vine.go

// Copyright 2020 The vine Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package vine is a pluggable framework for vine services
package service

import (
	"context"

	"github.com/lack-io/vine/service/client"
	"github.com/lack-io/vine/service/server"
)

type serviceKey struct{}

// Service is an interface that wraps the lower level libraries
// within vine. Its a convenience method for building
// and initialising services.
type Service interface {
	// The service name
	Name() string
	// Init initialises options
	Init(...Option)
	// Options returns the current options
	Options() Options
	// Client is used to call services
	Client() client.Client
	// Server is for handling requests and events
	Server() server.Server
	// Run the service
	Run() error
	// The service implementation
	String() string
}

// Function is a one time executing Service
type Function interface {
	// Inherits Service interface
	Service
	// Done signals to complete execution
	Done() error
	// Handle registers an RPC handler
	Handle(v interface{}) error
	// Subscribe registers a subscriber
	Subscribe(topic string, v interface{}) error
}

// Event is used to publish messages to topic
type Event interface {
	// Publish publishes a message to the event topic
	Publish(ctx context.Context, msg interface{}, opts ...client.PublishOption) error
}

type Option func(*Options)

var (
	HeaderPrefix = "Vine-"
)

// NewService creates and returns a new Service based on the packages within.
func NewService(opts ...Option) Service {
	return newService(opts...)
}

// FromContext retrieves a Service from the Context.
func FromContext(ctx context.Context) (Service, bool) {
	s, ok := ctx.Value(serviceKey{}).(Service)
	return s, ok
}

// NewContext returns a new Context with the Service embedded within it.
func NewContext(ctx context.Context, s Service) context.Context {
	return context.WithValue(ctx, serviceKey{}, s)
}

// NewFunction returns a new Function for a one time executing Service
func NewFunction(opts ...Option) Function {
	return newFunction(opts...)
}

// NewEvent creates a new event pulisher
func NewEvent(topic string, c client.Client) Event {
	if c == nil {
		c = client.DefaultClient
	}
	return &event{c, topic}
}

// RegisterHandler is syntactic sugar for registering a handler
func RegisterHandler(s server.Server, h interface{}, opts ...server.HandlerOption) error {
	return s.Handle(s.NewHandler(h, opts...))
}

// RegisterSubscriber is syntactic sugar for registering a subscriber
func RegisterSubscriber(topic string, s server.Server, h interface{}, opts ...server.SubscriberOption) error {
	return s.Subscribe(s.NewSubscriber(topic, h, opts...))
}