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    //! [`BuildRunner`] is the mutable state used during the build process.

    use std::collections::{BTreeSet, HashMap, HashSet};
    use std::path::{Path, PathBuf};
    use std::sync::{Arc, Mutex};

    use crate::core::compiler::compilation::{self, UnitOutput};
    use crate::core::compiler::{self, artifact, Unit};
    use crate::core::PackageId;
    use crate::util::cache_lock::CacheLockMode;
    use crate::util::errors::CargoResult;
    use anyhow::{bail, Context as _};
    use filetime::FileTime;
    use itertools::Itertools;
    use jobserver::Client;

    use super::build_plan::BuildPlan;
    use super::custom_build::{self, BuildDeps, BuildScriptOutputs, BuildScripts};
    use super::fingerprint::Fingerprint;
    use super::job_queue::JobQueue;
    use super::layout::Layout;
    use super::lto::Lto;
    use super::unit_graph::UnitDep;
    use super::{
        BuildContext, Compilation, CompileKind, CompileMode, Executor, FileFlavor, RustDocFingerprint,
    };

    mod compilation_files;
    use self::compilation_files::CompilationFiles;
    pub use self::compilation_files::{Metadata, OutputFile};

    /// Collection of all the stuff that is needed to perform a build.
    ///
    /// Different from the [`BuildContext`], `Context` is a _mutable_ state used
    /// throughout the entire build process. Everything is coordinated through this.
    ///
    /// [`BuildContext`]: crate::core::compiler::BuildContext
    pub struct BuildRunner<'a, 'gctx> {
        /// Mostly static information about the build task.
        pub bcx: &'a BuildContext<'a, 'gctx>,
        /// A large collection of information about the result of the entire compilation.
        pub compilation: Compilation<'gctx>,
        /// Output from build scripts, updated after each build script runs.
        pub build_script_outputs: Arc<Mutex<BuildScriptOutputs>>,
        /// Dependencies (like rerun-if-changed) declared by a build script.
        /// This is *only* populated from the output from previous runs.
        /// If the build script hasn't ever been run, then it must be run.
        pub build_explicit_deps: HashMap<Unit, BuildDeps>,
        /// Fingerprints used to detect if a unit is out-of-date.
        pub fingerprints: HashMap<Unit, Arc<Fingerprint>>,
        /// Cache of file mtimes to reduce filesystem hits.
        pub mtime_cache: HashMap<PathBuf, FileTime>,
        /// A set used to track which units have been compiled.
        /// A unit may appear in the job graph multiple times as a dependency of
        /// multiple packages, but it only needs to run once.
        pub compiled: HashSet<Unit>,
        /// Linking information for each `Unit`.
        /// See `build_map` for details.
        pub build_scripts: HashMap<Unit, Arc<BuildScripts>>,
        /// Job server client to manage concurrency with other processes.
        pub jobserver: Client,
        /// "Primary" packages are the ones the user selected on the command-line
        /// with `-p` flags. If no flags are specified, then it is the defaults
        /// based on the current directory and the default workspace members.
        primary_packages: HashSet<PackageId>,
        /// An abstraction of the files and directories that will be generated by
        /// the compilation. This is `None` until after `unit_dependencies` has
        /// been computed.
        files: Option<CompilationFiles<'a, 'gctx>>,

        /// A set of units which are compiling rlibs and are expected to produce
        /// metadata files in addition to the rlib itself.
        rmeta_required: HashSet<Unit>,

        /// Map of the LTO-status of each unit. This indicates what sort of
        /// compilation is happening (only object, only bitcode, both, etc), and is
        /// precalculated early on.
        pub lto: HashMap<Unit, Lto>,

        /// Map of Doc/Docscrape units to metadata for their -Cmetadata flag.
        /// See Context::find_metadata_units for more details.
        pub metadata_for_doc_units: HashMap<Unit, Metadata>,

