llmlint 0.2.13

//! Render the judge's system prompt from a (user-customizable) template.
//!
//! Templates are [minijinja] (Jinja2-style). The context exposes `rules` (each
//! with `name`, `description`, and `rationale` — whether that rule wants a
//! justification), `files` (the target paths), and `rationales` (whether any
//! rule in this batch wants one, to gate the rationale guidance block). The
//! built-in default template lives in `assets/default_template.md` and is
//! embedded via [`crate::io::assets`].

use serde::Serialize;

use crate::errors::{Error, Result};

/// One rule as presented to the judge in the rendered prompt.
#[derive(Debug, Clone, Serialize)]
pub struct RuleSpec {
    pub name: String,
    pub description: String,
    /// Whether this rule requires a `rationale` in the judge's verdict.
    pub rationale: bool,
    /// The relevance condition the judge must decide before evaluating this rule,
    /// or `None` for an always-evaluated rule. Exposed to the template so it can
    /// show the condition and gate the verdict on a `relevant` decision.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub relevance: Option<String>,
}

#[derive(Serialize)]
struct Context<'a> {
    rules: &'a [RuleSpec],
    files: &'a [String],
    /// True when at least one rule in this batch wants a rationale, so the
    /// template can show (or omit) the rationale guidance.
    rationales: bool,
    /// True when at least one rule in this batch carries a relevance condition,
    /// so the template can show (or omit) the relevance guidance.
    relevance: bool,
}

/// Render `template` with the given rules and target file paths. `rationales`
/// gates the rationale guidance (true when any rule in this batch wants one) and
/// `relevance` gates the relevance guidance (true when any rule is conditional).
pub fn render(
    template: &str,
    rules: &[RuleSpec],
    files: &[String],
    rationales: bool,
    relevance: bool,
) -> Result<String> {
    let mut env = minijinja::Environment::new();
    env.set_keep_trailing_newline(true);
    let ctx = Context {
        rules,
        files,
        rationales,
        relevance,
    };
    env.render_str(template, ctx)
        .map_err(|e| Error::Template(e.to_string()))
}

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

    fn rules() -> Vec<RuleSpec> {
        vec![
            RuleSpec {
                name: "no_inline_sql".into(),
                description: "true when no SQL is inline; false otherwise.".into(),
                rationale: true,
                relevance: None,
            },
            RuleSpec {
                name: "layered".into(),
                description: "true when layered.".into(),
                rationale: true,
                relevance: None,
            },
        ]
    }

    #[test]
    fn renders_rules_and_files() {
        let tmpl = "Files:\n{% for f in files %}- {{ f }}\n{% endfor %}\
                    Rules:\n{% for r in rules %}* {{ r.name }}: {{ r.description }}\n{% endfor %}";
        let out = render(
            tmpl,
            &rules(),
            &["src/a.rs".into(), "src/b.rs".into()],
            true,
            false,
        )
        .unwrap();
        assert!(out.contains("- src/a.rs"));
        assert!(out.contains("- src/b.rs"));
        assert!(out.contains("* no_inline_sql: true when no SQL is inline"));
        assert!(out.contains("* layered: true when layered."));
    }

    #[test]
    fn rationales_flag_and_per_rule_rationale_are_in_scope() {
        let tmpl = "{% if rationales %}WANT{% else %}SKIP{% endif %}\n\
                    {% for r in rules %}{{ r.name }}={{ r.rationale }}\n{% endfor %}";
        let on = render(tmpl, &rules(), &[], true, false).unwrap();
        assert!(on.contains("WANT"));
        assert!(on.contains("no_inline_sql=true"));
        let off = render(tmpl, &rules(), &[], false, false).unwrap();
        assert!(off.contains("SKIP"));
    }

    #[test]
    fn relevance_flag_and_per_rule_condition_are_in_scope() {
        let tmpl = "{% if relevance %}GATE{% else %}NOGATE{% endif %}\n\
                    {% for r in rules %}{% if r.relevance %}{{ r.name }}: {{ r.relevance }}\n\
                    {% endif %}{% endfor %}";
        let mut rs = rules();
        rs[0].relevance = Some("the change touches SQL".into());
        let on = render(tmpl, &rs, &[], true, true).unwrap();
        assert!(on.contains("GATE"));
        assert!(on.contains("no_inline_sql: the change touches SQL"));
        // The always-evaluated rule renders no condition line.
        assert!(!on.contains("layered:"));
        let off = render(tmpl, &rules(), &[], true, false).unwrap();
        assert!(off.contains("NOGATE"));
    }

    #[test]
    fn invalid_template_is_a_template_error() {
        let err = render("{% for x in %}", &rules(), &[], true, false).unwrap_err();
        assert!(matches!(err, Error::Template(_)));
    }
}