package main

import (
	"bufio"
	"crypto/rand"
	"fmt"
	"io"
	"math/big"
	"os"
	"strings"

	"golang.org/x/term"
)

const (
	alnum   = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	symbols = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"
)

// readSecret reads a new secret for name. With echo (or when stdin is not a
// terminal, e.g. piped input) it reads a single line; otherwise it prompts
// twice without echo and checks the two entries match.
func readSecret(name string, echo bool) ([]byte, error) {
	if echo || !term.IsTerminal(int(os.Stdin.Fd())) {
		line, err := bufio.NewReader(os.Stdin).ReadString('\n')
		if err != nil && err != io.EOF {
			return nil, err
		}
		return []byte(strings.TrimRight(line, "\r\n")), nil
	}

	fmt.Fprintf(os.Stderr, "Enter password for %s: ", name)
	p1, err := term.ReadPassword(int(os.Stdin.Fd()))
	fmt.Fprintln(os.Stderr)
	if err != nil {
		return nil, err
	}
	fmt.Fprintf(os.Stderr, "Retype password for %s: ", name)
	p2, err := term.ReadPassword(int(os.Stdin.Fd()))
	fmt.Fprintln(os.Stderr)
	if err != nil {
		return nil, err
	}
	if string(p1) != string(p2) {
		return nil, errf("the entered passwords do not match")
	}
	return p1, nil
}

// genPassword returns a cryptographically random password.
func genPassword(length int, withSymbols bool) (string, error) {
	if length <= 0 {
		length = 25
	}
	charset := alnum
	if withSymbols {
		charset += symbols
	}
	buf := make([]byte, length)
	max := big.NewInt(int64(len(charset)))
	for i := range buf {
		n, err := rand.Int(rand.Reader, max)
		if err != nil {
			return "", err
		}
		buf[i] = charset[n.Int64()]
	}
	return string(buf), nil
}

func defaultLength() int {
	return atoiDefault(os.Getenv("PASSWORD_STORE_GENERATED_LENGTH"), 25)
}