%************************************************************************
%*									*
\section[Driver-iface-thing]{Interface-file handling}
%*									*
%************************************************************************

\begin{code}
sub postprocessHiFile {
    local($hsc_hi,		# The iface info produced by hsc.
	  $hifile_target,	# The name both of the .hi file we
				# already have and which we *might*
				# replace.
	  $going_interactive) = @_;

    local($new_hi) = "$Tmp_prefix.hi-new";

#   print STDERR `$Cat $hsc_hi`;

    &constructNewHiFile($hsc_hi, $hifile_target, $new_hi);

    # run diff if they asked for it
    if ($HiDiff_flag && ! $HiOnStdout && ! $going_interactive && -f $hifile_target) {
	if ( $HiDiff_flag eq 'usages' ) {
	    # lots of near-useless info; but if you want it...
	    &run_something("$Cmp -s $hifile_target $new_hi || $Diff $hifile_target $new_hi 1>&2 || exit 0",
		"Diff'ing old and new .$HiSuffix files"); # NB: to stderr
	} else {
	    # strip out usages, *then* run diff
	    local($hi_before) = "$Tmp_prefix.hi-before";
	    local($hi_after)  = "$Tmp_prefix.hi-now";

	    &deUsagifyHi($hifile_target, $hi_before);
	    &deUsagifyHi($new_hi,	 $hi_after);

	    &run_something("$Cmp -s $hi_before $hi_after || $Diff $hi_before $hi_after 1>&2 || exit 0",
		"Diff'ing old and new .$HiSuffix files"); # NB: to stderr
	}
    }

    # if we produced an interface file "no matter what",
    # print what we got on stderr (ToDo: honor -ohi flag)
    if ( $HiOnStdout ) {
	print STDERR `$Cat $new_hi`;
    } else {
	&run_something("$Cmp -s $hifile_target $new_hi || ( $Rm $hifile_target && $Cp $new_hi $hifile_target )",
	   "Replace .$HiSuffix file, if changed");
    }
}

sub deUsagifyHi {
    local($ifile,$ofile) = @_;

    open(OLDHIF, "< $ifile") || &tidy_up_and_die(1,"Can't open $ifile (read)\n");
    open(NEWHIF, "> $ofile") || &tidy_up_and_die(1,"Can't open $ofile (write)\n");

    # read up to __usages__ line
    $_ = <OLDHIF>;
    while ($_ ne '' && ! /^__usages__/) {
	print NEWHIF $_ unless /^(interface |\{-# GHC_PRAGMA)/;
	$_ = <OLDHIF>;
    }
    if ( $_ ne '' ) {
	# skip to next __<anything> line
	$_ = <OLDHIF>;
	while ($_ ne '' && ! /^__/) { $_ = <OLDHIF>; }

	# print the rest
	while ($_ ne '') {
	    print NEWHIF $_;
	    $_ = <OLDHIF>;
	}
    }

    close(OLDHIF) || &tidy_up_and_die(1,"Failed reading from $ifile\n");
    close(NEWHIF) || &tidy_up_and_die(1,"Failed writing to $ofile\n");
}
\end{code}

\begin{code}
sub constructNewHiFile {
    local($hsc_hi,	    # The iface info produced by hsc.
	  $hifile_target,   # Pre-existing .hi filename (if it exists)
	  $new_hi) = @_;    # Filename for new one

    &readHiFile('old',$hifile_target) unless $HiHasBeenRead{'old'} == 1;
    &readHiFile('new',$hsc_hi)	      unless $HiHasBeenRead{'new'} == 1;

    open(NEWHI, "> $new_hi") || &tidy_up_and_die(1,"Can't open $new_hi (write)\n");

    local($new_module_version) = &calcNewModuleVersion();
    print NEWHI "interface ", $ModuleName{'new'}, " $new_module_version\n";

    print NEWHI "__usages__\n", $Stuff{'new:usages'} unless $Stuff{'new:usages'} eq '';

    local(@version_keys) = sort (keys %Version);
    local($num_ver_things) = 0;
    foreach $v (@version_keys) {
	next unless $v =~ /^new:(.*$)/;
	last if $num_ver_things >= 1;
	$num_ver_things++;
    }

    print NEWHI "__versions__\n" unless $num_ver_things < 1;
    foreach $v (@version_keys) {
	next unless $v =~ /^new:(.*$)/;
	$v = $1;

