#!/bin/bash
# Copyright (c) 2015, David Martin
# All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
# 
# * Redistributions of source code must retain the above copyright notice, this
#   list of conditions and the following disclaimer.
# 
# * Redistributions in binary form must reproduce the above copyright notice,
#   this list of conditions and the following disclaimer in the documentation
#   and/or other materials provided with the distribution.
# 
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#  git pre-commit hook that runs an clang-format stylecheck.
#  Features:
#   - abort commit when commit does not comply with the style guidelines
#   - create a patch of the proposed style changes

# modifications for clang-format by rene.milk@wwu.de
# This file is part of a set of unofficial pre-commit hooks available
# at github.
# Link:    https://github.com/githubbrowser/Pre-commit-hooks
# Contact: David Martin, david.martin.mailbox@googlemail.com


##################################################################
# SETTINGS
# set path to clang-format binary
CLANG_FORMAT=$(which clang-format-3.8)

# git subcommand that we want to us
for name in git-clang-format-3.9 git-clang-format-3.8 git-clang-format ; do
 where=$(which $name)
 if [ x != "x$where" ] ; then
   GIT_SUBCOMMAND=`echo $name|sed 's/git-//'`
   break
 fi
done
if [ -z $GIT_SUBCOMMAND ] ; then
  echo "Cannot find git-clang-format (in version >=3.8). Did you install the right package?"
  exit 1
fi

# remove any older patches from previous commits. Set to true or false.
DELETE_OLD_PATCHES=false

# only parse files with the extensions in FILE_EXTS. Set to true or false.
# if false every changed file in the commit will be parsed with clang-format.
# if true only files matching one of the extensions are parsed with clang-format.
PARSE_EXTS=true

# file types to parse. Only effective when PARSE_EXTS is true.
# FILE_EXTS=".c .h .cpp .hpp"
FILE_EXTS=".c .h .cpp .hpp .cc .hh .cxx"

##################################################################
# There should be no need to change anything below this line.

# Reference: http://stackoverflow.com/questions/1055671/how-can-i-get-the-behavior-of-gnus-readlink-f-on-a-mac
canonicalize_filename () {
    local target_file=$1
    local physical_directory=""
    local result=""

    # Need to restore the working directory after work.
    pushd `pwd` > /dev/null

    cd "$(dirname "$target_file")"
    target_file=`basename $target_file`

    # Iterate down a (possible) chain of symlinks
    while [ -L "$target_file" ]
    do
        target_file=$(readlink "$target_file")
        cd "$(dirname "$target_file")"
        target_file=$(basename "$target_file")
    done

    # Compute the canonicalized name by finding the physical path
    # for the directory we're in and appending the target file.
    physical_directory=`pwd -P`
    result="$physical_directory"/"$target_file"

    # restore the working directory after work.
    popd > /dev/null

    echo "$result"
}

# exit on error
set -e

# check whether the given file matches any of the set extensions
matches_extension() {
    local filename=$(basename "$1")
    local extension=".${filename##*.}"
    local ext

    for ext in $FILE_EXTS; do [[ "$ext" == "$extension" ]] && return 0; done

    return 1
}

# necessary check for initial commit
if git rev-parse --verify HEAD >/dev/null 2>&1 ; then
    against=HEAD
else
    # Initial commit: diff against an empty tree object
    against=foobaridonotexist
fi

if [ ! -x "$CLANG_FORMAT" ] ; then
    printf "Error: clang-format executable not found. sudo apt-get install clang-format-3.8\n"
    printf "Set the correct path in $(canonicalize_filename "$0").\n"
    exit 1
fi

# create a random filename to store our generated patch
prefix="pre-commit-clang-format"
suffix="$(date +%s)"
patch="/tmp/$prefix-$suffix.patch"

# clean up any older clang-format patches
$DELETE_OLD_PATCHES && rm -f /tmp/$prefix*.patch

# create one patch containing all changes to the files
git diff-index --cached --diff-filter=ACMR --name-only $against -- | while read file;
do
    # ignore file if we do check for file extensions and the file
    # does not match any of the extensions specified in $FILE_EXTS
    if $PARSE_EXTS && ! matches_extension "$file"; then
        continue;
    fi

    # clang-format our sourcefile, create a patch with diff and append it to our $patch
    # The sed call is necessary to transform the patch from
    #    --- $file timestamp
    #    +++ - timestamp
    # to both lines working on the same file and having a a/ and b/ prefix.
    # Else it can not be applied with 'git apply'.
    git ${GIT_SUBCOMMAND} --binary ${CLANG_FORMAT} --diff -q >> "$patch"
    #"$CLANG_FORMAT" -style=file "$file" | \
        #diff -u "$file" - | \
        #sed -e "1s|--- |--- a/|" -e "2s|+++ -|+++ b/$file|" >> "$patch"
done

# if no patch has been generated all is ok, clean up the file stub and exit
if [ ! -s "$patch" ] ; then
    printf "Files in this commit comply with the clang-format rules.\n"
    rm -f "$patch"
    exit 0
fi

# a patch has been created, notify the user and exit
printf "\nThe following differences were found between the code to commit "
printf "and the clang-format rules:\n\n"
cat "$patch"

printf "\nYou can apply these changes and readd the files with:\n"
printf "  git apply $patch &&  git apply --cached $patch\n"
printf "(call this command from the root directory of your repository)\n"
printf "\n\n\n"
printf "Aborting commit. Apply changes and commit again.\n"
# printf "Skip checking with: --no-verify (not recommended).\n"

exit 1