package bicycle

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"math"
	"net/http"
	"os"
	"path"
	"strconv"
	"sync"
	"time"

	influxdb2 "github.com/influxdata/influxdb-client-go/v2"
)

type drive struct {
	StartTime     time.Time
	TotalDistance float64
}

type distance struct {
	Value float64 `json:"value"`
	Unit  string  `json:"unit"`
}

type year_collect struct {
	TotalDistance distance            `json:"total_distance"`
	YearResult    distance            `json:"year_result"`
	Months        map[string]distance `json:"months"`
}

type api_cycle struct {
	Years map[string]year_collect
}

type config struct {
	InfluxUrl    string `json:"influx_url"`
	InfluxToken  string `json:"influx_token"`
	InfluxBucket string `json:"influx_bucket"`
	InfluxOrg    string `json:"influx_org"`
}

const (
	DISTANCE_UNIT = "km"
)

var (
	logger       log.Logger = *log.Default()
	cycle_api    api_cycle
	api_mutex    sync.Mutex
	config_cache = config{ // Default config - written if not existing @ config_path
		InfluxUrl:    "http://nuc:8086",
		InfluxToken:  "",
		InfluxBucket: "home",
		InfluxOrg:    "tkl",
	}
	config_path string = "/var/lib/apiservice/bicycle/config.json"
)

func init() {
	logger.SetPrefix("apiservice/bike: ")
}

func configure() {
	_, err := os.Stat(config_path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			logger.Printf("Config file does not exist at '%s'. Creating one...", config_path)

			// Create config directory
			dir := path.Dir(config_path)
			err := os.MkdirAll(dir, os.ModePerm)
			if err != nil {
				logger.Fatal(err)
			}

			file, err := os.OpenFile(config_path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
			if err != nil {
				logger.Fatal(err)
			}
			defer file.Close()

			content, err := json.Marshal(config_cache)
			if err != nil {
				logger.Fatal(err)
			}
			file.Write(content)
			return
		} else {
			logger.Fatal(err)
		}
	}
	data, err := os.ReadFile(config_path)
	if err != nil {
		logger.Fatal(err)
	}
	err = json.Unmarshal(data, &config_cache)
	if err != nil {
		logger.Fatal(err)
	}
}

func roundFloat(val float64, precision uint) float64 {
	ratio := math.Pow(10, float64(precision))
	return math.Round(val*ratio) / ratio
}

func get_total_distances(client *influxdb2.Client, org string, bucket string, start time.Time, stop time.Time) ([]drive, error) {
	var res []drive
	queryAPI := (*client).QueryAPI(org)
	query := fmt.Sprintf(`from(bucket: "%s")
	|> range(start: %s, stop: %s)
	|> filter(fn: (r) => r._measurement == "activity")
	|> filter(fn: (r) => r["_field"] == "TotalDistance")`, bucket, start.Format(time.RFC3339), stop.Format(time.RFC3339))
	result, err := queryAPI.Query(context.Background(), query)
	if err != nil {
		fmt.Print(err)
		return nil, err
	}
	for result.Next() {
		var tmp drive
		tmp.StartTime = result.Record().Time()
		tmp.TotalDistance = result.Record().Value().(float64) / 100000.0
		res = append(res, tmp)
	}
	return res, nil
}

func api_endpoint_cycle(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-type", "application/json; charset=utf-8;")
	if r.Method == http.MethodGet {
		// build json object of api struct
		api_mutex.Lock()
		res, err := json.Marshal(cycle_api)
		api_mutex.Unlock()
		if err != nil {
			logger.Print(err)
			w.WriteHeader(http.StatusInternalServerError)
			w.Write(json.RawMessage(`{"error": "cannot marshal object to json"}`))
		} else {
			w.WriteHeader(http.StatusOK)
			w.Write(res)
		}
	} else {
		w.WriteHeader(http.StatusMethodNotAllowed)
	}
}

func api_builder() {
	// create influx client
	client := influxdb2.NewClient(config_cache.InfluxUrl, config_cache.InfluxToken)
	defer client.Close()
	for {
		// end date for query
		stop := time.Now()

		// start date for query (1st january of the same year as stop)
		start := time.Date(stop.Year(), time.January, 1, 0, 0, 0, 0, time.UTC)

		// get TotalDistance(s) between start and stop
		distances, err := get_total_distances(&client, config_cache.InfluxOrg, config_cache.InfluxBucket, start, stop)
		if err != nil {
			logger.Print(err)
			time.Sleep(time.Second)
			continue
		}

		// get number of years
		var year_list []int
		for i := range distances {
			year := distances[i].StartTime.Year()
			exists := false
			for _, value := range year_list {
				if value == year {
					exists = true
					break
				}
			}
			if !exists {
				year_list = append(year_list, year)
			}
		}

		api_mutex.Lock()
		// init api structs
		cycle_api.Years = make(map[string]year_collect)
		for _, value := range year_list {
			years := cycle_api.Years
			months := make(map[string]distance)
			var tmp year_collect
			tmp.Months = months
			years[strconv.Itoa(value)] = tmp
			cycle_api.Years = years
		}

		// take over values into api struct
		for i := range distances {
			// get nested struct elements
			year_key := strconv.Itoa(distances[i].StartTime.Year())
			year := cycle_api.Years[year_key]
			months := year.Months
			year_distance := year.TotalDistance
			key := distances[i].StartTime.Month()
			entry := months[key.String()]

			// takeover values
			entry.Value = roundFloat(entry.Value+distances[i].TotalDistance, 2)
			entry.Unit = DISTANCE_UNIT
			year_distance.Value = roundFloat(year_distance.Value+distances[i].TotalDistance, 2)
			year_distance.Unit = DISTANCE_UNIT
			// year result
			var year_result distance
			year_result.Unit = DISTANCE_UNIT
			if distances[i].StartTime.Year() == time.Now().Year() {
				elapsed_days := time.Now().YearDay()
				relation := float64(elapsed_days) * 100 / 365
				year_result.Value = roundFloat(year_distance.Value*relation, 2)
			} else {
				year_result = year_distance
			}

			// replace nested struct elements
			months[key.String()] = entry
			year.TotalDistance = year_distance
			year.YearResult = year_result
			year.Months = months
			cycle_api.Years[year_key] = year
		}

		api_mutex.Unlock()
		time.Sleep(time.Minute)
	}
}

func Start() {
	configure()
	http.HandleFunc("/api/bicycle", api_endpoint_cycle)
	go api_builder()
}