        /// Set of metadata of Docscrape units that fail before completion, e.g.
        /// because the target has a type error. This is in an Arc<Mutex<..>>
        /// because it is continuously updated as the job progresses.
        pub failed_scrape_units: Arc<Mutex<HashSet<Metadata>>>,
    }

    impl<'a, 'gctx> BuildRunner<'a, 'gctx> {
        pub fn new(bcx: &'a BuildContext<'a, 'gctx>) -> CargoResult<Self> {
            // Load up the jobserver that we'll use to manage our parallelism. This
            // is the same as the GNU make implementation of a jobserver, and
            // intentionally so! It's hoped that we can interact with GNU make and
            // all share the same jobserver.
            //
            // Note that if we don't have a jobserver in our environment then we
            // create our own, and we create it with `n` tokens, but immediately
            // acquire one, because one token is ourself, a running process.
            let jobserver = match bcx.gctx.jobserver_from_env() {
                Some(c) => c.clone(),
                None => {
                    let client =
                        Client::new(bcx.jobs() as usize).context("failed to create jobserver")?;
                    client.acquire_raw()?;
                    client
                }
            };

            Ok(Self {
                bcx,
                compilation: Compilation::new(bcx)?,
                build_script_outputs: Arc::new(Mutex::new(BuildScriptOutputs::default())),
                fingerprints: HashMap::new(),
                mtime_cache: HashMap::new(),
                compiled: HashSet::new(),
                build_scripts: HashMap::new(),
                build_explicit_deps: HashMap::new(),
                jobserver,
                primary_packages: HashSet::new(),
                files: None,
                rmeta_required: HashSet::new(),
                lto: HashMap::new(),
                metadata_for_doc_units: HashMap::new(),
                failed_scrape_units: Arc::new(Mutex::new(HashSet::new())),
            })
        }

        /// Starts compilation, waits for it to finish, and returns information
        /// about the result of compilation.
        ///
        /// See [`ops::cargo_compile`] for a higher-level view of the compile process.
        ///
        /// [`ops::cargo_compile`]: ../../../ops/cargo_compile/index.html
        #[tracing::instrument(skip_all)]
        pub fn compile(mut self, exec: &Arc<dyn Executor>) -> CargoResult<Compilation<'gctx>> {
            // A shared lock is held during the duration of the build since rustc
            // needs to read from the `src` cache, and we don't want other
            // commands modifying the `src` cache while it is running.
            let _lock = self
                .bcx
                .gctx
                .acquire_package_cache_lock(CacheLockMode::Shared)?;
            let mut queue = JobQueue::new(self.bcx);
            let mut plan = BuildPlan::new();
            let build_plan = self.bcx.build_config.build_plan;
            self.lto = super::lto::generate(self.bcx)?;
            self.prepare_units()?;
            self.prepare()?;
            custom_build::build_map(&mut self)?;
            self.check_collisions()?;
            self.compute_metadata_for_doc_units();

            // We need to make sure that if there were any previous docs
            // already compiled, they were compiled with the same Rustc version that we're currently
            // using. Otherwise we must remove the `doc/` folder and compile again forcing a rebuild.
            //
            // This is important because the `.js`/`.html` & `.css` files that are generated by Rustc don't have
            // any versioning (See https://github.com/rust-lang/cargo/issues/8461).
            // Therefore, we can end up with weird bugs and behaviours if we mix different
            // versions of these files.
            if self.bcx.build_config.mode.is_doc() {
                RustDocFingerprint::check_rustdoc_fingerprint(&self)?
            }

            for unit in &self.bcx.roots {
                let force_rebuild = self.bcx.build_config.force_rebuild;
                super::compile(&mut self, &mut queue, &mut plan, unit, exec, force_rebuild)?;
            }

            // Now that we've got the full job queue and we've done all our
            // fingerprint analysis to determine what to run, bust all the memoized
            // fingerprint hashes to ensure that during the build they all get the
            // most up-to-date values. In theory we only need to bust hashes that
            // transitively depend on a dirty build script, but it shouldn't matter
            // that much for performance anyway.
            for fingerprint in self.fingerprints.values() {
                fingerprint.clear_memoized();
            }

            // Now that we've figured out everything that we're going to do, do it!
            queue.execute(&mut self, &mut plan)?;

            if build_plan {
                plan.set_inputs(self.build_plan_inputs()?);
                plan.output_plan(self.bcx.gctx);
            }

