<#
.Synopsis
   Sorts picture files from camera sources into appropriate
   folders for filing.
.DESCRIPTION
   Compares the set of pictures in the camera source folder
   and the backup folder, then merges/sorts the contents into
   a third location based on how they need to be filed.

   Items get sorted into one of four groups:
   - To File: Items only in camera or items in camera and backup.
   - Only In Backup: Items only in backup.
   - Duplicate Camera Items: Items that appear multiple times in the camera folder.
   - Backups To Remove After Filing: Items that were in the backup folder where originals are ready to file.
.EXAMPLE
   .\Sort-PictureFiles.ps1 -CameraFolder .\camera -BackupFolder .\backup -DestinationFolder .\destination
#>
[CmdletBinding()]
Param(
    [Parameter(
        Mandatory=$True,
        HelpMessage="The folder where all the pictures and videos from cameras are located. All subfolders will be considered picture sources. THIS FOLDER WILL BE EMPTIED AFTER SORTING.")]
    [ValidateNotNullOrEmpty()]
    [string]
    $CameraFolder,

    [Parameter(
        Mandatory=$True,
        HelpMessage="The folder where pictures are automatically backed up. All subfolders will be considered picture sources. THIS FOLDER WILL BE EMPTIED AFTER SORTING.")]
    [ValidateNotNullOrEmpty()]
    [string]
    $BackupFolder,

    [Parameter(
        Mandatory=$True,
        HelpMessage="The folder where sorted pictures and videos should be placed. All camera and backup pictures will be sorted into folders in here.")]
    [ValidateNotNullOrEmpty()]
    [string]
    $DestinationFolder,

    [Parameter(
        Mandatory=$False,
        HelpMessage="The folder where sorted pictures and videos should be placed. All camera and backup pictures will be sorted into folders in here.")]
    [ValidateNotNullOrEmpty()]
    [string]
    $ExifTool = "exiftool.exe"
)
Begin
{
    If (-Not (Test-Path $CameraFolder -PathType Container))
    {
        throw "The camera folder $CameraFolder does not exist."
    }
    If (-Not (Test-Path $BackupFolder -PathType Container))
    {
        throw "The backup folder $BackupFolder does not exist."
    }
    If (-Not (Test-Path $DestinationFolder -PathType Container))
    {
        throw "The sort destination folder $DestinationFolder does not exist."
    }
    if ((Get-Command $ExifTool -ErrorAction SilentlyContinue) -eq $NULL)
    {
        Write-Host "Unable to find exiftool.exe in your path."
    }

    $toFileFolder = New-Item -Path "$DestinationFolder" -Name "To File" -ItemType Directory -Force
    $onlyInBackupFolder = New-Item -Path "$DestinationFolder" -Name "Only In Backup" -ItemType Directory -Force
    $duplicateFolder = New-Item -Path "$DestinationFolder" -Name "Duplicate Camera Items" -ItemType Directory -Force
    $removeAfterFiling = New-Item -Path "$DestinationFolder" -Name "Backups To Remove After Filing" -ItemType Directory -Force

    function SafeMove()
    {
        Param($SourceFile, $DestinationFolder)
        Write-Verbose "Moving $SourceFile"
        $name = [System.IO.Path]::GetFileNameWithoutExtension($SourceFile)
        $ext = [System.IO.Path]::GetExtension($SourceFile)
        if(-Not (Test-Path (Join-Path -Path $DestinationFolder -ChildPath "$name$ext")))
        {
            Move-Item -Force -Path $SourceFile -Destination $DestinationFolder
            return;
        }

        $count = 0
        while(Test-Path (Join-Path -Path $DestinationFolder -ChildPath "$name-$count$ext"))
        {
            $count++
        }

        Move-Item -Force -Path $SourceFile -Destination (Join-Path -Path $DestinationFolder -ChildPath "$name-$count$ext")
    }
}
Process
{
    # Get pairs of hash/path for camera folder.
    $cameraHashes = Get-ChildItem -Path $CameraFolder -Recurse -File | Sort-Object -Property FullName | Get-FileHash
    Write-Verbose "Camera file hashes:"
    $cameraHashes | Write-Verbose
    $cameraMoved = @()
    for($i = 0; $i -lt $cameraHashes.length; $i++)
    {
        $current = $cameraHashes[$i];
        if($cameraMoved -contains $current.Hash)
        {
            # It's a duplicate in the camera folder (e.g., one person mailed a copy of a photo to another).
            SafeMove $current.Path $duplicateFolder.FullName
        }
        else
        {
            # It's a one-of-a-kind in the camera folder - file it!
            SafeMove $current.Path $toFileFolder.FullName
            $cameraMoved += $current.Hash
        }
    }

    # Get pairs of hash/path for backup folder.
    $backupHashes = Get-ChildItem -Path $BackupFolder -Recurse -File | Sort-Object -Property FullName | Get-FileHash
    Write-Verbose "Backup file hashes:"
    $backupHashes | Write-Verbose
    $backupsMoved = @()
    for($i = 0; $i -lt $backupHashes.length; $i++)
    {
        $current = $backupHashes[$i];
        if($backupsMoved -contains $current.Hash)
        {
            # It's a duplicate backup - assume it can be removed after filing.
            SafeMove $current.Path $removeAfterFiling.FullName
            continue;
        }

        $found = $cameraHashes | Where-Object { $_.Hash -eq $current.Hash }
        if ($found -ne $NULL)
        {
            # It's a backup of an item found in the camera folder - assume it can be removed after filing.
            SafeMove $current.Path $removeAfterFiling.FullName
            $backupsMoved += $current.Hash
            continue;
        }

        # It wasn't a duplicate backup and it wasn't in the camera folder - possible recovery?
        SafeMove $current.Path $onlyInBackupFolder.FullName
        $backupsMoved += $current.Hash
    }

    foreach($location in ($toFileFolder.FullName, $onlyInBackupFolder.FullName, $duplicateFolder.FullName, $removeAfterFiling.FullName))
    {
        Push-Location $location
        & $ExifTool "-FileName<DateTimeOriginal" -d "%Y%m%d_%H%M%S%%-c.%%e" *.jpg
        Pop-Location
    }
}