Code your own modules to create modular resources

// Package mybase implements a base that only supports SetPower (basic forward/back/turn controls), IsMoving (check if in motion), and Stop (stop all motion).
// It extends the built-in resource subtype Base and implements methods to handle resource construction, attribute configuration, and reconfiguration.

package mybase

import (
    "context"
    "fmt"
    "math"

    "github.com/edaniels/golog"
    "github.com/golang/geo/r3"
    "github.com/pkg/errors"
    "go.uber.org/multierr"

    "go.viam.com/rdk/components/base"
    "go.viam.com/rdk/components/base/kinematicbase"
    "go.viam.com/rdk/components/motor"
    "go.viam.com/rdk/resource"
    "go.viam.com/rdk/spatialmath"
)

// Here is where we define your new model's colon-delimited-triplet (acme:demo:mybase)
// acme = namespace, demo = family, mybase = model name.
var (
    Model            = resource.NewModel("acme", "demo", "mybase")
    errUnimplemented = errors.New("unimplemented")
)

const (
    myBaseWidthMm        = 500.0 // Base has a wheel tread of 500 millimeters
    myBaseTurningRadiusM = 0.3   // Base turns around a circle of radius .3 meters
)

func init() {
    resource.RegisterComponent(base.API, Model, resource.Registration[base.Base, *Config]{
        Constructor: newBase,
    })
}

func newBase(ctx context.Context, deps resource.Dependencies, conf resource.Config, logger golog.Logger) (base.Base, error) {
    b := &myBase{
        Named:  conf.ResourceName().AsNamed(),
        logger: logger,
    }
    if err := b.Reconfigure(ctx, deps, conf); err != nil {
        return nil, err
    }
    return b, nil
}


// Reconfigure reconfigures with new settings.
func (b *myBase) Reconfigure(ctx context.Context, deps resource.Dependencies, conf resource.Config) error {
    b.left = nil
    b.right = nil

    // This takes the generic resource.Config passed down from the parent and converts it to the
    // model-specific (aka "native") Config structure defined, above making it easier to directly access attributes.
    baseConfig, err := resource.NativeConfig[*Config](conf)
    if err != nil {
        return err
    }

    b.left, err = motor.FromDependencies(deps, baseConfig.LeftMotor)
    if err != nil {
        return errors.Wrapf(err, "unable to get motor %v for mybase", baseConfig.LeftMotor)
    }

    b.right, err = motor.FromDependencies(deps, baseConfig.RightMotor)
    if err != nil {
        return errors.Wrapf(err, "unable to get motor %v for mybase", baseConfig.RightMotor)
    }

    geometries, err := kinematicbase.CollisionGeometry(conf.Frame)
    if err != nil {
        b.logger.Warnf("base %v %s", b.Name(), err.Error())
    }
    b.geometries = geometries

    // Stop motors when reconfiguring.
    return multierr.Combine(b.left.Stop(context.Background(), nil), b.right.Stop(context.Background(), nil))
}

// DoCommand simply echos whatever was sent.
func (b *myBase) DoCommand(ctx context.Context, cmd map[string]interface{}) (map[string]interface{}, error) {
    return cmd, nil
}

// Config contains two component (motor) names.
type Config struct {
    LeftMotor  string `json:"motorL"`
    RightMotor string `json:"motorR"`
}

// Validate validates the config and returns implicit dependencies,
// this Validate checks if the left and right motors exist for the module's base model.
func (cfg *Config) Validate(path string) ([]string, error) {
    // check if the attribute fields for the right and left motors are non-empty
    // this makes them reuqired for the model to successfully build
    if cfg.LeftMotor == "" {
        return nil, fmt.Errorf(`expected "motorL" attribute for mybase %q`, path)
    }
    if cfg.RightMotor == "" {
        return nil, fmt.Errorf(`expected "motorR" attribute for mybase %q`, path)
    }

    // Return the left and right motor names so that `newBase` can access them as dependencies.
    return []string{cfg.LeftMotor, cfg.RightMotor}, nil
}

type myBase struct {
    resource.Named
    left       motor.Motor
    right      motor.Motor
    logger     golog.Logger
    geometries []spatialmath.Geometry
}

