alint-core 0.2.0

//! Facts — cached properties of the repository evaluated once per run and
//! referenced by `when` clauses on rules (shipping in a later commit).
//!
//! Each fact has an `id` and exactly one kind-specific top-level field that
//! names its type. Example:
//!
//! ```yaml
//! facts:
//!   - id: is_rust
//!     any_file_exists: ["Cargo.toml"]
//!   - id: is_monorepo
//!     all_files_exist: ["packages", "pnpm-workspace.yaml"]
//!   - id: n_java_files
//!     count_files: "**/*.java"
//! ```
//!
//! Evaluation is declarative and cheap — facts see the walked `FileIndex`
//! but not arbitrary filesystem state outside the repo root.

use std::collections::HashMap;
use std::path::Path;

use serde::Deserialize;

use crate::error::Result;
use crate::scope::Scope;
use crate::walker::FileIndex;

/// A value a fact evaluates to. Keeps the surface small for v0.2; richer
/// types (list, map) arrive with the `when` expression language.
#[derive(Debug, Clone, PartialEq)]
pub enum FactValue {
    Bool(bool),
    Int(i64),
    String(String),
}

impl FactValue {
    /// Boolean coercion — `Bool(b)` → b; `Int(n)` → `n != 0`; `String(s)` →
    /// `!s.is_empty()`. Used by `when` evaluation's truthiness checks.
    pub fn truthy(&self) -> bool {
        match self {
            Self::Bool(b) => *b,
            Self::Int(n) => *n != 0,
            Self::String(s) => !s.is_empty(),
        }
    }
}

/// A string or a list of strings — accepted by fact kinds whose input is
/// glob-shaped.
#[derive(Debug, Clone, Deserialize)]
#[serde(untagged)]
pub enum OneOrMany {
    One(String),
    Many(Vec<String>),
}

impl OneOrMany {
    pub fn to_vec(&self) -> Vec<String> {
        match self {
            Self::One(s) => vec![s.clone()],
            Self::Many(v) => v.clone(),
        }
    }
}

/// YAML-level declaration of a single fact.
#[derive(Debug, Clone, Deserialize)]
pub struct FactSpec {
    pub id: String,
    #[serde(flatten)]
    pub kind: FactKind,
}

/// The closed set of built-in fact kinds. Serde dispatches via `untagged`
/// — the first variant whose required field is present in the YAML wins.
#[derive(Debug, Clone, Deserialize)]
#[serde(untagged)]
pub enum FactKind {
    AnyFileExists { any_file_exists: OneOrMany },
    AllFilesExist { all_files_exist: OneOrMany },
    CountFiles { count_files: String },
}

/// The resolved map from fact id to value, produced once per `Engine::run`.
#[derive(Debug, Default, Clone)]
pub struct FactValues(HashMap<String, FactValue>);

impl FactValues {
    pub fn new() -> Self {
        Self::default()
    }

    pub fn insert(&mut self, id: String, v: FactValue) {
        self.0.insert(id, v);
    }

    pub fn get(&self, id: &str) -> Option<&FactValue> {
        self.0.get(id)
    }

    pub fn len(&self) -> usize {
        self.0.len()
    }

    pub fn is_empty(&self) -> bool {
        self.0.is_empty()
    }

    pub fn as_map(&self) -> &HashMap<String, FactValue> {
        &self.0
    }
}

/// Evaluate a whole fact list against a prebuilt `FileIndex`. Invoked by
/// `Engine::run` before any rule evaluates.
pub fn evaluate_facts(facts: &[FactSpec], _root: &Path, index: &FileIndex) -> Result<FactValues> {
    let mut out = FactValues::new();
    for spec in facts {
        let value = evaluate_one(spec, index)?;
        out.insert(spec.id.clone(), value);
    }
    Ok(out)
}

fn evaluate_one(spec: &FactSpec, index: &FileIndex) -> Result<FactValue> {
    match &spec.kind {
        FactKind::AnyFileExists { any_file_exists } => {
            let globs = any_file_exists.to_vec();
            let scope = Scope::from_patterns(&globs)?;
            let found = index.files().any(|e| scope.matches(&e.path));
            Ok(FactValue::Bool(found))
        }
        FactKind::AllFilesExist { all_files_exist } => {
            let globs = all_files_exist.to_vec();
            for glob in &globs {
                let scope = Scope::from_patterns(std::slice::from_ref(glob))?;
                if !index.files().any(|e| scope.matches(&e.path)) {
                    return Ok(FactValue::Bool(false));
                }
            }
            Ok(FactValue::Bool(true))
        }
        FactKind::CountFiles { count_files } => {
            let scope = Scope::from_patterns(std::slice::from_ref(count_files))?;
            let count = index.files().filter(|e| scope.matches(&e.path)).count();
            Ok(FactValue::Int(i64::try_from(count).unwrap_or(i64::MAX)))
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::walker::FileEntry;
    use std::path::PathBuf;

