gam_solve/

progress_log.rs

//! Stderr progress logger for the `gam` CLI and the `gamfit` Python bindings.
//!
//! Installs a global [`log`] backend that timestamps each record (elapsed since
//! process start), strips terminal control / escape sequences, and writes to
//! stderr under a write-lock so concurrent solver threads never interleave
//! partial lines. This is the sole logger bootstrap for the CLI binary and the
//! Python extension module.
//!
//! (Extracted from the former TUI `visualizer` module, which has been removed
//! along with its `crossterm`/`ratatui` dependencies; only the stderr logging
//! survives — the live chart / progress lanes were non-essential opt-in cruft.)

use log::{LevelFilter, Log, Metadata, Record};
use std::io::{self, Write};
use std::sync::{Mutex, OnceLock};
use std::time::{Duration, Instant};

static LOGGER: ProgressLogger = ProgressLogger;
static LOG_START: OnceLock<Instant> = OnceLock::new();
static LOG_WRITE_LOCK: Mutex<()> = Mutex::new(());

struct ProgressLogger;

impl Log for ProgressLogger {
    fn enabled(&self, metadata: &Metadata<'_>) -> bool {
        metadata.level() <= log::max_level()
    }

    fn log(&self, record: &Record<'_>) {
        if !self.enabled(record.metadata()) {
            return;
        }
        let lines = format_log_record(record);
        let log_lock_guard = LOG_WRITE_LOCK.lock().unwrap_or_else(|p| p.into_inner());
        let mut stderr = io::stderr().lock();
        for line in lines {
            // stderr is gone (closed pipe, full disk): further lines cannot land
            // either, and logging the failure would recurse into this `Log` impl,
            // so stop writing this record rather than spin through every line.
            if writeln!(stderr, "{line}").is_err() {
                break;
            }
        }
        drop(log_lock_guard);
    }

    fn flush(&self) {}
}

fn format_log_record(record: &Record<'_>) -> Vec<String> {
    let elapsed = LOG_START.get_or_init(Instant::now).elapsed();
    let prefix = format!("[{}]", human_elapsed(elapsed));
    sanitize_log_message(&record.args().to_string())
        .lines()
        .map(|line| format!("{prefix} {line}"))
        .collect()
}

fn sanitize_log_message(message: &str) -> String {
    let mut sanitized = String::with_capacity(message.len());
    let mut chars = message.chars().peekable();
    while let Some(ch) = chars.next() {
        match ch {
            '\x1b' => {
                strip_escape_sequence(&mut chars);
            }
            '\r' => sanitized.push('\n'),
            '\n' | '\t' => sanitized.push(ch),
            ch if ch.is_control() => {}
            ch => sanitized.push(ch),
        }
    }
    sanitized
}

fn strip_escape_sequence<I>(chars: &mut std::iter::Peekable<I>)
where
    I: Iterator<Item = char>,
{
    match chars.next() {
        Some('[') => {
            for seq_ch in chars.by_ref() {
                if ('@'..='~').contains(&seq_ch) {
                    break;
                }
            }
        }
        Some(']') => strip_string_escape(chars),
        Some('P' | 'X' | '^' | '_') => strip_string_escape(chars),
        Some(_) | None => {}
    }
}

fn strip_string_escape<I>(chars: &mut std::iter::Peekable<I>)
where
    I: Iterator<Item = char>,
{
    while let Some(seq_ch) = chars.next() {
        if seq_ch == '\x07' {
            break;
        }
        if seq_ch == '\x1b' && chars.next_if_eq(&'\\').is_some() {
            break;
        }
    }
}

fn human_elapsed(elapsed: Duration) -> String {
    let total_secs = elapsed.as_secs();
    let hours = total_secs / 3600;
    let minutes = (total_secs / 60) % 60;
    let seconds = total_secs % 60;
    if hours > 0 {
        format!("{hours}h {minutes:02}m {seconds:02}s")
    } else if minutes > 0 {
        format!("{minutes}m {seconds:02}s")
    } else {
        format!("{seconds}s")
    }
}

/// Default verbosity when the user has not requested an explicit level.
///
/// A single ordinary fit (e.g. a 400-row `s(x)` P-spline) emits thousands of
/// per-iteration `[OUTER ...]` / `[GAM ALO]` `info!`/`warn!` records. Writing
/// them to stderr under a write-lock is not free — when stderr is a terminal
/// or a pipe it is *measurable* fit overhead (#1689), and for the common case
/// (a library call from Python that just wants the model back) the stream is
/// pure noise. So the out-of-the-box level is `Warn`: genuine problems still
/// surface, but the routine progress chatter is silent unless explicitly
/// requested. Power users opt back in by calling [`set_log_level`] (e.g.
/// `set_log_level("info")`) or [`log::set_max_level`] directly — verbosity is
/// set through an explicit API, not a process-global env var.
const DEFAULT_LOG_LEVEL: LevelFilter = LevelFilter::Warn;