// MoveStraight does nothing.
func (b *myBase) MoveStraight(ctx context.Context, distanceMm int, mmPerSec float64, extra map[string]interface{}) error {
    return errUnimplemented
}

// Spin does nothing.
func (b *myBase) Spin(ctx context.Context, angleDeg, degsPerSec float64, extra map[string]interface{}) error {
    return errUnimplemented
}

// SetVelocity does nothing.
func (b *myBase) SetVelocity(ctx context.Context, linear, angular r3.Vector, extra map[string]interface{}) error {
    return errUnimplemented
}

// SetPower computes relative power between the wheels and sets power for both motors.
func (b *myBase) SetPower(ctx context.Context, linear, angular r3.Vector, extra map[string]interface{}) error {
    b.logger.Debugf("SetPower Linear: %.2f Angular: %.2f", linear.Y, angular.Z)
    if math.Abs(linear.Y) < 0.01 && math.Abs(angular.Z) < 0.01 {
        return b.Stop(ctx, extra)
    }
    sum := math.Abs(linear.Y) + math.Abs(angular.Z)
    err1 := b.left.SetPower(ctx, (linear.Y-angular.Z)/sum, extra)
    err2 := b.right.SetPower(ctx, (linear.Y+angular.Z)/sum, extra)
    return multierr.Combine(err1, err2)
}

// Stop halts motion.
func (b *myBase) Stop(ctx context.Context, extra map[string]interface{}) error {
    b.logger.Debug("Stop")
    err1 := b.left.Stop(ctx, extra)
    err2 := b.right.Stop(ctx, extra)
    return multierr.Combine(err1, err2)
}

// IsMoving returns true if either motor is active.
func (b *myBase) IsMoving(ctx context.Context) (bool, error) {
    for _, m := range []motor.Motor{b.left, b.right} {
        isMoving, _, err := m.IsPowered(ctx, nil)
        if err != nil {
            return false, err
        }
        if isMoving {
            return true, err
        }
    }
    return false, nil
}

// Properties returns details about the physics of the base.
func (b *myBase) Properties(ctx context.Context, extra map[string]interface{}) (base.Properties, error) {
    return base.Properties{
        TurningRadiusMeters: myBaseTurningRadiusM,
        WidthMeters:         myBaseWidthMm * 0.001, // converting millimeters to meters
    }, nil
}

// Geometries returns physical dimensions.
func (b *myBase) Geometries(ctx context.Context, extra map[string]interface{}) ([]spatialmath.Geometry, error) {
    return b.geometries, nil
}

// Close stops motion during shutdown.
func (b *myBase) Close(ctx context.Context) error {
    return b.Stop(ctx, nil)
}

// Package main is a module which serves the mybase custom model.
package main

import (
    "context"

    "github.com/edaniels/golog"

    "go.viam.com/rdk/components/base"
    "go.viam.com/rdk/module"
    "go.viam.com/utils"

    // NOTE: You must update the following line to import your local package "mybase"
    "go.viam.com/rdk/examples/customresources/models/mybase"
)

func main() {
    // NewLoggerFromArgs will create a golog.Logger at "DebugLevel" if
    // "--log-level=debug" is an argument in os.Args and at "InfoLevel" otherwise.
    utils.ContextualMain(mainWithArgs, module.NewLoggerFromArgs("yourmodule"))
}

func mainWithArgs(ctx context.Context, args []string, logger golog.Logger) (err error) {
    myMod, err := module.NewModuleFromArgs(ctx, logger)
    if err != nil {
        return err
    }

    // Models and APIs add helpers to the registry during their init().
    // They can then be added to the module here.
    err = myMod.AddModelFromRegistry(ctx, base.API, mybase.Model)
    if err != nil {
        return err
    }

    err = myMod.Start(ctx)
    defer myMod.Close(ctx)
    if err != nil {
        return err
    }
    <-ctx.Done()
    return nil
}