package gpass

import (
	"bufio"
	"encoding/hex"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"os/user"
	"path"
	"regexp"
	"sort"
	"strings"

	"github.com/jcmdev0/gpgagent"

	"golang.org/x/crypto/openpgp"
	"golang.org/x/crypto/openpgp/armor"
	"golang.org/x/crypto/openpgp/packet"
)

var (
	basename *regexp.Regexp
	ask openpgp.PromptFunction
)

func init() {
	basename = regexp.MustCompile(".gpg$")
}

type Store struct {
	Dir string
	keyring openpgp.KeyRing
}

func GetStore() (*Store, error) {
	ret := &Store{}
        u, err := user.Current()
        if err != nil {
                return ret, fmt.Errorf("Can't get current user.")
        }
	ret.Dir = path.Join(u.HomeDir,".password-store")

	fd, err := os.Open(path.Join(u.HomeDir,".gnupg/secring.gpg"))
	defer fd.Close()
	if err != nil {
		return ret, fmt.Errorf("Can't open keyring file")
	}
	kr, err := openpgp.ReadKeyRing(fd)
	if err != nil {
		return ret, fmt.Errorf("Can't open gnupg keyring.")
	}
	ret.keyring = kr
        return ret, nil
}

type caseInsensitive []os.FileInfo

func (fs caseInsensitive) Len() int { return len(fs) }
func (fs caseInsensitive) Swap(i, j int) { fs[i], fs[j] = fs[j], fs[i] }
func (fs caseInsensitive) Less(i, j int) bool {
        return strings.ToLower(fs[i].Name()) < strings.ToLower(fs[j].Name())
}

type Pass struct {
	Pathname string
	Level int
	Dir bool
}

func (s *Store) List() ([]Pass,error) {
	return s.list(0,"")
}

func (s *Store) list(level int, p string) ([]Pass,error) {
	ret := make([]Pass,0)
	dir := path.Join(s.Dir,p)
	fd, err := os.Open(dir)
	defer fd.Close()
	if err != nil {
		return nil, fmt.Errorf("Cannot open password store")
	}
	files, err := fd.Readdir(0)
	if err != nil {
		return nil, fmt.Errorf("Cannot read password store")
	}
	sort.Sort(caseInsensitive(files))
	for _, x := range files {
		n := basename.ReplaceAllLiteralString(x.Name(),"")
		entry := Pass{Pathname: path.Join(p,n),Level: level}

		if n[0] == '.' {
			continue
		}
		if x.IsDir() {
			entry.Dir = true
			ret = append(ret,entry)
			l,err := s.list(level+1,path.Join(p,x.Name()))
			if err != nil {
				return nil,err
			}
			ret = append(ret,l...)
		} else {
			ret = append(ret,entry)
		}
	}
	return ret,nil
}

func AskPass(prompts ...func() []byte) openpgp.PromptFunction {
	var prompt func() []byte
	if len(prompts) > 0 {
		prompt = prompts[0]
	} else {
		prompt = func() []byte {
			fmt.Print("AskPass(): enter passphrase: ")
			reader := bufio.NewReader(os.Stdin)
			text, _ := reader.ReadString('\n')
			return []byte(text[:len(text)-1])
		}
	}

	var err error
	var passphrase []byte
	dec := func(p *packet.PrivateKey) {
		for i := 0; i<3; i++ {
			if err = p.Decrypt(passphrase); err == nil {
				break
			}
			passphrase = prompt()
		}
	}

	var ret openpgp.PromptFunction
	ret = func(keys []openpgp.Key, symmetric bool) ([]byte, error) {
		if !symmetric {
			for _,k := range keys {
				if p := k.PrivateKey; p != nil && p.Encrypted {
					dec(p)
				}
				for _, s := range k.Entity.Subkeys {
					if p := s.PrivateKey; p != nil && p.Encrypted {
						dec(p)
					}
				}
			}
		}
		return passphrase, err
	}
	return ret
}

//https://github.com/jcmdev0/gpgagent/blob/master/example/example.go
func GPGPrompt(keys []openpgp.Key, symmetric bool) ([]byte, error) {
	conn, err := gpgagent.NewGpgAgentConn()
	if err != nil {
		return nil, err
	}
	defer conn.Close()

	for _, key := range keys {
		cacheId := strings.ToUpper(hex.EncodeToString(key.PublicKey.Fingerprint[:]))
		request := gpgagent.PassphraseRequest{CacheKey: cacheId}
		passphrase, err := conn.GetPassphrase(&request)
		if err != nil {
			return nil, err
		}
		err = key.PrivateKey.Decrypt([]byte(passphrase))
		if err != nil {
			return nil, err
		}
		return []byte(passphrase), nil
	}
	return nil, fmt.Errorf("Unable to find key")
}

func (s *Store) Decrypt(name string, prompts ...func() []byte) (string,error) {
	if ask == nil {
		ask = AskPass(prompts...)
	}
	file := path.Join(s.Dir, strings.Join([]string{name,".gpg"},""))
	if _, err := os.Stat(file); os.IsNotExist(err) {
		return "",fmt.Errorf("Not in password store.")
	}
	fd, err := os.Open(file)
	defer fd.Close()
	if err != nil {
		return "",err
	}
	var reader io.Reader
	unarmor, err := armor.Decode(fd)
	if err == nil {
		reader = unarmor.Body
	} else {
		fd.Close()
		fd, err = os.Open(file)
		defer fd.Close()
		if err != nil {
			return "",err
		}
		reader = fd
	}
	md, err := openpgp.ReadMessage(reader,s.keyring,ask,nil)
	if err != nil {
		fmt.Println("Error reading message")
		return "",err
	}
	ra, err := ioutil.ReadAll(md.UnverifiedBody)
	if err != nil {
		return "",err
	}
	return string(ra), nil
}