//! This module specifies the input to rust-analyzer. In some sense, this is
//! **the** most important module, because all other fancy stuff is strictly
//! derived from this input.
//!
//! Note that neither this module, nor any other part of the analyzer's core do
//! actual IO. See `vfs` and `project_model` in the `rust-analyzer` crate for how
//! actual IO is done and lowered to input.

use std::{fmt, mem, ops, panic::RefUnwindSafe, str::FromStr, sync};

use cfg::CfgOptions;
use la_arena::{Arena, Idx};
use rustc_hash::{FxHashMap, FxHashSet};
use syntax::SmolStr;
use triomphe::Arc;
use tt::token_id::Subtree;
use vfs::{file_set::FileSet, AbsPathBuf, AnchoredPath, FileId, VfsPath};

// Map from crate id to the name of the crate and path of the proc-macro. If the value is `None`,
// then the crate for the proc-macro hasn't been build yet as the build data is missing.
pub type ProcMacroPaths = FxHashMap<CrateId, Result<(Option<String>, AbsPathBuf), String>>;
pub type ProcMacros = FxHashMap<CrateId, ProcMacroLoadResult>;

/// Files are grouped into source roots. A source root is a directory on the
/// file systems which is watched for changes. Typically it corresponds to a
/// Rust crate. Source roots *might* be nested: in this case, a file belongs to
/// the nearest enclosing source root. Paths to files are always relative to a
/// source root, and the analyzer does not know the root path of the source root at
/// all. So, a file from one source root can't refer to a file in another source
/// root by path.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct SourceRootId(pub u32);

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SourceRoot {
    /// Sysroot or crates.io library.
    ///
    /// Libraries are considered mostly immutable, this assumption is used to
    /// optimize salsa's query structure
    pub is_library: bool,
    file_set: FileSet,
}

impl SourceRoot {
    pub fn new_local(file_set: FileSet) -> SourceRoot {
        SourceRoot { is_library: false, file_set }
    }

    pub fn new_library(file_set: FileSet) -> SourceRoot {
        SourceRoot { is_library: true, file_set }
    }

    pub fn path_for_file(&self, file: &FileId) -> Option<&VfsPath> {
        self.file_set.path_for_file(file)
    }

    pub fn file_for_path(&self, path: &VfsPath) -> Option<&FileId> {
        self.file_set.file_for_path(path)
    }

    pub fn resolve_path(&self, path: AnchoredPath<'_>) -> Option<FileId> {
        self.file_set.resolve_path(path)
    }

    pub fn iter(&self) -> impl Iterator<Item = FileId> + '_ {
        self.file_set.iter()
    }
}

/// `CrateGraph` is a bit of information which turns a set of text files into a
/// number of Rust crates.
///
/// Each crate is defined by the `FileId` of its root module, the set of enabled
/// `cfg` flags and the set of dependencies.
///
/// Note that, due to cfg's, there might be several crates for a single `FileId`!
///
/// For the purposes of analysis, a crate does not have a name. Instead, names
/// are specified on dependency edges. That is, a crate might be known under
/// different names in different dependent crates.
///
/// Note that `CrateGraph` is build-system agnostic: it's a concept of the Rust
/// language proper, not a concept of the build system. In practice, we get
/// `CrateGraph` by lowering `cargo metadata` output.
///
/// `CrateGraph` is `!Serialize` by design, see
/// <https://github.com/rust-lang/rust-analyzer/blob/master/docs/dev/architecture.md#serialization>
#[derive(Clone, Default)]
pub struct CrateGraph {
    arena: Arena<CrateData>,
}

impl fmt::Debug for CrateGraph {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_map()
            .entries(self.arena.iter().map(|(id, data)| (u32::from(id.into_raw()), data)))
            .finish()
    }
}

pub type CrateId = Idx<CrateData>;

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct CrateName(SmolStr);

impl CrateName {
    /// Creates a crate name, checking for dashes in the string provided.
    /// Dashes are not allowed in the crate names,
    /// hence the input string is returned as `Err` for those cases.
    pub fn new(name: &str) -> Result<CrateName, &str> {
        if name.contains('-') {
            Err(name)
        } else {
            Ok(Self(SmolStr::new(name)))
        }
    }

