#!/bin/sh
#
# pash - simple password manager.

pw_add() {
    name=$1

    if yn "Generate a password?"; then
        # Use 'gpg' to generate the password. This could have
        # been 'openssl', '/dev/[u]random' or another utility,
        # however sticking to 'gpg' removes the need for another
        # dependency.
        #
        # The '-a' flag outputs the random bytes as a 'base64'
        # encoded string to allow for the password to be used as
        # well, a password.
        #
        # The 'cut' is required to actually truncate the password
        # to the set length as the 'base64' encoding makes the
        # resulting string longer than the given length.
        pass=$("$gpg" -a --gen-random 1 "${PASH_LENGTH:-50}" |\
               cut -c -"${PASH_LENGTH:-50}")

    else
        printf 'Enter password: '

        stty -echo
        read -r pass
        stty echo

        printf '\n'
    fi

    [ "$pass" ] || die "Failed to generate a password."

    # Mimic the use of an array for storing arguments by... using
    # the function's argument list. This is very apt isn't it?
    if [ "$PASH_KEYID" ]; then
        set -- --trust-model always -aer "$PASH_KEYID"
    else
        set -- -c
    fi

    # Use 'gpg' to store the password in an encrypted file. The
    # 'GPG_TTY' environment variable is set to workaround cases
    # where 'gpg' cannot find an attached terminal.
    echo "$pass" | GPG_TTY=$(tty) "$gpg" "$@" -o "$name.gpg" &&
        printf '%s\n' "Saved '$name' to the store."
}

pw_del() {
    yn "Delete pass file '$1'?" && {
        rm -f "$1.gpg"
        rmdir -p "${1%/*}" 2>/dev/null
    }
}

pw_show() {
    pass=$("$gpg" -dq "$1.gpg")

    # If '$2' is defined, don't print the password to the
    # terminal. For example, this is used when the password is
    # copied to the clipboard.
    [ "$2" ] || printf '%s\n' "$pass"
}

pw_copy() {
    pw_show "$1" copy

    if [ "$TMUX" ]; then
        tmux load-buffer "$pass"

    elif hash xclip; then
        echo "$pass" | xclip -selection clipboard
    fi
}

pw_list() {
    if hash tree 2>/dev/null; then
        tree --noreport
    else
        find . -mindepth 1
    fi
}

yn() {
    printf '%s [y/n]: ' "$1"

    # Enable raw input to allow for a single byte to be read from
    # stdin without needing to wait for the user to press Return.
    stty -icanon

    # Read a single byte from stdin using 'dd'. POSIX 'read' has
    # no support for single/'N' byte based input from the user.
    REPLY=$(dd ibs=1 count=1 2>/dev/null)

    # Disable raw input, leaving the terminal how we *should*
    # have found it.
    stty icanon

    printf '\n'

    # Handle the answer here directly, enabling this function's
    # return status to be used in place of checking for '[yY]'
    # throughout this program.
    glob "$REPLY" '[yY]' || return 1 && return 0
}

glob() {
    # This is a simple wrapper around a case statement to allow
    # for simple string comparisons against globs.
    #
    # Example: if glob "Hello World" '* World'; then
    case $1 in $2) return 0; esac; return 1
}

die() {
    printf 'error: %s\n' "$1" >&2
    exit 1
}

usage() { printf %s "\
pash 1.0.0 - simple password manager.

=> [a]dd  [name] - Create a new password entry.
=> [c]opy [name] - Copy entry to the clipboard.
=> [d]el  [name] - Delete a password entry.
=> [l]ist        - List all entries.
=> [s]how [name] - Show password for an entry.

Using a key pair: export PASH_KEYID=XXXXXXXX
Password length:  export PASH_LENGTH=50
Store location:   export PASH_DIR=~/.local/share/pash
"
exit 1
}

main() {
    : "${PASH_DIR:=${XDG_DATA_HOME:=$HOME/.local/share}/pash}"

    [ "$1" = '-?' ] || [ -z "$1" ] &&
        usage

    # Look for both 'gpg' and 'gpg2',
    # preferring 'gpg2' if it is available.
    hash gpg  2>/dev/null && gpg=gpg
    hash gpg2 2>/dev/null && gpg=gpg2

    [ "$gpg" ] || die "GPG not found."

    mkdir -p "$PASH_DIR" ||
        die "Couldn't create password directory."

    cd "$PASH_DIR" ||
        die "Can't access password directory."

    glob "$1" '[acds]*' && [ -z "$2" ] &&
        die "Missing [name] argument."

    glob "$1" '[cds]*' && [ ! -f "$2.gpg" ] &&
        die "Pass file '$2' doesn't exist."

    glob "$1" 'a*' && [ -f "$2.gpg" ] &&
        die "Pass file '$2' already exists."

    glob "$2" '*/*' && glob "$2" '*../*' &&
        die "Category went out of bounds."

    glob "$2" '/*' &&
        die "Category can't start with '/'."

    glob "$2" '*/*' && {
        mkdir -p "${2%/*}" ||
            die "Couldn't create category '${2%/*}'."
    }

    umask 077

    case $1 in
        a*) pw_add  "$2" ;;
        c*) pw_copy "$2" ;;
        d*) pw_del  "$2" ;;
        s*) pw_show "$2" ;;
        l*) pw_list ;;
        *)  usage
    esac
}

main "$@"