// +build !solaris

package logparser

import (
	"fmt"
	"strings"
	"sync"

	"github.com/influxdata/tail"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/internal/globpath"
	"github.com/influxdata/telegraf/plugins/inputs"
	"github.com/influxdata/telegraf/plugins/parsers"
)

const (
	defaultWatchMethod = "inotify"
)

var (
	offsets      = make(map[string]int64)
	offsetsMutex = new(sync.Mutex)
)

// LogParser in the primary interface for the plugin
type GrokConfig struct {
	MeasurementName    string `toml:"measurement"`
	Patterns           []string
	NamedPatterns      []string
	CustomPatterns     string
	CustomPatternFiles []string
	Timezone           string
	UniqueTimestamp    string
}

type logEntry struct {
	path string
	line string
}

// LogParserPlugin is the primary struct to implement the interface for logparser plugin
type LogParserPlugin struct {
	Files         []string
	FromBeginning bool
	WatchMethod   string

	Log telegraf.Logger

	tailers map[string]*tail.Tail
	offsets map[string]int64
	lines   chan logEntry
	done    chan struct{}
	wg      sync.WaitGroup
	acc     telegraf.Accumulator

	sync.Mutex

	GrokParser parsers.Parser
	GrokConfig GrokConfig `toml:"grok"`
}

func NewLogParser() *LogParserPlugin {
	offsetsMutex.Lock()
	offsetsCopy := make(map[string]int64, len(offsets))
	for k, v := range offsets {
		offsetsCopy[k] = v
	}
	offsetsMutex.Unlock()

	return &LogParserPlugin{
		WatchMethod: defaultWatchMethod,
		offsets:     offsetsCopy,
	}
}

const sampleConfig = `
  ## Log files to parse.
  ## These accept standard unix glob matching rules, but with the addition of
  ## ** as a "super asterisk". ie:
  ##   /var/log/**.log     -> recursively find all .log files in /var/log
  ##   /var/log/*/*.log    -> find all .log files with a parent dir in /var/log
  ##   /var/log/apache.log -> only tail the apache log file
  files = ["/var/log/apache/access.log"]

  ## Read files that currently exist from the beginning. Files that are created
  ## while telegraf is running (and that match the "files" globs) will always
  ## be read from the beginning.
  from_beginning = false

  ## Method used to watch for file updates.  Can be either "inotify" or "poll".
  # watch_method = "inotify"

  ## Parse logstash-style "grok" patterns:
  [inputs.logparser.grok]
    ## This is a list of patterns to check the given log file(s) for.
    ## Note that adding patterns here increases processing time. The most
    ## efficient configuration is to have one pattern per logparser.
    ## Other common built-in patterns are:
    ##   %{COMMON_LOG_FORMAT}   (plain apache & nginx access logs)
    ##   %{COMBINED_LOG_FORMAT} (access logs + referrer & agent)
    patterns = ["%{COMBINED_LOG_FORMAT}"]

    ## Name of the outputted measurement name.
    measurement = "apache_access_log"

    ## Full path(s) to custom pattern files.
    custom_pattern_files = []

    ## Custom patterns can also be defined here. Put one pattern per line.
    custom_patterns = '''
    '''

    ## Timezone allows you to provide an override for timestamps that
    ## don't already include an offset
    ## e.g. 04/06/2016 12:41:45 data one two 5.43µs
    ##
    ## Default: "" which renders UTC
    ## Options are as follows:
    ##   1. Local             -- interpret based on machine localtime
    ##   2. "Canada/Eastern"  -- Unix TZ values like those found in https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
    ##   3. UTC               -- or blank/unspecified, will return timestamp in UTC
    # timezone = "Canada/Eastern"

	## When set to "disable", timestamp will not incremented if there is a
	## duplicate.
    # unique_timestamp = "auto"
`

// SampleConfig returns the sample configuration for the plugin
func (l *LogParserPlugin) SampleConfig() string {
	return sampleConfig
}

// Description returns the human readable description for the plugin
func (l *LogParserPlugin) Description() string {
	return "Stream and parse log file(s)."
}

// Gather is the primary function to collect the metrics for the plugin
func (l *LogParserPlugin) Gather(acc telegraf.Accumulator) error {
	l.Lock()
	defer l.Unlock()

	// always start from the beginning of files that appear while we're running
	return l.tailNewfiles(true)
}

// Start kicks off collection of stats for the plugin
func (l *LogParserPlugin) Start(acc telegraf.Accumulator) error {
	l.Lock()
	defer l.Unlock()

	l.acc = acc
	l.lines = make(chan logEntry, 1000)
	l.done = make(chan struct{})
	l.tailers = make(map[string]*tail.Tail)

	mName := "logparser"
	if l.GrokConfig.MeasurementName != "" {
		mName = l.GrokConfig.MeasurementName
	}

