// +build linux,apparmor

package apparmor

import (
	"bufio"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"path"
	"strconv"
	"strings"
	"text/template"

	runcaa "github.com/opencontainers/runc/libcontainer/apparmor"
)

// IsEnabled returns true if AppArmor is enabled on the host.
func IsEnabled() bool {
	return runcaa.IsEnabled()
}

// profileData holds information about the given profile for generation.
type profileData struct {
	// Name is profile name.
	Name string
	// Imports defines the apparmor functions to import, before defining the profile.
	Imports []string
	// InnerImports defines the apparmor functions to import in the profile.
	InnerImports []string
	// Version is the {major, minor, patch} version of apparmor_parser as a single number.
	Version int
}

// generateDefault creates an apparmor profile from ProfileData.
func (p *profileData) generateDefault(out io.Writer) error {
	compiled, err := template.New("apparmor_profile").Parse(libpodProfileTemplate)
	if err != nil {
		return err
	}

	if macroExists("tunables/global") {
		p.Imports = append(p.Imports, "#include <tunables/global>")
	} else {
		p.Imports = append(p.Imports, "@{PROC}=/proc/")
	}

	if macroExists("abstractions/base") {
		p.InnerImports = append(p.InnerImports, "#include <abstractions/base>")
	}

	ver, err := getAAParserVersion()
	if err != nil {
		return err
	}
	p.Version = ver

	return compiled.Execute(out, p)
}

// macrosExists checks if the passed macro exists.
func macroExists(m string) bool {
	_, err := os.Stat(path.Join(profileDirectory, m))
	return err == nil
}

// InstallDefault generates a default profile in a temp directory determined by
// os.TempDir(), then loads the profile into the kernel using 'apparmor_parser'.
func InstallDefault(name string) error {
	p := profileData{
		Name: name,
	}

	// Install to a temporary directory.
	f, err := ioutil.TempFile("", name)
	if err != nil {
		return err
	}
	profilePath := f.Name()

	defer f.Close()
	defer os.Remove(profilePath)

	if err := p.generateDefault(f); err != nil {
		return err
	}

	return loadProfile(profilePath)
}

// IsLoaded checks if a profile with the given name has been loaded into the
// kernel.
func IsLoaded(name string) (bool, error) {
	file, err := os.Open("/sys/kernel/security/apparmor/profiles")
	if err != nil {
		if os.IsNotExist(err) {
			return false, nil
		}
		return false, err
	}
	defer file.Close()

	r := bufio.NewReader(file)
	for {
		p, err := r.ReadString('\n')
		if err == io.EOF {
			break
		}
		if err != nil {
			return false, err
		}
		if strings.HasPrefix(p, name+" ") {
			return true, nil
		}
	}

	return false, nil
}

// execAAParser runs `apparmor_parser` with the passed arguments.
func execAAParser(dir string, args ...string) (string, error) {
	c := exec.Command("apparmor_parser", args...)
	c.Dir = dir

	output, err := c.CombinedOutput()
	if err != nil {
		return "", fmt.Errorf("running `%s %s` failed with output: %s\nerror: %v", c.Path, strings.Join(c.Args, " "), output, err)
	}

	return string(output), nil
}

// loadProfile runs `apparmor_parser -Kr` on a specified apparmor profile to
// replace the profile. The `-K` is necessary to make sure that apparmor_parser
// doesn't try to write to a read-only filesystem.
func loadProfile(profilePath string) error {
	_, err := execAAParser("", "-Kr", profilePath)
	return err
}

// getAAParserVersion returns the major and minor version of apparmor_parser.
func getAAParserVersion() (int, error) {
	output, err := execAAParser("", "--version")
	if err != nil {
		return -1, err
	}
	return parseAAParserVersion(output)
}

// parseAAParserVersion parses the given `apparmor_parser --version` output and
// returns the major and minor version number as an integer.
func parseAAParserVersion(output string) (int, error) {
	// output is in the form of the following:
	// AppArmor parser version 2.9.1
	// Copyright (C) 1999-2008 Novell Inc.
	// Copyright 2009-2012 Canonical Ltd.
	lines := strings.SplitN(output, "\n", 2)
	words := strings.Split(lines[0], " ")
	version := words[len(words)-1]

	// split by major minor version
	v := strings.Split(version, ".")
	if len(v) == 0 || len(v) > 3 {
		return -1, fmt.Errorf("parsing version failed for output: `%s`", output)
	}

	// Default the versions to 0.
	var majorVersion, minorVersion, patchLevel int

	majorVersion, err := strconv.Atoi(v[0])
	if err != nil {
		return -1, err
	}

	if len(v) > 1 {
		minorVersion, err = strconv.Atoi(v[1])
		if err != nil {
			return -1, err
		}
	}
	if len(v) > 2 {
		patchLevel, err = strconv.Atoi(v[2])
		if err != nil {
			return -1, err
		}
	}

	// major*10^5 + minor*10^3 + patch*10^0
	numericVersion := majorVersion*1e5 + minorVersion*1e3 + patchLevel
	return numericVersion, nil

}