#!/usr/bin/env bash

# A simple script that uses ag
# <https://github.com/ggreer/the_silver_searcher> and perl to perform
# a project-wide search and replace; it shows you the results and asks
# for confirmation before committing the changes.
#
# Usage: replace [pattern] [replace] [options for ag]

TMP_FILE="/tmp/ag-repl"
RED=`printf "\033[31m"`
NC=`printf "\033[0m"`

sanitize() {
    # For text that we interpolate into perl search/replace regex
    echo "$1" | sed -e "s_/_\\\/_g"
}

# Begin
input=$1
search=`sanitize "$1"`
replace=`sanitize "$2"`

shift
shift

# Show the search/replace results
if ag $input $* -s --group --color --break --stats \
    | perl -p -e "s/(?<=.)$search/$NC$RED$replace$NC/g" \
    | perl -p -e "s/^([0-9]+ matches$)/\n\$1/g" \
    > "$TMP_FILE"; then

    # Show the results
    less -XF "$TMP_FILE"

    # Calculate if there were results
    lines=`wc -l $TMP_FILE | awk '{print $1}'`
    rm -rf "$TMP_FILE"
    [ "$lines" -lt 6 ] && exit 2

    # Ask for confirmation
    echo
    echo -n "Apply changes? (y/n) "
    read -n1 REPLY
    echo

    if [[ $REPLY =~ ^[Yy]$ ]]; then
        # Now actually do the search replace! This is destructive. No, no
        # backups are made. You better have read the earlier prompt!
        ag -l $input $* | xargs perl -pi -e "s/$search/$replace/g"
        echo "Done!"
        exit
    else
        echo $RED"Aborted!"$NC
        exit 3
    fi
fi

exit 1