            // Add `OUT_DIR` to env vars if unit has a build script.
            let units_with_build_script = &self
                .bcx
                .roots
                .iter()
                .filter(|unit| self.build_scripts.contains_key(unit))
                .dedup_by(|x, y| x.pkg.package_id() == y.pkg.package_id())
                .collect::<Vec<_>>();
            for unit in units_with_build_script {
                for dep in &self.bcx.unit_graph[unit] {
                    if dep.unit.mode.is_run_custom_build() {
                        let out_dir = self
                            .files()
                            .build_script_out_dir(&dep.unit)
                            .display()
                            .to_string();
                        let script_meta = self.get_run_build_script_metadata(&dep.unit);
                        self.compilation
                            .extra_env
                            .entry(script_meta)
                            .or_insert_with(Vec::new)
                            .push(("OUT_DIR".to_string(), out_dir));
                    }
                }
            }

            // Collect the result of the build into `self.compilation`.
            for unit in &self.bcx.roots {
                // Collect tests and executables.
                for output in self.outputs(unit)?.iter() {
                    if output.flavor == FileFlavor::DebugInfo || output.flavor == FileFlavor::Auxiliary
                    {
                        continue;
                    }

                    let bindst = output.bin_dst();

                    if unit.mode == CompileMode::Test {
                        self.compilation
                            .tests
                            .push(self.unit_output(unit, &output.path));
                    } else if unit.target.is_executable() {
                        self.compilation
                            .binaries
                            .push(self.unit_output(unit, bindst));
                    } else if unit.target.is_cdylib()
                        && !self.compilation.cdylibs.iter().any(|uo| uo.unit == *unit)
                    {
                        self.compilation
                            .cdylibs
                            .push(self.unit_output(unit, bindst));
                    }
                }

                // Collect information for `rustdoc --test`.
                if unit.mode.is_doc_test() {
                    let mut unstable_opts = false;
                    let mut args = compiler::extern_args(&self, unit, &mut unstable_opts)?;
                    args.extend(compiler::lto_args(&self, unit));
                    args.extend(compiler::features_args(unit));
                    args.extend(compiler::check_cfg_args(unit)?);

                    let script_meta = self.find_build_script_metadata(unit);
                    if let Some(meta) = script_meta {
                        if let Some(output) = self.build_script_outputs.lock().unwrap().get(meta) {
                            for cfg in &output.cfgs {
                                args.push("--cfg".into());
                                args.push(cfg.into());
                            }

                            for check_cfg in &output.check_cfgs {
                                args.push("--check-cfg".into());
                                args.push(check_cfg.into());
                            }

                            for (lt, arg) in &output.linker_args {
                                if lt.applies_to(&unit.target) {
                                    args.push("-C".into());
                                    args.push(format!("link-arg={}", arg).into());
                                }
                            }
                        }
                    }
                    args.extend(unit.rustdocflags.iter().map(Into::into));

                    use super::MessageFormat;
                    let format = match self.bcx.build_config.message_format {
                        MessageFormat::Short => "short",
                        MessageFormat::Human => "human",
                        MessageFormat::Json { .. } => "json",
                    };
                    args.push("--error-format".into());
                    args.push(format.into());

                    self.compilation.to_doc_test.push(compilation::Doctest {
                        unit: unit.clone(),
                        args,
                        unstable_opts,
                        linker: self.compilation.target_linker(unit.kind).clone(),
                        script_meta,
                        env: artifact::get_env(&self, self.unit_deps(unit))?,
                    });
                }

                super::output_depinfo(&mut self, unit)?;
            }

            for (script_meta, output) in self.build_script_outputs.lock().unwrap().iter() {
                self.compilation
                    .extra_env
                    .entry(*script_meta)
                    .or_insert_with(Vec::new)
                    .extend(output.env.iter().cloned());

                for dir in output.library_paths.iter() {
                    self.compilation.native_dirs.insert(dir.clone());
                }
            }
            Ok(self.compilation)
        }

        /// Returns the executable for the specified unit (if any).
        pub fn get_executable(&mut self, unit: &Unit) -> CargoResult<Option<PathBuf>> {
            let is_binary = unit.target.is_executable();
            let is_test = unit.mode.is_any_test();
            if !unit.mode.generates_executable() || !(is_binary || is_test) {
                return Ok(None);
            }
            Ok(self
                .outputs(unit)?
                .iter()
                .find(|o| o.flavor == FileFlavor::Normal)
                .map(|output| output.bin_dst().clone()))
        }

