#### SETTINGS ####

# Behavior:
# prompt = Prompt to confirm each file change, run if yes and log the new name (if enabled).
# build = Build a file in 'pwd' that contains all 'mv' statements to peruse and/or run later.
# now = Run each mv statement after it is generated, log new file name (if enabled).
behavior=build

# Name of log file. Leave blank to disable logging.
loglog=mvdate.log

# Directory (must exist) to store the log. Leave blank to use the defaults below.
logdir=

#### END OF SETTINGS ####

# We want to log all files altered in case something shouldn't have been.
# Apparently macOS (nee OS X) is the only Unix with a default user log directory.
# GNU doesn't have one either. Lovely. :/
if [ ! "$logdir" ]; then
if [ -d ~/Library/Logs ]
then
logdir=~/Library/Logs
else
logdir=~/.log
if [ ! -d $logdir ]; then mkdir $logdir; fi
fi
fi
if [ "$loglog" ]; then
mlog=$logdir/$loglog
echo "NOTICE: This script writes time ran and filenames altered to $mlog"
echo `date` >> $mlog
fi

# Here, 'tail' reverses the order of 'find' after 'egrep' filters the result.
# That way files in a directory are renamed before the directory is.
# 'find' might be able to use the regex, but I couldn't work it out. YMMV.
# This only looks for the pattern at the end of the line or just before an extension.
find "`pwd`" | egrep '([0-9]{2}[.-/,]){2}[0-9]{2,4}(\.[[:alnum:]]+)?$' | tail -r | while read f
do

# Escape certain characters so they don't wreck the 'mv' statement later.
# double quote, single quote, parens, dollar sign, [space]
# Single quote and parens are escaped for the shell after breaking out of the 'sed' statement.
f=$(echo "$f" | sed -E 's/(["'\'\(\)\&'[:space:]$])/\\\1/g')

# Suck out the last instance of our hated date pattern (00.00.00 or 00.00.0000).
# Also replace dashes, slashes, and errant commas for dots because we've come too far not to.
d=$(echo $f | egrep -o '([0-9]{1,2}[.-/,]){2}[0-9]{2,4}' | tail -1 | sed -E 's/[-/,]/\./g')
if [ "$d" != "" ]; then

# 'date' will not accept a 2 OR 4 digit year.
if [ $(echo $d | egrep -o "[0-9]{4}$") ]; then
dform="%m.%d.%Y"; else
dform="%m.%d.%y"
fi
d2="$(date -j -f "$dform" "$d" "+%Y-%m-%d")"

# This is the 'sed' that finds the date and replaces it with what we made just above.
# It looks for the pattern at the end of the line (path) but includes the extension if there.
# It is possible that a version number of some sort will also match. This is why it prompts.
# Also possible to do away with the EOL in the regex and just go for the pattern.
f2="$(echo "$f" | sed -E 's/([0-9]{1,2}[.,-]){2}[0-9]{2,4}(\.[[:alnum:]]+)?$/'$d2'\2/')"

# And double spaces....fml.
# Which won't work unless we start over and look for them at the tail of the path.
# f2="$(echo "$f2" | sed 's/\ \ /\ /g')"
m="mv -- $f $f2"

case "$behavior" in
"prompt")
# We echo the 'mv' statement for approval to be sure it's doing what we want.
# This 'read' here has to come from somewhere other than stdin.e
echo "$m"
read -r -p "Run 'mv' (as shown)? [y,n] " response < /dev/tty if [[ $response =~ ^([yY])$ ]]; then eval $m if [ "$loglog" ]; then echo $f2 >> $mlog; fi
fi
;;
"build")
# Add every 'mv' statement to a file for later evaluation.
echo "$m" >> "!items to rename.txt"
;;
# Run the 'mv' statements as they are created.
"now")
eval $m
if [ "$loglog" ]; then echo $f2 >> $mlog; fi
;;
esac
fi
done