    /// Creates a crate name, unconditionally replacing the dashes with underscores.
    pub fn normalize_dashes(name: &str) -> CrateName {
        Self(SmolStr::new(name.replace('-', "_")))
    }

    pub fn as_smol_str(&self) -> &SmolStr {
        &self.0
    }
}

impl fmt::Display for CrateName {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

impl ops::Deref for CrateName {
    type Target = str;
    fn deref(&self) -> &str {
        &self.0
    }
}

/// Origin of the crates.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum CrateOrigin {
    /// Crates that are from the rustc workspace.
    Rustc { name: String },
    /// Crates that are workspace members.
    Local { repo: Option<String>, name: Option<String> },
    /// Crates that are non member libraries.
    Library { repo: Option<String>, name: String },
    /// Crates that are provided by the language, like std, core, proc-macro, ...
    Lang(LangCrateOrigin),
}

impl CrateOrigin {
    pub fn is_local(&self) -> bool {
        matches!(self, CrateOrigin::Local { .. })
    }

    pub fn is_lib(&self) -> bool {
        matches!(self, CrateOrigin::Library { .. })
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum LangCrateOrigin {
    Alloc,
    Core,
    ProcMacro,
    Std,
    Test,
    Other,
}

impl From<&str> for LangCrateOrigin {
    fn from(s: &str) -> Self {
        match s {
            "alloc" => LangCrateOrigin::Alloc,
            "core" => LangCrateOrigin::Core,
            "proc-macro" => LangCrateOrigin::ProcMacro,
            "std" => LangCrateOrigin::Std,
            "test" => LangCrateOrigin::Test,
            _ => LangCrateOrigin::Other,
        }
    }
}

impl fmt::Display for LangCrateOrigin {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let text = match self {
            LangCrateOrigin::Alloc => "alloc",
            LangCrateOrigin::Core => "core",
            LangCrateOrigin::ProcMacro => "proc_macro",
            LangCrateOrigin::Std => "std",
            LangCrateOrigin::Test => "test",
            LangCrateOrigin::Other => "other",
        };
        f.write_str(text)
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct CrateDisplayName {
    // The name we use to display various paths (with `_`).
    crate_name: CrateName,
    // The name as specified in Cargo.toml (with `-`).
    canonical_name: String,
}

impl CrateDisplayName {
    pub fn canonical_name(&self) -> &str {
        &self.canonical_name
    }
    pub fn crate_name(&self) -> &CrateName {
        &self.crate_name
    }
}

impl From<CrateName> for CrateDisplayName {
    fn from(crate_name: CrateName) -> CrateDisplayName {
        let canonical_name = crate_name.to_string();
        CrateDisplayName { crate_name, canonical_name }
    }
}

impl fmt::Display for CrateDisplayName {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.crate_name.fmt(f)
    }
}

impl ops::Deref for CrateDisplayName {
    type Target = str;
    fn deref(&self) -> &str {
        &self.crate_name
    }
}

impl CrateDisplayName {
    pub fn from_canonical_name(canonical_name: String) -> CrateDisplayName {
        let crate_name = CrateName::normalize_dashes(&canonical_name);
        CrateDisplayName { crate_name, canonical_name }
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct ProcMacroId(pub u32);

#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]
pub enum ProcMacroKind {
    CustomDerive,
    FuncLike,
    Attr,
}

pub trait ProcMacroExpander: fmt::Debug + Send + Sync + RefUnwindSafe {
    fn expand(
        &self,
        subtree: &Subtree,
        attrs: Option<&Subtree>,
        env: &Env,
    ) -> Result<Subtree, ProcMacroExpansionError>;
}

#[derive(Debug)]
pub enum ProcMacroExpansionError {
    Panic(String),
    /// Things like "proc macro server was killed by OOM".
    System(String),
}

pub type ProcMacroLoadResult = Result<Vec<ProcMacro>, String>;
pub type TargetLayoutLoadResult = Result<Arc<str>, Arc<str>>;