	// Looks for fields which implement LogParser interface
	config := &parsers.Config{
		MetricName:             mName,
		GrokPatterns:           l.GrokConfig.Patterns,
		GrokNamedPatterns:      l.GrokConfig.NamedPatterns,
		GrokCustomPatterns:     l.GrokConfig.CustomPatterns,
		GrokCustomPatternFiles: l.GrokConfig.CustomPatternFiles,
		GrokTimezone:           l.GrokConfig.Timezone,
		GrokUniqueTimestamp:    l.GrokConfig.UniqueTimestamp,
		DataFormat:             "grok",
	}

	var err error
	l.GrokParser, err = parsers.NewParser(config)
	if err != nil {
		return err
	}

	l.wg.Add(1)
	go l.parser()

	err = l.tailNewfiles(l.FromBeginning)

	// clear offsets
	l.offsets = make(map[string]int64)
	// assumption that once Start is called, all parallel plugins have already been initialized
	offsetsMutex.Lock()
	offsets = make(map[string]int64)
	offsetsMutex.Unlock()

	return err
}

// check the globs against files on disk, and start tailing any new files.
// Assumes l's lock is held!
func (l *LogParserPlugin) tailNewfiles(fromBeginning bool) error {
	var poll bool
	if l.WatchMethod == "poll" {
		poll = true
	}

	// Create a "tailer" for each file
	for _, filepath := range l.Files {
		g, err := globpath.Compile(filepath)
		if err != nil {
			l.Log.Errorf("Glob %q failed to compile: %s", filepath, err)
			continue
		}
		files := g.Match()

		for _, file := range files {
			if _, ok := l.tailers[file]; ok {
				// we're already tailing this file
				continue
			}

			var seek *tail.SeekInfo
			if !fromBeginning {
				if offset, ok := l.offsets[file]; ok {
					l.Log.Debugf("Using offset %d for file: %v", offset, file)
					seek = &tail.SeekInfo{
						Whence: 0,
						Offset: offset,
					}
				} else {
					seek = &tail.SeekInfo{
						Whence: 2,
						Offset: 0,
					}
				}
			}

			tailer, err := tail.TailFile(file,
				tail.Config{
					ReOpen:    true,
					Follow:    true,
					Location:  seek,
					MustExist: true,
					Poll:      poll,
					Logger:    tail.DiscardingLogger,
				})
			if err != nil {
				l.acc.AddError(err)
				continue
			}

			l.Log.Debugf("Tail added for file: %v", file)

			// create a goroutine for each "tailer"
			l.wg.Add(1)
			go l.receiver(tailer)
			l.tailers[file] = tailer
		}
	}

	return nil
}

// receiver is launched as a goroutine to continuously watch a tailed logfile
// for changes and send any log lines down the l.lines channel.
func (l *LogParserPlugin) receiver(tailer *tail.Tail) {
	defer l.wg.Done()

	var line *tail.Line
	for line = range tailer.Lines {

		if line.Err != nil {
			l.Log.Errorf("Error tailing file %s, Error: %s",
				tailer.Filename, line.Err)
			continue
		}

		// Fix up files with Windows line endings.
		text := strings.TrimRight(line.Text, "\r")

		entry := logEntry{
			path: tailer.Filename,
			line: text,
		}

		select {
		case <-l.done:
		case l.lines <- entry:
		}
	}
}

// parse is launched as a goroutine to watch the l.lines channel.
// when a line is available, parse parses it and adds the metric(s) to the
// accumulator.
func (l *LogParserPlugin) parser() {
	defer l.wg.Done()

	var m telegraf.Metric
	var err error
	var entry logEntry
	for {
		select {
		case <-l.done:
			return
		case entry = <-l.lines:
			if entry.line == "" || entry.line == "\n" {
				continue
			}
		}
		m, err = l.GrokParser.ParseLine(entry.line)
		if err == nil {
			if m != nil {
				tags := m.Tags()
				tags["path"] = entry.path
				l.acc.AddFields(m.Name(), m.Fields(), tags, m.Time())
			}
		} else {
			l.Log.Errorf("Error parsing log line: %s", err.Error())
		}

	}
}

// Stop will end the metrics collection process on file tailers
func (l *LogParserPlugin) Stop() {
	l.Lock()
	defer l.Unlock()

	for _, t := range l.tailers {
		if !l.FromBeginning {
			// store offset for resume
			offset, err := t.Tell()
			if err == nil {
				l.offsets[t.Filename] = offset
				l.Log.Debugf("Recording offset %d for file: %v", offset, t.Filename)
			} else {
				l.acc.AddError(fmt.Errorf("error recording offset for file %s", t.Filename))
			}
		}
		err := t.Stop()

		//message for a stopped tailer
		l.Log.Debugf("Tail dropped for file: %v", t.Filename)

		if err != nil {
			l.Log.Errorf("Error stopping tail on file %s", t.Filename)
		}
	}
	close(l.done)
	l.wg.Wait()

	// persist offsets
	offsetsMutex.Lock()
	for k, v := range l.offsets {
		offsets[k] = v
	}
	offsetsMutex.Unlock()
}

func init() {
	inputs.Add("logparser", func() telegraf.Input {
		return NewLogParser()
	})
}
