#!/bin/sh
# build one vrt per (hc, arc); run from the dir containing the tifs

set -eu
hc_list="p f g"
arc_list="i ii iii"
vrt_dir="vrt"
mkdir -p "$vrt_dir"

for hc in $hc_list; do
  for arc in $arc_list; do
    out="cn_${hc}_${arc}.vrt"
    list="$vrt_dir/cn_${hc}_${arc}.txt"

    # gather matching tif files
    set -- cn_${hc}_${arc}_*.tif
    [ -e "$1" ] || { echo "skip $hc/$arc"; continue; }

    : > "$list"
    for f in "$@"; do
      echo "../$f" >> "$list"
    done

    echo "build $vrt_dir/$out"
    ( cd "$vrt_dir" && gdalbuildvrt -overwrite -input_file_list "$(basename "$list")" "$out" )
    rm -f "$list"
  done
done

echo "done."