64 lines
2.2 KiB
Rust
64 lines
2.2 KiB
Rust
use crate::Pronoun;
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use time::{Date, Month, OffsetDateTime};
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/// The start of the COVID-19 lockdowns
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///
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/// This is used as an epoch in order to convert from a given date to an integer seed. This is
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/// specified as part of the algorithm for randomly selecting from a weighted list.
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pub const COVID_EPOCH: Date = match Date::from_calendar_date(2020, Month::January, 26) {
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Ok(d) => d,
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Err(_) => Date::MIN, // This never runs, but we can't unwrap, so this is what we're stuck with
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};
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/// A list of pronouns and their associated weights, used for random selection
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///
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/// Weights are typically representative of a user's preference towards a pronoun. A pronoun with
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/// a weight of 10 is twice as likely to be selected as a pronoun with a weight of 5.
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///
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/// This struct is use to represent these weights before they are used to randomly select a
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/// pronoun. Additional methods are provided to perform this random selection on a weighted list,
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/// using as a seed both an arbitrary string of bytes and a Date.
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pub struct WeightedTable<'a>(pub Vec<(&'a Pronoun, u8)>);
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impl<'a> WeightedTable<'a> {
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/// A shorthand for calling [`WeightedTable::select_on_date()`] with today's date
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///
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/// The date is generated for the system's time and timezone
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pub fn select_today(&self, seed: &[u8]) -> &Pronoun {
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self.select_on_date(
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seed,
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OffsetDateTime::now_local()
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.unwrap_or_else(|_| OffsetDateTime::now_utc())
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.date()
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)
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}
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/// Randomly select a pronoun set for a given date and name.
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///
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/// Is a wrapper for calling [`WeightedTable::select`] with the given date mixed into the seed.
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pub fn select_on_date(&self, seed: &[u8], date: Date) -> &Pronoun {
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let mut new_seed: Vec<u8> = Vec::with_capacity(seed.len() + 4);
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new_seed.extend(
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(
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(date - COVID_EPOCH)
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.whole_days()
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as u32
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).to_le_bytes()
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);
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new_seed.extend(seed);
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self.select(seed.as_ref())
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}
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/// Randomly select a pronoun set for a given seed
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///
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/// This function is *pure*, and any randomness is produced internally using PRNG seeded with
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/// the given date and seed. That is to say, for any given seed, this table must always
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/// produce the same pronoun set.
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pub fn select(&self, seed: &[u8]) -> &Pronoun {
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todo!()
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}
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}
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