#[derive(Debug, Clone)]
pub struct ProcMacro {
    pub name: SmolStr,
    pub kind: ProcMacroKind,
    pub expander: sync::Arc<dyn ProcMacroExpander>,
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum ReleaseChannel {
    Stable,
    Beta,
    Nightly,
}

impl ReleaseChannel {
    pub fn as_str(self) -> &'static str {
        match self {
            ReleaseChannel::Stable => "stable",
            ReleaseChannel::Beta => "beta",
            ReleaseChannel::Nightly => "nightly",
        }
    }

    pub fn from_str(str: &str) -> Option<Self> {
        Some(match str {
            "" => ReleaseChannel::Stable,
            "nightly" => ReleaseChannel::Nightly,
            _ if str.starts_with("beta") => ReleaseChannel::Beta,
            _ => return None,
        })
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct CrateData {
    pub root_file_id: FileId,
    pub edition: Edition,
    pub version: Option<String>,
    /// A name used in the package's project declaration: for Cargo projects,
    /// its `[package].name` can be different for other project types or even
    /// absent (a dummy crate for the code snippet, for example).
    ///
    /// For purposes of analysis, crates are anonymous (only names in
    /// `Dependency` matters), this name should only be used for UI.
    pub display_name: Option<CrateDisplayName>,
    pub cfg_options: CfgOptions,
    /// The cfg options that could be used by the crate
    pub potential_cfg_options: Option<CfgOptions>,
    pub env: Env,
    pub dependencies: Vec<Dependency>,
    pub origin: CrateOrigin,
    pub is_proc_macro: bool,
    // FIXME: These things should not be per crate! These are more per workspace crate graph level things
    pub target_layout: TargetLayoutLoadResult,
    pub channel: Option<ReleaseChannel>,
}

impl CrateData {
    /// Check if [`other`] is almost equal to [`self`] ignoring `CrateOrigin` value.
    pub fn eq_ignoring_origin_and_deps(&self, other: &CrateData, ignore_dev_deps: bool) -> bool {
        // This method has some obscure bits. These are mostly there to be compliant with
        // some patches. References to the patches are given.
        if self.root_file_id != other.root_file_id {
            return false;
        }

        if self.display_name != other.display_name {
            return false;
        }

        if self.is_proc_macro != other.is_proc_macro {
            return false;
        }

        if self.edition != other.edition {
            return false;
        }

        if self.version != other.version {
            return false;
        }

        let mut opts = self.cfg_options.diff(&other.cfg_options).into_iter();
        match opts.len() {
            0 => (),
            1 => {
                // Don't care if rust_analyzer CfgAtom is the only cfg in the difference set of self's and other's cfgs.
                // https://github.com/rust-lang/rust-analyzer/blob/0840038f02daec6ba3238f05d8caa037d28701a0/crates/project-model/src/workspace.rs#L894
                if let Some(cfg) = opts.next() {
                    if cfg.to_string() != "rust_analyzer" {
                        return false;
                    }
                }
            }
            _ => return false,
        };

        if self.env != other.env {
            return false;
        }

        let slf_deps = self.dependencies.iter();
        let other_deps = other.dependencies.iter();

        if ignore_dev_deps {
            return slf_deps
                .clone()
                .filter(|it| it.kind == DependencyKind::Normal)
                .eq(other_deps.clone().filter(|it| it.kind == DependencyKind::Normal));
        }

        slf_deps.eq(other_deps)
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum Edition {
    Edition2015,
    Edition2018,
    Edition2021,
}

impl Edition {
    pub const CURRENT: Edition = Edition::Edition2021;
}

#[derive(Default, Debug, Clone, PartialEq, Eq)]
pub struct Env {
    entries: FxHashMap<String, String>,
}

impl Env {
    pub fn new_for_test_fixture() -> Self {
        Env {
            entries: FxHashMap::from_iter([(
                String::from("__ra_is_test_fixture"),
                String::from("__ra_is_test_fixture"),
            )]),
        }
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum DependencyKind {
    Normal,
    Dev,
    Build,
}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Dependency {
    pub crate_id: CrateId,
    pub name: CrateName,
    kind: DependencyKind,
    prelude: bool,
}

impl Dependency {
    pub fn new(name: CrateName, crate_id: CrateId, kind: DependencyKind) -> Self {
        Self { name, crate_id, prelude: true, kind }
    }

    pub fn with_prelude(
        name: CrateName,
        crate_id: CrateId,
        prelude: bool,
        kind: DependencyKind,
    ) -> Self {
        Self { name, crate_id, prelude, kind }
    }

