#!/bin/sh

photodir="stream"
galleryfile="index.html"

bfile="$(sed '/<!-- GB -->/q' $galleryfile )"
efile="$(sed '1,/<!-- GE -->/d' $galleryfile )"

perfour() {
  # One out of every five lines:
  batch="$(awk 'NR == 1 || NR % 5 == 0' - )"
  # Add the html fluff:
  list="$(
    for i in $batch; do
      base="$(echo "$i" | cut -f 1 -d "." )"
      printf "\t\t<img src=\"$photodir/$i\" alt=\"$base\">\n"
    done
  )"
  printf "\t<div class=\"column\">\n$list\n\t</div>"

}

all="$(ls -t $photodir)"
col1="$(echo "$all" | perfour)"
all="$(echo "$all" | sed '1d' )"
col2="$(echo "$all" | perfour)"
all="$(echo "$all" | sed '1d' )"
col3="$(echo "$all" | perfour)"
all="$(echo "$all" | sed '1d' )"
col4="$(echo "$all" | perfour)"

gallery="$(printf "<div class=\"gallery\">\n$col1\n$col2\n$col3\n$col4\n</div>\n<!-- GE -->\n")"

echo "$bfile
$gallery
$efile" > index.html