package saltyim

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	"github.com/keys-pub/keys"
	"go.mills.io/salty"
)

func readUser(fd io.Reader) (*Addr, error) {
	scan := bufio.NewScanner(fd)

	for scan.Scan() {
		if strings.HasPrefix(scan.Text(), "# user:") {
			addr, err := ParseAddr(strings.TrimSpace(strings.TrimPrefix(scan.Text(), "# user:")))
			if err == nil {
				return addr, nil
			}
		}
	}
	return nil, scan.Err()
}

// DefaultIdentity returns a default identity file (if one exists) otherwise
// returns an empty string
func DefaultIdentity() string {
	return os.ExpandEnv("$HOME/.config/salty/$USER.key")
}

// CreateIdentity ...
func CreateIdentity(options ...IdentityOption) (*Identity, error) {
	ident := &Identity{}
	for _, option := range options {
		option(ident)
	}

	if ident.addr == nil || ident.addr.IsZero() {
		return nil, fmt.Errorf("unable to find user address in options")
	}

	buf := &bytes.Buffer{}

	key, _ := salty.GenerateKeys(buf)
	ident.key = key

	buf.Write([]byte(fmt.Sprintf("# user: %s\n", ident.addr.String())))

	ident.contents = buf.Bytes()

	if ident.path == "" {
		return ident, nil
	}

	fn := ident.path
	fn = FixUnixHome(fn)

	f, err := os.OpenFile(fn, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0600)
	if err != nil {
		return ident, fmt.Errorf("error opening identity %q for writing: %w", fn, err)
	}
	defer f.Close()

	if _, err := f.Write(ident.contents); err != nil {
		return ident, fmt.Errorf("error writing identity %q: %w", fn, err)
	}

	if err := f.Sync(); err != nil {
		return ident, fmt.Errorf("error syncing identity %q for writing: %w", fn, err)
	}

	if err := f.Close(); err != nil {
		return ident, fmt.Errorf("error closing identity %q for writing: %w", fn, err)
	}

	return ident, nil
}

// GetIdentity ...
func GetIdentity(options ...IdentityOption) (*Identity, error) {
	ident := &Identity{}
	for _, option := range options {
		option(ident)
	}

	if ident.key != nil && ident.addr != nil {
		return ident, nil
	}

	if ident.path != "" {
		fn := ident.path
		fn = FixUnixHome(fn)

		id, err := os.Open(fn)
		if err != nil {
			return ident, fmt.Errorf("error opening identity %q: %w", ident.Source(), err)
		}
		defer id.Close()
		identityBytes, err := ioutil.ReadAll(id)
		if err != nil {
			return ident, fmt.Errorf("error opening identity %q: %w", ident.Source(), err)
		}
		ident.contents = identityBytes
	}

	key, err := salty.ParseIdentity(bytes.NewBuffer(ident.contents))
	if err != nil {
		return ident, fmt.Errorf("error reading identity %q: %w", ident.Source(), err)
	}
	ident.key = key

	me, err := readUser(bytes.NewBuffer(ident.contents))
	ident.addr = me

	return ident, err
}

// GetOrCreateIdentity ...
func GetOrCreateIdentity(options ...IdentityOption) (*Identity, error) {
	ident, err := GetIdentity(options...)
	if err != nil {
		ident, err = CreateIdentity(options...)
	}
	return ident, err
}

// Identity allows interaction with CreateIdentity, GetIdentity, and NewClient
type Identity struct {
	// path where identity is read or written to
	path string

	// contents where identity is read from or stored
	contents []byte

	// key is the identity key
	key *keys.EdX25519Key

	// addr is the user / endpoint
	addr *Addr
}

func (i *Identity) Source() string {
	if i != nil && i.path != "" {
		return i.path
	}
	return "[]byte"
}

func (i *Identity) Contents() []byte {
	return i.contents
}

func (i *Identity) Key() *keys.EdX25519Key {
	return i.key
}

func (i *Identity) Addr() *Addr {
	return i.addr
}

// IdentityOption represents functional options for various identity operations
type IdentityOption func(*Identity)

// WithIdentityAddr sets the identity Addr option
func WithIdentityAddr(addr *Addr) IdentityOption {
	return func(i *Identity) { i.addr = addr }
}

// WithIdentity indicates that an identity should be passed in
func WithIdentity(ident *Identity) IdentityOption {
	return func(i *Identity) {
		i.key = ident.key
		i.addr = ident.addr
	}
}

// WithIdentityPath indicates that an identity should be read / written from a file path
func WithIdentityPath(path string) IdentityOption {
	return func(i *Identity) { i.path = path }
}

// WithIdentityBytes indicates that the identity should be read from a byte array
func WithIdentityBytes(contents []byte) IdentityOption {
	return func(i *Identity) { i.contents = contents }
}

// Handle unix home with `~`
func FixUnixHome(p string) string {
	// Handle unix home with `~`
	if strings.HasPrefix(p, "~/") {
		dirname, _ := os.UserHomeDir()
		return filepath.Join(dirname, p[2:])
	}
	return p
}