#!/bin/bash
#
# Sends an ascii-art text file to a parallel port needle/dot-matrix printer.
#
# Usage: ./txt2printr.sh [ascii-art.txt]
# Env:   PRINTER_DEV - printer device node (default: /dev/lp0)
# Reads printer.conf for PRINTER_A4 (landscape rotation) and PRINTER_MAX_LINES
# (per-page line capacity, measured with pagetest.sh).

dir="$(dirname "$0")"
[ -f "$dir/printer.conf" ] && source "$dir/printer.conf"
: "${PRINTER_A4:=false}"
: "${PRINTER_MAX_LINES:=64}"

infile="${1:-ascii-img.txt}"
# Source - https://stackoverflow.com/a/638980
# Posted by John Feminella, modified by community. See post 'Timeline' for change history
# Retrieved 2026-07-14, License - CC BY-SA 4.0

if [ -n "$PRINTER_DEV" ]; then
    dev="$PRINTER_DEV"
elif [ -e /dev/lp0 ]; then
    dev=/dev/lp0
elif [ -e /dev/usb/lp0 ]; then
    dev=/dev/usb/lp0
else
    dev=/dev/stdout
fi

if [ ! -f "$infile" ]; then
    echo "txt2printr: file not found: $infile" >&2
    exit 1
fi

if [ ! -w "$dev" ]; then
    echo "txt2printr: cannot write to printer device: $dev" >&2
    echo "txt2printr: set PRINTER_DEV to override, or check permissions/parport module" >&2
    exit 1
fi

# Rotates the ascii art 90 degrees clockwise so it reads correctly once the
# printed page itself is turned 90 degrees counter-clockwise - the printer's
# scan/feed directions are fixed, so this is the only way to get a landscape
# reading orientation out of it.
rotate90() {
    awk '
        { if (length($0) > maxlen) maxlen = length($0); lines[NR] = $0 }
        END {
            for (c = 1; c <= maxlen; c++) {
                row = ""
                for (r = NR; r >= 1; r--) {
                    ch = substr(lines[r], c, 1)
                    if (ch == "") ch = " "
                    row = row ch
                }
                print row
            }
        }
    ' "$infile"
}

body() {
    if [ "$PRINTER_A4" = "true" ]; then
        rotate90
    else
        cat "$infile"
    fi
}

line_count=$(body | wc -l)

{
    printf '\x1b\x40'                # ESC @ - reset printer (ESC/P and IBM Proprinter compatible)
    body | sed 's/$/\r/'             # CRLF line endings, needed for raw writes to avoid staircasing
    # Skip the form feed once the page is already full: printers commonly
    # auto-advance to a new page as soon as content hits the bottom margin,
    # so an explicit form feed on top of that just ejects a blank extra page.
    if [ "$line_count" -lt "$PRINTER_MAX_LINES" ]; then
        printf '\x0c'                # form feed - eject the page
    fi
} > "$dev"