coding-agent-search 0.5.0

//! Derived metric computation for analytics buckets.
//!
//! All division operations are safe against zero denominators and produce
//! `None` (rendered as JSON `null`) rather than NaN / Infinity.

use super::types::{DerivedMetrics, UsageBucket};

/// Compute all derived metrics from a [`UsageBucket`].
pub fn compute_derived(bucket: &UsageBucket) -> DerivedMetrics {
    let api_coverage_pct = safe_pct(bucket.api_coverage_message_count, bucket.message_count);

    let api_tokens_per_assistant_msg =
        safe_div(bucket.api_tokens_total, bucket.assistant_message_count);

    let content_tokens_per_user_msg =
        safe_div(bucket.content_tokens_est_total, bucket.user_message_count);

    let tool_calls_per_1k_api_tokens = if bucket.api_tokens_total > 0 {
        Some(bucket.tool_call_count as f64 / (bucket.api_tokens_total as f64 / 1000.0))
    } else {
        None
    };

    let tool_calls_per_1k_content_tokens = if bucket.content_tokens_est_total > 0 {
        Some(bucket.tool_call_count as f64 / (bucket.content_tokens_est_total as f64 / 1000.0))
    } else {
        None
    };

    let plan_message_pct = if bucket.message_count > 0 {
        Some((bucket.plan_message_count as f64 / bucket.message_count as f64) * 100.0)
    } else {
        None
    };

    let plan_token_share_content = safe_div(
        bucket.plan_content_tokens_est_total,
        bucket.content_tokens_est_total,
    );
    let plan_token_share_api = safe_div(bucket.plan_api_tokens_total, bucket.api_tokens_total);

    DerivedMetrics {
        api_coverage_pct,
        api_tokens_per_assistant_msg,
        content_tokens_per_user_msg,
        tool_calls_per_1k_api_tokens,
        tool_calls_per_1k_content_tokens,
        plan_message_pct,
        plan_token_share_content,
        plan_token_share_api,
    }
}

/// Percentage safe against zero denominator.  Returns 0.0 when denominator is
/// zero. Result is rounded to 2 decimal places (matching the original CLI
/// rounding: `(pct * 100.0).round() / 100.0`).
pub fn safe_pct(numerator: i64, denominator: i64) -> f64 {
    if denominator == 0 {
        0.0
    } else {
        let pct = (numerator as f64 / denominator as f64) * 100.0;
        (pct * 100.0).round() / 100.0
    }
}

/// Safe division returning `None` when the denominator is zero.
pub fn safe_div(numerator: i64, denominator: i64) -> Option<f64> {
    if denominator == 0 {
        None
    } else {
        Some(numerator as f64 / denominator as f64)
    }
}

/// Safe division for f64 numerator with i64 denominator.
/// Returns `None` when the denominator is zero.
pub fn safe_div_f64(numerator: f64, denominator: i64) -> Option<f64> {
    if denominator == 0 {
        None
    } else {
        Some(numerator / denominator as f64)
    }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn safe_div_zero_denominator() {
        assert_eq!(safe_div(100, 0), None);
    }

    #[test]
    fn safe_div_normal() {
        assert_eq!(safe_div(100, 50), Some(2.0));
    }

    #[test]
    fn safe_div_f64_zero_denominator() {
        assert_eq!(safe_div_f64(1.50, 0), None);
    }

    #[test]
    fn safe_div_f64_normal() {
        let result = safe_div_f64(3.0, 2);
        assert_eq!(result, Some(1.5));
    }

    #[test]
    fn safe_pct_zero_denominator() {
        assert_eq!(safe_pct(50, 0), 0.0);
    }

    #[test]
    fn safe_pct_normal() {
        let pct = safe_pct(75, 100);
        assert!((pct - 75.0).abs() < 0.01);
    }

    #[test]
    fn safe_pct_rounding() {
        // 1/3 = 33.333...% → should round to 33.33
        let pct = safe_pct(1, 3);
        assert!((pct - 33.33).abs() < 0.01);
    }

    #[test]
    fn compute_derived_empty_bucket() {
        let bucket = UsageBucket::default();
        let d = compute_derived(&bucket);
        assert_eq!(d.api_coverage_pct, 0.0);
        assert_eq!(d.api_tokens_per_assistant_msg, None);
        assert_eq!(d.content_tokens_per_user_msg, None);
        assert_eq!(d.tool_calls_per_1k_api_tokens, None);
        assert_eq!(d.tool_calls_per_1k_content_tokens, None);
        assert_eq!(d.plan_message_pct, None);
        assert_eq!(d.plan_token_share_content, None);
        assert_eq!(d.plan_token_share_api, None);
    }

    #[test]
    fn compute_derived_realistic_bucket() {
        let bucket = UsageBucket {
            message_count: 100,
            user_message_count: 50,
            assistant_message_count: 50,
            tool_call_count: 10,
            plan_message_count: 5,
            plan_content_tokens_est_total: 2_500,
            plan_api_tokens_total: 3_000,
            api_coverage_message_count: 80,
            content_tokens_est_total: 50_000,
            api_tokens_total: 60_000,
            estimated_cost_usd: 3.00,
            ..Default::default()
        };
        let d = compute_derived(&bucket);
        assert!((d.api_coverage_pct - 80.0).abs() < 0.01);
        assert_eq!(d.api_tokens_per_assistant_msg, Some(1200.0));
        assert_eq!(d.content_tokens_per_user_msg, Some(1000.0));
        assert!(d.tool_calls_per_1k_api_tokens.is_some());
        assert!(d.tool_calls_per_1k_content_tokens.is_some());
        assert!((d.plan_message_pct.unwrap() - 5.0).abs() < 0.01);
        assert_eq!(d.plan_token_share_content, Some(0.05));
        assert_eq!(d.plan_token_share_api, Some(0.05));
    }

    #[test]
    fn no_nan_or_infinity() {
        // Even with weird values, we should never get NaN or Infinity
        let bucket = UsageBucket {
            message_count: 0,
            api_tokens_total: 0,
            content_tokens_est_total: 0,
            ..Default::default()
        };
        let d = compute_derived(&bucket);
        assert!(!d.api_coverage_pct.is_nan());
        assert!(!d.api_coverage_pct.is_infinite());
    }
}