#!/bin/bash
# Implementation of the Aliens interface for Haskell Cabal packages.
# Requires installation of Cabal-Install package

# $2 is name of package

alien_cabal--have-manager() {
    which cabal >/dev/null 2>&1 || exit 1
}

alien_cabal--get-manager-rule() {
    echo "Cabal-Install"
}

alien_cabal__in_version_range() {
   # $1=inclusive lower ver, $2=ver to check, $3=exclusive upper ver ($2==$3 iff $1==$3)
   [ "$2" ] || return 1
   [ "$2" != "$1" -a "$(GuessLatest "$2" "$1")" = "$1" ] && return 1
   [ "$3" ] || return 0
   [ "$(GuessLatest "$2" "$3")" = "$3" ] || return 1
   [ "$2" = "$3" -a "$2" != "$1" ] && return 1
   return 0
}

alien_cabal--met() {
    # $1=package, $2=lower version inclusive, [$3=upper version exclusive]
    ver=$(alien_cabal--getversion $1)
    alien_cabal__in_version_range "$2" "$ver" "$3"
}
alien_cabal--greater-than() { alien_cabal--met "$@"; }
alien_cabal--within-range() { alien_cabal--met "$@"; }
alien_cabal--interval()     { alien_cabal--met "$@"; }

alien_cabal__getvers()
{
    # $1="installed" or "available", $2=package, [$3=min ver incl. [$4=max ver excl.]]
    set -e
    cabal info $2 | awk "
        /Latest version $1: \[ Not installed \]/ { exit 1 }
        /Latest version $1: / { print \$4; exit 0; }"
}

alien_cabal--getversion()        { alien_cabal__getvers installed "$@"; }
alien_cabal--getinstallversion() {
    if [ -z "$2" -a -z "$3" ]
    then
        alien_cabal__getvers available "$@";
        return $?;
    fi
    pred=$( if   [ -z "$3" ]      ; then echo ">= $2"
            elif [ "$2" == "$3" ] ; then echo "== $2"
            elif [ -z "$2" ]      ; then echo  "< $3"
            else                         echo  ">= $2 && < $3"
            fi
          )
    cabal install --dry-run "$1 $pred" | sed -n -e "/^${1}-/s/^${1}-//p"
}

alien_cabal--install() {
    if [ -z "$2" ]
    then
        cabal install --global "$1"
    else
        cabal install --global "$1-$2"
    fi
}

func="${1:---have-manager}"
shift 1
alien_cabal$func "$@"