resources.go

// Copyright 2019 Torben Schinke
//
// 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
//
//     https://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 main

import (
	"encoding/xml"
	"fmt"
	"io/ioutil"
	"runtime"
)

// A Resource has a unique combination of name, version, os and architecture.
type Resource struct {
	// Name of the resource e.g. go
	Name string `xml:"name,attr"`

	// URL to download, e.g. https://dl.google.com/go/go1.12.4.darwin-amd64.tar.gz
	URL string `xml:"url,attr"`

	// Version of the resource e.g. 1.12.4
	Version string `xml:"version,attr"`

	// OS e.g. darwin
	OS string `xml:"os,attr"`

	// Arch e.g. amd64
	Arch string `xml:"arch,attr"`
}

func (r Resource) String() string {
	return r.Name + "@" + r.Version + "[" + r.OS + "|" + r.Arch + "]"
}

type resources struct {
	XMLName   xml.Name   `xml:"resources"`
	Resources []Resource `xml:"r"`
}

// Resources is just a slice of resources
type Resources []Resource

// Get loops over all resources and returns the fitting resource for the current os/arch combination
func (r *Resources) Get(name string, version string) (Resource, error) {
	for _, e := range *r {
		if e.Name == name && e.Version == version && e.Arch == runtime.GOARCH && e.OS == runtime.GOOS {
			return e, nil
		}
	}
	// try to find something unspecific
	for _, e := range *r {
		if e.Name == name && e.Version == version && e.Arch == "" && e.OS == "" {
			return e, nil
		}
	}

	return Resource{}, fmt.Errorf("no such resource: %s@%s for os=%s and arch=%s", name, version, runtime.GOOS, runtime.GOARCH)
}

// Load parses a local xml file and replaces the contents of resources
func (r *Resources) Load(fname Path) error {
	tmp := &resources{}
	*r = make([]Resource, 0)
	data, err := ioutil.ReadFile(fname.String())
	if err != nil {
		return fmt.Errorf("unable to read xml file: %v", err)
	}
	err = xml.Unmarshal(data, tmp)
	if err != nil {
		return fmt.Errorf("unable to parse xml: %v", err)
	}
	*r = tmp.Resources
	return nil
}