#!/bin/zsh

##################
# License Notice #
##################
#
# This githook script consists of two parts:
#
# * get current Git branch, and
# * edit commit message.
#
# The first part is borrowed from Z shell. Follow the license described below.
# The second part is written by me, licensed under Public Domain.


##########################
# Get current Git branch #
##########################
#
# Original:
# https://github.com/zsh-users/zsh/blob/5c60ec46ec087e7e58c8fc00c6821060e8caecb8/Functions/VCS_Info/Backends/VCS_INFO_get_data_git
#
# File copyright:
# git support by: Frank Terbeck <ft@bewatermyfriend.org>
# Distributed under the same BSD-ish license as zsh itself.
#
# Zsh License:
# https://github.com/zsh-users/zsh/blob/5c60ec46ec087e7e58c8fc00c6821060e8caecb8/LICENCE
#
# ------------------------------------------------------------------------------
# Unless otherwise noted in the header of specific files, files in this
# distribution have the licence shown below.
# 
# However, note that certain shell functions are licensed under versions
# of the GNU General Public Licence.  Anyone distributing the shell as a
# binary including those files needs to take account of this.  Search
# shell functions for "Copyright" for specific copyright information.
# None of the core functions are affected by this, so those files may
# simply be omitted.
# 
# --
# 
# The Z Shell is copyright (c) 1992-2017 Paul Falstad, Richard Coleman,
# Zoltán Hidvégi, Andrew Main, Peter Stephenson, Sven Wischnowsky, and
# others.  All rights reserved.  Individual authors, whether or not
# specifically named, retain copyright in all changes; in what follows, they
# are referred to as `the Zsh Development Group'.  This is for convenience
# only and this body has no legal status.  The Z shell is distributed under
# the following licence; any provisions made in individual files take
# precedence.
# 
# Permission is hereby granted, without written agreement and without
# licence or royalty fees, to use, copy, modify, and distribute this
# software and to distribute modified versions of this software for any
# purpose, provided that the above copyright notice and the following
# two paragraphs appear in all copies of this software.
# 
# In no event shall the Zsh Development Group be liable to any party for
# direct, indirect, special, incidental, or consequential damages arising out
# of the use of this software and its documentation, even if the Zsh
# Development Group have been advised of the possibility of such damage.
# 
# The Zsh Development Group specifically disclaim any warranties, including,
# but not limited to, the implied warranties of merchantability and fitness
# for a particular purpose.  The software provided hereunder is on an "as is"
# basis, and the Zsh Development Group have no obligation to provide
# maintenance, support, updates, enhancements, or modifications.
# ------------------------------------------------------------------------------

setopt localoptions extendedglob NO_shwordsplit

local gitdir=.git
local gitbranch
local gitsymref="git symbolic-ref HEAD"

local tmp actiondir
actiondir=''
for tmp in "${gitdir}/rebase-apply" \
           "${gitdir}/rebase"; do
    if [[ -d ${tmp} ]]; then
        actiondir=${tmp}
        break
    fi
done
if [[ -n ${actiondir} ]] ; then
    gitbranch="$(${(z)gitsymref} 2> /dev/null)"
    [[ -z ${gitbranch} ]] && [[ -r ${actiondir}/head-name ]] \
        && gitbranch="$(< ${actiondir}/head-name)"
    [[ -z ${gitbranch} || ${gitbranch} == 'detached HEAD' ]] && [[ -r ${actiondir}/onto ]] \
        && gitbranch="$(< ${actiondir}/onto)"

elif [[ -f "${gitdir}/MERGE_HEAD" ]] ; then
    gitbranch="$(${(z)gitsymref} 2> /dev/null)"
    [[ -z ${gitbranch} ]] && gitbranch="$(< ${gitdir}/ORIG_HEAD)"

elif [[ -d "${gitdir}/rebase-merge" ]] ; then
    gitbranch="$(< ${gitdir}/rebase-merge/head-name)"
    if [[ $gitbranch == 'detached HEAD' ]]; then
        # get a sha1
        gitbranch="$(< ${gitdir}/rebase-merge/orig-head)"
    fi

elif gitbranch="$(${(z)gitsymref} 2> /dev/null)" ; then
elif gitbranch="refs/tags/$(git describe --all --exact-match HEAD 2>/dev/null)" ; then
elif gitbranch="$(git describe --contains HEAD 2>/dev/null)" ; then
## Commented out because we don't know of a case in which 'describe --contains' fails and 'name-rev --tags' succeeds.
#elif gitbranch="$(git name-rev --name-only --no-undefined --tags HEAD 2>/dev/null)" ; then
elif gitbranch="$(git name-rev --name-only --no-undefined --always HEAD 2>/dev/null)" ; then
fi

if [[ -z ${gitbranch} ]] ; then
    gitbranch="${${"$(< $gitdir/HEAD)"}[1,7]}..."
fi

gitbranch="${gitbranch##refs/[^/]##/}"


#######################
# Edit commit message #
#######################

if [[ -z ${gitbranch} ]]; then
    # Failed to get Git branch. Leave the commit message as it is.
    return 0
fi

# Extract issue number from branch name.
local issue_number="$(echo "${gitbranch}" | grep -o '[0-9][0-9]*' | head -1)"
if [[ -z ${issue_number} ]]; then
    # Failed to extract. Leave the commit message as it is.
    return 0
fi

# Substitute '###' with '#NNNNN', where 'NNNNN' is the issue number.
# '$1' is passed by Git, the file name that holds commit message.
sed -i '' -e "s|###|#${issue_number}|g" $1