Public/Get-PlexCollection.ps1

function Get-PlexCollection
{
    <#
        .SYNOPSIS
            Gets collections.
        .DESCRIPTION
            Gets collections.
        .PARAMETER Id
            The id of the collection to get.
        .PARAMETER LibraryId
            The id of the library to get collections from.
        .PARAMETER IncludeItems
            If specified, the items in the collection are returned.
        .EXAMPLE
            Get-PlexCollection -LibraryId 1
        .EXAMPLE
            Get-PlexCollection -Id 723 -IncludeItems
    #>


    [CmdletBinding()]
    param(
        [Parameter(Mandatory = $true, ParameterSetName = "CollectionId")]
        [PSObject]
        $Id,

        [Parameter(Mandatory = $true, ParameterSetName = "LibraryId")]
        [PSObject]
        $LibraryId,

        [Parameter(Mandatory = $false)]
        [Switch]
        $IncludeItems
    )

    #############################################################################
    #Region Import Plex Configuration
    if(!$script:PlexConfigData)
    {
        try
        {
            Import-PlexConfiguration -WhatIf:$False
        }
        catch
        {
            throw $_
        }
    }
    #EndRegion

    #############################################################################
    #Region Construct Uri
    if($Id)
    {
        $RestEndpoint = "library/collections/$($Id)"
    }

    if($LibraryId)
    {
        $RestEndpoint = "library/sections/$($LibraryId)/collections"
        #?includeCollections=1&includeExternalMedia=1&includeAdvanced=1&includeMeta=1"
        $Params = [Ordered]@{
            "includeCollections"   = 1
            "includeExternalMedia" = 0
            "includeAdvanced"      = 1
            "includeMeta"          = 1
        }
    }

    $DataUri = Get-PlexAPIUri -RestEndpoint $RestEndpoint -Params $Params
    #EndRegion

    #############################################################################
    #Region Get data
    try
    {
        $Data = Invoke-RestMethod -Uri $DataUri -Method GET
        if($Data.MediaContainer.metadata.count -eq 0)
        {
            return
        }
    }
    catch
    {
        throw $_
    }
    #EndRegion

    #############################################################################
    #Region Get items
    if($IncludeItems)
    {
        if($Id)
        {
            Write-Verbose -Message "Function: $($MyInvocation.MyCommand): Appending collection item(s) for collection $($Data.MediaContainer.metadata.Title)"
            try
            {
                $Params = [Ordered]@{
                    excludeAllLeaves = 1
                }
                $ItemsUri = Get-PlexAPIUri -RestEndpoint "library/collections/$($Id)/children" -Params $Params
                $Items = Invoke-RestMethod -Uri $ItemsUri -Method GET
                $Data.MediaContainer.metadata | Add-Member -NotePropertyName 'Items' -NotePropertyValue $Items.MediaContainer.metadata
            }
            catch
            {
                throw $_
            }
        }
        else
        {
            # Iterate over each collection, make a lookup for the items and append them:
            foreach($Collection in $Data.MediaContainer.Metadata)
            {
                Write-Verbose -Message "Function: $($MyInvocation.MyCommand): Appending collection item(s) for collection $($Collection.title)"
                try
                {
                    $Params = [Ordered]@{
                        excludeAllLeaves = 1
                    }
                    $ItemsUri = Get-PlexAPIUri -RestEndpoint "library/collections/$($Collection.RatingKey)/children" -Params $Params
                    $Items = Invoke-RestMethod -Uri $ItemsUri -Method GET
                    $Collection | Add-Member -NotePropertyName 'Items' -NotePropertyValue $Items.MediaContainer.Metadata
                }
                catch
                {
                    throw $_
                }
            }
        }
    }
    #EndRegion

    return $Data.MediaContainer.Metadata
}