    /// Whether this dependency is to be added to the depending crate's extern prelude.
    pub fn is_prelude(&self) -> bool {
        self.prelude
    }

    pub fn kind(&self) -> DependencyKind {
        self.kind
    }
}

impl CrateGraph {
    pub fn add_crate_root(
        &mut self,
        root_file_id: FileId,
        edition: Edition,
        display_name: Option<CrateDisplayName>,
        version: Option<String>,
        cfg_options: CfgOptions,
        potential_cfg_options: Option<CfgOptions>,
        env: Env,
        is_proc_macro: bool,
        origin: CrateOrigin,
        target_layout: Result<Arc<str>, Arc<str>>,
        channel: Option<ReleaseChannel>,
    ) -> CrateId {
        let data = CrateData {
            root_file_id,
            edition,
            version,
            display_name,
            cfg_options,
            potential_cfg_options,
            env,
            dependencies: Vec::new(),
            origin,
            target_layout,
            is_proc_macro,
            channel,
        };
        self.arena.alloc(data)
    }

    /// Remove the crate from crate graph. If any crates depend on this crate, the dependency would be replaced
    /// with the second input.
    pub fn remove_and_replace(
        &mut self,
        id: CrateId,
        replace_with: CrateId,
    ) -> Result<(), CyclicDependenciesError> {
        for (x, data) in self.arena.iter() {
            if x == id {
                continue;
            }
            for edge in &data.dependencies {
                if edge.crate_id == id {
                    self.check_cycle_after_dependency(edge.crate_id, replace_with)?;
                }
            }
        }
        // if everything was ok, start to replace
        for (x, data) in self.arena.iter_mut() {
            if x == id {
                continue;
            }
            for edge in &mut data.dependencies {
                if edge.crate_id == id {
                    edge.crate_id = replace_with;
                }
            }
        }
        Ok(())
    }

    pub fn add_dep(
        &mut self,
        from: CrateId,
        dep: Dependency,
    ) -> Result<(), CyclicDependenciesError> {
        let _p = profile::span("add_dep");

        self.check_cycle_after_dependency(from, dep.crate_id)?;

        self.arena[from].add_dep_unchecked(dep);
        Ok(())
    }

    /// Check if adding a dep from `from` to `to` creates a cycle. To figure
    /// that out, look for a  path in the *opposite* direction, from `to` to
    /// `from`.
    fn check_cycle_after_dependency(
        &self,
        from: CrateId,
        to: CrateId,
    ) -> Result<(), CyclicDependenciesError> {
        if let Some(path) = self.find_path(&mut FxHashSet::default(), to, from) {
            let path = path.into_iter().map(|it| (it, self[it].display_name.clone())).collect();
            let err = CyclicDependenciesError { path };
            assert!(err.from().0 == from && err.to().0 == to);
            return Err(err);
        }
        Ok(())
    }

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

    pub fn iter(&self) -> impl Iterator<Item = CrateId> + '_ {
        self.arena.iter().map(|(idx, _)| idx)
    }

    // FIXME: used for `handle_hack_cargo_workspace`, should be removed later
    #[doc(hidden)]
    pub fn iter_mut(&mut self) -> impl Iterator<Item = (CrateId, &mut CrateData)> + '_ {
        self.arena.iter_mut()
    }

    /// Returns an iterator over all transitive dependencies of the given crate,
    /// including the crate itself.
    pub fn transitive_deps(&self, of: CrateId) -> impl Iterator<Item = CrateId> {
        let mut worklist = vec![of];
        let mut deps = FxHashSet::default();

        while let Some(krate) = worklist.pop() {
            if !deps.insert(krate) {
                continue;
            }

            worklist.extend(self[krate].dependencies.iter().map(|dep| dep.crate_id));
        }

        deps.into_iter()
    }

    /// Returns all transitive reverse dependencies of the given crate,
    /// including the crate itself.
    pub fn transitive_rev_deps(&self, of: CrateId) -> impl Iterator<Item = CrateId> {
        let mut worklist = vec![of];
        let mut rev_deps = FxHashSet::default();
        rev_deps.insert(of);

        let mut inverted_graph = FxHashMap::<_, Vec<_>>::default();
        self.arena.iter().for_each(|(krate, data)| {
            data.dependencies
                .iter()
                .for_each(|dep| inverted_graph.entry(dep.crate_id).or_default().push(krate))
        });

