//! Loads a Cargo project into a static instance of analysis, without support
//! for incorporating changes.
// Note, don't remove any public api from this. This API is consumed by external tools
// to run rust-analyzer as a library.
use std::{collections::hash_map::Entry, iter, mem, path::Path, sync};

use crossbeam_channel::{unbounded, Receiver};
use hir_expand::proc_macro::{
    ProcMacro, ProcMacroExpander, ProcMacroExpansionError, ProcMacroKind, ProcMacroLoadResult,
    ProcMacros,
};
use ide_db::{
    base_db::{CrateGraph, CrateWorkspaceData, Env, SourceRoot, SourceRootId},
    prime_caches, ChangeWithProcMacros, FxHashMap, RootDatabase,
};
use itertools::Itertools;
use proc_macro_api::{MacroDylib, ProcMacroServer};
use project_model::{
    CargoConfig, PackageRoot, ProjectManifest, ProjectWorkspace, ProjectWorkspaceKind,
};
use span::Span;
use vfs::{
    file_set::FileSetConfig,
    loader::{Handle, LoadingProgress},
    AbsPath, AbsPathBuf, VfsPath,
};

#[derive(Debug)]
pub struct LoadCargoConfig {
    pub load_out_dirs_from_check: bool,
    pub with_proc_macro_server: ProcMacroServerChoice,
    pub prefill_caches: bool,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ProcMacroServerChoice {
    Sysroot,
    Explicit(AbsPathBuf),
    None,
}

pub fn load_workspace_at(
    root: &Path,
    cargo_config: &CargoConfig,
    load_config: &LoadCargoConfig,
    progress: &dyn Fn(String),
) -> anyhow::Result<(RootDatabase, vfs::Vfs, Option<ProcMacroServer>)> {
    let root = AbsPathBuf::assert_utf8(std::env::current_dir()?.join(root));
    let root = ProjectManifest::discover_single(&root)?;
    let mut workspace = ProjectWorkspace::load(root, cargo_config, progress)?;

    if load_config.load_out_dirs_from_check {
        let build_scripts = workspace.run_build_scripts(cargo_config, progress)?;
        workspace.set_build_scripts(build_scripts)
    }

    load_workspace(workspace, &cargo_config.extra_env, load_config)
}

pub fn load_workspace(
    ws: ProjectWorkspace,
    extra_env: &FxHashMap<String, String>,
    load_config: &LoadCargoConfig,
) -> anyhow::Result<(RootDatabase, vfs::Vfs, Option<ProcMacroServer>)> {
    let (sender, receiver) = unbounded();
    let mut vfs = vfs::Vfs::default();
    let mut loader = {
        let loader = vfs_notify::NotifyHandle::spawn(sender);
        Box::new(loader)
    };

    tracing::debug!(?load_config, "LoadCargoConfig");
    let proc_macro_server = match &load_config.with_proc_macro_server {
        ProcMacroServerChoice::Sysroot => ws
            .find_sysroot_proc_macro_srv()
            .and_then(|it| ProcMacroServer::spawn(&it, extra_env).map_err(Into::into))
            .map_err(|e| (e, true)),
        ProcMacroServerChoice::Explicit(path) => {
            ProcMacroServer::spawn(path, extra_env).map_err(Into::into).map_err(|e| (e, true))
        }
        ProcMacroServerChoice::None => {
            Err((anyhow::format_err!("proc macro server disabled"), false))
        }
    };
    match &proc_macro_server {
        Ok(server) => {
            tracing::info!(path=%server.path(), "Proc-macro server started")
        }
        Err((e, _)) => {
            tracing::info!(%e, "Failed to start proc-macro server")
        }
    }

    let (crate_graph, proc_macros) = ws.to_crate_graph(
        &mut |path: &AbsPath| {
            let contents = loader.load_sync(path);
            let path = vfs::VfsPath::from(path.to_path_buf());
            vfs.set_file_contents(path.clone(), contents);
            vfs.file_id(&path)
        },
        extra_env,
    );
    let proc_macros = {
        let proc_macro_server = match &proc_macro_server {
            Ok(it) => Ok(it),
            Err((e, hard_err)) => Err((e.to_string(), *hard_err)),
        };
        proc_macros
            .into_iter()
            .map(|(crate_id, path)| {
                (
                    crate_id,
                    path.map_or_else(
                        |e| Err((e, true)),
                        |(_, path)| {
                            proc_macro_server.as_ref().map_err(Clone::clone).and_then(
                                |proc_macro_server| load_proc_macro(proc_macro_server, &path, &[]),
                            )
                        },
                    ),
                )
            })
            .collect()
    };

    let project_folders = ProjectFolders::new(std::slice::from_ref(&ws), &[]);
    loader.set_config(vfs::loader::Config {
        load: project_folders.load,
        watch: vec![],
        version: 0,
    });

    let db = load_crate_graph(
        &ws,
        crate_graph,
        proc_macros,
        project_folders.source_root_config,
        &mut vfs,
        &receiver,
    );

    if load_config.prefill_caches {
        prime_caches::parallel_prime_caches(&db, 1, &|_| ());
    }
    Ok((db, vfs, proc_macro_server.ok()))
}