        #[tracing::instrument(skip_all)]
        pub fn prepare_units(&mut self) -> CargoResult<()> {
            let dest = self.bcx.profiles.get_dir_name();
            let host_layout = Layout::new(self.bcx.ws, None, &dest)?;
            let mut targets = HashMap::new();
            for kind in self.bcx.all_kinds.iter() {
                if let CompileKind::Target(target) = *kind {
                    let layout = Layout::new(self.bcx.ws, Some(target), &dest)?;
                    targets.insert(target, layout);
                }
            }
            self.primary_packages
                .extend(self.bcx.roots.iter().map(|u| u.pkg.package_id()));
            self.compilation
                .root_crate_names
                .extend(self.bcx.roots.iter().map(|u| u.target.crate_name()));

            self.record_units_requiring_metadata();

            let files = CompilationFiles::new(self, host_layout, targets);
            self.files = Some(files);
            Ok(())
        }

        /// Prepare this context, ensuring that all filesystem directories are in
        /// place.
        #[tracing::instrument(skip_all)]
        pub fn prepare(&mut self) -> CargoResult<()> {
            self.files
                .as_mut()
                .unwrap()
                .host
                .prepare()
                .context("couldn't prepare build directories")?;
            for target in self.files.as_mut().unwrap().target.values_mut() {
                target
                    .prepare()
                    .context("couldn't prepare build directories")?;
            }

            let files = self.files.as_ref().unwrap();
            for &kind in self.bcx.all_kinds.iter() {
                let layout = files.layout(kind);
                self.compilation
                    .root_output
                    .insert(kind, layout.dest().to_path_buf());
                self.compilation
                    .deps_output
                    .insert(kind, layout.deps().to_path_buf());
            }
            Ok(())
        }

        pub fn files(&self) -> &CompilationFiles<'a, 'gctx> {
            self.files.as_ref().unwrap()
        }

        /// Returns the filenames that the given unit will generate.
        pub fn outputs(&self, unit: &Unit) -> CargoResult<Arc<Vec<OutputFile>>> {
            self.files.as_ref().unwrap().outputs(unit, self.bcx)
        }

        /// Direct dependencies for the given unit.
        pub fn unit_deps(&self, unit: &Unit) -> &[UnitDep] {
            &self.bcx.unit_graph[unit]
        }

        /// Returns the RunCustomBuild Unit associated with the given Unit.
        ///
        /// If the package does not have a build script, this returns None.
        pub fn find_build_script_unit(&self, unit: &Unit) -> Option<Unit> {
            if unit.mode.is_run_custom_build() {
                return Some(unit.clone());
            }
            self.bcx.unit_graph[unit]
                .iter()
                .find(|unit_dep| {
                    unit_dep.unit.mode.is_run_custom_build()
                        && unit_dep.unit.pkg.package_id() == unit.pkg.package_id()
                })
                .map(|unit_dep| unit_dep.unit.clone())
        }

        /// Returns the metadata hash for the RunCustomBuild Unit associated with
        /// the given unit.
        ///
        /// If the package does not have a build script, this returns None.
        pub fn find_build_script_metadata(&self, unit: &Unit) -> Option<Metadata> {
            let script_unit = self.find_build_script_unit(unit)?;
            Some(self.get_run_build_script_metadata(&script_unit))
        }

        /// Returns the metadata hash for a RunCustomBuild unit.
        pub fn get_run_build_script_metadata(&self, unit: &Unit) -> Metadata {
            assert!(unit.mode.is_run_custom_build());
            self.files().metadata(unit)
        }

        pub fn is_primary_package(&self, unit: &Unit) -> bool {
            self.primary_packages.contains(&unit.pkg.package_id())
        }

        /// Returns the list of filenames read by cargo to generate the [`BuildContext`]
        /// (all `Cargo.toml`, etc.).
        pub fn build_plan_inputs(&self) -> CargoResult<Vec<PathBuf>> {
            // Keep sorted for consistency.
            let mut inputs = BTreeSet::new();
            // Note: dev-deps are skipped if they are not present in the unit graph.
            for unit in self.bcx.unit_graph.keys() {
                inputs.insert(unit.pkg.manifest_path().to_path_buf());
            }
            Ok(inputs.into_iter().collect())
        }

