#!/bin/bash
#
# Rename JPEGs to reflect the creation date stored in their metadata.
#
# Copyright (C) 2010-2011 W. Trevor King <wking@drexel.edu>
#
# 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; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
#
# usage: name-by-date.sh $(find . -name '*.jpg')

# check for required utilities
DIRNAME=$(which dirname) || exit 1
EXIF=$(which exif) || exit 1
FILE_=$(which file) || exit 1
GREP=$(which grep) || exit 1
MV=$(which mv) || exit 1
SED=$(which sed) || exit 1
TEST=$(which '[') || exit 1  # but I just use [ in the script


while [ -n "$1" ]; do
	FILE=$1
	TYPE=$("${FILE_}" "$FILE" | "${GREP}" JPEG)
	if [ -n "$TYPE" ]; then
		FIELD_NAME="$NAME_BY_DATE_FIELD_NAME"
		if [ -z "$FIELD_NAME" ]; then
				FIELD_NAME='Date and Time'
		fi
		ASCII_DATE=$("${EXIF}" -m -t "$FIELD_NAME" "$FILE")  # 2010:07:02 08:36:20
		if [ $? -ne 0 ]; then  # use similar field, e.g. 'Date and Time (original)'
			FIELD=$("${EXIF}" -m "$FILE" | "${GREP}" "$FIELD_NAME" | head -n1)
			FIELD_NAME=$(echo "$FIELD" | "${SED}" 's/\t.*//')
			if [ -z "$FIELD_NAME" ]; then
				echo "$FILE has no stored date"
				ASCII_DATE=""
			else
				echo "$FILE using date from $FIELD_NAME"
				ASCII_DATE=$("${EXIF}" -m -t "$FIELD_NAME" "$FILE")  # 2010:07:02 08:36:20
			fi
		fi
		DATE=$(echo "$ASCII_DATE" | "${SED}" 's/:/./g' | "${SED}" 's/ /./g')
		if [ -z "$DATE" ]; then
			echo "$FILE has no stored date"
	 	else
			echo "$FILE taken on \"$DATE\""
			FILE_DIR=$("${DIRNAME}" "$FILE")
			NEW_NAME="$FILE_DIR/$DATE.jpg"
			if [ -e "$NEW_NAME" ] && [ "$NEW_NAME" != "$FILE" ]; then
				i=1
				NEW_NAME="$FILE_DIR/${DATE}_$i.jpg"
				while [ -e "$NEW_NAME" ] && [ "$NEW_NAME" != "$FILE" ]; do
					echo "File \"$NEW_NAME\" already exists!"
					NEW_NAME="$FILE_DIR/${DATE}_$i.jpg"
					let "i += 1"
				done
			fi
			if [ "$NEW_NAME" != "$FILE" ]; then
				"${MV}" "$FILE" "$NEW_NAME"
			fi
		fi
	fi
	shift
done