Add delta plugin (#26897)

Author: andig

plugin/delta.go

@@ -0,0 +1,102 @@
+package plugin
+
+import (
+	"context"
+
+	"github.com/evcc-io/evcc/plugin/pipeline"
+	"github.com/evcc-io/evcc/util"
+)
+
+type deltaPlugin struct {
+	ctx   context.Context
+	total float64
+	set   Config
+	get   *Config
+}
+
+func init() {
+	registry.AddCtx("delta", NewDeltaFromConfig)
+}
+
+// NewDeltaFromConfig creates delta provider
+func NewDeltaFromConfig(ctx context.Context, other map[string]any) (Plugin, error) {
+	var cc struct {
+		pipeline.Settings `mapstructure:",squash"`
+		Set               Config
+		Get               *Config
+	}
+
+	if err := util.DecodeOther(other, &cc); err != nil {
+		return nil, err
+	}
+
+	p := &deltaPlugin{
+		ctx: ctx,
+		set: cc.Set,
+		get: cc.Get,
+	}
+
+	return p, nil
+}
+
+var _ IntSetter = (*deltaPlugin)(nil)
+
+func (p *deltaPlugin) IntSetter(param string) (func(int64) error, error) {
+	set, err := p.set.IntSetter(p.ctx, param)
+	if err != nil {
+		return nil, err
+	}
+
+	get, err := p.get.IntGetter(p.ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	return func(val int64) error {
+		if get != nil {
+			total, err := get()
+			if err != nil {
+				return err
+			}
+			p.total = float64(total)
+		}
+
+		delta := float64(val) - p.total
+		err := set(int64(delta))
+		if err == nil {
+			p.total = float64(val)
+		}
+		return err
+	}, err
+}
+
+var _ FloatSetter = (*deltaPlugin)(nil)
+
+func (p *deltaPlugin) FloatSetter(param string) (func(float64) error, error) {
+	set, err := p.set.FloatSetter(p.ctx, param)
+	if err != nil {
+		return nil, err
+	}
+
+	get, err := p.get.FloatGetter(p.ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	return func(val float64) error {
+		if get != nil {
+			total, err := get()
+			if err != nil {
+				return err
+			}
+			p.total = total
+		}
+
+		delta := val - p.total
+		err := set(delta)
+		if err == nil {
+			p.total = val
+		}
+		return err
+	}, err
+}