#[derive(Default)]
pub struct ProjectFolders {
    pub load: Vec<vfs::loader::Entry>,
    pub watch: Vec<usize>,
    pub source_root_config: SourceRootConfig,
}

impl ProjectFolders {
    pub fn new(workspaces: &[ProjectWorkspace], global_excludes: &[AbsPathBuf]) -> ProjectFolders {
        let mut res = ProjectFolders::default();
        let mut fsc = FileSetConfig::builder();
        let mut local_filesets = vec![];

        // Dedup source roots
        // Depending on the project setup, we can have duplicated source roots, or for example in
        // the case of the rustc workspace, we can end up with two source roots that are almost the
        // same but not quite, like:
        // PackageRoot { is_local: false, include: [AbsPathBuf(".../rust/src/tools/miri/cargo-miri")], exclude: [] }
        // PackageRoot {
        //     is_local: true,
        //     include: [AbsPathBuf(".../rust/src/tools/miri/cargo-miri"), AbsPathBuf(".../rust/build/x86_64-pc-windows-msvc/stage0-tools/x86_64-pc-windows-msvc/release/build/cargo-miri-85801cd3d2d1dae4/out")],
        //     exclude: [AbsPathBuf(".../rust/src/tools/miri/cargo-miri/.git"), AbsPathBuf(".../rust/src/tools/miri/cargo-miri/target")]
        // }
        //
        // The first one comes from the explicit rustc workspace which points to the rustc workspace itself
        // The second comes from the rustc workspace that we load as the actual project workspace
        // These `is_local` differing in this kind of way gives us problems, especially when trying to filter diagnostics as we don't report diagnostics for external libraries.
        // So we need to deduplicate these, usually it would be enough to deduplicate by `include`, but as the rustc example shows here that doesn't work,
        // so we need to also coalesce the includes if they overlap.

        let mut roots: Vec<_> = workspaces
            .iter()
            .flat_map(|ws| ws.to_roots())
            .update(|root| root.include.sort())
            .sorted_by(|a, b| a.include.cmp(&b.include))
            .collect();

        // map that tracks indices of overlapping roots
        let mut overlap_map = FxHashMap::<_, Vec<_>>::default();
        let mut done = false;

        while !mem::replace(&mut done, true) {
            // maps include paths to indices of the corresponding root
            let mut include_to_idx = FxHashMap::default();
            // Find and note down the indices of overlapping roots
            for (idx, root) in roots.iter().enumerate().filter(|(_, it)| !it.include.is_empty()) {
                for include in &root.include {
                    match include_to_idx.entry(include) {
                        Entry::Occupied(e) => {
                            overlap_map.entry(*e.get()).or_default().push(idx);
                        }
                        Entry::Vacant(e) => {
                            e.insert(idx);
                        }
                    }
                }
            }
            for (k, v) in overlap_map.drain() {
                done = false;
                for v in v {
                    let r = mem::replace(
                        &mut roots[v],
                        PackageRoot { is_local: false, include: vec![], exclude: vec![] },
                    );
                    roots[k].is_local |= r.is_local;
                    roots[k].include.extend(r.include);
                    roots[k].exclude.extend(r.exclude);
                }
                roots[k].include.sort();
                roots[k].exclude.sort();
                roots[k].include.dedup();
                roots[k].exclude.dedup();
            }
        }

        for root in roots.into_iter().filter(|it| !it.include.is_empty()) {
            let file_set_roots: Vec<VfsPath> =
                root.include.iter().cloned().map(VfsPath::from).collect();

            let entry = {
                let mut dirs = vfs::loader::Directories::default();
                dirs.extensions.push("rs".into());
                dirs.extensions.push("toml".into());
                dirs.include.extend(root.include);
                dirs.exclude.extend(root.exclude);
                for excl in global_excludes {
                    if dirs
                        .include
                        .iter()
                        .any(|incl| incl.starts_with(excl) || excl.starts_with(incl))
                    {
                        dirs.exclude.push(excl.clone());
                    }
                }

                vfs::loader::Entry::Directories(dirs)
            };

            if root.is_local {
                res.watch.push(res.load.len());
            }
            res.load.push(entry);

            if root.is_local {
                local_filesets.push(fsc.len() as u64);
            }
            fsc.add_file_set(file_set_roots)
        }

