Add tariff provider for Octopus Energy (#5799)

Adds a rudimentary provider for the British energy supplier, Octopus Energy. Supplying the tariff code and region code is mandatory.

Supports both time-of-use (Agile, Go, etc) and fixed-rate tariffs.

A full list of tariff codes are available at https://api.octopus.energy/v1/products/ - more details on the API used at https://developer.octopus.energy/docs/api/

tariff/octopus.go

@@ -0,0 +1,103 @@
+package tariff
+
+import (
+	"errors"
+	"github.com/evcc-io/evcc/tariff/octopus"
+	"sync"
+	"time"
+
+	"github.com/evcc-io/evcc/api"
+	"github.com/evcc-io/evcc/util"
+	"github.com/evcc-io/evcc/util/request"
+)
+
+type Octopus struct {
+	mux     sync.Mutex
+	log     *util.Logger
+	uri     string
+	region  string
+	data    api.Rates
+	updated time.Time
+}
+
+var _ api.Tariff = (*Octopus)(nil)
+
+func init() {
+	registry.Add("octopusenergy", NewOctopusFromConfig)
+}
+
+func NewOctopusFromConfig(other map[string]interface{}) (api.Tariff, error) {
+	var cc struct {
+		Region string
+		Tariff string
+	}
+
+	if err := util.DecodeOther(other, &cc); err != nil {
+		return nil, err
+	}
+
+	if cc.Region == "" {
+		return nil, errors.New("missing region")
+	}
+	if cc.Tariff == "" {
+		return nil, errors.New("missing tariff code")
+	}
+
+	t := &Octopus{
+		log:    util.NewLogger("octopus"),
+		uri:    octopus.ConstructRatesAPI(cc.Tariff, cc.Region),
+		region: cc.Tariff,
+	}
+
+	done := make(chan error)
+	go t.run(done)
+	err := <-done
+
+	return t, err
+}
+
+func (t *Octopus) run(done chan error) {
+	var once sync.Once
+	client := request.NewHelper(t.log)
+
+	for ; true; <-time.NewTicker(time.Hour).C {
+		var res octopus.UnitRates
+		if err := client.GetJSON(t.uri, &res); err != nil {
+			once.Do(func() { done <- err })
+
+			t.log.ERROR.Println(err)
+			continue
+		}
+
+		once.Do(func() { close(done) })
+
+		t.mux.Lock()
+		t.updated = time.Now()
+
+		t.data = make(api.Rates, 0, len(res.Results))
+		for _, r := range res.Results {
+			ar := api.Rate{
+				Start: r.ValidityStart,
+				End:   r.ValidityEnd,
+				// UnitRates are supplied inclusive of tax, though this could be flipped easily with a config flag.
+				Price: r.PriceInclusiveTax / 1e2,
+			}
+			t.data = append(t.data, ar)
+		}
+
+		t.mux.Unlock()
+	}
+}
+
+// Unit implements the api.Tariff interface
+// Stubbed because supplier always works in GBP
+func (t *Octopus) Unit() string {
+	return "GBP"
+}
+
+// Rates implements the api.Tariff interface
+func (t *Octopus) Rates() (api.Rates, error) {
+	t.mux.Lock()
+	defer t.mux.Unlock()
+	return append([]api.Rate{}, t.data...), outdatedError(t.updated, time.Hour)
+}

tariff/octopus/api.go

@@ -0,0 +1,35 @@
+package octopus
+
+import (
+	"fmt"
+	"strings"
+	"time"
+)
+
+// ProductURI defines the location of the tariff information page. Substitute %s with tariff name.
+const ProductURI = "https://api.octopus.energy/v1/products/%s/"
+
+// RatesURI defines the location of the full tariff rates page, including speculation.
+// Substitute first %s with tariff name, second with region code.
+const RatesURI = ProductURI + "electricity-tariffs/E-1R-%s-%s/standard-unit-rates/"
+
+// ConstructRatesAPI returns a validly formatted, fully qualified URI to the unit rate information.
+func ConstructRatesAPI(tariff string, region string) string {
+	t := strings.ToUpper(tariff)
+	r := strings.ToUpper(region)
+	return fmt.Sprintf(RatesURI, t, t, r)
+}
+
+type UnitRates struct {
+	Count    uint64 `json:"count"`
+	Next     string `json:"next"`
+	Previous string `json:"previous"`
+	Results  []Rate `json:"results"`
+}
+
+type Rate struct {
+	ValidityStart     time.Time `json:"valid_from"`
+	ValidityEnd       time.Time `json:"valid_to"`
+	PriceInclusiveTax float64   `json:"value_inc_vat"`
+	PriceExclusiveTax float64   `json:"value_exc_vat"`
+}