    fn idx(paths: &[&str]) -> FileIndex {
        FileIndex {
            entries: paths
                .iter()
                .map(|p| FileEntry {
                    path: PathBuf::from(p),
                    is_dir: false,
                    size: 1,
                })
                .collect(),
        }
    }

    fn parse(yaml: &str) -> Vec<FactSpec> {
        serde_yaml_ng::from_str(yaml).unwrap()
    }

    #[test]
    fn any_file_exists_true_when_match_found() {
        let facts = parse("- id: is_rust\n  any_file_exists: [Cargo.toml]\n");
        let v =
            evaluate_facts(&facts, Path::new("/"), &idx(&["Cargo.toml", "src/lib.rs"])).unwrap();
        assert_eq!(v.get("is_rust"), Some(&FactValue::Bool(true)));
    }

    #[test]
    fn any_file_exists_false_when_no_match() {
        let facts = parse("- id: is_rust\n  any_file_exists: [Cargo.toml]\n");
        let v = evaluate_facts(&facts, Path::new("/"), &idx(&["src/lib.rs"])).unwrap();
        assert_eq!(v.get("is_rust"), Some(&FactValue::Bool(false)));
    }

    #[test]
    fn any_file_exists_accepts_single_string() {
        let facts = parse("- id: has_readme\n  any_file_exists: README.md\n");
        let v = evaluate_facts(&facts, Path::new("/"), &idx(&["README.md"])).unwrap();
        assert_eq!(v.get("has_readme"), Some(&FactValue::Bool(true)));
    }

    #[test]
    fn all_files_exist_true_when_all_match() {
        let facts = parse("- id: is_monorepo\n  all_files_exist: [Cargo.toml, README.md]\n");
        let v = evaluate_facts(
            &facts,
            Path::new("/"),
            &idx(&["Cargo.toml", "README.md", "src/main.rs"]),
        )
        .unwrap();
        assert_eq!(v.get("is_monorepo"), Some(&FactValue::Bool(true)));
    }

    #[test]
    fn all_files_exist_false_when_any_missing() {
        let facts = parse("- id: is_monorepo\n  all_files_exist: [Cargo.toml, README.md]\n");
        let v = evaluate_facts(&facts, Path::new("/"), &idx(&["Cargo.toml"])).unwrap();
        assert_eq!(v.get("is_monorepo"), Some(&FactValue::Bool(false)));
    }

    #[test]
    fn count_files_returns_integer() {
        let facts = parse("- id: n_rs\n  count_files: \"**/*.rs\"\n");
        let v = evaluate_facts(
            &facts,
            Path::new("/"),
            &idx(&["a.rs", "b.rs", "src/c.rs", "README.md"]),
        )
        .unwrap();
        assert_eq!(v.get("n_rs"), Some(&FactValue::Int(3)));
    }

    #[test]
    fn multiple_facts_all_resolved() {
        let facts = parse(
            r#"
- id: is_rust
  any_file_exists: [Cargo.toml]
- id: n_rs
  count_files: "**/*.rs"
- id: has_readme
  any_file_exists: README.md
"#,
        );
        let v = evaluate_facts(
            &facts,
            Path::new("/"),
            &idx(&["Cargo.toml", "src/lib.rs", "README.md"]),
        )
        .unwrap();
        assert_eq!(v.len(), 3);
        assert_eq!(v.get("is_rust"), Some(&FactValue::Bool(true)));
        assert_eq!(v.get("n_rs"), Some(&FactValue::Int(1)));
        assert_eq!(v.get("has_readme"), Some(&FactValue::Bool(true)));
    }

    #[test]
    fn truthy_coercion() {
        assert!(FactValue::Bool(true).truthy());
        assert!(!FactValue::Bool(false).truthy());
        assert!(FactValue::Int(1).truthy());
        assert!(!FactValue::Int(0).truthy());
        assert!(FactValue::String("x".into()).truthy());
        assert!(!FactValue::String(String::new()).truthy());
    }
}