DownloadTo-Mp3.ps1

param(
    [string[]] $videoId,
    [switch] $setup,
    [double] $trimPercentage = 0.015
)

function Ensure-Path
{
    param([string]$Path)
    if (!(Test-Path $Path)) {
        New-Item -ItemType Directory -Path $Path
    }
}

function Expand-PartialArchive
{
    param(
        [string] $Path,
        [string] $DestinationPath,
        [string] $like
    )

    Ensure-Path -Path $DestinationPath

    Add-Type -AssemblyName System.IO.Compression.FileSystem

    $zip = [System.IO.Compression.ZipFile]::OpenRead($Path)

    $zip.Entries `
        | Where-Object { $_.FullName -like $like -and $_.Name } `
        | ForEach-Object {
            [System.IO.Compression.ZipFileExtensions]::ExtractToFile(
                $_,
                "$DestinationPath\$($_.Name)",
                $true
            )
        }

    $zip.Dispose()
}

function Get-Duration
{
    param(
        [string] $executable,
        [string] $mediaFilePath
    )

    $durationCommand = "$executable -i $mediaFilePath 2>&1"
    Write-Host "Duration:" $durationCommand
    $durationResult = Invoke-Expression $durationCommand
    $match = $durationResult | Select-String -Pattern "Duration:\s+(\d{2}:\d{2}:\d{2}.\d{2}),.*"

    [System.TimeSpan]::Parse($match.Matches.Groups[1].Value)
}

function Run-Setup
{
    if ($IsWindows) 
    {
        # https://www.gyan.dev/ffmpeg/builds/
        $url = (Invoke-WebRequest "https://www.gyan.dev/ffmpeg/builds/ffmpeg-release-full.zip" -ErrorAction Ignore -SkipHttpErrorCheck).Headers.Location[0]
        Invoke-WebRequest $url -OutFile ffmpeg.zip
        Expand-PartialArchive -Path ffmpeg.zip -DestinationPath $binPath -like "*/bin/*"
        Remove-Item .\ffmpeg.zip

        # http://ytdl-org.github.io/youtube-dl/download.html
        $url = "https://yt-dl.org/downloads/2020.09.14/youtube-dl.exe"
        Ensure-Path $binPath
        Invoke-WebRequest $url -OutFile $ytdlRuntime
    }

    if ($IsLinux) 
    {
        # docker run -it --rm -v ".:/project" -w "/project" --entrypoint pwsh mcr.microsoft.com/dotnet/core/sdk
        # run ".\script.ps1 -setup" in the container
        # commit the container for later use
        # or use a dockerfile ...

        Add-Content /etc/apt/sources.list -Value "deb http://ftp.de.debian.org/debian sid main"
        & apt-get update 
        # ffmpeg is auto-installed with ytdl
        & apt-get install -y youtube-dl
        & apt-get remove --purge -y ((& apt-mark showauto) -join " ")
        Remove-Item "/var/lib/apt/lists/*" -Force
    }
}

function DownloadTo-Mp3 
{
    param(
        [string] $executable,
        [string] $videoIdentifier,
        [string] $targetFileName = $videoIdentifier,
        [string] $targetFolder
    )

    $downloadFilePath = Join-Path $targetFolder "$targetFileName.mp3"
    $outArgument = Join-Path $targetFolder ($targetFileName+'.%(ext)s');
    $downloadCommand = "$executable -x -f bestaudio --audio-format mp3 --add-metadata -o `"$outArgument`" $videoIdentifier"

    Write-Host "Download:" $downloadCommand
    Invoke-Expression $downloadCommand | Write-Host

    $downloadFilePath
}

function Trim-Mp3
{
    param(
        [string] $executable,
        [string] $sourceFilePath,
        [string] $targetFolderPath,
        [double] $trimPercentage,
        [switch] $deleteSource
    )

    $sourceDuration = Get-Duration `
        -executable $executable `
        -mediaFilePath $sourceFilePath

    $trimSeconds = [int]($sourceDuration.TotalSeconds * $trimPercentage)
    $ss = [System.TimeSpan]::FromSeconds($trimSeconds)
    $to = $sourceDuration.Add([System.TimeSpan]::FromSeconds(-$trimSeconds))
    $targetDuration = $to-$ss
    $diffDuration = $sourceDuration - $targetDuration

    Write-Host "Source Duration:" $sourceDuration
    Write-Host "Target Duration:" $targetDuration
    Write-Host "Removing $($diffDuration.TotalSeconds) Seconds from the Track"

    $targetFilePath = Join-Path $targetFolderPath (Split-Path $sourceFilePath -Leaf)
    $trimCommand = "$executable -hide_banner -ss $ss -to $to -i $sourceFilePath -y -c copy $targetFilePath"
    
    Write-Host "Trim:" $trimCommand
    Invoke-Expression $trimCommand | Write-Host

    if ($deleteSource) 
    {
        Remove-Item $sourceFilePath
    } 
}

#######################
###                 ###
###  ACTUAL SCRIPT  ###
###                 ###
#######################

$location = Get-Location
$binPath = Join-Path $location "bin"
$tempPath = Join-Path $location "temp"
$outPath = Join-Path $location "out"

Ensure-Path $tempPath
Ensure-Path $outPath

$ytdlRuntime = "youtube-dl"
$ffmpegRuntime = "ffmpeg"

if ($IsWindows) 
{
    $ffmpegRuntime = Join-Path $binPath "ffmpeg.exe"
    $ytdlRuntime = Join-Path $binPath "youtube-dl.exe"
}

if ($setup)
{
    Run-Setup
}

# https://stackoverflow.com/questions/46508055/using-ffmpeg-to-cut-audio-from-to-position
# https://superuser.com/questions/23930/how-to-decode-aac-m4a-audio-files-into-wav#:~:text=7%20Answers&text=The%20easiest%20way%20to%20do,this%20to%20them%20in%20bulk.
# https://spapas.github.io/2018/03/06/easy-youtube-mp3-downloading/

# .\youtube-dl.exe -x --audio-format mp3 --audio-quality 9 --postprocessor-args "-ss 600" mcQc3UdkSow

# https://ffmpeg.org/ffmpeg.html
# .\ffmpeg.exe -ss 600 -t 1:00:00  -i $m4aPath $m4aPath+".mp3"

$videoId | Where-Object { $_ } | ForEach-Object {
    $downloadedFile = DownloadTo-Mp3 `
        -executable $ytdlRuntime `
        -targetFolder $tempPath `
        -videoIdentifier $_

    Trim-Mp3 `
        -executable $ffmpegRuntime `
        -sourceFilePath $downloadedFile `
        -targetFolderPath $outPath `
        -trimPercentage $trimPercentage `
        -deleteSource
}

# https://github.com/ytdl-org/youtube-dl/blob/master/README.md#readme

# normalize: https://superuser.com/a/323127/1191155
# http://ffmpeg.org/ffmpeg-all.html#loudnorm

# overlaying mulitple files
# https://www.reddit.com/r/ffmpeg/comments/7kpqxa/merging_two_audio_files/drh8dm9/