#!/bin/sh
#
# a small shell script for automatic ordering of TV channels in MythTV
#
# BIG FAT WARNING: this script was tested only with MythTV v0.23.
# Future versions of mythtv possibly use an incompatible database layout.
#
# The following workflow is recommended:
#  1) backup the current channel settings:
#	./channel_sort_mythtv.sh dump >mythtv_channels_dump.sql
#  2) retrieve the current list of channel names
#	./channel_sort_mythtv.sh get >channels.list
#  3) sort the channels in 'channels.list' with your favourite text editor
#  4) upload the new channel order (starting from channum=1):
#	./channel_sort_mythtv.sh set <channel.list
#
# After another channel scan you can run this script again with the
# 'merge' argument. It reads your current channel order from stdin
# and appends all 'new' channels (taken from the database).
# 
#
# Copyright 2010 Lars Kruse <devel@sumpfralle.de>
#
# This script 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 2 of the License, or
# (at your option) any later version.
#
# This script 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 script.  If not, see <http://www.gnu.org/licenses/>.


set -eu

# you can override the mysql.txt location by providing it via an environment variable
MYSQL_CONF_FILE=${MYSQL_CONF_FILE:-}

# only used for "set" operation:
# 	use this channel number for all channels, that are listed in stdin
#	set it to an empty string, if the channels, that are not listed, should remain untouched
DEFAULT_CHANNEL=10000

# set DEBUG to a non-empty string to output the result sql statements instead of executing them
# use something like "export DEBUG=true" before running this script to enable debug mode
DEBUG=${DEBUG:-false}
export DEBUG

# read the mysql connection settings from the myth config
# this exposes DBHostName, DBUserName, DBName and DBPassword
for mysql_config in "$MYSQL_CONF_FILE" ~/.mythtv/mysql.txt /etc/mythtv/mysql.txt; do
	if test -n "$mysql_config" && test -r "$mysql_config"; then
		. "$mysql_config"
		break
	 fi
 done
# temporarily disable the "unset variable check" of bash
set +u
if test -z "$DBHostName" -o -z "$DBUserName" -o -z "$DBName" -o -z "$DBPassword"; then
	echo "Failed to read the mysql settings file of MythTV." >&2
	echo "You can set the environement variable MYSQL_CONF_FILE to specify a custom location." >&2
 fi
set -u


send_mysql_statement() {
	if test "$DEBUG" != "false"; then
		# only output the sql statements - don't execute them
		cat -
	 else
		mysql -h "$DBHostName" -u "$DBUserName" --password="$DBPassword" --skip-column-names "$DBName"
	 fi
}

show_syntax() {
	echo "Syntax: $(basename "$0") ACTION"
	echo "Possible actions:"
	echo "	get	- get all unsorted channel names from the database (to stdout)"
	echo "	set	- read the desired order of channels (by name) from stdin"
	echo "	merge	- output stdin and add all channel names (from the database)"
	echo "		  that were not listed before (to stdout)"
	echo "	dump	- dump the current state of the 'channel' table (as a backup)"
	echo "	help	- show this syntax description"
	echo "Hint: the 'get' operation does to same as 'merge' with empty stdin."
}


ACTION=invalid
test $# -gt 0 && ACTION="$1"

case "$ACTION" in
	get)
		# get distinct names and ignore empty lines
		echo "SELECT DISTINCT BINARY name FROM channel ORDER BY LPAD(channum, 3, 0) ASC;" \
			| send_mysql_statement \
			| grep -v "^$"
		;;
	set)
		(
			# reset all channel numbers to the default value if it is not empty
			test -n "$DEFAULT_CHANNEL" && echo "update channel set channum='$DEFAULT_CHANNEL';"
			current_num=1
			cat - | grep -v "^$" | while read channel; do
				# escape single quotes
				channel=$(echo "$channel" | sed "s/'/\\\\'/g")
				echo "update channel set channum=$current_num where BINARY name='$channel';"
				current_num=$((current_num + 1))
			 done
		) | send_mysql_statement
		;;
	merge)
		input="$(cat -)"
		echo "$input"
		"$0" get | while read channel; do echo "$input" | grep -q "^$channel$" || echo "$channel"; done
		;;
	dump)
		mysqldump -h "$DBHostName" -u "$DBUserName" --password="$DBPassword" "$DBName" channel
		;;
	help|--help|invalid)
		if test "$ACTION" = "invalid"; then
			show_syntax >&2
			exit 1
		 else
			show_syntax
		fi
		;;
 esac

exit 0