#! /usr/bin/perl
# Copyright (C) 2015 The Qt Company Ltd.
# Contact: http://www.qt.io/licensing/
#
# You may use this file under the terms of the 3-clause BSD license.
# See the file LICENSE from this package for details.
#

use warnings;
use strict;

my $invocationCommand = '';
if ($#ARGV >= 0) {
    $invocationCommand = $ARGV[0];
}

if ($invocationCommand ne 'commit' and $invocationCommand ne 'stash' and $invocationCommand ne '') {
    print STDERR <<EOF ;
Usage: $0 [commit | stash]
Removes white space only change chunks from the HEAD commit.
If invoked with commit, WS changes are committed as a separate commit on top.
If invoked with stash, WS changes are stashed.
Otherwise it will merely reapply the WS changes to the working tree.
EOF
    exit 2;
}

sub printerr()
{
    die "cannot run git: ".$! if ($? < 0);
    die "git crashed with signal ".$? if ($? & 127);
    die "git exited with status ".($? >> 8) if ($?);
}

open STATUS, "git status --porcelain |" or printerr;
while (<STATUS>) {
    if (/^[^ ?!]/) {
        print STDERR "Index is not clean. Aborting.\n";
        exit 1;
    }
}
close STATUS or printerr;

my $patch = "";

my $file = "";
my @filehdr = ("", "");
my $fileHdrShown = 0;

my $chunk = 0;
my @addi = ();
my @deli = ();
my $nonws;
my $ws;
my $mixws_check = 0;
my $lineno = 0;
my $lineno2 = 0;
my @ws_files = ();
my %ws_lines = (); # hash of lists
my $braces = 0;
my $open_key = qr/\s*#\s*if|.*{/;
my $close_key = qr/\s*#\s*endif|.*}/;
my $kill_all_ws = qr/\s+((?:\"(?:\\.|[^\"])*\"|\S)+)/; # Collapse all whitespace not inside strings.
my $kill_nl_ws = qr/((?:\"(?:\\.|[^\"])*\"|\S)+)\s+/; # Collapse all non-leading whitespace not inside strings.

sub flushChunk()
{
    my $loc_nonws = 0;
    my $nlonly = 1;
    my ($ai, $di) = (0, 0);
    while (!$loc_nonws) {
        my ($a, $d) = ("", "");
        while ($ai < @addi) {
            $a = $addi[$ai++];
            $a =~ s/\s+$//;
            if (length($a)) {
                $nlonly = 0;
                last;
            }
        }
        while ($di < @deli) {
            $d = $deli[$di++];
            $d =~ s/\s+$//;
            if (length($d)) {
                $nlonly = 0;
                last;
            }
        }
        last if (!length($a) && !length($d));

        $a =~ /^$close_key/o and $braces--;
        $d =~ /^$close_key/o and $braces++;
        if ($braces) {
            $a =~ s/$kill_nl_ws/$1/go;
            $d =~ s/$kill_nl_ws/$1/go;
        } else {
            $a =~ s/$kill_all_ws/$1/go;
            $d =~ s/$kill_all_ws/$1/go;
        }
        $loc_nonws = 1 if ($a ne $d);
        $a =~ /^$open_key/o and $braces++;
        $d =~ /^$open_key/o and $braces--;
    }
    while ($ai < @addi) {
        my $a = $addi[$ai++];
        $a =~ /^$close_key/o and $braces--;
        $a =~ /^$open_key/o and $braces++;
    }
    while ($di < @deli) {
        my $d = $deli[$di++];
        $d =~ /^$close_key/o and $braces++;
        $d =~ /^$open_key/o and $braces--;
    }
    if ($loc_nonws) {
        $nonws = 1;
    } elsif (!$nlonly) {
        $ws = 1;
        my $chunkhdr = "@@ -".($lineno2 - $#deli).",".($#deli + 1)." +".($lineno - $#addi).",".($#addi + 1)." @@\n";
        if (!$fileHdrShown) {
            $fileHdrShown = 1;
            $patch .= join("", @filehdr);
        }
        $patch .= $chunkhdr."-".join("-", @deli)."+".join("+", @addi);
        push @ws_files, $file if (!defined($ws_lines{$file}));
        push @{$ws_lines{$file}}, $lineno - $#addi;
    }
    @addi = @deli = ();
    $chunk = 0;
}

open DIFF, "git diff-tree --no-commit-id --diff-filter=ACMR --src-prefix=\@old\@/ --dst-prefix=\@new\@/ --full-index -r -U100000 --cc -M --root HEAD |" or printerr;
while (<DIFF>) {
    if (/^-/) {
        if ($mixws_check) {
            if (/^--- /) {
                $filehdr[0] = $_;
                next;
            }
            push @deli, substr($_, 1);
            $chunk = 1;
        }
        $lineno2++;
        next;
    }
    if (/^\+/) {
        if (/^\+\+\+ /) {
            $filehdr[1] = $_;
            next;
        }
        $lineno++;
        $_ = substr($_, 1);
        if ($mixws_check) {
            push @addi, $_;
            $chunk = 1;
        }
    } else {
        flushChunk() if ($chunk);
        if (/^ /) {
            $lineno++;
            $lineno2++;
            next;
        }
        if (/^\@\@ -(\d+),\d+ \+(\d+)/) {
            $lineno2 = $1 - 1;
            $lineno = $2 - 1;
            next;
        }
        if (/^diff /) {
            if (/^diff --git \@old\@\/.+ \@new\@\/(.+)$/) {
            } elsif (/^diff --cc (.+)$/) {
                print STDERR "Cannot operate on merge commits.\n";
                exit 1;
            } else {
                print STDERR "Warning: cannot parse diff header '".$_."'\n";
                next;
            }
            $fileHdrShown = 0;
            $file = $1;
            #print "*** got file ".$file.".\n";
            my $clike = ($file =~ /\.(c|cc|cpp|c\+\+|cxx|qdoc|m|mm|h|hpp|hxx|cs|java|js|qs|qml|g|y|ypp|pl|glsl)$/i);
            my $foreign = ($file =~ /\/3rdparty\//);
            $mixws_check = !$foreign && $clike;
            $braces = 0;
            next;
        }
    }
}
close DIFF or printerr;
flushChunk() if ($chunk);
if (!$ws) {
    print STDERR "No WS only changes, not touching this.\n";
    exit 1;
}
if (!$nonws and $ws) {
    print STDERR "Entirely WS changes, not touching this.\n";
    exit 1;
}
# $patch contains the patch for appling the WS changes (-R to remove them). Now apply git-foo.
system "git reset --soft HEAD^" or printerr;
open PATCH_A, "| git apply --unidiff-zero -R --index -" or printerr;
print PATCH_A $patch;
close PATCH_A or printerr;
system "git commit -C ORIG_HEAD" or printerr;
if ($invocationCommand ne '') {
    open PATCH_B, "| git apply --unidiff-zero --index -" or printerr;
    print PATCH_B $patch;
    close PATCH_B or printerr;
    if ($invocationCommand eq 'commit') {
        system "git commit -m \"Whitespace Changes\"" or printerr;
    } else {
        system "git stash save \"Whitespace Changes\"" or printerr;
    }
} else {
    open PATCH_C, "| git apply --unidiff-zero -" or printerr;
    print PATCH_C $patch;
    close PATCH_C or printerr;
}
exit 0;