loader.go

// MIT License
//
// Copyright (c) 2020 Lack
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

// Package loader manages loading from multiple sources
package loader

import (
	"context"

	"github.com/vine-io/vine/lib/config/reader"
	"github.com/vine-io/vine/lib/config/source"
)

// Loader manages loading sources
type Loader interface {
	// Close stops the loader
	Close() error
	// Load the sources
	Load(...source.Source) error
	// A Snapshot of loaded config
	Snapshot() (*Snapshot, error)
	// Sync force sync of sources
	Sync() error
	// Watch for changes
	Watch(...string) (Watcher, error)
	// String the name of loader
	String() string
}

// Watcher lets you watch sources and returns a merged ChangeSet
type Watcher interface {
	// Next first call to next may return the current Snapshot
	// If you are watching a path then only the data from
	// that path is returned.
	Next() (*Snapshot, error)
	// Stop watching for changes
	Stop() error
}

// Snapshot is a merged ChangeSet
type Snapshot struct {
	// The merged ChangeSet
	ChangeSet *source.ChangeSet
	// Deterministic and comparable version of the snapshot
	Version string
}

type Options struct {
	Reader reader.Reader
	Source []source.Source

	// for alternative data
	Context context.Context
}

type Option func(o *Options)

// Copy shapshot
func Copy(s *Snapshot) *Snapshot {
	cs := *(s.ChangeSet)

	return &Snapshot{
		ChangeSet: &cs,
		Version:   s.Version,
	}
}