// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.

//! The one table mapping tree-sitter capture names onto fabrica's stable, themeable
//! CSS class names.
//!
//! Themes style code by these class names alone and never need to know tree-sitter
//! internals; the full list is documented in `docs/theming.md`. Capture names are
//! hierarchical and dotted (`keyword.control.return`, `constant.numeric.integer`);
//! we map on the first component, with `constant.numeric*` special-cased to the
//! number class. Captures with no mapping render unhighlighted (no wrapping span).

/// The complete set of highlight classes a theme may style. Kept in sync with the
/// `--fb-hl-*` token family in `docs/theming.md`.
pub const HL_CLASSES: &[&str] = &[
    "hl-keyword",
    "hl-function",
    "hl-type",
    "hl-string",
    "hl-number",
    "hl-comment",
    "hl-constant",
    "hl-variable",
    "hl-operator",
    "hl-punctuation",
    "hl-attribute",
    "hl-tag",
];

/// Map a tree-sitter capture name to a fabrica highlight class, or `None` when the
/// capture has no styling (it renders as plain text within its line).
#[must_use]
pub fn class_for(capture: &str) -> Option<&'static str> {
    // `constant.numeric.*` is a constant in the grammar but a number to us.
    if capture.starts_with("constant.numeric") {
        return Some("hl-number");
    }
    let head = capture.split('.').next().unwrap_or(capture);
    Some(match head {
        "keyword" | "label" => "hl-keyword",
        "function" | "method" => "hl-function",
        "type" | "constructor" | "namespace" => "hl-type",
        "string" | "escape" | "char" | "regex" => "hl-string",
        "number" | "float" | "boolean" => "hl-number",
        "comment" => "hl-comment",
        "constant" => "hl-constant",
        "variable" | "property" | "parameter" | "field" => "hl-variable",
        "operator" => "hl-operator",
        "punctuation" => "hl-punctuation",
        "attribute" | "annotation" | "decorator" => "hl-attribute",
        "tag" => "hl-tag",
        _ => return None,
    })
}

#[cfg(test)]
mod tests {
    #![allow(clippy::unwrap_used)]

    use super::*;

    #[test]
    fn maps_common_captures() {
        assert_eq!(class_for("keyword"), Some("hl-keyword"));
        assert_eq!(class_for("keyword.control.return"), Some("hl-keyword"));
        assert_eq!(class_for("function.macro"), Some("hl-function"));
        assert_eq!(class_for("type.builtin"), Some("hl-type"));
        assert_eq!(class_for("string"), Some("hl-string"));
        assert_eq!(class_for("constant.numeric.integer"), Some("hl-number"));
        assert_eq!(class_for("constant.builtin"), Some("hl-constant"));
        assert_eq!(class_for("punctuation.delimiter"), Some("hl-punctuation"));
        assert_eq!(class_for("variable.parameter"), Some("hl-variable"));
    }

    #[test]
    fn unmapped_captures_are_none() {
        assert_eq!(class_for("markup.heading"), None);
        assert_eq!(class_for("diff.plus"), None);
        assert_eq!(class_for("something.unknown"), None);
    }

    #[test]
    fn every_class_is_documented_in_the_list() {
        for capture in ["keyword", "function", "type", "string", "comment"] {
            let class = class_for(capture).unwrap();
            assert!(
                HL_CLASSES.contains(&class),
                "{class} missing from HL_CLASSES"
            );
        }
    }
}