orch-cli 0.98.7

//! Hash-based selection utilities for load-balanced routing.
//!
//! Provides deterministic-ish hash functions used by `AgentWeights::weighted_select`
//! to distribute tasks across agents without requiring an external RNG crate.

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

/// Global sequence counter to decorrelate hash inputs across rapid calls.
pub(crate) static HASH_COUNTER: AtomicU64 = AtomicU64::new(0);

/// Simple deterministic-ish fraction [0.0, 1.0) based on time + task data.
/// Not cryptographic, but sufficient for load distribution.
pub(super) fn simple_hash_fraction_for(task_id: &str) -> f64 {
    // Use SystemTime since Instant::now().elapsed() measures time since
    // the instant was created and is nearly always ~0 here. SystemTime
    // gives a clock relative to the UNIX epoch which varies across calls.
    let nanos = u64::try_from(
        SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap_or_default()
            .as_nanos(),
    )
    .unwrap_or(u64::MAX);

    let seq = HASH_COUNTER.fetch_add(1, Ordering::Relaxed);
    let task_hash = hash_task_id(task_id);
    let seed = nanos ^ seq ^ task_hash;

    // Mix bits using a simple hash
    let hash = seed
        .wrapping_mul(6_364_136_223_846_793_005)
        .wrapping_add(1_442_695_040_888_963_407);
    f64::from(u16::try_from(hash % 10000).unwrap_or(0)) / 10000.0
}

/// Simple index selection using instant-based hash.
pub(crate) fn simple_hash_index_for(len: usize, task_id: &str) -> usize {
    if len == 0 {
        return 0;
    }

    // Use SystemTime for a variable seed instead of Instant::now().elapsed().
    let nanos = u64::try_from(
        SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap_or_default()
            .as_nanos(),
    )
    .unwrap_or(u64::MAX);

    let seq = HASH_COUNTER.fetch_add(1, Ordering::Relaxed);
    let task_hash = hash_task_id(task_id);
    let seed = nanos ^ seq ^ task_hash;

    let hash = seed
        .wrapping_mul(6_364_136_223_846_793_005)
        .wrapping_add(1_442_695_040_888_963_407);
    usize::try_from(hash % len as u64).unwrap_or(0)
}

fn hash_task_id(task_id: &str) -> u64 {
    task_id.bytes().fold(0u64, |acc, b| {
        acc.wrapping_mul(31).wrapping_add(u64::from(b))
    })
}