#!/bin/bash
#
# hg_commit_message.sh
#
# Copyright (C) 2013, Branko Majic <branko@majic.rs>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

program="hg_commit_message.sh"
version="0.1-dev"

function usage() {
    cat <<EOF
$program $version, a Mercurial hook that can be used for validating commit
message format.

Usage: $program [OPTIONS] (regex|hgrc)

$program is a Mercurial hook that can be used for validating commit message
format. The hook allows validation of commit messages against a regular
expression.

The hook can be configured either through command-line arguments, or via hgrc
"commit_message" section.

The hook accepts a single positional argument, that should either be the regular
expression that will be used to validate the commit messages, or constant
"hgrc", which indicates that the hook should read its configurtion from the
Mercurial configuration files. If set to "hgrc", set the option "regex" in
Mercurial configuration files instead.

The validation will try to match _any_ part of the message with the specified
regular expression. Therefore, if it's necesasry to match the _whole_ message,
using '^' and '$' at beginning/end of the regex string is necessary.

The hook can be used as one of the following hook types:

- pretxncommit (on downstream side, to run the commit message validation before
  the content is committed locally)
- pretxnchangegroup (on upstream side, to run the commit message validation
  before the pushed content is accepted)

Downstream example, using command-line arguments for configuration:

[hooks]
pretxncommit.message = /path/to/$program -e "^(TST-[[:digit:]]+|Noticket): "

Downstream example, using Mercurial configuration files:

[hooks]
pretxncommit.message = /path/to/$program hgrc

[commit_message]
extended_regex = True
regex = ^(TST-[[:digit:]]+|Noticket):[[:space:]]

Upstream example, using command-line arguments for configuration:

[hooks]
pretxnchangegroup.message = /path/to/$program -e "^(TST-[[:digit:]]+|Noticket): "

Upstream example, using Mercurial configuration files:

[hooks]
pretxnchangegroup.message = /path/to/$program hgrc

[commit_message]
extended_regex = True
regex = ^(TST-[[:digit:]]+|Noticket):[[:space:]]


$program accepts the following options:

    -e        Treat the provided regular expression as extended. Default is to
              treat the expression as plain regular expression. If configuring
              inside of hgrc use option "extended_regex" (set to True or
              False).
    -m msg    An alternative error message that should be output to the
              user. Default is to output the regular expression used for
              validation. If configuring inside of hgrc use option
              "error_message". If custom message contains string "%s", it will
              be replaced by the actual regular expression.

    -v        show script version and licensing information
    -h        show usage help


Please report bugs and send feature requests to <branko@majic.rs>.
EOF
}

function version() {
        cat <<EOF
$program, version $version

+-----------------------------------------------------------------------+
| Copyright (C) 2013, Branko Majic <branko@majic.rs>                    |
|                                                                       |
| This program is free software: you can redistribute it and/or modify  |
| it under the terms of the GNU General Public License as published by  |
| the Free Software Foundation, either version 3 of the License, or     |
| (at your option) any later version.                                   |
|                                                                       |
| This program is distributed in the hope that it will be useful,       |
| but WITHOUT ANY WARRANTY; without even the implied warranty of        |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         |
| GNU General Public License for more details.                          |
|                                                                       |
| You should have received a copy of the GNU General Public License     |
| along with this program.  If not, see <http://www.gnu.org/licenses/>. |
+-----------------------------------------------------------------------+

EOF
}

# Set-up colours for message printing if we're not piping and terminal is
# capable of outputting the colors.
_color_terminal=$(tput colors 2>&1)
if [[ -t 1 ]] && (( ${_color_terminal} > 0 )); then
    _text_bold=$(tput bold)
    _text_white=$(tput setaf 7)
    _text_blue=$(tput setaf 6)
    _text_green=$(tput setaf 2)
    _text_yellow=$(tput setaf 3)
    _text_red=$(tput setaf 1)
    _text_reset=$(tput sgr0)
else
    _text_bold=""
    _text_white=""
    _text_blue=""
    _text_green=""
    _text_yellow=""
    _text_red=""
    _text_reset=""
fi

# Set-up functions for printing coloured messages.
function debug() {
    echo "${_text_bold}${_text_blue}[DEBUG]${_text_reset}" "$@"
}

function info() {
    echo "${_text_bold}${_text_white}[INFO] ${_text_reset}" "$@"
}

function success() {
    echo "${_text_bold}${_text_green}[OK]   ${_text_reset}" "$@"
}

function warning() {
    echo "${_text_bold}${_text_yellow}[WARN] ${_text_reset}" "$@"
}

function error() {
    echo "${_text_bold}${_text_red}[ERROR]${_text_reset}" "$@" >&2
}

# Set-up the error codes.
ERR_INVALID_ARGUMENT=1
ERR_INVALID_FORMAT=2
ERR_INVALID_CALL=3

# If no arguments were given, just show usage help.
if [[ -z $1 ]]; then
    usage
    exit 0
fi

# Set-up some defaults.
grep_options="-qe"
error_message="The following commit message did not validate against the regular expression '%s':"
config_section="commit_message"

# Parse the arguments
while getopts "em:vh" opt; do
    case "$opt" in
        e) grep_options="-qEe";;
        m) error_message="$OPTARG";;
        v) version
           exit 0;;
        h) usage
           exit 0;;
        *) usage
           exit $ERR_INVALID_ARGUMENT;;
    esac
done
i=$OPTIND
shift $(($i-1))

# Make sure that only one positional argument was provided.
if [[ ${#@} != 1 ]]; then
    error "Incorrect number of positional arguments was provided (${#@} instead of 1)."
    exit $ERR_INVALID_ARGUMENT
fi

# Read the positional arguments.
regex="$1"

# Read options from the Mercurial configuration files.
if [[ $regex == "hgrc" ]]; then
    regex=$(hg showconfig "${config_section}.regex")

    if [[ $(hg showconfig "${config_section}.extended_regex") == "True" ]]; then
        grep_options="-qEe"
    fi

    hgrc_error_message=$(hg showconfig "${config_section}.error_message")

    if [[ -n "$hgrc_error_message" ]]; then
        error_message="$hgrc_error_message"
    fi
fi

# Verify the arguments.
if [[ -z $regex ]]; then
    error "Regular expression may not be empty."
    exit $ERR_INVALID_ARGUMENT
fi

if [[ -z $error_message ]]; then
    error "Error message may not be empty."
    exit $ERR_INVALID_ARGUMENT
fi

if [[ -z $HG_NODE ]]; then
    error "Improper use of hook. No HG_NODE variable was set prior to hook execution."
    exit $ERR_INVALID_CALL
fi

# Validate all commit messages, starting from the first new node, all the way up
# to the tip.
for node in $(hg log -r "${HG_NODE}:tip" --template '{node}\n'); do
    message=$(hg log -r "$node" --template '{desc}')
    if ! echo "$message" | grep "$grep_options" "$regex"; then
        error "$(printf "$error_message" "$regex")"
        error "Changeset: $node"
        error "^${message}$"
        exit $ERR_INVALID_FORMAT
    fi
done

success "All commit messages have passed the format validation."

exit 0