        /// Returns a [`UnitOutput`] which represents some information about the
        /// output of a unit.
        pub fn unit_output(&self, unit: &Unit, path: &Path) -> UnitOutput {
            let script_meta = self.find_build_script_metadata(unit);
            UnitOutput {
                unit: unit.clone(),
                path: path.to_path_buf(),
                script_meta,
            }
        }

        /// Check if any output file name collision happens.
        /// See <https://github.com/rust-lang/cargo/issues/6313> for more.
        #[tracing::instrument(skip_all)]
        fn check_collisions(&self) -> CargoResult<()> {
            let mut output_collisions = HashMap::new();
            let describe_collision = |unit: &Unit, other_unit: &Unit, path: &PathBuf| -> String {
                format!(
                    "The {} target `{}` in package `{}` has the same output \
                         filename as the {} target `{}` in package `{}`.\n\
                         Colliding filename is: {}\n",
                    unit.target.kind().description(),
                    unit.target.name(),
                    unit.pkg.package_id(),
                    other_unit.target.kind().description(),
                    other_unit.target.name(),
                    other_unit.pkg.package_id(),
                    path.display()
                )
            };
            let suggestion =
                "Consider changing their names to be unique or compiling them separately.\n\
                 This may become a hard error in the future; see \
                 <https://github.com/rust-lang/cargo/issues/6313>.";
            let rustdoc_suggestion =
                "This is a known bug where multiple crates with the same name use\n\
                 the same path; see <https://github.com/rust-lang/cargo/issues/6313>.";
            let report_collision = |unit: &Unit,
                                    other_unit: &Unit,
                                    path: &PathBuf,
                                    suggestion: &str|
             -> CargoResult<()> {
                if unit.target.name() == other_unit.target.name() {
                    self.bcx.gctx.shell().warn(format!(
                        "output filename collision.\n\
                         {}\
                         The targets should have unique names.\n\
                         {}",
                        describe_collision(unit, other_unit, path),
                        suggestion
                    ))
                } else {
                    self.bcx.gctx.shell().warn(format!(
                        "output filename collision.\n\
                        {}\
                        The output filenames should be unique.\n\
                        {}\n\
                        If this looks unexpected, it may be a bug in Cargo. Please file a bug report at\n\
                        https://github.com/rust-lang/cargo/issues/ with as much information as you\n\
                        can provide.\n\
                        cargo {} running on `{}` target `{}`\n\
                        First unit: {:?}\n\
                        Second unit: {:?}",
                        describe_collision(unit, other_unit, path),
                        suggestion,
                        crate::version(),
                        self.bcx.host_triple(),
                        self.bcx.target_data.short_name(&unit.kind),
                        unit,
                        other_unit))
                }
            };

            fn doc_collision_error(unit: &Unit, other_unit: &Unit) -> CargoResult<()> {
                bail!(
                    "document output filename collision\n\
                     The {} `{}` in package `{}` has the same name as the {} `{}` in package `{}`.\n\
                     Only one may be documented at once since they output to the same path.\n\
                     Consider documenting only one, renaming one, \
                     or marking one with `doc = false` in Cargo.toml.",
                    unit.target.kind().description(),
                    unit.target.name(),
                    unit.pkg,
                    other_unit.target.kind().description(),
                    other_unit.target.name(),
                    other_unit.pkg,
                );
            }

