#!/bin/sh

# Copyright 2006 Alan Grow.
# All rights reserved.
# Licensed under the terms contained in the file 'COPYING' in the 
# source directory.

# plopdb - manipulate the plop database:
#
#   plopdb add /path/to/file          # make a file available
#   plopdb update file 1158556433     # expire a file
#   plopdb rm file                    # remove all trace of a file
#
# this program is an almost generic flat-file database interface. transactioning
# is handled by the unix fs. locking, however, is not: if you expect concurrent
# usage, you should surround all calls to this program with a lock wrapper.
# i suggest setlock from daemontools: http://cr.yp.to/daemontools/setlock.html.
#
# TODO sh pipelines discard errors, so their use is not truly safe here
# TODO creative self-exec'ing could make the lock window narrower
#

set -e

for d in /etc/plop /usr/local/etc/plop; do
  for f in plop.conf.default plop.conf; do
    test -f "$d/$f" && . "$d/$f"
  done
done

plopdbdir="$plopdir/db"
plopfiledir="$plopdir/files"
ploptmpdir="$plopdir/tmp"
plopmasterdb="$plopdbdir/master"

die() { echo "$@"; exit 111; }

genkey() {
  path="$1"
  base=`basename "$path"`
  { echo "$base"; cat "$path"; } | $cmd_genkey | cut -f1 -d' '
  return 0
}

rmtxn() {
  key="$1"
  cd "$plopdbdir"
  for d in add remove update; do
    test -f "$d/$key" && rm "$d/$key"
  done
  return 0
}

lstxns() {
  cd "$plopdbdir"
  for d in "$@"; do
    ( cd "$d"; ls | sed -e "s#^#$d/#" )
  done
  return 0
}

txncount() {
  lstxns "$@" | wc -l
  return 0
}

add() {
  path="$1"

  if [ $# -gt 1 ]; then
    extra="$2"
  else
    now="`date +%s`"
    extra=$(( $now + $plopdefaultexpire ))
  fi

  base=`basename "$path"`
  test -e "$plopfiledir/$base" && die "error, file $base already in database."

  genkey "$path" |
  (
    read key

    tmpfile="`$cmd_mktemp`"
    cp "$path" "$tmpfile"
    mv "$tmpfile" "$plopfiledir/$base"

    record="$key $base $extra"
    tmptxn="`$cmd_mktemp`"
    echo "$record" > "$tmptxn"
    rmtxn "$key"
    mv "$tmptxn" "$plopdbdir/add/$key"
  )
  return 0
}

remove() {
  file="$1"
  base=`basename "$file"`

  test -e "$plopfiledir/$base" || die "error, file $base not in database."

  genkey "$plopfiledir/$base" |
  (
    read key

    record="$key $base"
    tmptxn="`$cmd_mktemp`"
    echo "$record" > "$tmptxn"
    rmtxn "$key"
    mv "$tmptxn" "$plopdbdir/remove/$key"
  )
  return 0
}

update() {
  file="$1"
  extra="$2"

  base=`basename "$file"`
  test -e "$plopfiledir/$base" || die "error, file $base not in database."

  genkey "$plopfiledir/$base" |
  (
    read key

    record="$key $base $extra"
    tmptxn="`$cmd_mktemp`"
    echo "$record" > "$tmptxn"
    rmtxn "$key"
    mv "$tmptxn" "$plopdbdir/update/$key"
  )
  return 0
}

rebuild() {
  tmptxn="`$cmd_mktemp`"
  tmpmaster="`$cmd_mktemp`"
  master="$plopdbdir/master"

  if [ "`txncount remove update`" -gt 0 ]; then
    lstxns remove update | \
      while read f; do cat "$plopdbdir/$f"; done | \
      sort -k 1 -t' ' -u | \
      join -v 2 - "$master" | \
      sort -k 1 -t' ' -u > "$tmptxn"

    mv "$tmptxn" "$tmpmaster"
    master="$tmpmaster"
  fi

  if [ "`txncount add update`" -gt 0 ]; then
    lstxns add update | \
      while read f; do cat "$plopdbdir/$f"; done | \
      { cat; cat "$master"; } | \
      sort -k 1 -t' ' -u > "$tmptxn"

    mv "$tmptxn" "$tmpmaster"
    master="$tmpmaster"
  fi

  if [ "$master" != "$plopdbdir/master" ]; then
    mv "$master" "$plopdbdir/master"
  fi

  lstxns add update remove | \
    while read f; do rm "$plopdbdir/$f"; done

  return 0
}

cleanup() {
  tmplist="`$cmd_mktemp`"
  cut -f2 -d' ' "$plopdbdir/master" | sort -u > "$tmplist"
  ls "$plopfiledir" | sort -u | join -v 1 - "$tmplist" | \
    while read f; do rm "$plopfiledir/$f"; done
  rm -f "$ploptmpdir/"*
  return 0
}

cmd="$1"
shift

case "$cmd" in
  add)
    add "$@"
    rebuild
    cleanup
    ;;
  remove|rm)
    remove "$1"
    rebuild
    cleanup
    ;;
  update)
    update "$@"
    rebuild
    cleanup
    ;;
  rebuild)
    rebuild
    ;;
  cleanup)
    cleanup
    ;;
  *)
    die "usage: $0 add|rm|update file"
    ;;
esac