package alamo

import (
	"bytes"
	"encoding/json"
	"fmt"
)

type controlSettings struct {
	Mode              string  `json:"mode"`
	TargetTemperature float64 `json:"target_temperature"`
}

func decodeControl(value json.RawMessage) (controlSettings, error) {
	var fields struct {
		Mode   *string  `json:"mode"`
		Target *float64 `json:"target_temperature"`
	}

	decoder := json.NewDecoder(bytes.NewReader(value))
	decoder.DisallowUnknownFields()

	err := decoder.Decode(&fields)
	if err != nil {
		return controlSettings{}, fmt.Errorf("decode control settings: %w", err)
	}

	if !json.Valid(value) || fields.Mode == nil || fields.Target == nil {
		return controlSettings{}, fmt.Errorf("control settings must contain mode and target temperature")
	}

	if *fields.Mode != "off" && *fields.Mode != "heat" {
		return controlSettings{}, fmt.Errorf("control mode must be off or heat")
	}

	if !finite(*fields.Target) {
		return controlSettings{}, fmt.Errorf("target temperature must be finite")
	}

	return controlSettings{
		Mode:              *fields.Mode,
		TargetTemperature: *fields.Target,
	}, nil
}