// SPDX-FileCopyrightText: 2022-2024 Simon Bruder <simon@sbruder.de>
//
// SPDX-License-Identifier: AGPL-3.0-or-later

package main

import (
	"context"
	"encoding/json"
	"io"
	"log"
	"net"
	"net/http"
	"net/url"
	"os"
	"strconv"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"github.com/prometheus/exporter-toolkit/web"
)

type ApiClient struct {
	apiSocket string
}

type ApiError struct {
	ReturnCode int
}

type TorrentInfo struct {
	Auto            bool   `json:"auto_tmm"`
	DownloadLimit   int    `json:"dl_limit"`
	Downloaded      int    `json:"completed"`
	Hash            string `json:"hash"`
	LeechsConnected int    `json:"num_leechs"`
	LeechsSwarm     int    `json:"num_incomplete"`
	Name            string `json:"name"`
	SeedsConnected  int    `json:"num_seeds"`
	SeedsSwarm      int    `json:"num_complete"`
	Size            int    `json:"size"`
	TotalSize       int    `json:"total_size"`
	UploadLimit     int    `json:"ul_limit"`
	Uploaded        int    `json:"uploaded"`
}

type Exporter struct {
	Api ApiClient
}

var (
	qbittorrentTorrentDownloaded = prometheus.NewDesc(
		"qbittorrent_torrent_downloaded_bytes_total",
		"Amount of data downloaded",
		[]string{"hash", "name"}, nil,
	)
	qbittorrentTorrentLeechsConnected = prometheus.NewDesc(
		"qbittorrent_torrent_leechs_connected",
		"Number of leechs connected to",
		[]string{"hash", "name"}, nil,
	)
	qbittorrentTorrentLeechsSwarm = prometheus.NewDesc(
		"qbittorrent_torrent_leechs_swarm",
		"Number of leechs in the swarm",
		[]string{"hash", "name"}, nil,
	)
	qbittorrentTorrentSeedsConnected = prometheus.NewDesc(
		"qbittorrent_torrent_seeds_connected",
		"Number of seeds connected to",
		[]string{"hash", "name"}, nil,
	)
	qbittorrentTorrentSeedsSwarm = prometheus.NewDesc(
		"qbittorrent_torrent_seeds_swarm",
		"Number of seeds in the swarm",
		[]string{"hash", "name"}, nil,
	)
	qbittorrentTorrentSize = prometheus.NewDesc(
		"qbittorrent_torrent_size_bytes_total",
		"Size of selected torrent data",
		[]string{"hash", "name"}, nil,
	)
	qbittorrentTorrentUploaded = prometheus.NewDesc(
		"qbittorrent_torrent_uploaded_bytes_total",
		"Amount of data uploaded",
		[]string{"hash", "name"}, nil,
	)
)

func (e ApiError) Error() string {
	return strconv.Itoa(e.ReturnCode)
}

func CreateApiClient(apiSocket string) (c ApiClient) {
	return ApiClient{
		apiSocket: apiSocket,
	}
}

func (c ApiClient) doRequest(group string, method string, parameters url.Values) (body []byte, err error) {
	destinationUrl, err := url.Parse("http://unix/api/v2/" + group + "/" + method)
	if err != nil {
		log.Println(err)
		return []byte{}, err
	}
	req := http.Request{
		Method: "GET",
		URL:    destinationUrl,
		Header: http.Header{},
		Form:   parameters,
	}
	httpClient := http.Client{
		Transport: &http.Transport{
			DialContext: func(_ context.Context, _, _ string) (net.Conn, error) {
				return net.Dial("unix", c.apiSocket)
			},
		},
	}
	res, err := httpClient.Do(&req)
	if err != nil {
		log.Println(err)
		return []byte{}, err
	}
	bodyBytes, err := io.ReadAll(res.Body)
	if err != nil {
		return []byte{}, err
	}
	body = bodyBytes
	if res.StatusCode != 200 {
		err = ApiError{ReturnCode: res.StatusCode}
	}
	return
}

