#!/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)

# 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.\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
    #    --- $file timestamp
    #    +++ - timestamp
    # to both lines working on the same file and having a a/ and b/ prefix.
    # Else it can not be applied with 'git apply'.
    git clang-format --diff -q >> "$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 with:\n git apply $patch\n"
printf "(may need to be called from the root directory of your repository)\n"
printf "\nNote: git apply only modifies your working directory, but not your index, i.e., not what you want to commit.\n"
printf "You need to run 'git add' again after you applied this patch OR just run git apply a second time:"
printf "\n git apply --cached $patch\n\n"
printf "Aborting commit. Apply changes and commit again or skip checking with"
printf " --no-verify (not recommended).\n"

exit 1