#!/bin/zsh
# vim:ft=zsh

local ALPHA_SET='A-Za-z'
local NUMERIC_SET='0-9'
local SYM_SET='!@#$%^&*'
local XSYM_SET="${SYM_SET}.;:-+="
local ALNUM_SET="${ALPHA_SET}${NUMERIC_SET}"
local ALL_SET="${ALNUM_SET}${SYM_SET}"
local XALL_SET="${ALNUM_SET}${XSYM_SET}"

local -i length=16 count=1
local charset="$ALL_SET"

while getopts 'c:l:s:' opt; do
    case $opt in
        c) count=$OPTARG;;
        l) length=$OPTARG;;
        s) case $OPTARG in
               alpha) charset="$ALPHA_SET";;
               num) charset="$NUMERIC_SET";;
               alnum) charset="$ALNUM_SET";;
               sym) charset="$SYM_SET";;
               xsym) charset="$XSYM_SET";;
               all) charset="$ALL_SET";;
               xall) charset="$XALL_SET";;
               *) echo "Invalid set name: $OPTARG" 1>&2; return -2;;
           esac
           ;;
        *) echo "Invalid argument: $opt" 1>&2; return -1;;
    esac
done

local cmd='tr -dc "$charset" < /dev/urandom | fold -w $length | head -n $count'

if [[ $SYS == 'darwin' ]]; then
    # The way OS X >=10.6 handles unicode characters causes tr to fail with an
    # 'Illegal byte sequence' error. Setting the locale here fixes that.
    #
    # See: http://nerdbynature.de/s9y/?176
    cmd="LC_CTYPE=C $cmd"
fi

eval "$cmd"