package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"time"
)

type ChargerReading struct {
	Time  time.Time
	Power float32 // W total
	EtoWh int64   // Wh cumulative
}

type chargerStatus struct {
	Nrg []float64 `json:"nrg"` // [0..15] voltages/currents/powers; [11] = total W
	Eto int64     `json:"eto"` // cumulative Wh
}

var chargerClient = &http.Client{Timeout: 5 * time.Second}

func PollCharger(host string) (ChargerReading, error) {
	url := "http://" + host + "/api/status?filter=nrg,eto"
	resp, err := chargerClient.Get(url)
	if err != nil {
		return ChargerReading{}, fmt.Errorf("get: %w", err)
	}
	defer resp.Body.Close()

	var s chargerStatus
	if err := json.NewDecoder(resp.Body).Decode(&s); err != nil {
		return ChargerReading{}, fmt.Errorf("decode: %w", err)
	}
	if len(s.Nrg) < 12 {
		return ChargerReading{}, fmt.Errorf("nrg array too short (%d)", len(s.Nrg))
	}
	return ChargerReading{
		Time:  time.Now(),
		Power: float32(s.Nrg[11]),
		EtoWh: s.Eto,
	}, nil
}