#!/bin/bash
#
# pbrisbin 2009
#
# http://pbrisbin.com:8080/bin/downgrade
#
# downgrade one or more packages from cache or A.R.M.
#
# updated to properly validate input and handle downgrading
# uninstalled packages
#
###

### constants

PD="$HOME/Packages"             # where to put packages
PACMAN="sudo pacman-color"      # package installer

### functions

# set the term title
set_title() { echo -ne "\033]0;$(basename "$0")\007"; }

# help message
message() {
  echo "usage: downgrade [package1] [package2] ..."
  echo
  exit 1
}

# error message
errorout() {
  echo "error: $*"
  echo
  exit 1
}

# returns true if results are found
search_local() {
  local LC_ALL="C"

  # "$term-[0-9].*" limits it to exactly the package passed
  LOCALS=( $(find /var/cache/pacman/pkg -name "$term-[0-9].*" | sort -r) )

  [ ${#LOCALS[@]} -ne 0 ] && return 0 || return 1
} 

# returns true if user makes a selection
print_local() {
  echo -e "\n The following packages are available in your cache:"

  for ((i=0; i<${#LOCALS[@]}; i++)); do 
    local n=$((i+1))
    local repo='local'
    local pack=$(basename ${LOCALS[$i]})

    case $pack in
      ${installed// /-}*) echo -e "\t$n\t$repo\t$pack [installed]" ;;
      *)                  echo -e "\t$n\t$repo\t$pack" ;;
    esac
  done

  echo -en "\n\tplease choose a version, type s to [s]earch A.R.M.: " && read NUM

  [ "$NUM" = "q" ] && exit 0
  [ "$NUM" = "s" ] && return 1 || return 0
}

# errors out on bad choice
get_local() {
  [ -n "${NUM//[0-9/}" ] && errorout "invalid choice, quitting..."

  PACK=${LOCALS[$((NUM-1))]}

  [ -z "$PACK" ] && errorout "invalid choice, quitting..."
}

# errors out on no results
# returns true if user makes a selection
search_and_print_arm() {
  local LC_ALL="C"

  REPOS=""
  for repo in ${repos[@]}; do
    REPOS="${REPOS}&${repo}=1"
  done

  url="http://arm.kh.nu/search/raw.php?a=$arch&q=^$term\$$REPOS"

  ARMS=( $(wget -q -O - "$url" | sort -r) )

  if [ ${#ARMS[@]} -ne 0 ]; then
    echo -e "\n The following packages are available from the A.R.M.:"

    # separate repo and packagename
    for ((i=0; i<${#ARMS[@]}; i++)); do 
      local n=$((i+1))
      local repo="$(echo ${ARMS[$i]} | awk -F '/' '{print $4}')"
      local pack="$(echo ${ARMS[$i]} | awk -F '/' '{print $7}')"
      
      # flag the installed version
      case $pack in
        ${installed// /-}*) echo -e "\t$n\t$repo\t$pack [installed]" ;;
        *)                  echo -e "\t$n\t$repo\t$pack" ;;
      esac
    done

    echo -en "\n\tplease choose a version, type q to [q]uit: " && read NUM

    [ "$NUM" = "q" ] && return 1 || return 0
  else
    exit 0
  fi
}

# errors out on bad choice or failed copy
get_arm() {
  [ -n "${NUM//[0-9/}" ] && errorout "invalid choice, quitting..."

  URL=${ARMS[$((NUM-1))]}

  [ -z "$URL" ] && errorout "invalid choice, quitting..."

  PACK="$PD/$(basename $URL)"
  wget -O "$PACK" "$URL" || errorout "could not download package $PACK"
}

### set up

[ -d "$PD" ] || mkdir -p "$PD"

[ $# -lt 1 ] && message

# get arch from uname, you can also harcode this
[ "$(uname -m)" = "x86_64" ] && arch=64 || arch=32

# get repos from pacman.conf, you could also hardcode these
repos=( $(grep -x '\[.*\]' /etc/pacman.conf | grep -v options | sed 's/\[//g;s/\]//g') )

### run it
set_title

for term in $@; do

  installed=$(pacman -Q $term 2>/dev/null)
  installed=${installed:-DummyPkg}

  if search_local; then
    if print_local; then
      get_local

    elif search_and_print_arm; then
      get_arm
    else
      exit 0
    fi

  elif search_and_print_arm; then
    get_arm
  else
    exit 0
  fi

  $PACMAN -U $PACK || errorout "could not install package $PACK"

done