use crate::core::event::EventSource;
use crate::retro::types::{Bet, Inputs};
const MIN_CALLS: usize = 20;
const MIN_CACHE_HIT_RATIO: f64 = 0.2;
pub fn run(inputs: &Inputs) -> Vec<Bet> {
let (total_calls, total_in, total_cache_read) = sum_proxy_cache(inputs);
if total_calls < MIN_CALLS {
return vec![];
}
let denominator = total_in + total_cache_read;
if denominator == 0 {
return vec![];
}
let hit_ratio = total_cache_read as f64 / denominator as f64;
if hit_ratio >= MIN_CACHE_HIT_RATIO {
return vec![];
}
let savings = (MIN_CACHE_HIT_RATIO - hit_ratio) * total_in as f64 * 0.1;
vec![Bet {
id: format!("H20:cache_hit:{:.2}", hit_ratio),
heuristic_id: "H20".into(),
title: format!(
"Low Anthropic cache hit ratio ({:.0}% over {total_calls} calls)",
hit_ratio * 100.0
),
hypothesis: format!(
"Cache hit ratio {:.1}% < {:.0}%. Unstable system prompt prevents prefix caching.",
hit_ratio * 100.0,
MIN_CACHE_HIT_RATIO * 100.0
),
expected_tokens_saved_per_week: savings,
effort_minutes: 60,
evidence: vec![format!(
"{total_calls} proxy calls, cache_read={total_cache_read}, tokens_in={total_in}"
)],
apply_step: "Stabilize the system prompt and promote it to a cached prefix block.".into(),
evidence_recency_ms: inputs.window_end_ms,
confidence: None,
category: None,
}]
}
fn sum_proxy_cache(inputs: &Inputs) -> (usize, u64, u64) {
let mut calls = 0usize;
let mut total_in = 0u64;
let mut total_cache_read = 0u64;
for (_, event) in &inputs.events {
if event.source != EventSource::Proxy {
continue;
}
let (Some(cache_read), Some(tin)) = (event.cache_read_tokens, event.tokens_in) else {
continue;
};
calls += 1;
total_in += tin as u64;
total_cache_read += cache_read as u64;
}
(calls, total_in, total_cache_read)
}