#!/usr/bin/env sh
# YES_ZSH YES_BASH YES_DASH YES_ASH

__recolor_install() {
    ForegroundColour() { recolor RAW 10 "$@"; }
    BackgroundColour() { recolor RAW 11 "$@"; }
        CursorColour() { recolor RAW 12 "$@"; }
               Black() { recolor      0 "$@"; }
           BoldBlack() { recolor      8 "$@"; }
                 Red() { recolor      1 "$@"; }
             BoldRed() { recolor      9 "$@"; }
               Green() { recolor      2 "$@"; }
           BoldGreen() { recolor     10 "$@"; }
              Yellow() { recolor      3 "$@"; }
          BoldYellow() { recolor     11 "$@"; }
                Blue() { recolor      4 "$@"; }
            BoldBlue() { recolor     12 "$@"; }
             Magenta() { recolor      5 "$@"; }
         BoldMagenta() { recolor     13 "$@"; }
                Cyan() { recolor      6 "$@"; }
            BoldCyan() { recolor     14 "$@"; }
               White() { recolor      7 "$@"; }
           BoldWhite() { recolor     15 "$@"; }
}

__recolor() {
    # TODO: clean up and optimize the heck out of this, i.e.
    #       don't require 19+ subshells to replace every color.
    pre='\033]'
    post='\033\\'

    tmuxy=0 screeny=0 linuxy=0
    [ "${TERM#tmux}"   = "$TERM" ] || tmuxy=1
    [ "${TERM#screen}" = "$TERM" ] || { tmuxy=1; screeny=1; }
    [ "${TERM#linux}"  = "$TERM" ] || linuxy=1
    [ -z "$TMUX" ] || tmuxy=0
    [ "$tmuxy$screeny" = 00 ] || linuxy=0

    if [ $tmuxy = 1 ]; then
        pre='\033Ptmux;\033'"$pre"
        post='\007'"$post"
    elif [ $screeny = 1 ]; then
        pre='\033P\033'"$pre"
        post='\007'"$post"
    fi

    malarg() {
        printf >&2 '%s: malformed argument #%s: %s\n' "$@"
        exit 2
    }

    byteranged() {
        [ "$1" -ge 0 ] && [ "$1" -le 255 ]
    } 2>&-

    valid_rex() {
        [ -z "${2#[0-9a-f][0-9a-f]/[0-9a-f][0-9a-f]/[0-9a-f][0-9a-f]}" ]
    }

    rex() {
        byteranged "$1" || malarg rex 1 "$1"
        valid_rex || malarg rex 2 "$2"
        if [ $linuxy = 1 ]; then
            #local IFS=/
            #set -- $1 $2
            set -- "${1%%/*}" "${2#*/}"
            set -- "$1" "${2%%/*}"
            [ "$1" -ge 16 ] || printf '\e]P%x%s%s%s' "$@"
        else
            printf "${pre}4;%s;rgb:%s${post}" "$1" "$2"
        fi
    }

    rexr() {
        byteranged "$1" || malarg rexr 1 "$1"
        valid_rex || malarg rexr 2 "$2"
        if [ $linuxy = 1 ]; then
            : # unsupported
        else
            printf "${pre}%s;rgb:%s${post}" "$1" "$2"
        fi
    }

    colour_split() {
        # use blue channel as a temporary variable.
        b="${c%??}" r="${b%??}" g="${b#??}" b="${c#????}"
    }

    dirty=0 plus=0
    n= r=ff g=ff b=ff a= c= i= raw=0

    if [ "$1" = RAW ]; then raw=1; shift; fi
    n="$1"

    byteranged "$n" || malarg recolor 1 "$c"

    if c="${2#\#}"; [ "$c" != "$2" ]; then
        [ "${#c}" = 6 ] || malarg recolor 2 "$2"
        v_lower c || return
        colour_split || return

    elif c="${2#0x}"; [ "$c" != "$2" ] && [ "${#c}" = 6 ]; then
        v_lower c || return
        colour_split || return

    else
        i=1
        for a in "$2" "$3" "$4"; do
            : $((i+=1))
            if c="${a#0x}"; [ "$c" = "$a" ]; then
                byteranged "$c" || malarg recolor $i "$c"
                c="$(printf '%02x' "$c")" # TODO: avoid subshell.
            fi
            [ "${#c}" != 1 ] || c="0$c"
            [ "${#c}" = 2 ] || malarg recolor $i "$c"
            v_lower c || return
            [ $i = 2 ] && r="$c" || [ $i = 3 ] && g="$c" || [ $i = 4 ] && b="$c"
        done
    fi

    if [ $raw = 1 ]; then
        rexr "$n" "$r/$g/$b"
    else
        rex "$n" "$r/$g/$b"
        if [ "$n" -eq 21 ] && [ $plus = 1 ]; then
            # use base16 "Bright White" for foreground as well.
            rexr 10 "$r/$g/$b"
        fi
    fi
    dirty=1
} >/dev/tty

recolor()(__recolor "$@")
[ -n "${preload+-}" ] || . ~/sh/preload || exit 2
eval ${preload:-preload} v_lower v_upper
[ -n "${preload+-}" ] || __recolor "$@"