package simulator

import (
	"fmt"
	"sync"
)

var (
	driversMu sync.RWMutex
	drivers   = make(map[string]Driver)
)

// Driver creates new simulators
type Driver interface {
	// Name gets the name of the driver
	Name() string
	// New creates a new simulator
	New(m Model, info Info) (Simulator, error)
	// Valid checks if the template information contains enough data to start the simulator
	Valid(info Info) bool
}

// Drivers returns a sorted list of the names of the registered drivers.
func Drivers() []Driver {
	var list []Driver

	driversMu.RLock()
	defer driversMu.RUnlock()

	for _, driver := range drivers {
		list = append(list, driver)
	}

	return list
}

// Register makes the simulator available by the provided name.
// If Register is called twice with the same name or if driver is nil,
// it panics
func Register(name string, driver Driver) {
	driversMu.Lock()
	defer driversMu.Unlock()
	if driver == nil {
		panic("simulator: Register driver is nil")
	}
	if _, dup := drivers[name]; dup {
		panic("simulator: Register is called twice for driver " + name)
	}
	drivers[name] = driver
}

// NewSimulator creates a new simulator specified by its simulator driver name
func NewSimulator(driverName string, m Model, info Info) (Simulator, error) {
	driversMu.RLock()
	driveri, ok := drivers[driverName]
	driversMu.RUnlock()
	if !ok {
		return nil, fmt.Errorf("simulator: unknown driver %q (forgotten import?)", driverName)
	}
	return driveri.New(m, info)
}