#
# executeInterval.ps1
#
# Start a program every couple of days. 
# Reads program name and interval from configuration file
#
# History:
#  ?.?   Initial version without version number
#  0.2   Added removal of backup of log-file before renaming log-file
#  0.3   ... and now the removal of backup of log-file even works!
# 

# Some constants
$logFile="executeInterval.log"
$cfgFile="executeInterval.cfg"
$runFile="executeInterval.run"
$interval=1
$programToExecute="echo `"NOTHING TO DO`""
$lastRun=$(Get-Date –month 1 -day 1 -year 1900)

# Log file writer
function writeToLog
{
  "$(Get-Date -uformat `"%Y-%m-%d %T`"): $args" | Out-File -filePath $logFile -append
} 

# check for existance and size of log file
if ((Test-Path $logFile) -eq $false) {
  #create log file
  new-item -path . -name $logfile -type "file" > $null
  #write to log file 
  writeToLog("-- New log file created")
} 
elseif ( $(Get-Item $logFile).Length -gt 100000 ) { 
  # remove backup file if necessary
  if ((Test-Path "$logFile.bak") -eq $true) {
    remove-item "$logFile.bak"
  }
  # move file to backup
  Rename-Item $logFile -newName "$logFile.bak"
  # create log file
  new-item -path . -name $logFile -type "file" > $null
  # write to log file
  writeToLog("-- Created Backup of log file and new log file")
}

# Log start time
writeToLog("-- Script executeInterval started")
writeToLog("Working in: $(Get-Location)")

# Read configuration file; use defaults if nothing available
if ((Test-Path $cfgFile) -eq $true) {
  # read file
  $lines = Get-Content $cfgFile
  $programToExecute = $lines[0]
  $interval = $lines[1]
}
else
{
  writeToLog("No cfg file found - using defaults")
}
writeToLog("Using interval=$interval and programToExecute=$programToExecute")

# Read run file; use defaults if nothing available
if ((Test-Path $runFile) -eq $true) {
  # read file
  $lines = Get-Content $runFile
  $lastRun = [System.DateTime] $lines
}
else
{
  writeToLog("No run file found - using defaults")
}
writeToLog("Using lastRun=$lastRun")

# Check whether it is time to run the program
if (($(Get-Date)-$lastRun).Days -ge $interval ) {
  &"$programToExecute"
  $lastRun=$(Get-Date)
  new-item -path . -name $runFile -type "file" -value "$lastRun" -force > $null
  writeToLog("External program executed with exit code $lastexitcode")
}
else
{
  writeToLog("External program NOT executed")
}

# Log end time
writeToLog ("-- Script executeInterval finished")