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

use hir::CRATE_HIR_ID;
use rustc_data_structures::fx::FxHashSet;
use rustc_expand::base::resolve_path;
use rustc_hir as hir;
use rustc_hir::HirId;
use rustc_middle::ty::TyCtxt;
use rustc_middle::{query::LocalCrate, ty::query::Providers};
use rustc_span::{sym, DebuggerVisualizerFile, DebuggerVisualizerType};

use std::sync::Arc;

use crate::errors::DebugVisualizerUnreadable;

fn check_for_debugger_visualizer(
    tcx: TyCtxt<'_>,
    hir_id: HirId,
    debugger_visualizers: &mut FxHashSet<DebuggerVisualizerFile>,
) {
    let attrs = tcx.hir().attrs(hir_id);
    for attr in attrs {
        if attr.has_name(sym::debugger_visualizer) {
            let Some(list) = attr.meta_item_list() else {
                continue
            };

            let meta_item = match list.len() {
                1 => match list[0].meta_item() {
                    Some(meta_item) => meta_item,
                    _ => continue,
                },
                _ => continue,
            };

            let visualizer_type = match meta_item.name_or_empty() {
                sym::natvis_file => DebuggerVisualizerType::Natvis,
                sym::gdb_script_file => DebuggerVisualizerType::GdbPrettyPrinter,
                _ => continue,
            };

            let file = match meta_item.value_str() {
                Some(value) => {
                    match resolve_path(&tcx.sess.parse_sess, value.as_str(), attr.span) {
                        Ok(file) => file,
                        _ => continue,
                    }
                }
                None => continue,
            };

            match std::fs::read(&file) {
                Ok(contents) => {
                    debugger_visualizers
                        .insert(DebuggerVisualizerFile::new(Arc::from(contents), visualizer_type));
                }
                Err(error) => {
                    tcx.sess.emit_err(DebugVisualizerUnreadable {
                        span: meta_item.span,
                        file: &file,
                        error,
                    });
                }
            }
        }
    }
}

/// Traverses and collects the debugger visualizers for a specific crate.
fn debugger_visualizers(tcx: TyCtxt<'_>, _: LocalCrate) -> Vec<DebuggerVisualizerFile> {
    // Initialize the collector.
    let mut debugger_visualizers = FxHashSet::default();

    // Collect debugger visualizers in this crate.
    tcx.hir().for_each_module(|id| {
        check_for_debugger_visualizer(
            tcx,
            tcx.hir().local_def_id_to_hir_id(id),
            &mut debugger_visualizers,
        )
    });

    // Collect debugger visualizers on the crate attributes.
    check_for_debugger_visualizer(tcx, CRATE_HIR_ID, &mut debugger_visualizers);

    // Extract out the found debugger_visualizer items.
    let mut visualizers = debugger_visualizers.into_iter().collect::<Vec<_>>();

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

pub fn provide(providers: &mut Providers) {
    providers.debugger_visualizers = debugger_visualizers;
}