#!/bin/sh
#
#   Copyright (C) 2006-2007 Jaroslaw Staniek <js@iidea.pl>
#
#   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 2 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; see the file COPYING.  If not, write to
#   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
#   Boston, MA 02110-1301, USA.
#

usage {
	echo "This script deletes a single table column from a .kexi (SQLite 3)
database file without removing data from the table.

Usage:
 $0 database_name table_name column_name

- {database_name}.old backup file is created before proceeding
- database_name, table_name, column_name must exist
- note that queries, forms and other objects referencing 
   to the altered table can become invalid and have to be 
   fixed by hand

Example: to delete 'price' column from table 'products', type
 $0 db.kexi products price"
}

exit_with_error {
	rm -f "$temp_db"
	echo $*
	echo "Error."
	exit 1
}

check {
	[ -n "$*" ] && exit_with_error "$*"
}

ksqlite="ksqlite -noheader"
ksqlite_header="ksqlite -header"

if [ $# -lt 3 ] ; then
	usage
	exit 0
fi
database_name=$1
table_name=$2
column_name=$3

temp_db=`mktemp "$database_name"XXXXXXXX` || exit_with_error
cp "$database_name" "$temp_db" || exit_with_error

# 1. alter the table physically

prepare_new_create_table_statement {
	# possible problems: typename ( number , number ) may contain ","
	
	schema=`echo ".schema '$table_name';" | $ksqlite "$database_name" | \
		grep "^CREATE TABLE $table_name " | \
		sed -e "s/[^(]*(\(.*\));/\1/" || exit_with_error`
	
	IFS=","
	for coldef in $schema ; do
		col=`echo $coldef | sed "s/^[ ]*\([^ ]*\) .*$/\1/"`
		if [ "$col" != "$column_name" ] ; then
			echo -n ,$coldef
		fi
	done | cut -c2-
	IFS=" "
}

get_sql_column_names {
	names=`$ksqlite_header "$temp_db" "SELECT * FROM '$temp_table_name' LIMIT 1;" | \
		head -n 1 || exit_with_error`
	IFS="|"
	for col in $names ; do
		if [ "$col" != "$column_name" ] ; then
			echo -n ", $col"
		fi
	done | cut -c3-
	IFS=" "
}

# 1.1. rename the original table to a temp name
temp_table_name=`mktemp "$table_name"XXXXXXXX`
msg=`$ksqlite "$temp_db" "ALTER TABLE '$table_name' RENAME TO '$temp_table_name';"`
check "$msg"

# 1.2. create a new table without the removed column and copy the data
new_create_table_statement=`prepare_new_create_table_statement`
msg=`$ksqlite "$temp_db" "CREATE TABLE '$table_name' ($new_create_table_statement);"`
check "$msg"

sql_column_names=`get_sql_column_names`
msg=`$ksqlite "$temp_db" "INSERT INTO '$table_name' SELECT $sql_column_names FROM '$temp_table_name';"`
check "$msg"

# 1.3. drop the temporary table
msg=`$ksqlite "$temp_db" "DROP TABLE '$temp_table_name';"`
check "$msg"


# 2. alter information in the kexi__fields system table (schema)

# 2.1. Get table's ID
table_id=`$ksqlite "$temp_db" "SELECT o_id FROM kexi__objects WHERE o_type=1 AND o_name='$table_name';" || exit_with_error`

# 2.1. Get column's number
column_order=`$ksqlite "$temp_db" "SELECT f_order FROM kexi__fields WHERE t_id=$table_id AND f_name='$column_name';" || exit_with_error`

$ksqlite "$temp_db" "DELETE FROM kexi__fields WHERE t_id=$table_id AND f_name='$column_name';"

for fname in `$ksqlite "$temp_db" \
	"SELECT f_name FROM kexi__fields WHERE t_id=$table_id AND f_order>=$column_order ORDER BY f_order DESC;"` ; do
	msg=`$ksqlite "$temp_db" "UPDATE kexi__fields SET f_order=$column_order WHERE t_id=$table_id AND f_name='$fname';"`
	check "$msg"
	column_order=`expr $column_order + 1`
done

# 3. Copy the original database file to .old file and replace 
#     the original with the new one
cp "$database_name" "$database_name.old" || exit_with_error
mv "$temp_db" "$database_name" || exit_with_error

exit 1