zesdex/crates/zesdex-backend/src/app/runtime/context/window.rs

#![allow(dead_code)]
//! Single source of truth for resolving the active model's context
//! window size, replacing three copies of the same lookup that had
//! drifted (`Action::Compact`, `spawn_turn`, and `view/status.rs` each
//! had their own inline version — the status bar's copy additionally
//! displayed "?" on no match instead of falling back like the other two,
//! an inconsistency this unifies away).
use zesdex_cms::domain::app_config::AppConfig;
use zesdex_cms::domain::settings::Settings;

/// Resolve the context-window size (in tokens) for the currently
/// configured provider/model.
///
/// Flow: find the `ModelRole` whose `provider`+`model` match
/// `settings` -> use its `context_window` if set -> otherwise fall back
/// to `app_config.default_context_window`.
///
/// Return: always a concrete token count, never "unknown".
pub fn resolve(app_config: &AppConfig, settings: &Settings) -> usize {
    app_config
        .model_roles
        .values()
        .find(|role| role.provider == settings.provider && role.model == settings.model)
        .and_then(|role| role.context_window)
        .unwrap_or(app_config.default_context_window) as usize
}

#[cfg(test)]
mod tests {
    use super::*;
    use zesdex_cms::domain::app_config::ModelRole;

    #[test]
    fn resolves_context_window_from_matching_model_role() {
        let mut app_config = AppConfig::default();
        app_config.model_roles.insert(
            "default".to_string(),
            ModelRole {
                provider: "zen".to_string(),
                model: "deepseek-v4-flash-free".to_string(),
                max_tokens: None,
                context_window: Some(128_000),
                temperature: None,
            },
        );
        let settings = Settings {
            provider: "zen".to_string(),
            model: "deepseek-v4-flash-free".to_string(),
            ..Default::default()
        };

        assert_eq!(resolve(&app_config, &settings), 128_000);
    }

    #[test]
    fn falls_back_to_default_context_window_when_no_role_matches() {
        let app_config = AppConfig::default();
        let settings = Settings {
            provider: "nonexistent".to_string(),
            model: "nonexistent-model".to_string(),
            ..Default::default()
        };

        assert_eq!(
            resolve(&app_config, &settings),
            app_config.default_context_window as usize
        );
    }

    #[test]
    fn falls_back_to_default_when_matching_role_has_no_context_window_set() {
        let mut app_config = AppConfig::default();
        app_config.model_roles.insert(
            "default".to_string(),
            ModelRole {
                provider: "zen".to_string(),
                model: "deepseek-v4-flash-free".to_string(),
                max_tokens: None,
                context_window: None,
                temperature: None,
            },
        );
        let settings = Settings {
            provider: "zen".to_string(),
            model: "deepseek-v4-flash-free".to_string(),
            ..Default::default()
        };

        assert_eq!(
            resolve(&app_config, &settings),
            app_config.default_context_window as usize
        );
    }
}