#!/bin/bash

REVERSE="\x1b[7m"
RESET="\x1b[m"

if [ "$1" == "-v" ]; then
  SPLIT=1
  shift
fi

if [ -z "$1" ]; then
  echo "usage: $0 [-v] FILENAME[:LINENO][:IGNORED]"
  exit 1
fi

IFS=':' read -r -a INPUT <<< "$1"
FILE=${INPUT[0]}
CENTER=${INPUT[1]}

if [[ $1 =~ ^[A-Z]:\\ ]]; then
  FILE=$FILE:${INPUT[1]}
  CENTER=${INPUT[2]}
fi

if [ ! -r "$FILE" ]; then
  echo "File not found ${FILE}"
  exit 1
fi

if [[ "$(file --mime "$FILE")" =~ binary ]]; then
  echo "$1 is a binary file"
  exit 0
fi

if [ -z "$CENTER" ]; then
  CENTER=1
fi

if [ -z "$LINES" ]; then
  if [ -r /dev/tty ]; then
    LINES=$(stty size < /dev/tty | awk '{print $1}')
  else
    LINES=40
  fi
  if [ -n "$SPLIT" ]; then
    LINES=$(($LINES/2)) # using horizontal split
  fi
  LINES=$(($LINES-2)) # remove preview border
fi

FIRST=$(($CENTER-$LINES/3))
FIRST=$(($FIRST < 1 ? 1 : $FIRST))
LAST=$((${FIRST}+${LINES}-1))

if which bat >/dev/null; then
  CAT="bat --style=numbers --color=always"
  $CAT $FILE | awk "NR >= $FIRST && NR <= $LAST { \
      if (NR == $CENTER) \
          { gsub(/\x1b[[0-9;]*m/, \"&$REVERSE\"); printf(\"$REVERSE%s\n$RESET\", \$0); } \
      else printf(\"$RESET%s\n\", \$0); \
      }"
else
  awk "NR >= $FIRST && NR <= $LAST { \
      if (NR == $CENTER) printf(\"$REVERSE%5d %s\n$RESET\", NR, \$0); \
      else printf(\"%5d %s\n\", NR, \$0); \
      }" $FILE
fi