/*
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 dockerfile implements the required components for working with dockerfile image definitions
package dockerfile

import (
	"errors"
	"fmt"
	"os"
	"strings"

	log "github.com/sirupsen/logrus"

	buildkitDockerfileInstructions "github.com/moby/buildkit/frontend/dockerfile/instructions"
	buildkitDockerfileParser "github.com/moby/buildkit/frontend/dockerfile/parser"

	"sothr.com/warricksothr/pinned-package-updater/internal/parser"
)

// Parse reads a Dockerfile, interprets the AST and returns information about the image(s) and package(s) defined
func Parse(dockerfilePath string) (parser.ParseResult, error) {
	dockerfile, err := os.Open(dockerfilePath)
	if err != nil {
		log.Fatalf("Unexpected error reading file %s: %s", dockerfilePath, err)
		return parser.ParseResult{}, err
	}
	defer func(dockerfile *os.File) {
		err := dockerfile.Close()
		if err != nil {
			log.Error("Unexpected error closing file %s: %s", dockerfilePath, err)
		}
	}(dockerfile)

	dockerfileParseResults, err := buildkitDockerfileParser.Parse(dockerfile)
	if err != nil {
		log.Fatalf("Unexpected error parsing Dockerfile %s: %s", dockerfilePath, err)
		return parser.ParseResult{}, err
	}

	dockerfileParseResult, err := parseDockerfileAST(dockerfileParseResults.AST)
	if err != nil {
		log.Fatalf("Unexpected error while parsing AST for %s: %s", dockerfilePath, err)
		return parser.ParseResult{}, err
	}

	return dockerfileParseResult, nil
}

type ASTStage struct {
	children []*buildkitDockerfileParser.Node
}

// parseDockerfileAST Read the parsed AST and extract the required information from each stage
func parseDockerfileAST(dockerfileAST *buildkitDockerfileParser.Node) (parser.ParseResult, error) {

	dockerfileStages, _, err := buildkitDockerfileInstructions.Parse(dockerfileAST)
	if err != nil {
		log.Fatal("Unexpected error while parsing Dockerfile Instructions")
		return parser.ParseResult{}, err
	}

	var stages []*parser.Stage
	for stageIndex, stage := range dockerfileStages {
		stage, err := parseDockerfileStage(stage)
		if err != nil {
			log.Fatal("Unexpected error while parsing stage %d", stageIndex)
			return parser.ParseResult{}, err
		}
		stages = append(stages, &stage)
	}

	return parser.ParseResult{Stages: stages}, nil
}

func parseDockerfileStage(dockerfileStage buildkitDockerfileInstructions.Stage) (parser.Stage, error) {

	imageParts := strings.Split(dockerfileStage.BaseName, ":")

	if len(imageParts) < 2 {
		message := fmt.Sprintf("Not enough information in image (%s) to determine base", imageParts)
		log.Fatal(message)
		return parser.Stage{}, errors.New(message)
	}

	name := dockerfileStage.Name
	image := parser.Image{
		Name: imageParts[0],
		Tag:  imageParts[1],
	}

	commandParser, err := parser.GetCommandParser(image)
	if err != nil {
		log.Fatalf("Unexpected error while determining command parser for image %s", image)
		return parser.Stage{}, err
	}

	repositories, err := parseRepositoriesFromDockerfileStage(dockerfileStage, commandParser)
	if err != nil {
		message := fmt.Sprintf("Unexpected error while parsing repositories from stage")
		log.Fatal(message)
		return parser.Stage{}, errors.New(message)
	}

	packages, err := parsePackagesFromDockerfileStage(dockerfileStage, commandParser)
	if err != nil {
		message := fmt.Sprintf("Unexpected error while parsing packages from stage")
		log.Fatal(message)
		return parser.Stage{}, errors.New(message)
	}

	return parser.Stage{
		Name:         name,
		Image:        &image,
		Repositories: repositories,
		Packages:     packages,
	}, nil
}

func parseRepositoriesFromDockerfileStage(dockerfileStage buildkitDockerfileInstructions.Stage, commandParser *parser.CommandParser) ([]*parser.Repository, error) {
	var repositories []*parser.Repository
	typedCommandParser := *commandParser

	for _, command := range dockerfileStage.Commands {
		switch command.(type) {
		case *buildkitDockerfileInstructions.RunCommand:
			runCommand := command.(*buildkitDockerfileInstructions.RunCommand)

			log.Tracef("Parsing RunCommand \"%s\" for repositories", runCommand.CmdLine)

			_, err := typedCommandParser.GetRepositories(runCommand.CmdLine[0])
			if err != nil {
				return nil, err
			}
		}
	}

	return repositories, nil
}

func parsePackagesFromDockerfileStage(dockerfileStage buildkitDockerfileInstructions.Stage, commandParser *parser.CommandParser) ([]*parser.Package, error) {
	var packages []*parser.Package
	typedCommandParser := *commandParser

	for _, command := range dockerfileStage.Commands {
		switch command.(type) {
		case *buildkitDockerfileInstructions.RunCommand:
			runCommand := command.(*buildkitDockerfileInstructions.RunCommand)

			log.Tracef("Parsing RunCommand \"%s\" for packages", runCommand.CmdLine)

			_, err := typedCommandParser.GetPinnedPackages(runCommand.CmdLine[0])
			if err != nil {
				return nil, err
			}
		}
	}

	return packages, nil
}