pdk-rate-limit-lib 1.7.0

PDK Rate Limit Library
Documentation 
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// Copyright (c) 2026, Salesforce, Inc.,
// All rights reserved.
// For full license text, see the LICENSE.txt file

use pdk_core::policy_context::api::Tier;
use serde::{Deserialize, Serialize};

use super::{LimitStats, RequestAllowed};

/// Local bucket configured by a vector of time window limits per tier.
#[derive(Serialize, Deserialize, Debug, Clone)]
pub struct LocalBucket {
    limits: Vec<LocalLimit>,
}

impl LocalBucket {
    /// Create new local bucket with time window limits per tier.
    pub fn new(start_time: u128, tiers: &[Tier]) -> Self {
        Self {
            limits: tiers
                .iter()
                .map(|tier| LocalLimit::from(start_time, tier))
                .collect(),
        }
    }

    /// Check if request is allowed based on time window limits per tier.
    pub fn request_allowed(&mut self, now: u128, amount: usize) -> RequestAllowed {
        self.set_time(now);

        if !self.limits.is_empty() && self.limits.iter().all(|l| l.remaining(amount)) {
            self.limits.iter_mut().for_each(|l| l.allow_request(amount));
            RequestAllowed::Allowed
        } else {
            RequestAllowed::OutOfQuota
        }
    }

    /// Get current status of the bucket.
    pub fn status(&self) -> Option<LimitStats> {
        self.limits
            .iter()
            .map(LocalLimit::stats)
            .reduce(LimitStats::most_restrictive)
    }

    /// Set limit time for the bucket.
    fn set_time(&mut self, now: u128) {
        self.limits.iter_mut().for_each(|limit| limit.set_time(now));
    }
}

/// Represents a single rate limit tier within a [`LocalBucket`].
/// Each tier has a maximum number of requests in a given period, the quota is refilled
/// at the end of each period and decremented on each allowed request.
///
/// Fields:
/// - `available`: Number of requests remaining in the current period.
/// - `max_requests`: Maximum requests allowed in a single period.
/// - `period`: Length of the time window in milliseconds.
/// - `reset`: Timestamp (in milliseconds) when the rate limit will reset and replenish quota.
#[derive(Serialize, Deserialize, Debug, Clone)]
pub struct LocalLimit {
    available: u64,
    max_requests: u64,
    period: u128,
    reset: u128,
}

impl LocalLimit {
    fn from(start_time: u128, tier: &Tier) -> Self {
        Self {
            available: tier.requests,
            max_requests: tier.requests,
            period: tier.period_in_millis as u128,
            reset: start_time + tier.period_in_millis as u128,
        }
    }

    fn stats(&self) -> LimitStats {
        LimitStats::new(self.available, self.max_requests, self.reset)
    }

    fn set_time(&mut self, now: u128) {
        while self.reset <= now {
            self.reset += self.period;
            self.available = self.max_requests;
        }
    }

    fn remaining(&self, amount: usize) -> bool {
        self.available >= amount as u64
    }

    fn allow_request(&mut self, amount: usize) {
        self.available -= amount as u64;
    }
}