// handleIgnoreOlder handles states which fall under ignore older
// Based on the state information it is decided if the state information has to be updated or not
func (p *ProspectorLog) handleIgnoreOlder(lastState, newState file.State) error {
	logp.Debug("prospector", "Ignore file because ignore_older reached: %s", newState.Source)

	if !lastState.IsEmpty() {
		if !lastState.Finished {
			logp.Info("File is falling under ignore_older before harvesting is finished. Adjust your close_* settings: %s", newState.Source)
		}
		// Old state exist, no need to update it
		return nil
	}

	// Make sure file is not falling under clean_inactive yet
	if p.isCleanInactive(newState) {
		logp.Debug("prospector", "Do not write state for ignore_older because clean_inactive reached")
		return nil
	}

	// Set offset to end of file to be consistent with files which were harvested before
	// See https://github.com/elastic/beats/pull/2907
	newState.Offset = newState.Fileinfo.Size()

	// Write state for ignore_older file as none exists yet
	newState.Finished = true
	err := p.Prospector.updateState(input.NewEvent(newState))
	if err != nil {
		return err
	}

	return nil
}

// handleIgnoreOlder handles states which fall under ignore older
// Based on the state information it is decided if the state information has to be updated or not
func (p *ProspectorLog) handleIgnoreOlder(lastState, newState file.State) error {
	logp.Debug("prospector", "Ignore file because ignore_older reached: %s", newState.Source)

	if !lastState.IsEmpty() {
		if !lastState.Finished {
			logp.Info("File is falling under ignore_older before harvesting is finished. Adjust your close_* settings: %s", newState.Source)
		}
		// Old state exist, no need to update it
		return nil
	}

	// Make sure file is not falling under clean_inactive yet
	if p.isCleanInactive(newState) {
		logp.Debug("prospector", "Do not write state for ignore_older because clean_inactive reached")
		return nil
	}

	// Write state for ignore_older file as none exists yet
	newState.Finished = true
	err := p.Prospector.updateState(input.NewEvent(newState))
	if err != nil {
		return err
	}

	return nil
}

// startHarvester starts a new harvester with the given offset
// In case the HarvesterLimit is reached, an error is returned
func (p *Prospector) startHarvester(state file.State, offset int64) error {

	if p.config.HarvesterLimit > 0 && atomic.LoadUint64(&p.harvesterCounter) >= p.config.HarvesterLimit {
		harvesterSkipped.Add(1)
		return fmt.Errorf("Harvester limit reached.")
	}

	state.Offset = offset
	// Create harvester with state
	h, err := p.createHarvester(state)
	if err != nil {
		return err
	}

	p.wg.Add(1)
	// startHarvester is not run concurrently, but atomic operations are need for the decrementing of the counter
	// inside the following go routine
	atomic.AddUint64(&p.harvesterCounter, 1)
	go func() {
		defer func() {
			atomic.AddUint64(&p.harvesterCounter, ^uint64(0))
			p.wg.Done()
		}()
		// Starts harvester and picks the right type. In case type is not set, set it to defeault (log)
		h.Harvest()
	}()

	return nil
}

// harvestExistingFile continues harvesting a file with a known state if needed
func (p *ProspectorLog) harvestExistingFile(newState file.State, oldState file.State) {

	logp.Debug("prospector", "Update existing file for harvesting: %s, offset: %v", newState.Source, oldState.Offset)

	// No harvester is running for the file, start a new harvester
	// It is important here that only the size is checked and not modification time, as modification time could be incorrect on windows
	// https://blogs.technet.microsoft.com/asiasupp/2010/12/14/file-date-modified-property-are-not-updating-while-modifying-a-file-without-closing-it/
	if oldState.Finished && newState.Fileinfo.Size() > oldState.Offset {
		// Resume harvesting of an old file we've stopped harvesting from
		// This could also be an issue with force_close_older that a new harvester is started after each scan but not needed?
		// One problem with comparing modTime is that it is in seconds, and scans can happen more then once a second
		logp.Debug("prospector", "Resuming harvesting of file: %s, offset: %v", newState.Source, oldState.Offset)
		err := p.Prospector.startHarvester(newState, oldState.Offset)
		if err != nil {
			logp.Err("Harvester could not be started on existing file: %s, Err: %s", newState.Source, err)
		}
		return
	}

