getter.go

/*
Copyright The Helm 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 getter

import (
	"bytes"
	"fmt"

	"k8s.io/helm/pkg/helm/environment"
)

// Getter is an interface to support GET to the specified URL.
type Getter interface {
	//Get file content by url string
	Get(url string) (*bytes.Buffer, error)
}

// Constructor is the function for every getter which creates a specific instance
// according to the configuration
type Constructor func(URL, CertFile, KeyFile, CAFile string) (Getter, error)

// Provider represents any getter and the schemes that it supports.
//
// For example, an HTTP provider may provide one getter that handles both
// 'http' and 'https' schemes.
type Provider struct {
	Schemes []string
	New     Constructor
}

// Provides returns true if the given scheme is supported by this Provider.
func (p Provider) Provides(scheme string) bool {
	for _, i := range p.Schemes {
		if i == scheme {
			return true
		}
	}
	return false
}

// Providers is a collection of Provider objects.
type Providers []Provider

// ByScheme returns a Provider that handles the given scheme.
//
// If no provider handles this scheme, this will return an error.
func (p Providers) ByScheme(scheme string) (Constructor, error) {
	for _, pp := range p {
		if pp.Provides(scheme) {
			return pp.New, nil
		}
	}
	return nil, fmt.Errorf("scheme %q not supported", scheme)
}

// All finds all of the registered getters as a list of Provider instances.
// Currently the build-in http/https getter and the discovered
// plugins with downloader notations are collected.
func All(settings environment.EnvSettings) Providers {
	result := Providers{
		{
			Schemes: []string{"http", "https"},
			New:     newHTTPGetter,
		},
	}
	pluginDownloaders, _ := collectPlugins(settings)
	result = append(result, pluginDownloaders...)
	return result
}

// ByScheme returns a getter for the given scheme.
//
// If the scheme is not supported, this will return an error.
func ByScheme(scheme string, settings environment.EnvSettings) (Provider, error) {
	// Q: What do you call a scheme string who's the boss?
	// A: Bruce Schemestring, of course.
	a := All(settings)
	for _, p := range a {
		if p.Provides(scheme) {
			return p, nil
		}
	}
	return Provider{}, fmt.Errorf("scheme %q not supported", scheme)
}