#!/bin/bash
# -*- coding: utf-8 -*-
# 
# Copyright by Scott Severance
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

# Auto-backup script
#
# Ensures that too much data doesn't get lost if $program
#   crashes during a save.

prog="$(basename $0)"
timeout="300" # 5 minutes
timeoutStep="5" #seconds
pid=
watchFiles=

# Color codes for an easier-to-read output
FILE_COLOR="\033[4;34m"
ERROR_COLOR="\033[0;31m"
MSG_COLOR="\033[0;32m"
NO_COLOR="\033[0m" #Transparent - don't change
TITLEBAR_START="\033]0;"
TITLEBAR_END="\007"

E_USAGE=65
E_NORMAL=0
E_BAD_ARGUMENT=66

function usage {
    echo -e "${MSG_COLOR}Usage:"
    echo -e "$prog program_pid filename [filename [...]]${NO_COLOR}"
    echo
    echo "$prog defends against files being ruined by misbehaving programs. To"
    echo "accomplish this, $prog makes a compressed copy of each file listed on"
    echo "the command line every $timeout seconds until the program with the specified pid"
    echo "terminates."
    echo
    echo "$prog keeps its backups in ~/.file-insurance/\$programName/\$filename."
    [ -z "$1" ] && exit $E_USAGE
}

function programAlive {
    local pid="$1"
    ps --pid "$pid" > /dev/null 2>&1
    return $?
}

function getNewestFile {
    ls -1t "$1" | while read "crud"; do
                      if [ -n "$crud" ]; then
                          echo "$crud"
                          break
                      fi
                  done
}

function makeBackup {
    local programName="$HOME/.file-insurance/$1"
    local filename="$2"

    echo -ne "$ERROR_COLOR"

    if [ ! -f "$filename" ]; then
        echo -e "Error: the file $filename doesn't exist. Aborting...${NO_COLOR}"
        exit "$E_BAD_ARGUMENT"
    fi

    [ -d "$programName" ] || mkdir -p "$programName"
    local dir="$programName/$filename"
    [ -d "$dir" ] || mkdir -p "$dir"

    local currentTime="$(date +'%Y-%m-%d_%H-%M-%S')"
    local backupFile="$dir/file-insurance.$currentTime"
    local lastBackupFile=
    if [ "$(ls -1 "$dir" | wc | awk '{print $1}')" != "0" ]; then
        globalTmp="$(getNewestFile "$dir")"
        lastBackupFile="${dir}/${globalTmp}"
    fi

    cp "$filename" "$backupFile"
    bzip2 "$backupFile"
    backupFile="${backupFile}.bz2"

    if [ -n "$lastBackupFile" ]; then # no sense in making multiple copies of identical files
        if $(diff "$lastBackupFile" "$backupFile" >/dev/null); then # diff exits 0 if there are no differences
            rm -f "$backupFile"
        fi
    fi

    echo -ne "$NO_COLOR"
}

function sleepCounter { # args: sleep time, time step, callback function, [callback function args...]
     local remaining="$1"; shift
     local step="$1";      shift
     local callback="$1";  shift

     while [[ $remaining > 0 ]]; do
         $callback "$@"
         (( remaining -= step ))
         sleep $step
     done
}

function exitIfProgramDead {
    if ! $(programAlive "$pid"); then
        echo -e "${MSG_COLOR}$pidName ($pid) is no longer running. Exiting.${NO_COLOR}"
        echo -e "\n\nConsider running file-insurance-cleanup to purge unnecessary files."
        exit "$E_NORMAL"
    fi
}

function initThis {
    if [ "z$1" = "z" -o "z$2" = "z" ]; then
        usage
    else
        pid="$1"; shift
        watchFiles=("$@")
    fi
    echo -ne "$ERROR_COLOR"
    if ! $(programAlive "$pid"); then
        echo "Error: invalid pid"
        echo
        usage "false"
        exit "$E_BAD_ARGUMENT"
    fi
    if [ -z "${watchFiles[0]}" ]; then
        echo "Error: no file to watch"
        echo
        usage false
        exit "$E_BAD_ARGUMENT"
    fi
    echo -ne "$NO_COLOR"
}

function main {
    [ "$1" = "--help" ] && usage

    initThis "$@"
    shift

    local pidName="$(ps --pid "$pid" --no-headers | awk '{print $4}' | sed 's/\//_/g')"

    echo -ne "${MSG_COLOR}Monitoring $pidName ($pid) and the file(s)"
    for i in "$@"; do
        echo -en " \"${FILE_COLOR}${i}${MSG_COLOR}\""
    done
    echo -e "...${NO_COLOR}"

    echo -ne "${TITLEBAR_START}file-insurance monitoring ${pidName} (${pid})${TITLEBAR_END}"

    while : ; do
        for i in "${watchFiles[@]}"; do
            makeBackup "$pidName" "$i"
        done

        sleepCounter "$timeout" "$timeoutStep" "exitIfProgramDead"
    done
}

main "$@"