From a technical perspective, that's more or less baked into HLS: these are just discrete files being served over HTTP, so you can save the files to disk along with the manifest file and you have the content.
In practice, there is a little more to it. For example, when DRM is enabled, you need some way to preserve the decryption keys. And for live content, the manifest file usually just tells the client about a sliding window of files, so you need a tiny bit of additional client side logic to pay attention to this fact.
One cool thing about DASH/HLS is that you can do some pretty complex mixing of content - you can build a traditional TV-channel like experience that mixes live and prerecorded content, you can replace and inject ads, you can make live content immediately available for on-demand playback, etc.
In practice, there is a little more to it. For example, when DRM is enabled, you need some way to preserve the decryption keys. And for live content, the manifest file usually just tells the client about a sliding window of files, so you need a tiny bit of additional client side logic to pay attention to this fact.
One cool thing about DASH/HLS is that you can do some pretty complex mixing of content - you can build a traditional TV-channel like experience that mixes live and prerecorded content, you can replace and inject ads, you can make live content immediately available for on-demand playback, etc.