package metrics

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"regexp"
	"strconv"
	"strings"
	"time"

	log "github.com/sirupsen/logrus"
)

type LokiMetricConfig struct {
	Url           string
	BotUserAgents *[]regexp.Regexp
	Enabled       bool
}

// Checks if we should send a metric ping to Loki based on the served path.
func (c *LokiMetricConfig) ShouldSendMetrics(path, userAgent string) bool {
	if !strings.HasSuffix(path, ".html") || !c.Enabled {
		return false
	}

	// Filter out bots
	for _, pattern := range *c.BotUserAgents {
		if pattern.MatchString(userAgent) {
			return false
		}
	}

	return true
}

func (c *LokiMetricConfig) SendMetricPing(domain, path, referrer string) {
	msg := fmt.Sprintf("path=\"%s\" referrer=\"%s\"", path, referrer)
	data := map[string]interface{}{
		"streams": []map[string]interface{}{
			{
				"stream": map[string]string{
					// Labels
					"service": "rio",
					"domain":  domain,
					"type":    "metric",
				},
				"values": [][]interface{}{
					{
						strconv.Itoa(int(time.Now().UnixNano())),
						msg,
					},
				},
			},
		},
	}
	jsonData, err := json.Marshal(data)
	if err != nil {
		log.Errorf("Failed to send metric ping to Loki: %v", err)
		return
	}

	log.Debugf("Sending payload %s", string(jsonData))

	// Send the ping to the Loki server
	go func() {
		res, err := http.Post(
			c.Url,
			"application/json",
			strings.NewReader(string(jsonData)),
		)
		if err != nil {
			log.Errorf("Failed to send payload to Loki: %v", err)
			return
		}

		defer res.Body.Close()
		if res.StatusCode != 204 {
			log.Errorf("Loki returned non-204 status code %d", res.StatusCode)
			body, err := ioutil.ReadAll(res.Body)
			if err != nil {
				log.Warnf("Failed to read body. No more specific error message")
				return
			}
			log.Errorf("-> %s", body)
		}
	}()
}

// Reads a JSON array of bot user agents from disk and parses them
// into regular expressions.
func ReadBotPatterns(file string) ([]regexp.Regexp, error) {
	content, err := ioutil.ReadFile(file)
	if err != nil {
		log.Warnf("Failed to read bot metrics file: %v", err)
		return []regexp.Regexp{}, err
	}

	var payload []string
	err = json.Unmarshal(content, &payload)
	if err != nil {
		log.Warnf("Failed to unmarshal file: %v", err)
		return []regexp.Regexp{}, err
	}

	patterns := make([]regexp.Regexp, 0)
	for _, v := range payload {
		patterns = append(
			patterns,
			*regexp.MustCompile(v),
		)
	}

	return patterns, nil
}