package stats

import (
	"fmt"
	"os/exec"

	"github.com/go-errors/errors"
	"github.com/goccy/go-json"
)

const (
	vnstatBin = "/usr/bin/vnstat"
)

type VnstatTrafficRecord struct {
	Date struct {
		Year  uint `json:"year"`
		Month uint `json:"month"`
		Day   uint `json:"day"`
	} `json:"date"`
	Time struct {
		Hour   uint `json:"hour"`
		Minute uint `json:"minute"`
	} `json:"time"`
	Rx uint64 `json:"rx"`
	Tx uint64 `json:"tx"`
}

type vnstatResponse struct {
	Interfaces []struct {
		Name    string `json:"name"`
		Traffic struct {
			FiveMinute []VnstatTrafficRecord `json:"fiveminute"`
			Hour       []VnstatTrafficRecord `json:"hour"`
			Day        []VnstatTrafficRecord `json:"day"`
			Month      []VnstatTrafficRecord `json:"month"`
		} `json:"traffic"`
	} `json:"interfaces"`
}

func VnstatMonthlyTraffic(ifname string) ([]VnstatTrafficRecord, error) {
	resp, err := callVnstat("--json", "m")
	if err != nil {
		return nil, errors.WrapPrefix(err, "failed to run vnstat", 0)
	}

	for _, iface := range resp.Interfaces {
		if iface.Name == ifname {
			return iface.Traffic.Month, nil
		}
	}

	return nil, errors.New(fmt.Sprintf("interface %s not found", ifname))
}

func VnstatDailyTraffic(ifname string) ([]VnstatTrafficRecord, error) {
	resp, err := callVnstat("--json", "d")
	if err != nil {
		return nil, errors.WrapPrefix(err, "failed to run vnstat", 0)
	}

	for _, iface := range resp.Interfaces {
		if iface.Name == ifname {
			return iface.Traffic.Day, nil
		}
	}

	return nil, errors.New(fmt.Sprintf("interface %s not found", ifname))
}

func callVnstat(args ...string) (*vnstatResponse, error) {
	cmd := exec.Command(vnstatBin, args...)
	cmd.Stdin = nil
	output, err := cmd.Output()

	if err != nil {
		return nil, err
	}

	var resp vnstatResponse
	err = json.Unmarshal(output, &resp)
	if err != nil {
		return nil, errors.Wrap(err, 0)
	}
	return &resp, nil
}