//go:generate ../../../tools/readme_config_includer/generator
package filepath

import (
	_ "embed"
	"path/filepath"
	"strings"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/plugins/processors"
)

//go:embed sample.conf
var sampleConfig string

type Filepath struct {
	BaseName []baseOpts `toml:"basename"`
	DirName  []baseOpts `toml:"dirname"`
	Stem     []baseOpts `toml:"stem"`
	Clean    []baseOpts `toml:"clean"`
	Rel      []relOpts  `toml:"rel"`
	ToSlash  []baseOpts `toml:"toslash"`

	Log telegraf.Logger `toml:"-"`
}

type processorFunc func(s string) string

// baseOpts contains options applicable to every function
type baseOpts struct {
	Field string
	Tag   string
	Dest  string
}

type relOpts struct {
	baseOpts
	BasePath string
}

func (*Filepath) SampleConfig() string {
	return sampleConfig
}

func (o *Filepath) Apply(in ...telegraf.Metric) []telegraf.Metric {
	for _, m := range in {
		o.processMetric(m)
	}

	return in
}

// applyFunc applies the specified function to the metric
func applyFunc(bo baseOpts, fn processorFunc, metric telegraf.Metric) {
	if bo.Tag != "" {
		if v, ok := metric.GetTag(bo.Tag); ok {
			targetTag := bo.Tag

			if bo.Dest != "" {
				targetTag = bo.Dest
			}
			metric.AddTag(targetTag, fn(v))
		}
	}

	if bo.Field != "" {
		if v, ok := metric.GetField(bo.Field); ok {
			targetField := bo.Field

			if bo.Dest != "" {
				targetField = bo.Dest
			}

			// Only string fields are considered
			if v, ok := v.(string); ok {
				metric.AddField(targetField, fn(v))
			}
		}
	}
}

func stemFilePath(path string) string {
	return strings.TrimSuffix(filepath.Base(path), filepath.Ext(path))
}

// processMetric processes fields and tag values for a given metric applying the selected transformations
func (o *Filepath) processMetric(metric telegraf.Metric) {
	// Stem
	for _, v := range o.Stem {
		applyFunc(v, stemFilePath, metric)
	}
	// Basename
	for _, v := range o.BaseName {
		applyFunc(v, filepath.Base, metric)
	}
	// Rel
	for _, v := range o.Rel {
		applyFunc(v.baseOpts, func(s string) string {
			relPath, err := filepath.Rel(v.BasePath, s)
			if err != nil {
				o.Log.Errorf("filepath processor failed to process relative filepath %s: %v", s, err)
				return v.BasePath
			}
			return relPath
		}, metric)
	}
	// Dirname
	for _, v := range o.DirName {
		applyFunc(v, filepath.Dir, metric)
	}
	// Clean
	for _, v := range o.Clean {
		applyFunc(v, filepath.Clean, metric)
	}
	// ToSlash
	for _, v := range o.ToSlash {
		applyFunc(v, filepath.ToSlash, metric)
	}
}

func init() {
	processors.Add("filepath", func() telegraf.Processor {
		return &Filepath{}
	})
}