package service

import (
	"errors"
)

var (
	// ErrNotImplemented is the error when a service is accessed
	// and no implementation was provided
	ErrNotImplemented = errors.New("service not implemented")
)

// Provider is a provider for a service
type Provider func(ctn *Container) (interface{}, error)

// Container is a simple service container for dependency injection
type Container struct {
	providers map[Name]Provider
}

// Name is a name of a service
type Name string

// Provide registers a provider for the survey.Service
func (c *Container) Provide(name Name, provider Provider) {
	c.providers[name] = provider
}

// Service retrieves a service implementation based on its name
func (c *Container) Service(name Name) (interface{}, error) {
	provider, exists := c.providers[name]
	if !exists {
		return nil, ErrNotImplemented
	}
	return provider(c)
}

// NewContainer returns a new empty service container
func NewContainer() *Container {
	return &Container{
		providers: make(map[Name]Provider),
	}
}