	&printNewItemVersion($v, $new_module_version), "\n";
    }

    print NEWHI "__exports__\n";
    print NEWHI $Stuff{'new:exports'};

    if ( $Stuff{'new:instance_modules'} ) {
	print NEWHI "__instance_modules__\n";
	print NEWHI $Stuff{'new:instance_modules'};
    }

    if ( $Stuff{'new:fixities'} ) {
	print NEWHI "__fixities__\n";
	print NEWHI $Stuff{'new:fixities'};
    }

    if ( $Stuff{'new:declarations'} ) {
	print NEWHI "__declarations__\n";
	print NEWHI $Stuff{'new:declarations'};
    }

    if ( $Stuff{'new:instances'} ) {
	print NEWHI "__instances__\n";
	print NEWHI $Stuff{'new:instances'};
    }

    if ( $Stuff{'new:pragmas'} ) {
	print NEWHI "__pragmas__\n";
	print NEWHI $Stuff{'new:pragmas'};
    }

    close(NEWHI) || &tidy_up_and_die(1,"Failed writing to $new_hi\n");
}
\end{code}

\begin{code}
%Version = ();
%Decl	 = (); # details about individual definitions
%Stuff	 = (); # where we glom things together
%HiExists      = ('old',-1,  'new',-1); # 1 <=> definitely exists; 0 <=> doesn't
%HiHasBeenRead = ('old', 0,  'new', 0);
%ModuleVersion = ('old', 0,  'new', 0);

sub readHiFile {
    local($mod,		    # module to read; can be special tag 'old'
			    # (old .hi file for module being compiled) or
			    # 'new' (new proto-.hi file for...)
	  $hifile) = @_;    # actual file to read

    # info about the old version of this module's interface
    $HiExists{$mod}      = -1; # 1 <=> definitely exists; 0 <=> doesn't
    $HiHasBeenRead{$mod} = 0;
    $ModuleVersion{$mod} = 0;
    $Stuff{"$mod:usages"}	    = ''; # stuff glommed together
    $Stuff{"$mod:exports"}	    = '';
    $Stuff{"$mod:instance_modules"} = '';
    $Stuff{"$mod:instances"}	    = '';
    $Stuff{"$mod:fixities"}	    = '';
    $Stuff{"$mod:declarations"}	    = '';
    $Stuff{"$mod:pragmas"}	    = '';

    if (! -f $hifile) { # no pre-existing .hi file
	$HiExists{$mod} = 0;
	return();
    }

    open(HIFILE, "< $hifile") || &tidy_up_and_die(1,"Can't open $hifile (read)\n");
    $HiExists{$mod} = 1;
    local($now_in) = '';
    hi_line: while (<HIFILE>) {
	next if /^ *$/; # blank line
	next if /\{-# GHC_PRAGMA INTERFACE VERSION 20 #-\}/;

	# avoid pre-1.3 interfaces
#print STDERR "now_in:$now_in:$_";
	if ( /\{-# GHC_PRAGMA INTERFACE VERSION . #-\}/ ) {
	    $HiExists{$mod} = 0;
	    last hi_line;
	}

	if ( /^interface ([A-Z]\S*) (\d+)/ ) {
	    $ModuleName{$mod}	 = $1; # not sure this is used much...
	    $ModuleVersion{$mod} = $2;

	} elsif ( /^interface ([A-Z]\S*)/ && $mod eq 'new' ) { # special case: no version
	    $ModuleName{'new'} = $1;

	} elsif ( /^__([a-z]+)__$/ ) {
	    $now_in = $1;

	} elsif ( $now_in eq 'usages' && /^(\S+)\s+(\d+)\s+:: (.*)/ ) {
	    $Stuff{"$mod:usages"} .= $_; # save the whole thing

	} elsif ( $now_in eq 'versions' && /^(\S+) (\d+)/ ) {
	    local($item) = $1;
	    local($n)    = $2;
#print STDERR "version read:item=$item, n=$n, line=$_";
	    $Version{"$mod:$item"} = $n;

	} elsif ( $now_in eq 'versions' && /^(\S+)/ && $mod eq 'new') { # doesn't have versions
	    local($item) = $1;
#print STDERR "new version read:item=$item, line=$_";
	    $Version{"$mod:$item"} = 'y'; # stub value...