        while let Some(krate) = worklist.pop() {
            if let Some(krate_rev_deps) = inverted_graph.get(&krate) {
                krate_rev_deps
                    .iter()
                    .copied()
                    .filter(|&rev_dep| rev_deps.insert(rev_dep))
                    .for_each(|rev_dep| worklist.push(rev_dep));
            }
        }

        rev_deps.into_iter()
    }

    /// Returns all crates in the graph, sorted in topological order (ie. dependencies of a crate
    /// come before the crate itself).
    pub fn crates_in_topological_order(&self) -> Vec<CrateId> {
        let mut res = Vec::new();
        let mut visited = FxHashSet::default();

        for krate in self.iter() {
            go(self, &mut visited, &mut res, krate);
        }

        return res;

        fn go(
            graph: &CrateGraph,
            visited: &mut FxHashSet<CrateId>,
            res: &mut Vec<CrateId>,
            source: CrateId,
        ) {
            if !visited.insert(source) {
                return;
            }
            for dep in graph[source].dependencies.iter() {
                go(graph, visited, res, dep.crate_id)
            }
            res.push(source)
        }
    }

    // FIXME: this only finds one crate with the given root; we could have multiple
    pub fn crate_id_for_crate_root(&self, file_id: FileId) -> Option<CrateId> {
        let (crate_id, _) =
            self.arena.iter().find(|(_crate_id, data)| data.root_file_id == file_id)?;
        Some(crate_id)
    }

    pub fn sort_deps(&mut self) {
        self.arena
            .iter_mut()
            .for_each(|(_, data)| data.dependencies.sort_by_key(|dep| dep.crate_id));
    }

    /// Extends this crate graph by adding a complete disjoint second crate
    /// graph and adjust the ids in the [`ProcMacroPaths`] accordingly.
    ///
    /// This will deduplicate the crates of the graph where possible.
    /// Note that for deduplication to fully work, `self`'s crate dependencies must be sorted by crate id.
    /// If the crate dependencies were sorted, the resulting graph from this `extend` call will also have the crate dependencies sorted.
    pub fn extend(&mut self, mut other: CrateGraph, proc_macros: &mut ProcMacroPaths) {
        let topo = other.crates_in_topological_order();
        let mut id_map: FxHashMap<CrateId, CrateId> = FxHashMap::default();
        for topo in topo {
            let crate_data = &mut other.arena[topo];

            crate_data.dependencies.iter_mut().for_each(|dep| dep.crate_id = id_map[&dep.crate_id]);
            crate_data.dependencies.sort_by_key(|dep| dep.crate_id);
            let res = self.arena.iter().find_map(|(id, data)| {
                match (&data.origin, &crate_data.origin) {
                    (a, b) if a == b => {
                        if data.eq_ignoring_origin_and_deps(&crate_data, false) {
                            return Some((id, false));
                        }
                    }
                    (a @ CrateOrigin::Local { .. }, CrateOrigin::Library { .. })
                    | (a @ CrateOrigin::Library { .. }, CrateOrigin::Local { .. }) => {
                        // See #15656 for a relevant example.
                        if data.eq_ignoring_origin_and_deps(&crate_data, true) {
                            return Some((id, if a.is_local() { false } else { true }));
                        }
                    }
                    (_, _) => return None,
                }

                None
            });

            if let Some((res, should_update_lib_to_local)) = res {
                id_map.insert(topo, res);
                if should_update_lib_to_local {
                    let origin_old = self.arena[res].origin.clone();
                    assert!(origin_old.is_lib());

                    if let CrateOrigin::Library { repo, name } = origin_old {
                        self.arena[res].origin = CrateOrigin::Local { repo, name: Some(name) };
                    }

                    // Move local's dev dependencies into the newly-local-formerly-lib crate.
                    let dev_deps = crate_data
                        .dependencies
                        .clone()
                        .into_iter()
                        .filter(|dep| dep.kind() == DependencyKind::Dev)
                        .collect::<Vec<Dependency>>();

                    self.arena[res].add_dep(dev_deps).unwrap_or_default();
                }
            } else {
                let id = self.arena.alloc(crate_data.clone());
                id_map.insert(topo, id);
            }
        }

