#!/bin/bash

if [ $# -ne 1 ] || [ -n "${1##*/courierimapuiddb}" ]; then
  >&2 printf 'usage: %s dir/courierimapuiddb' "$0"
  exit 1
fi

dir="${1%/courierimapuiddb}"

>&2 printf 'reordering %s ...\n' "$dir"

cd "${dir}/cur"

tmp_dir=$(mktemp -d)
trap 'rm -rf --one-file-system "${tmp_dir}"' EXIT

while read -r n i; do
  is_ok=true
  if f=$(ls "${i}"*) \
  && d=$(
    sed -n '
      /^$/q
      s/^[Dd]ate: //
      T
      p
    ' "$f" \
    |head -n1
  ) \
  && [ -n "$d" ] \
  && d=$(date +%s -d"$d"); then
    printf '%s %s\n' "$d" "$i" \
    >>"${tmp_dir}/to-sort"
  else
    printf '%s %s\n' "${i%%.*}" "$i"
  fi
done \
< <(sed 1d ../courierimapuiddb)

{
  sed -n 1p ../courierimapuiddb
  sort -k1n,1 "${tmp_dir}/to-sort" \
  |cat -n \
  |sed '
    s/^\s*\(\S\+\)\s\+\S\+\s\+\(\S.*\)$/\1 \2/
  '
} \
>"${tmp_dir}/sorted"

if diff -u --color <(
  sed 's/^\S\+ //' ../courierimapuiddb | sort
) <(
  sed 's/^\S\+ //' "${tmp_dir}/sorted" | sort
); then
  mv "${tmp_dir}/sorted" ../courierimapuiddb
fi

>&2 printf '... done\n'