bbb_api_wrapper 1.0.2

A wrapper for BuiltByBit's Ultimate REST API.
Documentation 
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// Copyright (c) 2021 Harry [Majored] [hello@majored.pw]
// MIT License (https://github.com/Majored/rs-bbb-api-wrapper/blob/main/LICENSE)

//! Holds key types for tracking our compliance with the API's rate limits.

use std::convert::TryInto;
use std::sync::atomic::{AtomicU64, Ordering};
use std::time::{SystemTime, UNIX_EPOCH};

pub enum RequestType {
    READ,
    WRITE,
}

/// A strucutre for storing the relevant atomic values in order to track our compliance with the API's rate limits.
pub struct RateLimitStore {
    pub read_last_retry: AtomicU64,
    pub read_last_request: AtomicU64,

    pub write_last_retry: AtomicU64,
    pub write_last_request: AtomicU64,
}

impl RateLimitStore {
    pub fn new() -> Self {
        RateLimitStore {
            read_last_retry: AtomicU64::new(0),
            read_last_request: AtomicU64::new(unix_timestamp()),

            write_last_retry: AtomicU64::new(0),
            write_last_request: AtomicU64::new(unix_timestamp()),
        }
    }

    pub fn store_read(&self, retry: u64) {
        self.read_last_retry.store(retry, Ordering::Release);
        self.read_last_request.store(unix_timestamp(), Ordering::Release);
    }

    pub fn store_write(&self, retry: u64) {
        self.write_last_retry.store(retry, Ordering::Release);
        self.write_last_request.store(unix_timestamp(), Ordering::Release);
    }

    pub fn reset_read(&self) {
        self.read_last_retry.store(0, Ordering::Release);
        self.read_last_request.store(unix_timestamp(), Ordering::Release);
    }

    pub fn reset_write(&self) {
        self.write_last_retry.store(0, Ordering::Release);
        self.write_last_request.store(unix_timestamp(), Ordering::Release);
    }
}

/// Compute how long, if at all, we should stall the next request in order to be compliant with rate limiting.
///
/// Returned value is in milliseconds. A value of 0 indiciates that there's no need to stall the calling request.
pub fn stall_for(store: &RateLimitStore, request_type: RequestType) -> u64 {
    let time = unix_timestamp();
    let mut stall_for = 0;

    if let RequestType::READ = request_type {
        stall_for = stall_for_helper(&store.read_last_retry, &store.read_last_request, time);
    }
    if let RequestType::WRITE = request_type {
        stall_for = stall_for_helper(&store.write_last_retry, &store.write_last_request, time);
    }

    stall_for
}

/// A helper function for `stall_for` which computes over a generic set of rate limiting parameters.
fn stall_for_helper(a_last_retry: &AtomicU64, a_last_request: &AtomicU64, time: u64) -> u64 {
    let mut stall_for = 0;
    let last_retry = a_last_retry.load(Ordering::Acquire);
    let last_request = a_last_request.load(Ordering::Acquire);

    if last_retry > 0 && (time - last_request) < last_retry {
        stall_for = last_retry - (time - last_request);
    }

    stall_for
}

/// Return the current time as a UNIX millisecond timestamp.
pub fn unix_timestamp() -> u64 {
    SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_millis().try_into().unwrap()
}