mapdir

#! /usr/bin/env bash

set -eu

me=$(basename $0)

function usage {
    [ "${*-}" ] && echo "$me: $*" 1>&2
    cat 1>&2 <<EOF
Usage: $me [-n] [-h] directory ext prog [args]

'prog' is called, with args (see below), on each file in 'directory'
which has file type 'ext'.   'args' must contain at least one argument,
from the following two-character sequences.  They are converted as
follows, where 'file' refers to the matching file:

    %p => full pathname of file
    %d => dirname of file
    %b => basename of file
    %n => basename of file sans type

Options:

-n :: do not execute, just print the commands
-h :: ignore hidden files (ones that start with a dot)

Examples:

    \$ $me \$HOME md \$HOME/bin/convert-md-to-html -o %n.html %b
    \$ $me \$HOME md /bin/echo %p
EOF
    exit 1
}

function errordie {
    [ "${*-}" ] && echo "$me: $*" 1>&2
    exit 1
}

ignorehidden=
noexecute=

while [ $# -gt 0 ]; do
    case $1 in
	-h)      ignorehidden=$1 ;;
	-n)      noexecute=$1 ;;
	-*)      usage unknown command line argument: $1 ;;
	*)       break ;;
    esac
    shift
done

[ $# -ge 4 ] || usage too few arguments: $*

directory=$1; shift
ext=$1      ; shift
prog=$1     ; shift

# There is at least one argument
origin_args="$@"

[ -d "$directory" ]  || usage directory $directory does not exist

[ -L "$prog" ]     && prog="$(readlink "$prog")"
if [ -x "$prog" ]; then
    : # given pull path to prog
elif type -p "$prog" > /dev/null; then
    : # exists as a command
else
    usage program $prog does not exist
fi

function quote_for_sed {
    sed -e 's,&,\\\&,g'
}

# Input:  pathname [args ...]
# Output: [args ...] substituted with %x patterns.
function substitute {
    local p="$1"
    shift
    local d="$(dirname "$p")"
    local b="$(basename "$p")"
    local n="${b%.*}"

    for arg in "$@"; do
	echo $arg | substitute_sed
	echo -n " "
    done
}
function substitute_sed {
    local pp="$(echo $p | quote_for_sed)"
    local dd="$(echo $d | quote_for_sed)"
    local bb="$(echo $b | quote_for_sed)"
    local nn="$(echo $n | quote_for_sed)"
    local res="$(sed -e "s|%p|$pp|g" -e "s|%d|$dd|g" -e "s|%b|$bb|g" -e "s|%n|$nn|g")"
    # If the expansion has a space in it, we need to quote it
    if [[ "$res" =~ \  ]]; then
	echo -n \"$res\"
    else
	echo -n $res
    fi
}

# Check that arguments have at least one %x sequence.
[ "$*" = "$(substitute /a/b/c.txt $*)" ] &&
    usage did not find any % escapes

n=0

tempnames=/tmp/mapdirN$$
script=/tmp/mapdirS$$
rm -f $tempnames $script

# remove $script on SIGINT, but leave it around for debugging should
# the program dies, for some reason.
trap _my_trap_EXIT_handler EXIT
trap _my_trap_INT_handler  INT

function _my_trap_EXIT_handler {
    echo "# EXIT: removing $tempnames" 1>&2
    /bin/rm -f $tempnames
    if [ -f "$script" ]; then
	echo "ERROR executing this script: $script"
    fi
}

function _my_trap_INT_handler {
    echo "# SIGINT: removing $script" 1>&2
    /bin/rm -f $script
}

if [ "$ignorehidden" ]; then
    find $directory -iname "[^.]*${ext}" -print > $tempnames
else
    find $directory -name "*${ext}" -print > $tempnames
fi
wc=($(wc -l $tempnames))
max=${wc[0]}

## For some reason, executing the commands in a `while' loop
## reading from $tempnames exits after the first one.  So, convert
## it to a script that prints progress.

cat > $script <<EOF
#! /usr/bin/env bash

set -eu

EOF
chmod 755 $script

{
    IFS=
    while read line; do
	n=$(( n + 1 ))
	echo echo =============== $prog: doing $n of $max >> $script
	echo date                                         >> $script
	echo $prog $(substitute "$line" $@)               >> $script
    done <<< "$(cat $tempnames)"

    rm -f $tempnames

    if [ "$noexecute" ]; then
	cat <<EOF
Would have executed script $script
Contents:
$(cat $script)
EOF
    else
	$script
    fi

    rm -f $script
    if [ "$noexecute" ]; then
	trap "" EXIT
    else
	trap "echo $me: SUCCESS" EXIT
    fi
    exit 0
}