func (c *Client) Bind(instance *ServiceInstance, app bind.App, unit bind.Unit) (map[string]string, error) {
	log.Print("Attempting to call bind of service instance " + instance.Name + " and unit " + unit.GetIp() + " at " + instance.ServiceName + " api")
	var resp *http.Response
	params := map[string][]string{
		"unit-host": {unit.GetIp()},
		"app-host":  {app.GetIp()},
	}
	resp, err := c.issueRequest("/resources/"+instance.Name, "POST", params)
	if err != nil {
		if m, _ := regexp.MatchString("", err.Error()); m {
			return nil, fmt.Errorf("%s api is down.", instance.Name)
		}
		return nil, err
	}
	if err == nil && resp.StatusCode < 300 {
		var result map[string]string
		err = c.jsonFromResponse(resp, &result)
		if err != nil {
			return nil, err
		}
		return result, nil
	}
	if resp.StatusCode == http.StatusPreconditionFailed {
		return nil, &errors.HTTP{Code: resp.StatusCode, Message: "You cannot bind any app to this service instance because it is not ready yet."}
	}
	msg := "Failed to bind instance " + instance.Name + " to the unit " + unit.GetIp() + ": " + c.buildErrorMessage(err, resp)
	log.Print(msg)
	return nil, &errors.HTTP{Code: http.StatusInternalServerError, Message: msg}
}

// BindApp makes the bind between the service instance and an app.
func (si *ServiceInstance) BindApp(app bind.App) error {
	err := si.AddApp(app.GetName())
	if err != nil {
		return &errors.Http{Code: http.StatusConflict, Message: "This app is already bound to this service instance."}
	}
	err = si.update()
	if err != nil {
		return err
	}
	if len(app.GetUnits()) == 0 {
		return &errors.Http{Code: http.StatusPreconditionFailed, Message: "This app does not have an IP yet."}
	}
	envs := make(chan map[string]string, len(app.GetUnits())+1)
	for _, unit := range app.GetUnits() {
		go func(unit bind.Unit) {
			vars, _ := si.BindUnit(app, unit)
			envs <- vars
		}(unit)
	}
	var envVars []bind.EnvVar
	for k, v := range <-envs {
		envVars = append(envVars, bind.EnvVar{
			Name:         k,
			Value:        v,
			Public:       false,
			InstanceName: si.Name,
		})
	}
	return app.SetEnvs(envVars, false)
}

func (c *Client) Unbind(instance *ServiceInstance, app bind.App) (err error) {
	log.Print("Attempting to call unbind of service instance " + instance.Name + " and app " + app.GetName() + " at " + instance.ServiceName + " api")
	var resp *http.Response
	url := "/resources/" + instance.Name + "/hostname/" + app.GetUnits()[0].GetIp()
	if resp, err = c.issueRequest(url, "DELETE", nil); err == nil && resp.StatusCode > 299 {
		msg := "Failed to unbind instance " + instance.Name + " from the app " + app.GetName() + ": " + c.buildErrorMessage(err, resp)
		log.Print(msg)
		err = &errors.Http{Code: http.StatusInternalServerError, Message: msg}
	}
	return
}

func (c *Client) Bind(instance *ServiceInstance, app bind.App) (envVars map[string]string, err error) {
	log.Print("Attempting to call bind of service instance " + instance.Name + " and app " + app.GetName() + " at " + instance.ServiceName + " api")
	var resp *http.Response
	params := map[string][]string{
		"hostname": {app.GetUnits()[0].GetIp()},
	}
	if resp, err = c.issueRequest("/resources/"+instance.Name, "POST", params); err == nil && resp.StatusCode < 300 {
		return c.jsonFromResponse(resp)
	} else if resp.StatusCode == http.StatusPreconditionFailed {
		err = &errors.Http{Code: resp.StatusCode, Message: "You cannot bind any app to this service instance because it is not ready yet."}
	} else {
		msg := "Failed to bind instance " + instance.Name + " to the app " + app.GetName() + ": " + c.buildErrorMessage(err, resp)
		log.Print(msg)
		err = &errors.Http{Code: http.StatusInternalServerError, Message: msg}
	}
	return
}

func (si *ServiceInstance) Bind(app bind.App) error {
	err := si.AddApp(app.GetName())
	if err != nil {
		return &errors.Http{Code: http.StatusConflict, Message: "This app is already binded to this service instance."}
	}
	var envVars []bind.EnvVar
	var setEnv = func(env map[string]string) {
		for k, v := range env {
			envVars = append(envVars, bind.EnvVar{
				Name:         k,
				Value:        v,
				Public:       false,
				InstanceName: si.Name,
			})
		}
	}
	cli := si.Service().ProductionEndpoint()
	if len(app.GetUnits()) == 0 {
		return &errors.Http{Code: http.StatusPreconditionFailed, Message: "This app does not have an IP yet."}
	}
	env, err := cli.Bind(si, app)
	if err != nil {
		return err
	}
	setEnv(env)
	err = si.update()
	if err != nil {
		cli.Unbind(si, app)
		return err
	}
	return app.SetEnvs(envVars, false)
}

// UnbindApp makes the unbind between the service instance and an app.
func (si *ServiceInstance) UnbindApp(app bind.App) error {
	err := si.RemoveApp(app.GetName())
	if err != nil {
		return &errors.Http{Code: http.StatusPreconditionFailed, Message: "This app is not bound to this service instance."}
	}
	err = si.update()
	if err != nil {
		return err
	}
	for _, unit := range app.GetUnits() {
		go func(unit bind.Unit) {
			si.UnbindUnit(unit)
		}(unit)
	}
	var envVars []string
	for k := range app.InstanceEnv(si.Name) {
		envVars = append(envVars, k)
	}
	return app.UnsetEnvs(envVars, false)
}

func (si *ServiceInstance) Unbind(app bind.App) error {
	err := si.RemoveApp(app.GetName())
	if err != nil {
		return &errors.Http{Code: http.StatusPreconditionFailed, Message: "This app is not binded to this service instance."}
	}
	err = si.update()
	if err != nil {
		return err
	}
	go func() {
		si.Service().ProductionEndpoint().Unbind(si, app)
	}()
	var envVars []string
	for k := range app.InstanceEnv(si.Name) {
		envVars = append(envVars, k)
	}
	return app.UnsetEnvs(envVars, false)
}