func (c ApiClient) TorrentsInfo() (torrentsInfo []TorrentInfo, err error) {
	torrentsInfo = []TorrentInfo{}
	body, err := c.doRequest("torrents", "info", url.Values{})
	if err != nil {
		return []TorrentInfo{}, err
	}
	json.Unmarshal(body, &torrentsInfo)
	return
}

func (e Exporter) Describe(ch chan<- *prometheus.Desc) {
	ch <- qbittorrentTorrentDownloaded
	ch <- qbittorrentTorrentLeechsConnected
	ch <- qbittorrentTorrentLeechsSwarm
	ch <- qbittorrentTorrentSeedsConnected
	ch <- qbittorrentTorrentSeedsSwarm
	ch <- qbittorrentTorrentSize
	ch <- qbittorrentTorrentUploaded
}

func (e Exporter) Collect(ch chan<- prometheus.Metric) {
	torrentsInfo, err := e.Api.TorrentsInfo()
	if err != nil {
		log.Println(err)
		return
	}
	for _, torrentInfo := range torrentsInfo {
		ch <- prometheus.MustNewConstMetric(qbittorrentTorrentDownloaded, prometheus.CounterValue, float64(torrentInfo.Downloaded), torrentInfo.Hash, torrentInfo.Name)
		ch <- prometheus.MustNewConstMetric(qbittorrentTorrentLeechsConnected, prometheus.GaugeValue, float64(torrentInfo.LeechsConnected), torrentInfo.Hash, torrentInfo.Name)
		ch <- prometheus.MustNewConstMetric(qbittorrentTorrentLeechsSwarm, prometheus.GaugeValue, float64(torrentInfo.LeechsSwarm), torrentInfo.Hash, torrentInfo.Name)
		ch <- prometheus.MustNewConstMetric(qbittorrentTorrentSeedsConnected, prometheus.GaugeValue, float64(torrentInfo.SeedsConnected), torrentInfo.Hash, torrentInfo.Name)
		ch <- prometheus.MustNewConstMetric(qbittorrentTorrentSeedsSwarm, prometheus.GaugeValue, float64(torrentInfo.SeedsSwarm), torrentInfo.Hash, torrentInfo.Name)
		ch <- prometheus.MustNewConstMetric(qbittorrentTorrentSize, prometheus.GaugeValue, float64(torrentInfo.Size), torrentInfo.Hash, torrentInfo.Name)
		ch <- prometheus.MustNewConstMetric(qbittorrentTorrentUploaded, prometheus.CounterValue, float64(torrentInfo.Uploaded), torrentInfo.Hash, torrentInfo.Name)
	}
}

func main() {
	e := Exporter{
		Api: CreateApiClient(
			os.Getenv("QBITTORRENT_API_SOCKET"),
		),
	}
	prometheus.MustRegister(e)
	http.Handle("/metrics", promhttp.Handler())

	landingPage, err := web.NewLandingPage(web.LandingConfig{
		Name: "qBittorrent Exporter",
		Links: []web.LandingLinks{
			{
				Address: "/metrics",
				Text:    "Metrics",
			},
			{
				Address: "https://git.sbruder.de/simon/nixos-config/src/branch/master/modules/qbittorrent/exporter",
				Text:    "Source Code",
			},
			{
				Address: "https://www.gnu.org/licenses/agpl-3.0.txt",
				Text:    "Released under the AGPLv3 or later",
			},
		},
	})
	if err != nil {
		log.Fatalf("Failed to create landing page: %v", err)
	}
	http.Handle("/", landingPage)

	listenAddress := os.Getenv("QBITTORRENT_EXPORTER_LISTEN_ADDRESS")
	if listenAddress == "" {
		listenAddress = ":9561" // this reuses the port number of fru1tstand’s exporter
	}
	log.Printf("Starting HTTP server at at %s", listenAddress)

	log.Fatalf("Failed to start http server: %v", http.ListenAndServe(listenAddress, nil))
}