            let mut keys = self
                .bcx
                .unit_graph
                .keys()
                .filter(|unit| !unit.mode.is_run_custom_build())
                .collect::<Vec<_>>();
            // Sort for consistent error messages.
            keys.sort_unstable();
            // These are kept separate to retain compatibility with older
            // versions, which generated an error when there was a duplicate lib
            // or bin (but the old code did not check bin<->lib collisions). To
            // retain backwards compatibility, this only generates an error for
            // duplicate libs or duplicate bins (but not both). Ideally this
            // shouldn't be here, but since there isn't a complete workaround,
            // yet, this retains the old behavior.
            let mut doc_libs = HashMap::new();
            let mut doc_bins = HashMap::new();
            for unit in keys {
                if unit.mode.is_doc() && self.is_primary_package(unit) {
                    // These situations have been an error since before 1.0, so it
                    // is not a warning like the other situations.
                    if unit.target.is_lib() {
                        if let Some(prev) = doc_libs.insert((unit.target.crate_name(), unit.kind), unit)
                        {
                            doc_collision_error(unit, prev)?;
                        }
                    } else if let Some(prev) =
                        doc_bins.insert((unit.target.crate_name(), unit.kind), unit)
                    {
                        doc_collision_error(unit, prev)?;
                    }
                }
                for output in self.outputs(unit)?.iter() {
                    if let Some(other_unit) = output_collisions.insert(output.path.clone(), unit) {
                        if unit.mode.is_doc() {
                            // See https://github.com/rust-lang/rust/issues/56169
                            // and https://github.com/rust-lang/rust/issues/61378
                            report_collision(unit, other_unit, &output.path, rustdoc_suggestion)?;
                        } else {
                            report_collision(unit, other_unit, &output.path, suggestion)?;
                        }
                    }
                    if let Some(hardlink) = output.hardlink.as_ref() {
                        if let Some(other_unit) = output_collisions.insert(hardlink.clone(), unit) {
                            report_collision(unit, other_unit, hardlink, suggestion)?;
                        }
                    }
                    if let Some(ref export_path) = output.export_path {
                        if let Some(other_unit) = output_collisions.insert(export_path.clone(), unit) {
                            self.bcx.gctx.shell().warn(format!(
                                "`--artifact-dir` filename collision.\n\
                                 {}\
                                 The exported filenames should be unique.\n\
                                 {}",
                                describe_collision(unit, other_unit, export_path),
                                suggestion
                            ))?;
                        }
                    }
                }
            }
            Ok(())
        }

        /// Records the list of units which are required to emit metadata.
        ///
        /// Units which depend only on the metadata of others requires the others to
        /// actually produce metadata, so we'll record that here.
        fn record_units_requiring_metadata(&mut self) {
            for (key, deps) in self.bcx.unit_graph.iter() {
                for dep in deps {
                    if self.only_requires_rmeta(key, &dep.unit) {
                        self.rmeta_required.insert(dep.unit.clone());
                    }
                }
            }
        }

        /// Returns whether when `parent` depends on `dep` if it only requires the
        /// metadata file from `dep`.
        pub fn only_requires_rmeta(&self, parent: &Unit, dep: &Unit) -> bool {
            // We're only a candidate for requiring an `rmeta` file if we
            // ourselves are building an rlib,
            !parent.requires_upstream_objects()
                && parent.mode == CompileMode::Build
                // Our dependency must also be built as an rlib, otherwise the
                // object code must be useful in some fashion
                && !dep.requires_upstream_objects()
                && dep.mode == CompileMode::Build
        }

        /// Returns whether when `unit` is built whether it should emit metadata as
        /// well because some compilations rely on that.
        pub fn rmeta_required(&self, unit: &Unit) -> bool {
            self.rmeta_required.contains(unit)
        }

        /// Finds metadata for Doc/Docscrape units.
        ///
        /// rustdoc needs a -Cmetadata flag in order to recognize StableCrateIds that refer to
        /// items in the crate being documented. The -Cmetadata flag used by reverse-dependencies
        /// will be the metadata of the Cargo unit that generated the current library's rmeta file,
        /// which should be a Check unit.
        ///
        /// If the current crate has reverse-dependencies, such a Check unit should exist, and so
        /// we use that crate's metadata. If not, we use the crate's Doc unit so at least examples
        /// scraped from the current crate can be used when documenting the current crate.
        #[tracing::instrument(skip_all)]
        pub fn compute_metadata_for_doc_units(&mut self) {
            for unit in self.bcx.unit_graph.keys() {
                if !unit.mode.is_doc() && !unit.mode.is_doc_scrape() {
                    continue;
                }

                let matching_units = self
                    .bcx
                    .unit_graph
                    .keys()
                    .filter(|other| {
                        unit.pkg == other.pkg
                            && unit.target == other.target
                            && !other.mode.is_doc_scrape()
                    })
                    .collect::<Vec<_>>();
                let metadata_unit = matching_units
                    .iter()
                    .find(|other| other.mode.is_check())
                    .or_else(|| matching_units.iter().find(|other| other.mode.is_doc()))
                    .unwrap_or(&unit);
                self.metadata_for_doc_units
                    .insert(unit.clone(), self.files().metadata(metadata_unit));
            }
        }
    }