        // register the workspace manifest as well, note that this currently causes duplicates for
        // non-virtual cargo workspaces! We ought to fix that
        for ws in workspaces.iter() {
            let mut file_set_roots: Vec<VfsPath> = vec![];
            let mut entries = vec![];

            if let Some(manifest) = ws.manifest().map(|it| it.to_path_buf()) {
                file_set_roots.push(VfsPath::from(manifest.to_owned()));
                entries.push(manifest.to_owned());
            }

            for buildfile in ws.buildfiles() {
                file_set_roots.push(VfsPath::from(buildfile.to_owned()));
                entries.push(buildfile.to_owned());
            }

            // In case of detached files we do **not** look for a rust-analyzer.toml.
            if !matches!(ws.kind, ProjectWorkspaceKind::DetachedFile { .. }) {
                let ws_root = ws.workspace_root();
                let ratoml_path = {
                    let mut p = ws_root.to_path_buf();
                    p.push("rust-analyzer.toml");
                    p
                };
                file_set_roots.push(VfsPath::from(ratoml_path.to_owned()));
                entries.push(ratoml_path.to_owned());
            }

            if !file_set_roots.is_empty() {
                let entry = vfs::loader::Entry::Files(entries);
                res.watch.push(res.load.len());
                res.load.push(entry);
                local_filesets.push(fsc.len() as u64);
                fsc.add_file_set(file_set_roots)
            }
        }

        let fsc = fsc.build();
        res.source_root_config = SourceRootConfig { fsc, local_filesets };

        res
    }
}

#[derive(Default, Debug)]
pub struct SourceRootConfig {
    pub fsc: FileSetConfig,
    pub local_filesets: Vec<u64>,
}

impl SourceRootConfig {
    pub fn partition(&self, vfs: &vfs::Vfs) -> Vec<SourceRoot> {
        self.fsc
            .partition(vfs)
            .into_iter()
            .enumerate()
            .map(|(idx, file_set)| {
                let is_local = self.local_filesets.contains(&(idx as u64));
                if is_local {
                    SourceRoot::new_local(file_set)
                } else {
                    SourceRoot::new_library(file_set)
                }
            })
            .collect()
    }

    /// Maps local source roots to their parent source roots by bytewise comparing of root paths .
    /// If a `SourceRoot` doesn't have a parent and is local then it is not contained in this mapping but it can be asserted that it is a root `SourceRoot`.
    pub fn source_root_parent_map(&self) -> FxHashMap<SourceRootId, SourceRootId> {
        let roots = self.fsc.roots();

        let mut map = FxHashMap::default();

        // See https://github.com/rust-lang/rust-analyzer/issues/17409
        //
        // We can view the connections between roots as a graph. The problem is
        // that this graph may contain cycles, so when adding edges, it is necessary
        // to check whether it will lead to a cycle.
        //
        // Since we ensure that each node has at most one outgoing edge (because
        // each SourceRoot can have only one parent), we can use a disjoint-set to
        // maintain the connectivity between nodes. If an edge’s two nodes belong
        // to the same set, they are already connected.
        let mut dsu = FxHashMap::default();
        fn find_parent(dsu: &mut FxHashMap<u64, u64>, id: u64) -> u64 {
            if let Some(&parent) = dsu.get(&id) {
                let parent = find_parent(dsu, parent);
                dsu.insert(id, parent);
                parent
            } else {
                id
            }
        }

        for (idx, (root, root_id)) in roots.iter().enumerate() {
            if !self.local_filesets.contains(root_id)
                || map.contains_key(&SourceRootId(*root_id as u32))
            {
                continue;
            }

            for (root2, root2_id) in roots[..idx].iter().rev() {
                if self.local_filesets.contains(root2_id)
                    && root_id != root2_id
                    && root.starts_with(root2)
                {
                    // check if the edge will create a cycle
                    if find_parent(&mut dsu, *root_id) != find_parent(&mut dsu, *root2_id) {
                        map.insert(SourceRootId(*root_id as u32), SourceRootId(*root2_id as u32));
                        dsu.insert(*root_id, *root2_id);
                    }