	// File size was reduced -> truncated file
	if oldState.Finished && newState.Fileinfo.Size() < oldState.Offset {
		logp.Debug("prospector", "Old file was truncated. Starting from the beginning: %s", newState.Source)
		err := p.Prospector.startHarvester(newState, 0)
		if err != nil {
			logp.Err("Harvester could not be started on truncated file: %s, Err: %s", newState.Source, err)
		}

		filesTrucated.Add(1)
		return
	}

	// Check if file was renamed
	if oldState.Source != "" && oldState.Source != newState.Source {
		// This does not start a new harvester as it is assume that the older harvester is still running
		// or no new lines were detected. It sends only an event status update to make sure the new name is persisted.
		logp.Debug("prospector", "File rename was detected: %s -> %s, Current offset: %v", oldState.Source, newState.Source, oldState.Offset)

		if oldState.Finished {
			logp.Debug("prospector", "Updating state for renamed file: %s -> %s, Current offset: %v", oldState.Source, newState.Source, oldState.Offset)
			// Update state because of file rotation
			oldState.Source = newState.Source
			event := input.NewEvent(oldState)
			err := p.Prospector.updateState(event)
			if err != nil {
				logp.Err("File rotation state update error: %s", err)
			}

			filesRenamed.Add(1)
		} else {
			logp.Debug("prospector", "File rename detected but harvester not finished yet.")
		}
	}

	if !oldState.Finished {
		// Nothing to do. Harvester is still running and file was not renamed
		logp.Debug("prospector", "Harvester for file is still running: %s", newState.Source)
	} else {
		logp.Debug("prospector", "File didn't change: %s", newState.Source)
	}
}

// startHarvester starts a new harvester with the given offset
// In case the HarvesterLimit is reached, an error is returned
func (p *Prospector) startHarvester(state file.State, offset int64) error {

	if p.config.HarvesterLimit > 0 && atomic.LoadUint64(&p.harvesterCounter) >= p.config.HarvesterLimit {
		harvesterSkipped.Add(1)
		return fmt.Errorf("Harvester limit reached.")
	}

	state.Offset = offset
	// Set state to "not" finished to indicate that a harvester is running
	state.Finished = false

	// Create harvester with state
	h, err := p.createHarvester(state)
	if err != nil {
		return err
	}

	reader, err := h.Setup()
	if err != nil {
		return fmt.Errorf("Error setting up harvester: %s", err)
	}

	// State is directly updated and not through channel to make state update immediate
	// State is only updated after setup is completed successfully
	err = p.updateState(input.NewEvent(state))
	if err != nil {
		return err
	}

	p.wg.Add(1)
	// startHarvester is not run concurrently, but atomic operations are need for the decrementing of the counter
	// inside the following go routine
	atomic.AddUint64(&p.harvesterCounter, 1)
	go func() {
		defer func() {
			atomic.AddUint64(&p.harvesterCounter, ^uint64(0))
			p.wg.Done()
		}()

		// Starts harvester and picks the right type. In case type is not set, set it to defeault (log)
		h.Harvest(reader)
	}()

	return nil
}

func (p *Prospector) startHarvester(state file.State, offset int64) (*harvester.Harvester, error) {
	state.Offset = offset
	// Create harvester with state
	h, err := p.createHarvester(state)
	if err != nil {
		return nil, err
	}

	p.wg.Add(1)
	go func() {
		defer p.wg.Done()
		// Starts harvester and picks the right type. In case type is not set, set it to defeault (log)
		h.Harvest()
	}()

	return h, nil
}