Binary search indexes for artist

[fsktom]

Similar to #39

https://youtu.be/KXJSjte_OAI

Don't know if it's necessary because the performance should now be good enough and it might bring unncessary overhead.
But it'd be fun to create an index for using binary search for artists as well.

Probably not really feasible, because the functions accept [SongEntry] and not SongEntries - meaning I'd have to put the index as another argument or make the argument SongEntries with the index as an attribute...

You could create the index while parsing the endsong files.

rusty-endsong-parser/src/display/date.rs

Lines 109 to 139 in 8c1944c

	pub fn gather_plays<Asp: Music>(
	entries: &[SongEntry],
	aspect: &Asp,
	start: &DateTime<Tz>,
	end: &DateTime<Tz>,
	) -> usize {
	assert!(start <= end, "Start date is after end date!");
	let begin = match entries.binary_search_by(|entry| entry.timestamp.cmp(start)) {
	// timestamp from entry
	Ok(i) => i,
	// user inputted date - i because you want it to begin at the closest entry
	Err(i) if i != entries.len() => i,
	// user inputted date that's after the last entry
	Err(_) => entries.len() - 1,
	};
	let stop = match entries.binary_search_by(|entry| entry.timestamp.cmp(end)) {
	// timestamp from entry
	Ok(i) => i,
	// user inputted date - i-1 becuase i would include one entry too much
	Err(i) if i != 0 => i - 1,
	// user inputted date that's before the first entry
	Err(_) => 0,
	};
	entries[begin..=stop]
	.iter()
	.filter(|entry| aspect.is_entry(entry))
	.count()
	}

instead of that linear scan at the bottom you could do something like (or similar, haven't thought exactly about how you'd access it)
artist_index[artist].unwrap()[begin..=stop].len()
And the index would be a collection of artists with a list of the indexes those artists appear at
Implementation details tbd

Ofc, this would also only work for artists, while this function accepts Artists, Albums and Songs... So you could create other indexes for them or separate the function
...or probably just let it be because it isn't a good idea :P

[fsktom]

Probably the best structure for the index would be a HashMap where the keys are the artist names (as Strings) and the values are Vec<DateTime<Tz>> with the timestamps of the corresponding entries