src/Get-Single.psm1

using module ./Invoke-Reader.psm1
using module ./Mapping/ConvertFrom-Record.psm1

<#
.SYNOPSIS
    Executes a parameterized SQL query and returns the single row.
.PARAMETER Connection
    The connection to the data source.
.PARAMETER Command
    The SQL query to be executed.
.PARAMETER Parameters
    The parameters of the SQL query.
.PARAMETER AsHashtable
    Value indicating whether to convert the record to a hash table.
.OUTPUTS
    [hashtable] The single row as a hash table. If not found: throws an error if `-ErrorAction` is set to `Stop`, otherwise returns `$null`.
.OUTPUTS
    [psobject] The single row as a custom object. If not found: throws an error if `-ErrorAction` is set to `Stop`, otherwise returns `$null`.
#>

function Get-Single {
    [CmdletBinding()]
    [OutputType([hashtable], [psobject])]
    param (
        [Parameter(Mandatory, Position = 0)]
        [System.Data.IDbConnection] $Connection,

        [Parameter(Mandatory, Position = 1)]
        [string] $Command,

        [Parameter(Position = 2)]
        [ValidateNotNull()]
        [hashtable] $Parameters = @{},

        [Parameter()]
        [switch] $AsHashtable
    )

    $reader = (Invoke-Reader $Connection -Command $Command -Parameters $Parameters).Reader
    $record = $null
    $rowCount = 0
    while ($reader.Read()) {
        if (++$rowCount -gt 1) { break }
        $record = ConvertFrom-Record $reader -AsHashtable:$AsHashtable
    }

    $reader.Close()
    $invalidOperation = $record -and ($rowCount -eq 1) ? $null : [InvalidOperationException] "Unable to fetch the single row."
    if ($invalidOperation -and ($ErrorActionPreference -eq "Stop")) { throw $invalidOperation }
    $record
}