//! Detecting usage of the `#[debugger_visualizer]` attribute.

use rustc_ast::Attribute;
use rustc_data_structures::sync::Lrc;
use rustc_expand::base::resolve_path;
use rustc_session::Session;
use rustc_span::{sym, DebuggerVisualizerFile, DebuggerVisualizerType};

use crate::errors::{DebugVisualizerInvalid, DebugVisualizerUnreadable};

impl DebuggerVisualizerCollector<'_> {
    fn check_for_debugger_visualizer(&mut self, attr: &Attribute) {
        if attr.has_name(sym::debugger_visualizer) {
            let Some(hints) = attr.meta_item_list() else {
            self.sess.emit_err(DebugVisualizerInvalid { span: attr.span });
                return;
            };

            let hint = if hints.len() == 1 {
                &hints[0]
            } else {
                self.sess.emit_err(DebugVisualizerInvalid { span: attr.span });
                return;
            };

            let Some(meta_item) = hint.meta_item() else {
                self.sess.emit_err(DebugVisualizerInvalid { span: attr.span });
                return;
            };

            let (visualizer_type, visualizer_path) =
                match (meta_item.name_or_empty(), meta_item.value_str()) {
                    (sym::natvis_file, Some(value)) => (DebuggerVisualizerType::Natvis, value),
                    (sym::gdb_script_file, Some(value)) => {
                        (DebuggerVisualizerType::GdbPrettyPrinter, value)
                    }
                    (_, _) => {
                        self.sess.emit_err(DebugVisualizerInvalid { span: meta_item.span });
                        return;
                    }
                };

            let file =
                match resolve_path(&self.sess.parse_sess, visualizer_path.as_str(), attr.span) {
                    Ok(file) => file,
                    Err(mut err) => {
                        err.emit();
                        return;
                    }
                };

            match std::fs::read(&file) {
                Ok(contents) => {
                    self.visualizers.push(DebuggerVisualizerFile::new(
                        Lrc::from(contents),
                        visualizer_type,
                        file,
                    ));
                }
                Err(error) => {
                    self.sess.emit_err(DebugVisualizerUnreadable {
                        span: meta_item.span,
                        file: &file,
                        error,
                    });
                }
            }
        }
    }
}

struct DebuggerVisualizerCollector<'a> {
    sess: &'a Session,
    visualizers: Vec<DebuggerVisualizerFile>,
}

impl<'ast> rustc_ast::visit::Visitor<'ast> for DebuggerVisualizerCollector<'_> {
    fn visit_attribute(&mut self, attr: &'ast Attribute) {
        self.check_for_debugger_visualizer(attr);
        rustc_ast::visit::walk_attribute(self, attr);
    }
}

/// Traverses and collects the debugger visualizers for a specific crate.
pub fn collect(sess: &Session, krate: &rustc_ast::ast::Crate) -> Vec<DebuggerVisualizerFile> {
    // Initialize the collector.
    let mut visitor = DebuggerVisualizerCollector { sess, visualizers: Vec::new() };
    rustc_ast::visit::Visitor::visit_crate(&mut visitor, krate);

    // Sort the visualizers so we always get a deterministic query result.
    visitor.visualizers.sort_unstable();
    visitor.visualizers
}