/// Parse one verbosity spelling into a [`LevelFilter`]. Case-insensitive,
/// surrounding whitespace ignored. Returns `None` for anything unrecognized so
/// the caller can fall through to the next source rather than guessing.
fn parse_log_level(value: &str) -> Option<LevelFilter> {
    match value.trim().to_ascii_lowercase().as_str() {
        "off" | "none" | "silent" => Some(LevelFilter::Off),
        "error" => Some(LevelFilter::Error),
        "warn" | "warning" => Some(LevelFilter::Warn),
        "info" => Some(LevelFilter::Info),
        "debug" => Some(LevelFilter::Debug),
        "trace" | "all" => Some(LevelFilter::Trace),
        _ => None,
    }
}

/// Map a caller-supplied verbosity spelling onto a [`LevelFilter`]. Wraps the
/// internal `parse_log_level` for out-of-crate callers (the CLI `--log-level`
/// flag, the Python `set_log_level` shim). Returns `None` for blank/unrecognized
/// input so the caller decides the fallback rather than guessing here.
pub fn parse_level_directive(raw: &str) -> Option<LevelFilter> {
    parse_log_level(raw)
}

/// Explicitly set the active log verbosity from a level spelling
/// (`off|error|warn|info|debug|trace`, case-insensitive). This is the supported
/// way to raise verbosity above the default — callers pass the level they want
/// rather than relying on a process-global env var. Returns the [`LevelFilter`]
/// actually installed (the default when `spelling` is unrecognized, so a typo never
/// silently disables logging). A no-op-safe wrapper over [`log::set_max_level`].
pub fn set_log_level(spelling: &str) -> LevelFilter {
    let level = parse_log_level(spelling).unwrap_or(DEFAULT_LOG_LEVEL);
    log::set_max_level(level);
    level
}

pub fn init_logging() {
    init_logging_at(DEFAULT_LOG_LEVEL);
}

/// Install the stderr logger at an explicit verbosity. Idempotent in the sense
/// that the first caller wins the global `log` backend registration; **every**
/// call (re-)applies the requested max level, so an embedding can call
/// `init_logging()` early and later raise the level via `init_logging_at` (e.g.
/// the Python `set_log_level` shim) without losing the override. This is how a
/// caller opts back into the verbose `Info`/`debug`/`trace` solver trace that
/// the `Warn` default suppresses for performance (#1688).
pub fn init_logging_at(level: LevelFilter) {
    LOG_START.get_or_init(Instant::now);
    // First caller wins the backend registration; an already-installed logger
    // is fine — we still want to (re-)apply the requested level below, so do
    // not gate `set_max_level` on the registration result.
    let installed_backend = log::set_logger(&LOGGER).is_ok();
    log::set_max_level(level);
    if !installed_backend {
        // Not an error, but it is the answer to "why does the trace not look
        // like ours?": some other backend owns the global sink, and all this
        // call did was move the level filter.
        log::debug!(
            "[log] a logging backend was already installed; re-applied max level {level} only"
        );
    }
    // Log the GPU backend inventory once at startup so the "are GPUs being
    // used?" answer is visible at the top of the log, before any solver
    // dispatch site lazily checks for device support.
    gam_gpu::log_backend_inventory_once();
}

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

    #[test]
    fn default_level_is_warn_when_no_explicit_level() {
        assert_eq!(DEFAULT_LOG_LEVEL, LevelFilter::Warn);
        init_logging();
        assert_eq!(log::max_level(), DEFAULT_LOG_LEVEL);
    }

    #[test]
    fn set_log_level_installs_explicit_level_and_defaults_on_typo() {
        // Explicit spelling installs that level and reports it back.
        assert_eq!(set_log_level("debug"), LevelFilter::Debug);
        assert_eq!(log::max_level(), LevelFilter::Debug);
        // A typo never silently disables logging — it falls back to the default.
        assert_eq!(set_log_level("verbose"), DEFAULT_LOG_LEVEL);
        assert_eq!(log::max_level(), DEFAULT_LOG_LEVEL);
        // Restore a quiet default so this process-global write cannot perturb
        // sibling tests that observe the level.
        log::set_max_level(DEFAULT_LOG_LEVEL);
    }

    #[test]
    fn unrecognized_values_fall_back_to_default_not_off() {
        // A typo must never silently disable logging or crank it to trace.
        assert_eq!(set_log_level("verbose"), DEFAULT_LOG_LEVEL);
        assert_eq!(set_log_level("yes"), DEFAULT_LOG_LEVEL);
        log::set_max_level(DEFAULT_LOG_LEVEL);
    }

    #[test]
    fn parse_level_directive_matches_internal_parser() {
        // The public out-of-crate entry point must behave exactly like the
        // internal parser the env-precedence helper uses.
        for spelling in [
            "off", "error", "warn", "info", "debug", "trace", "", "garbage",
        ] {
            assert_eq!(parse_level_directive(spelling), parse_log_level(spelling));
        }
    }

    #[test]
    fn parsing_is_case_and_whitespace_insensitive() {
        assert_eq!(parse_log_level("  INFO "), Some(LevelFilter::Info));
        assert_eq!(parse_log_level("Warn"), Some(LevelFilter::Warn));
        assert_eq!(parse_log_level("TRACE"), Some(LevelFilter::Trace));
        assert_eq!(parse_log_level("off"), Some(LevelFilter::Off));
        assert_eq!(parse_log_level("warning"), Some(LevelFilter::Warn));
        assert_eq!(parse_log_level("silent"), Some(LevelFilter::Off));
        assert_eq!(parse_log_level(""), None);
    }
}