pinned-package-updater/internal/parser/parser.go

/*
Copyright © 2021 Drew Short <warrick@sothr.com>

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 parser implements the required components for working with image definitions
package parser

import (
	"errors"
	"fmt"

	log "github.com/sirupsen/logrus"
)

// ParseResult is the standard representation for am image declaration
type ParseResult struct {
	Stages []*Stage
}

// Stage is the representation of a stage in the image declaration
type Stage struct {
	Name         string
	Image        *Image
	Repositories []*Repository
	Packages     []*Package
}

// Image is the representation of the reference to a container image layer
type Image struct {
	Name string
	Tag  string
}

// Package is the representation of an installed pinned package defined in an image stage declaration
type Package struct {
	Name    string
	Version string
}

// Repository is the representation of an added repository defined in a stage declaration
type Repository struct {
	Information string
}

// CommandParserType represents the recognized type of parser usable for a specific image
type CommandParserType int

const (
	CommandParserTypeDebian CommandParserType = iota
)

// CommandParserTypeIds is a lookup map between CommandParserType and a representation string
var commandParserTypeIds = map[CommandParserType][]string{
	CommandParserTypeDebian: {"debian"},
}

func lookupCommandParserTypeName(parserType CommandParserType) string {
	if parserTypeName, ok := commandParserTypeIds[parserType]; ok {
		return parserTypeName[0]
	} else {
		return "UNKNOWN"
	}
}

var availableCommandParsers = map[CommandParserType]CommandParser{}

// CommandParser handles parsing commands from RUN arguments dependent on the base image type
type CommandParser interface {
	GetRepositories(runCommand string) ([]*Repository, error)
	GetPinnedPackages(runCommand string) ([]*Package, error)
}

// InitCommandParsers exposes functionality to configure the behavior of mapping images to a CommandParser
func InitCommandParsers() error {

	// Registering known parsers
	availableCommandParsers[CommandParserTypeDebian] = newDebianCommandParser()

	return nil
}

func GetCommandParser(image Image) (*CommandParser, error) {
	parserType, determineParserErr := determineParserForImage(image)
	if determineParserErr != nil {
		log.Fatalf("Failed to determine a matching CommandParser for %s: %s", image, determineParserErr)
		return nil, determineParserErr
	}

	if requestedCommandParser, ok := availableCommandParsers[parserType]; ok {
		return &requestedCommandParser, nil
	} else {
		message := fmt.Sprintf("Unable to identify parser for %s", lookupCommandParserTypeName(parserType))
		log.Fatal(message)
		return nil, errors.New(message)
	}
}

// determineParserForImage matches image information to the correct CommandParserType
func determineParserForImage(_ Image) (CommandParserType, error) {

	// TODO: Map image information to the list of command parsers supported

	return CommandParserTypeDebian, nil
}