#!/usr/bin/perl --  #-*-perl-*-

# Alf-Christian Achilles <achilles@ira.uka.de>

#
# This script resolves crossreferences in BibTeX files.
# It replaces crossreferences with the data given in the crossreferenced entry.
#
#
# Usage: expand.crossrefs [bibtex-file[.gz] ...] > file.expanded.bib
#
# The bibtex file(s) must be given on the command line, they may be compressed
# with gzip. The bibtex data must have been successfully prettyprinted 
# with bibclean (available at ftp://ftp.math.utah.edu/pub/tex/bib/bibclean)
#
# The expanded BiTeX entries are written to stdout.
#
# If there is more than one file on the command line, then all the files
# will be treated as one happy bibliography in the order in which they appear.
# 
# This script does not care about the position of crossreferenced BibTeX 
# entries in the file. 
# If there are crossreferenced BibTeX entries with 
# the same key then only the one appearing later in the file will be 
# recognized.
# This does not comply with the BibTeX definition, but will be fine
# with most currently existing BibTeX bibliographies.

@bibfiles = ();
@crossrefsonly = ();

while( $ARGV[0] =~ /^-/ ) {
    $_ = $ARGV[0];
    shift;

    if (/^-crossrefs$/) {
	if (! -f $ARGV[0]) {
	    die "File $ARGV[0] does not exist! Stopped at";
	}
	push(@crossrefsonly,($ARGV[0]));
	shift;
	next;
    }
    print STDERR "Unknown option \"$_\"\n\n";
}
@bibfiles =(@ARGV);

if (scalar(@bibfiles) == 0) {
    die "No bibtex files given on command line, stopped at ";
} else {
    foreach (@bibfiles) {
	if (! -f $_) {
	    die "File $_ does not exist! Stopped at";
	}
    }
} 

%crossrefs = ();
foreach $file ((@crossrefsonly),(@bibfiles)) {
    if ($file =~ /\.(z|gz|Z)$/) {
	if (!open(CROSSREFS,"gunzip -c $file |")) {
	    die "Could not open pipe from \"gunzip -c $file |\"";
	}
    } else {
	if (!open(CROSSREFS,$file)) {
	    die "Could not open file $file";
	}
    }
    while ($_ = <CROSSREFS>) {
	# handle @string entries
	if (/^@(Book|Collection|Proceedings)\{(.*),$/i) {
	    $crossrefkey = $2;
	    $crossrefkey =~ y/A-Z/a-z/;
	    $crossref = '';
            while (($_ = <CROSSREFS>) && !/^\}$/) {
		$crossref .= $_;
	    }
	    $* = 1;
	    if ($crossref =~ /^  title/i) {
		if ($crossref =~ /^  booktitle =/i) {
		    $crossref =~ s/^  booktitle =(.|\n   )+\n//i;
		} 
		$crossref =~ s/  title =    /  booktitle =/i;
	    }    
	    $crossref =~ s/^  author =(.|\n   )+\n//i;
	    $* = 0;
	    $crossrefs{$crossrefkey} = $crossref;
	}
    }	
    close(CROSSREFS);
}

foreach $file (@bibfiles) {
    if ($file =~ /\.(z|gz|Z)$/) {
	if (!open(BIBTEX,"gunzip -c $file |")) {
	    die "Could not open pipe from \"gunzip -c $file |\"";
	}
    } else {
	if (!open(BIBTEX,$file)) {
	    die "Could not open file $file";
	}
    }
    while ($_ = <BIBTEX>) {
	if (/^  crossref = *"(\S+)",$/) {
	    ($crossrefkey = $1) =~ y/A-Z/a-z/;
	    if (defined($crossrefs{$crossrefkey})) {
		print $crossrefs{$crossrefkey};
	    } else {
		print $_;
	    } 
	} else {
	    print $_;
	}
    }
    close(BIBTEX);
}