        *proc_macros =
            mem::take(proc_macros).into_iter().map(|(id, macros)| (id_map[&id], macros)).collect();
    }

    fn find_path(
        &self,
        visited: &mut FxHashSet<CrateId>,
        from: CrateId,
        to: CrateId,
    ) -> Option<Vec<CrateId>> {
        if !visited.insert(from) {
            return None;
        }

        if from == to {
            return Some(vec![to]);
        }

        for dep in &self[from].dependencies {
            let crate_id = dep.crate_id;
            if let Some(mut path) = self.find_path(visited, crate_id, to) {
                path.push(from);
                return Some(path);
            }
        }

        None
    }

    // Work around for https://github.com/rust-lang/rust-analyzer/issues/6038.
    // As hacky as it gets.
    pub fn patch_cfg_if(&mut self) -> bool {
        // we stupidly max by version in an attempt to have all duplicated std's depend on the same cfg_if so that deduplication still works
        let cfg_if =
            self.hacky_find_crate("cfg_if").max_by_key(|&it| self.arena[it].version.clone());
        let std = self.hacky_find_crate("std").next();
        match (cfg_if, std) {
            (Some(cfg_if), Some(std)) => {
                self.arena[cfg_if].dependencies.clear();
                self.arena[std].dependencies.push(Dependency::new(
                    CrateName::new("cfg_if").unwrap(),
                    cfg_if,
                    DependencyKind::Normal,
                ));
                true
            }
            _ => false,
        }
    }

    fn hacky_find_crate<'a>(&'a self, display_name: &'a str) -> impl Iterator<Item = CrateId> + 'a {
        self.iter().filter(move |it| self[*it].display_name.as_deref() == Some(display_name))
    }
}

impl ops::Index<CrateId> for CrateGraph {
    type Output = CrateData;
    fn index(&self, crate_id: CrateId) -> &CrateData {
        &self.arena[crate_id]
    }
}

struct ExistingDepsError(Vec<Dependency>);

impl CrateData {
    /// Add a dependency to `self` without checking if the dependency
    // is existent among `self.dependencies`.
    fn add_dep_unchecked(&mut self, dep: Dependency) {
        self.dependencies.push(dep)
    }

    /// Add `deps` to `self` if the dependency is not already listed.
    /// Finally returning an `Err` propagating the dependencies it couldn't add.
    fn add_dep(&mut self, deps: Vec<Dependency>) -> Result<(), ExistingDepsError> {
        let mut existing_deps: Vec<Dependency> = vec![];

        deps.into_iter().for_each(|dep| {
            if !self.dependencies.contains(&dep) {
                self.dependencies.push(dep);
            } else {
                existing_deps.push(dep);
            }
        });

        if !existing_deps.is_empty() {
            return Err(ExistingDepsError(existing_deps));
        }

        Ok(())
    }
}

impl FromStr for Edition {
    type Err = ParseEditionError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let res = match s {
            "2015" => Edition::Edition2015,
            "2018" => Edition::Edition2018,
            "2021" => Edition::Edition2021,
            _ => return Err(ParseEditionError { invalid_input: s.to_string() }),
        };
        Ok(res)
    }
}

impl fmt::Display for Edition {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match self {
            Edition::Edition2015 => "2015",
            Edition::Edition2018 => "2018",
            Edition::Edition2021 => "2021",
        })
    }
}

impl Extend<(String, String)> for Env {
    fn extend<T: IntoIterator<Item = (String, String)>>(&mut self, iter: T) {
        self.entries.extend(iter);
    }
}

impl FromIterator<(String, String)> for Env {
    fn from_iter<T: IntoIterator<Item = (String, String)>>(iter: T) -> Self {
        Env { entries: FromIterator::from_iter(iter) }
    }
}

impl Env {
    pub fn set(&mut self, env: &str, value: String) {
        self.entries.insert(env.to_owned(), value);
    }

    pub fn get(&self, env: &str) -> Option<String> {
        self.entries.get(env).cloned()
    }

    pub fn iter(&self) -> impl Iterator<Item = (&str, &str)> {
        self.entries.iter().map(|(k, v)| (k.as_str(), v.as_str()))
    }
}