	} elsif ( $now_in =~ /^(exports|instance_modules|instances|fixities|pragmas)$/ ) {
	    $Stuff{"$mod:$1"} .= $_; # just save it up

	} elsif ( $now_in eq 'declarations' ) { # relatively special treatment needed...
	    $Stuff{"$mod:declarations"} .= $_; # just save it up

	    if ( /^[A-Z][A-Za-z0-9_']*\.(\S+)\s+::\s+/ ) {
		$Decl{"$mod:$1"} = $_;

	    } elsif ( /^type\s+[A-Z][A-Za-z0-9_']*\.(\S+)/ ) {
		$Decl{"$mod:$1"} = $_;

	    } elsif ( /^(newtype|data)\s+(.*\s+=>\s+)?[A-Z][A-Za-z0-9_']*\.(\S+)\s+/ ) {
		$Decl{"$mod:$3"} = $_;

	    } elsif ( /class\s+(.*\s+=>\s+)?[A-Z][A-Za-z0-9_']*\.(\S+)\s+.*where\s+\{.*\};/ ) {
		$Decl{"$mod:$2"} = $_; # must be wary of => bit matching after "where"...
	    } elsif ( /class\s+(.*\s+=>\s+)?[A-Z][A-Za-z0-9_']*\.(\S+)\s+/ ) {
		$Decl{"$mod:$2"} = $_;

	    } else { # oh, well...
		print STDERR "$Pgm: decl line didn't match?\n$_";
	    }

	} else {
	    print STDERR "$Pgm:junk old iface line?:section:$now_in:$_";
	}
    }

#   foreach $i ( sort (keys %Decl)) {
#	print STDERR "$i: ",$Decl{$i}, "\n";
#   }

    close(HIFILE) || &tidy_up_and_die(1,"Failed reading from $hifile\n");
    $HiHasBeenRead{$mod} = 1;
}
\end{code}

\begin{code}
sub calcNewModuleVersion {

    return(&mv_change(1,'no old .hi file')) if $HiExists{'old'} == 0;
	# could use "time()" as initial version; if a module existed, then was deleted,
	# then comes back, we don't want the resurrected one to have an
	# lower version number than the original (in case there are any
	# lingering references to the original in other .hi files).

    local($unchanged_version) = $ModuleVersion{'old'}; # will return one of these two
    local($changed_version)   = $unchanged_version + 1;

    return(&mv_change($changed_version,'usages changed')) if $Stuff{'old:usages'} ne $Stuff{'new:usages'};

    foreach $t ( 'exports', 'instance_modules', 'instances', 'fixities', 'declarations', 'pragmas' ) {
	return(&mv_change($changed_version,"$t changed")) if $Stuff{"old:$t"} ne $Stuff{"new:$t"};
    }

    return($unchanged_version);
}

sub mv_change {
    local($mv, $str) = @_;

    print STDERR "$Pgm: module version changed to $mv; reason: $str\n";
    return($mv);
}

sub printNewItemVersion {
    local($item, $mod_version) = @_;

    if (! defined($Decl{"new:$item"}) ) {
# it's OK, because the thing is almost-certainly wired-in
#	print STDERR "$item: no decl?! (nothing into __versions__)\n";
	return;
    }

    local($idecl) = $Decl{"new:$item"};

    if (! defined($Decl{"old:$item"})) {
	print STDERR "new: $item\n";
	print NEWHI  "$item $mod_version\n";
    } elsif ($idecl ne $Decl{"old:$item"})  {
	print STDERR "changed: $item\n";
	print NEWHI  "$item $mod_version\n";
    } elsif (! defined($Version{"old:$item"}) ) {
	print STDERR "$item: no old version?!\n" 
    } else {
	print NEWHI  "$item ", $Version{"old:$item"}, "\n";
    }
    return;
}
\end{code}

\begin{code}
sub findHiChanges {
    local($hsc_hi,	        # The iface info produced by hsc.
	  $hifile_target) = @_; # Pre-existing .hi filename (if it exists)
}
\end{code}

\begin{code}
# make "require"r happy...
1;
\end{code}