                    break;
                }
            }
        }

        map
    }
}

/// Load the proc-macros for the given lib path, disabling all expanders whose names are in `ignored_macros`.
pub fn load_proc_macro(
    server: &ProcMacroServer,
    path: &AbsPath,
    ignored_macros: &[Box<str>],
) -> ProcMacroLoadResult {
    let res: Result<Vec<_>, String> = (|| {
        let dylib = MacroDylib::new(path.to_path_buf());
        let vec = server.load_dylib(dylib).map_err(|e| format!("{e}"))?;
        if vec.is_empty() {
            return Err("proc macro library returned no proc macros".to_owned());
        }
        Ok(vec
            .into_iter()
            .map(|expander| expander_to_proc_macro(expander, ignored_macros))
            .collect())
    })();
    match res {
        Ok(proc_macros) => {
            tracing::info!(
                "Loaded proc-macros for {path}: {:?}",
                proc_macros.iter().map(|it| it.name.clone()).collect::<Vec<_>>()
            );
            Ok(proc_macros)
        }
        Err(e) => {
            tracing::warn!("proc-macro loading for {path} failed: {e}");
            Err((e, true))
        }
    }
}

fn load_crate_graph(
    ws: &ProjectWorkspace,
    crate_graph: CrateGraph,
    proc_macros: ProcMacros,
    source_root_config: SourceRootConfig,
    vfs: &mut vfs::Vfs,
    receiver: &Receiver<vfs::loader::Message>,
) -> RootDatabase {
    let ProjectWorkspace { toolchain, target_layout, .. } = ws;

    let lru_cap = std::env::var("RA_LRU_CAP").ok().and_then(|it| it.parse::<u16>().ok());
    let mut db = RootDatabase::new(lru_cap);
    let mut analysis_change = ChangeWithProcMacros::new();

    db.enable_proc_attr_macros();

    // wait until Vfs has loaded all roots
    for task in receiver {
        match task {
            vfs::loader::Message::Progress { n_done, .. } => {
                if n_done == LoadingProgress::Finished {
                    break;
                }
            }
            vfs::loader::Message::Loaded { files } | vfs::loader::Message::Changed { files } => {
                let _p =
                    tracing::info_span!("load_cargo::load_crate_craph/LoadedChanged").entered();
                for (path, contents) in files {
                    vfs.set_file_contents(path.into(), contents);
                }
            }
        }
    }
    let changes = vfs.take_changes();
    for (_, file) in changes {
        if let vfs::Change::Create(v, _) | vfs::Change::Modify(v, _) = file.change {
            if let Ok(text) = String::from_utf8(v) {
                analysis_change.change_file(file.file_id, Some(text))
            }
        }
    }
    let source_roots = source_root_config.partition(vfs);
    analysis_change.set_roots(source_roots);

    let ws_data = crate_graph
        .iter()
        .zip(iter::repeat(From::from(CrateWorkspaceData {
            proc_macro_cwd: None,
            data_layout: target_layout.clone(),
            toolchain: toolchain.clone(),
        })))
        .collect();
    analysis_change.set_crate_graph(crate_graph, ws_data);
    analysis_change.set_proc_macros(proc_macros);

    db.apply_change(analysis_change);
    db
}

fn expander_to_proc_macro(
    expander: proc_macro_api::ProcMacro,
    ignored_macros: &[Box<str>],
) -> ProcMacro {
    let name = expander.name();
    let kind = match expander.kind() {
        proc_macro_api::ProcMacroKind::CustomDerive => ProcMacroKind::CustomDerive,
        proc_macro_api::ProcMacroKind::Bang => ProcMacroKind::Bang,
        proc_macro_api::ProcMacroKind::Attr => ProcMacroKind::Attr,
    };
    let disabled = ignored_macros.iter().any(|replace| **replace == *name);
    ProcMacro {
        name: intern::Symbol::intern(name),
        kind,
        expander: sync::Arc::new(Expander(expander)),
        disabled,
    }
}

#[derive(Debug)]
struct Expander(proc_macro_api::ProcMacro);

impl ProcMacroExpander for Expander {
    fn expand(
        &self,
        subtree: &tt::Subtree<Span>,
        attrs: Option<&tt::Subtree<Span>>,
        env: &Env,
        def_site: Span,
        call_site: Span,
        mixed_site: Span,
        current_dir: Option<String>,
    ) -> Result<tt::Subtree<Span>, ProcMacroExpansionError> {
        match self.0.expand(
            subtree,
            attrs,
            env.clone(),
            def_site,
            call_site,
            mixed_site,
            current_dir,
        ) {
            Ok(Ok(subtree)) => Ok(subtree),
            Ok(Err(err)) => Err(ProcMacroExpansionError::Panic(err.0)),
            Err(err) => Err(ProcMacroExpansionError::System(err.to_string())),
        }
    }
}