#[derive(Debug)]
pub struct ParseEditionError {
    invalid_input: String,
}

impl fmt::Display for ParseEditionError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "invalid edition: {:?}", self.invalid_input)
    }
}

impl std::error::Error for ParseEditionError {}

#[derive(Debug)]
pub struct CyclicDependenciesError {
    path: Vec<(CrateId, Option<CrateDisplayName>)>,
}

impl CyclicDependenciesError {
    fn from(&self) -> &(CrateId, Option<CrateDisplayName>) {
        self.path.first().unwrap()
    }
    fn to(&self) -> &(CrateId, Option<CrateDisplayName>) {
        self.path.last().unwrap()
    }
}

impl fmt::Display for CyclicDependenciesError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let render = |(id, name): &(CrateId, Option<CrateDisplayName>)| match name {
            Some(it) => format!("{it}({id:?})"),
            None => format!("{id:?}"),
        };
        let path = self.path.iter().rev().map(render).collect::<Vec<String>>().join(" -> ");
        write!(
            f,
            "cyclic deps: {} -> {}, alternative path: {}",
            render(self.from()),
            render(self.to()),
            path
        )
    }
}

#[cfg(test)]
mod tests {
    use crate::{CrateOrigin, DependencyKind};

    use super::{CrateGraph, CrateName, Dependency, Edition::Edition2018, Env, FileId};

    #[test]
    fn detect_cyclic_dependency_indirect() {
        let mut graph = CrateGraph::default();
        let crate1 = graph.add_crate_root(
            FileId(1u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        let crate2 = graph.add_crate_root(
            FileId(2u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        let crate3 = graph.add_crate_root(
            FileId(3u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        assert!(graph
            .add_dep(
                crate1,
                Dependency::new(CrateName::new("crate2").unwrap(), crate2, DependencyKind::Normal)
            )
            .is_ok());
        assert!(graph
            .add_dep(
                crate2,
                Dependency::new(CrateName::new("crate3").unwrap(), crate3, DependencyKind::Normal)
            )
            .is_ok());
        assert!(graph
            .add_dep(
                crate3,
                Dependency::new(CrateName::new("crate1").unwrap(), crate1, DependencyKind::Normal)
            )
            .is_err());
    }

    #[test]
    fn detect_cyclic_dependency_direct() {
        let mut graph = CrateGraph::default();
        let crate1 = graph.add_crate_root(
            FileId(1u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        let crate2 = graph.add_crate_root(
            FileId(2u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        assert!(graph
            .add_dep(
                crate1,
                Dependency::new(CrateName::new("crate2").unwrap(), crate2, DependencyKind::Normal)
            )
            .is_ok());
        assert!(graph
            .add_dep(
                crate2,
                Dependency::new(CrateName::new("crate2").unwrap(), crate2, DependencyKind::Normal)
            )
            .is_err());
    }

    #[test]
    fn it_works() {
        let mut graph = CrateGraph::default();
        let crate1 = graph.add_crate_root(
            FileId(1u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        let crate2 = graph.add_crate_root(
            FileId(2u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        let crate3 = graph.add_crate_root(
            FileId(3u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        assert!(graph
            .add_dep(
                crate1,
                Dependency::new(CrateName::new("crate2").unwrap(), crate2, DependencyKind::Normal)
            )
            .is_ok());
        assert!(graph
            .add_dep(
                crate2,
                Dependency::new(CrateName::new("crate3").unwrap(), crate3, DependencyKind::Normal)
            )
            .is_ok());
    }

    #[test]
    fn dashes_are_normalized() {
        let mut graph = CrateGraph::default();
        let crate1 = graph.add_crate_root(
            FileId(1u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        let crate2 = graph.add_crate_root(
            FileId(2u32),
            Edition2018,
            None,
            None,
            Default::default(),
            Default::default(),
            Env::default(),
            false,
            CrateOrigin::Local { repo: None, name: None },
            Err("".into()),
            None,
        );
        assert!(graph
            .add_dep(
                crate1,
                Dependency::new(
                    CrateName::normalize_dashes("crate-name-with-dashes"),
                    crate2,
                    DependencyKind::Normal
                )
            )
            .is_ok());
        assert_eq!(
            graph[crate1].dependencies,
            vec![Dependency::new(
                CrateName::new("crate_name_with_dashes").unwrap(),
                crate2,
                DependencyKind::Normal
            )]
        );
    }
}