package plugin

import (
	"context"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"

	"golang.org/x/xerrors"
	yaml "gopkg.in/yaml.v3"

	"github.com/aquasecurity/trivy/pkg/downloader"
	"github.com/aquasecurity/trivy/pkg/log"
	"github.com/aquasecurity/trivy/pkg/utils"
)

const (
	configFile  = "plugin.yaml"
	xdgDataHome = "XDG_DATA_HOME"
)

var (
	pluginsRelativeDir = filepath.Join(".trivy", "plugins")

	officialPlugins = map[string]string{
		"kubectl": "github.com/aquasecurity/trivy-plugin-kubectl",
	}
)

// Plugin represents a plugin.
type Plugin struct {
	Name        string     `yaml:"name"`
	Repository  string     `yaml:"repository"`
	Version     string     `yaml:"version"`
	Usage       string     `yaml:"usage"`
	Description string     `yaml:"description"`
	Platforms   []Platform `yaml:"platforms"`

	// runtime environment for testability
	GOOS   string `yaml:"_goos"`
	GOARCH string `yaml:"_goarch"`
}

// Platform represents where the execution file exists per platform.
type Platform struct {
	Selector *Selector
	URI      string
	Bin      string
}

// Selector represents the environment.
type Selector struct {
	OS   string
	Arch string
}

// Run runs the plugin
func (p Plugin) Run(ctx context.Context, args []string) error {
	platform, err := p.selectPlatform()
	if err != nil {
		return xerrors.Errorf("platform selection error: %w", err)
	}

	execFile := filepath.Join(dir(), p.Name, platform.Bin)

	cmd := exec.CommandContext(ctx, execFile, args...)
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	cmd.Env = os.Environ()

	// If an error is found during the execution of the plugin, figure
	// out if the error was from not being able to execute the plugin or
	// an error set by the plugin itself.
	if err = cmd.Run(); err != nil {
		if _, ok := err.(*exec.ExitError); !ok {
			return xerrors.Errorf("exit: %w", err)
		}

		return xerrors.Errorf("plugin exec: %w", err)
	}

	return nil
}

func (p Plugin) selectPlatform() (Platform, error) {
	// These values are only filled in during unit tests.
	if p.GOOS == "" {
		p.GOOS = runtime.GOOS
	}
	if p.GOARCH == "" {
		p.GOARCH = runtime.GOARCH
	}

	for _, platform := range p.Platforms {
		if platform.Selector == nil {
			return platform, nil
		}

		selector := platform.Selector
		if (selector.OS == "" || p.GOOS == selector.OS) &&
			(selector.Arch == "" || p.GOARCH == selector.Arch) {
			log.Logger.Debugf("Platform found, os: %s, arch: %s", selector.OS, selector.Arch)
			return platform, nil
		}
	}
	return Platform{}, xerrors.New("platform not found")
}

func (p Plugin) install(ctx context.Context, dst, pwd string) error {
	log.Logger.Debugf("Installing the plugin to %s...", dst)
	platform, err := p.selectPlatform()
	if err != nil {
		return xerrors.Errorf("platform selection error: %w", err)
	}

	log.Logger.Debugf("Downloading the execution file from %s...", platform.URI)
	if err = downloader.Download(ctx, platform.URI, dst, pwd); err != nil {
		return xerrors.Errorf("unable to download the execution file (%s): %w", platform.URI, err)
	}
	return nil
}

func (p Plugin) dir() (string, error) {
	if p.Name == "" {
		return "", xerrors.Errorf("'name' is empty")
	}

	// e.g. ~/.trivy/plugins/kubectl
	return filepath.Join(dir(), p.Name), nil
}

// Install installs a plugin
func Install(ctx context.Context, url string, force bool) (Plugin, error) {
	// Replace short names with full qualified names
	// e.g. kubectl => github.com/aquasecurity/trivy-plugin-kubectl
	if v, ok := officialPlugins[url]; ok {
		url = v
	}

	if !force {
		// If the plugin is already installed, it skips installing the plugin.
		if p, installed := isInstalled(url); installed {
			return p, nil
		}
	}

	log.Logger.Infof("Installing the plugin from %s...", url)
	tempDir, err := downloader.DownloadToTempDir(ctx, url)
	if err != nil {
		return Plugin{}, xerrors.Errorf("download failed: %w", err)
	}
	defer os.RemoveAll(tempDir)

	log.Logger.Info("Loading the plugin metadata...")
	plugin, err := loadMetadata(tempDir)
	if err != nil {
		return Plugin{}, xerrors.Errorf("failed to load the plugin metadata: %w", err)
	}

	pluginDir, err := plugin.dir()
	if err != nil {
		return Plugin{}, xerrors.Errorf("failed to determine the plugin dir: %w", err)
	}

	if err = plugin.install(ctx, pluginDir, tempDir); err != nil {
		return Plugin{}, xerrors.Errorf("failed to install the plugin: %w", err)
	}

	// Copy plugin.yaml into the plugin dir
	if _, err = utils.CopyFile(filepath.Join(tempDir, configFile), filepath.Join(pluginDir, configFile)); err != nil {
		return Plugin{}, xerrors.Errorf("failed to copy plugin.yaml: %w", err)
	}

	return plugin, nil
}

// Uninstall installs the plugin
func Uninstall(name string) error {
	pluginDir := filepath.Join(dir(), name)
	return os.RemoveAll(pluginDir)
}

// LoadAll loads all plugins
func LoadAll() ([]Plugin, error) {
	pluginsDir := dir()
	dirs, err := os.ReadDir(pluginsDir)
	if err != nil {
		return nil, xerrors.Errorf("failed to read %s: %w", pluginsDir, err)
	}

	var plugins []Plugin
	for _, d := range dirs {
		if !d.IsDir() {
			continue
		}
		plugin, err := loadMetadata(filepath.Join(pluginsDir, d.Name()))
		if err != nil {
			log.Logger.Warnf("plugin load error: %s", err)
			continue
		}
		plugins = append(plugins, plugin)
	}
	return plugins, nil
}

func loadMetadata(dir string) (Plugin, error) {
	filePath := filepath.Join(dir, configFile)
	f, err := os.Open(filePath)
	if err != nil {
		return Plugin{}, xerrors.Errorf("file open error: %w", err)
	}

	var plugin Plugin
	if err = yaml.NewDecoder(f).Decode(&plugin); err != nil {
		return Plugin{}, xerrors.Errorf("yaml decode error: %w", err)
	}

	return plugin, nil
}

func dir() string {
	dataHome := os.Getenv(xdgDataHome)
	if dataHome != "" {
		return filepath.Join(dataHome, pluginsRelativeDir)
	}

	homeDir, _ := os.UserHomeDir()
	return filepath.Join(homeDir, pluginsRelativeDir)
}

func isInstalled(url string) (Plugin, bool) {
	installedPlugins, err := LoadAll()
	if err != nil {
		return Plugin{}, false
	}

	for _, plugin := range installedPlugins {
		if plugin.Repository == url {
			return plugin, true
		}
	}
	return Plugin{}, false
}