// Copyright 2014 The Gogs Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package models

import (
	"bufio"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/Unknwon/com"

	"github.com/gogits/gogs/modules/log"
)

const (
	// "### autogenerated by gitgos, DO NOT EDIT\n"
	TPL_PUBLICK_KEY = `command="%s serv key-%d",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty %s`
)

var (
	ErrKeyAlreadyExist = errors.New("Public key already exist")
)

var sshOpLocker = sync.Mutex{}

var (
	sshPath string
	appPath string
)

// exePath returns the executable path.
func exePath() (string, error) {
	file, err := exec.LookPath(os.Args[0])
	if err != nil {
		return "", err
	}
	return filepath.Abs(file)
}

// homeDir returns the home directory of current user.
func homeDir() string {
	home, err := com.HomeDir()
	if err != nil {
		return "/"
	}
	return home
}

func init() {
	var err error

	appPath, err = exePath()
	if err != nil {
		fmt.Printf("publickey.init(fail to get app path): %v\n", err)
		os.Exit(2)
	}

	// Determine and create .ssh path.
	sshPath = filepath.Join(homeDir(), ".ssh")
	if err = os.MkdirAll(sshPath, os.ModePerm); err != nil {
		fmt.Printf("publickey.init(fail to create sshPath(%s)): %v\n", sshPath, err)
		os.Exit(2)
	}
}

// PublicKey represents a SSH key of user.
type PublicKey struct {
	Id          int64
	OwnerId     int64  `xorm:"UNIQUE(s) INDEX NOT NULL"`
	Name        string `xorm:"UNIQUE(s) NOT NULL"`
	Fingerprint string
	Content     string    `xorm:"TEXT NOT NULL"`
	Created     time.Time `xorm:"CREATED"`
	Updated     time.Time `xorm:"UPDATED"`
}

// GenAuthorizedKey returns formatted public key string.
func GenAuthorizedKey(keyId int64, key string) string {
	return fmt.Sprintf(TPL_PUBLICK_KEY+"\n", appPath, keyId, key)
}

// AddPublicKey adds new public key to database and SSH key file.
func AddPublicKey(key *PublicKey) (err error) {
	// Check if public key name has been used.
	has, err := orm.Get(key)
	if err != nil {
		return err
	} else if has {
		return ErrKeyAlreadyExist
	}

	// Calculate fingerprint.
	tmpPath := strings.Replace(filepath.Join(os.TempDir(), fmt.Sprintf("%d", time.Now().Nanosecond()),
		"id_rsa.pub"), "\\", "/", -1)
	os.MkdirAll(path.Dir(tmpPath), os.ModePerm)
	if err = ioutil.WriteFile(tmpPath, []byte(key.Content), os.ModePerm); err != nil {
		return err
	}
	stdout, stderr, err := com.ExecCmd("ssh-keygen", "-l", "-f", tmpPath)
	if err != nil {
		return errors.New("ssh-keygen -l -f: " + stderr)
	} else if len(stdout) < 2 {
		return errors.New("Not enough output for calculating fingerprint")
	}
	key.Fingerprint = strings.Split(stdout, " ")[1]

	// Save SSH key.
	if _, err = orm.Insert(key); err != nil {
		return err
	}
	if err = SaveAuthorizedKeyFile(key); err != nil {
		if _, err2 := orm.Delete(key); err2 != nil {
			return err2
		}
		return err
	}

	return nil
}

func rewriteAuthorizedKeys(key *PublicKey, p, tmpP string) error {
	// Delete SSH key in SSH key file.
	sshOpLocker.Lock()
	defer sshOpLocker.Unlock()

	fr, err := os.Open(p)
	if err != nil {
		return err
	}
	defer fr.Close()

	fw, err := os.Create(tmpP)
	if err != nil {
		return err
	}
	defer fw.Close()

	buf := bufio.NewReader(fr)
	for {
		line, errRead := buf.ReadString('\n')
		line = strings.TrimSpace(line)

		if errRead != nil {
			if errRead != io.EOF {
				return errRead
			}

			// Reached end of file, if nothing to read then break,
			// otherwise handle the last line.
			if len(line) == 0 {
				break
			}
		}

		// Found the line and copy rest of file.
		if strings.Contains(line, fmt.Sprintf("key-%d", key.Id)) && strings.Contains(line, key.Content) {
			continue
		}
		// Still finding the line, copy the line that currently read.
		if _, err = fw.WriteString(line + "\n"); err != nil {
			return err
		}

		if errRead == io.EOF {
			break
		}
	}
	return nil
}

// DeletePublicKey deletes SSH key information both in database and authorized_keys file.
func DeletePublicKey(key *PublicKey) (err error) {
	// Delete SSH key in database.
	has, err := orm.Id(key.Id).Get(key)
	if err != nil {
		return err
	} else if !has {
		return errors.New("Public key does not exist")
	}
	if _, err = orm.Delete(key); err != nil {
		return err
	}

	p := filepath.Join(sshPath, "authorized_keys")
	tmpP := filepath.Join(sshPath, "authorized_keys.tmp")
	log.Trace("ssh.DeletePublicKey(authorized_keys): %s", p)

	if err = rewriteAuthorizedKeys(key, p, tmpP); err != nil {
		return err
	} else if err = os.Remove(p); err != nil {
		return err
	}
	return os.Rename(tmpP, p)
}

// ListPublicKey returns a list of public keys that user has.
func ListPublicKey(userId int64) ([]PublicKey, error) {
	keys := make([]PublicKey, 0)
	err := orm.Find(&keys, &PublicKey{OwnerId: userId})
	return keys, err
}

// SaveAuthorizedKeyFile writes SSH key content to SSH key file.
func SaveAuthorizedKeyFile(key *PublicKey) error {
	sshOpLocker.Lock()
	defer sshOpLocker.Unlock()

	p := filepath.Join(sshPath, "authorized_keys")
	f, err := os.OpenFile(p, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0600)
	if err != nil {
		return err
	}
	defer f.Close()

	_, err = f.WriteString(GenAuthorizedKey(key.Id, key.Content))
	return err
}