileSize    int64

  
  	splitCount int

  
  	directory string

  }

  // New ...

  func New(name, dir string, maxFileSize int64) (logger *Logger, err error) {

  	logger = &Logger{}

  	logger.outputFileName = name

  	logger.mu = &sync.Mutex{}
  	logger.maxFileSize = maxFileSize

  	logger.directory = dir

  	err = os.Mkdir(dir, os.ModePerm)

  	if err != nil {
  		if !os.IsExist(err) {

  			return nil, err

  		}
  	}

  	date := strings.Replace(time.Now().Format(dateTimeFormat), ":", ".", -1)
  	logger.outputFileName += " " + date

  	logger.fullName = logger.outputFileName + ".txt"

  	path := filepath.Join(dir, logger.fullName)
  	if logger.outputFile, err = os.Create(path); err != nil {

  		return nil, err

  	}

  	return logger, nil

  }

  // Log ...

  func (l *Logger) Log(format string, v ...interface{}) {

  	if l.outputFile == nil {
  		return
  	}
  
  	l.mu.Lock()
  	defer l.mu.Unlock()
  
  	msg := fmt.Sprintf(format, v...)

  	s := time.Now().Format(dateTimeFormat) + ": " + msg + "
  "

  	if l.shouldSplit(len(s)) {
  		l.split()

  	}

  	l.outputFile.WriteString(s)

  }

  // Print ...
  func (l *Logger) Print(format string, v ...interface{}) {
  	msg := fmt.Sprintf(format, v...)

  	fmt.Printf("%s: %s
  ", time.Now().Format(dateTimeFormat), msg)

  }

  const MaxStackDepth = 10000
  
  // CallStack
  func CallStack() (stack string) {
  	callers := make([]uintptr, MaxStackDepth) // min 1
  	stackDepth := runtime.Callers(2, callers)
  	frames := runtime.CallersFrames(callers)
  
  	for i := 0; i < stackDepth; i++ {
  		if i >= 2 { // skip runtime and startup
  			frame, next := frames.Next()
  			stack += fmt.Sprintf("[%s %d]
  ", frame.File, frame.Line)
  			if !next {
  				break
  			}
  		}
  	}
  
  	return

  }

  // PrintTrace ...
  func (l *Logger) PrintTrace(format string, v ...interface{}) {

  	stack := CallStack()

  	msg := fmt.Sprintf(format, v...)

  	fmt.Printf("%s:
  %s
  %s
  ", time.Now().Format(dateTimeFormat), stack, msg)

  }
  
  // Trace ...
  func (l *Logger) Trace(format string, v ...interface{}) {
  	if l.outputFile == nil {
  		return
  	}
  
  	l.mu.Lock()
  	defer l.mu.Unlock()

  	stack := CallStack()

  	msg := fmt.Sprintf(format, v...)

  	s := fmt.Sprintf("%s:
  %s
  %s
  
  ", time.Now().Format(dateTimeFormat), stack, msg)

  
  	if l.shouldSplit(len(s)) {
  		l.split()
  	}
  	l.outputFile.WriteString(s)
  }
  
  // PrintAndTrace ...
  func (l *Logger) PrintAndTrace(format string, v ...interface{}) {

  	l.Print(format, v...)
  	l.Trace(format, v...)

  }
  
  // LogHTTPRequest ...

  func (l *Logger) LogHTTPRequest(req *http.Request, userID string) string {

  	if userID == "" {
  		userID = "-"

  	}

  	var b strings.Builder

  	b.WriteString("Request:
  ")
  	// CLF-like header

  	fmt.Fprintf(&b, "%s %s %s
  ", req.RemoteAddr, userID, time.Now().Format(dateTimeFormat))

  	body, err := httputil.DumpRequest(req, true)
  	if err != nil {
  		fmt.Fprintf(os.Stderr, "%v
  ", err)

  	}

  
  	const sepStr = "\r
  \r
  "
  	sepIndex := bytes.Index(body, []byte(sepStr))
  	if sepIndex == -1 {
  		b.WriteString(string(body) + "
  
  ")
  	} else {
  		sepIndex += len(sepStr)
  		payload, _ := printJSON(body[sepIndex:])
  		b.WriteString(string(body[:sepIndex]) + string(payload) + "
  
  ")
  	}

  	return b.String()
  }

  const splitLine = "=============================================================="

  // LogHTTPResponse ...

  func (l *Logger) LogHTTPResponse(status int, duration time.Duration, size int) string {

  	return fmt.Sprintf("Response:
  %d %v %dB
  %s
  ", status, duration, size, splitLine)

  }

  // CombineHTTPLogs ...

  func (l *Logger) CombineHTTPLogs(in string, out string) {

  	if l.outputFile == nil {
  		return
  	}

  	l.mu.Lock()
  	defer l.mu.Unlock()

  	msg := in + out

  	if l.shouldSplit(len(msg)) {
  		l.split()

  	}

  	l.outputFile.WriteString(msg)

  }

  // Close ...

  func (l *Logger) Close() error {

  	if l.outputFile == nil {

  		return nil

  	}

  	return l.outputFile.Close()

  }

  func (l *Logger) split() error {

  	if l.outputFile == nil {

  		return nil

  	}

  	// close old file
  	err := l.outputFile.Close()
  	if err != nil {

  		return err

  	}

  	// open new file

  	l.splitCount++
  	path := filepath.Join(l.directory, l.outputFileName+fmt.Sprintf("(%d)", l.splitCount)+".txt")
  	l.outputFile, err = os.Create(path)

  	return err

  }

  func (l *Logger) shouldSplit(nextEntrySize int) bool {
  	stats, _ := l.outputFile.Stat()
  	return int64(nextEntrySize) >= (l.maxFileSize - stats.Size())

  }

  
  func printJSON(in []byte) (out []byte, err error) {
  	var buf bytes.Buffer
  	err = json.Indent(&buf, in, "", "    ")
  	return buf.Bytes(), err
  }