#[cfg(test)]
mod tests {
    use ide_db::base_db::SourceDatabase;
    use vfs::file_set::FileSetConfigBuilder;

    use super::*;

    #[test]
    fn test_loading_rust_analyzer() {
        let path = Path::new(env!("CARGO_MANIFEST_DIR")).parent().unwrap().parent().unwrap();
        let cargo_config = CargoConfig { set_test: true, ..CargoConfig::default() };
        let load_cargo_config = LoadCargoConfig {
            load_out_dirs_from_check: false,
            with_proc_macro_server: ProcMacroServerChoice::None,
            prefill_caches: false,
        };
        let (db, _vfs, _proc_macro) =
            load_workspace_at(path, &cargo_config, &load_cargo_config, &|_| {}).unwrap();

        let n_crates = db.crate_graph().iter().count();
        // RA has quite a few crates, but the exact count doesn't matter
        assert!(n_crates > 20);
    }

    #[test]
    fn unrelated_sources() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1] };
        let vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();

        assert_eq!(vc, vec![])
    }

    #[test]
    fn unrelated_source_sharing_dirname() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/abc".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1] };
        let vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();

        assert_eq!(vc, vec![])
    }

    #[test]
    fn basic_child_parent() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc/def".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1] };
        let vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();

        assert_eq!(vc, vec![(SourceRootId(1), SourceRootId(0))])
    }

    #[test]
    fn basic_child_parent_with_unrelated_parents_sib() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/abc".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1, 2] };
        let vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();

        assert_eq!(vc, vec![(SourceRootId(2), SourceRootId(1))])
    }

    #[test]
    fn deep_sources_with_parent_missing() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/ghi".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/abc".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1, 2] };
        let vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();

        assert_eq!(vc, vec![])
    }

    #[test]
    fn ancestor_can_be_parent() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/ghi/jkl".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1, 2] };
        let vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();

        assert_eq!(vc, vec![(SourceRootId(2), SourceRootId(1))])
    }

    #[test]
    fn ancestor_can_be_parent_2() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/ghi/jkl".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/ghi/klm".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1, 2, 3] };
        let mut vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();
        vc.sort_by(|x, y| x.0 .0.cmp(&y.0 .0));

        assert_eq!(vc, vec![(SourceRootId(2), SourceRootId(1)), (SourceRootId(3), SourceRootId(1))])
    }

    #[test]
    fn non_locals_are_skipped() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/ghi/jkl".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/klm".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1, 3] };
        let mut vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();
        vc.sort_by(|x, y| x.0 .0.cmp(&y.0 .0));

        assert_eq!(vc, vec![(SourceRootId(3), SourceRootId(1)),])
    }

    #[test]
    fn child_binds_ancestor_if_parent_nonlocal() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/abc".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/klm".to_owned())]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/klm/jkl".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1, 3] };
        let mut vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();
        vc.sort_by(|x, y| x.0 .0.cmp(&y.0 .0));

        assert_eq!(vc, vec![(SourceRootId(3), SourceRootId(1)),])
    }

    #[test]
    fn parents_with_identical_root_id() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![
            VfsPath::new_virtual_path("/ROOT/def".to_owned()),
            VfsPath::new_virtual_path("/ROOT/def/abc/def".to_owned()),
        ]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/abc/def/ghi".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1] };
        let mut vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();
        vc.sort_by(|x, y| x.0 .0.cmp(&y.0 .0));

        assert_eq!(vc, vec![(SourceRootId(1), SourceRootId(0)),])
    }

    #[test]
    fn circular_reference() {
        let mut builder = FileSetConfigBuilder::default();
        builder.add_file_set(vec![
            VfsPath::new_virtual_path("/ROOT/def".to_owned()),
            VfsPath::new_virtual_path("/ROOT/def/abc/def".to_owned()),
        ]);
        builder.add_file_set(vec![VfsPath::new_virtual_path("/ROOT/def/abc".to_owned())]);
        let fsc = builder.build();
        let src = SourceRootConfig { fsc, local_filesets: vec![0, 1] };
        let mut vc = src.source_root_parent_map().into_iter().collect::<Vec<_>>();
        vc.sort_by(|x, y| x.0 .0.cmp(&y.0 .0));

        assert_eq!(vc, vec![(SourceRootId(1), SourceRootId(0)),])
    }
}