use std::path::PathBuf;
use std::result;
use std::sync::Arc;

use rustc_ast::{LitKind, MetaItemKind, token};
use rustc_codegen_ssa::traits::CodegenBackend;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::jobserver;
use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
use rustc_lint::LintStore;
use rustc_middle::ty;
use rustc_middle::ty::CurrentGcx;
use rustc_middle::util::Providers;
use rustc_parse::lexer::StripTokens;
use rustc_parse::new_parser_from_source_str;
use rustc_parse::parser::Recovery;
use rustc_query_impl::print_query_stack;
use rustc_session::config::{self, Cfg, CheckCfg, ExpectedValues, Input, OutFileName};
use rustc_session::parse::ParseSess;
use rustc_session::{CompilerIO, EarlyDiagCtxt, Session, lint};
use rustc_span::source_map::{FileLoader, RealFileLoader, SourceMapInputs};
use rustc_span::{FileName, sym};
use tracing::trace;

use crate::util;

pub type Result<T> = result::Result<T, ErrorGuaranteed>;

/// Represents a compiler session. Note that every `Compiler` contains a
/// `Session`, but `Compiler` also contains some things that cannot be in
/// `Session`, due to `Session` being in a crate that has many fewer
/// dependencies than this crate.
///
/// Can be used to run `rustc_interface` queries.
/// Created by passing [`Config`] to [`run_compiler`].
pub struct Compiler {
    pub sess: Session,
    pub codegen_backend: Box<dyn CodegenBackend>,
    pub(crate) override_queries: Option<fn(&Session, &mut Providers)>,

    /// A reference to the current `GlobalCtxt` which we pass on to `GlobalCtxt`.
    pub(crate) current_gcx: CurrentGcx,
}

/// Converts strings provided as `--cfg [cfgspec]` into a `Cfg`.
pub(crate) fn parse_cfg(dcx: DiagCtxtHandle<'_>, cfgs: Vec<String>) -> Cfg {
    cfgs.into_iter()
        .map(|s| {
            let psess = ParseSess::emitter_with_note(format!(
                "this occurred on the command line: `--cfg={s}`"
            ));
            let filename = FileName::cfg_spec_source_code(&s);

            macro_rules! error {
                ($reason: expr) => {
                    dcx.fatal(format!("invalid `--cfg` argument: `{s}` ({})", $reason));
                };
            }

            match new_parser_from_source_str(&psess, filename, s.to_string(), StripTokens::Nothing)
            {
                Ok(mut parser) => {
                    parser = parser.recovery(Recovery::Forbidden);
                    match parser.parse_meta_item() {
                        Ok(meta_item)
                            if parser.token == token::Eof
                                && parser.dcx().has_errors().is_none() =>
                        {
                            if meta_item.path.segments.len() != 1 {
                                error!("argument key must be an identifier");
                            }
                            match &meta_item.kind {
                                MetaItemKind::List(..) => {}
                                MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
                                    error!("argument value must be a string");
                                }
                                MetaItemKind::NameValue(..) | MetaItemKind::Word => {
                                    let ident = meta_item.ident().expect("multi-segment cfg key");

                                    if ident.is_path_segment_keyword() {
                                        error!(
                                            "malformed `cfg` input, expected a valid identifier"
                                        );
                                    }

                                    return (ident.name, meta_item.value_str());
                                }
                            }
                        }
                        Ok(..) => {}
                        Err(err) => err.cancel(),
                    }
                }
                Err(errs) => errs.into_iter().for_each(|err| err.cancel()),
            };

            // If the user tried to use a key="value" flag, but is missing the quotes, provide
            // a hint about how to resolve this.
            if s.contains('=') && !s.contains("=\"") && !s.ends_with('"') {
                error!(concat!(
                    r#"expected `key` or `key="value"`, ensure escaping is appropriate"#,
                    r#" for your shell, try 'key="value"' or key=\"value\""#
                ));
            } else {
                error!(r#"expected `key` or `key="value"`"#);
            }
        })
        .collect::<Cfg>()
}

/// Converts strings provided as `--check-cfg [specs]` into a `CheckCfg`.
pub(crate) fn parse_check_cfg(dcx: DiagCtxtHandle<'_>, specs: Vec<String>) -> CheckCfg {
    // If any --check-cfg is passed then exhaustive_values and exhaustive_names
    // are enabled by default.
    let exhaustive_names = !specs.is_empty();
    let exhaustive_values = !specs.is_empty();
    let mut check_cfg = CheckCfg { exhaustive_names, exhaustive_values, ..CheckCfg::default() };

    for s in specs {
        let psess = ParseSess::emitter_with_note(format!(
            "this occurred on the command line: `--check-cfg={s}`"
        ));
        let filename = FileName::cfg_spec_source_code(&s);

        const VISIT: &str =
            "visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details";

        macro_rules! error {
            ($reason:expr) => {{
                let mut diag = dcx.struct_fatal(format!("invalid `--check-cfg` argument: `{s}`"));
                diag.note($reason);
                diag.note(VISIT);
                diag.emit()
            }};
            (in $arg:expr, $reason:expr) => {{
                let mut diag = dcx.struct_fatal(format!("invalid `--check-cfg` argument: `{s}`"));

                let pparg = rustc_ast_pretty::pprust::meta_list_item_to_string($arg);
                if let Some(lit) = $arg.lit() {
                    let (lit_kind_article, lit_kind_descr) = {
                        let lit_kind = lit.as_token_lit().kind;
                        (lit_kind.article(), lit_kind.descr())
                    };
                    diag.note(format!("`{pparg}` is {lit_kind_article} {lit_kind_descr} literal"));
                } else {
                    diag.note(format!("`{pparg}` is invalid"));
                }

                diag.note($reason);
                diag.note(VISIT);
                diag.emit()
            }};
        }

        let expected_error = || -> ! {
            error!("expected `cfg(name, values(\"value1\", \"value2\", ... \"valueN\"))`")
        };

        let mut parser =
            match new_parser_from_source_str(&psess, filename, s.to_string(), StripTokens::Nothing)
            {
                Ok(parser) => parser.recovery(Recovery::Forbidden),
                Err(errs) => {
                    errs.into_iter().for_each(|err| err.cancel());
                    expected_error();
                }
            };

        let meta_item = match parser.parse_meta_item() {
            Ok(meta_item) if parser.token == token::Eof && parser.dcx().has_errors().is_none() => {
                meta_item
            }
            Ok(..) => expected_error(),
            Err(err) => {
                err.cancel();
                expected_error();
            }
        };

        let Some(args) = meta_item.meta_item_list() else {
            expected_error();
        };

        if !meta_item.has_name(sym::cfg) {
            expected_error();
        }

        let mut names = Vec::new();
        let mut values: FxHashSet<_> = Default::default();

        let mut any_specified = false;
        let mut values_specified = false;
        let mut values_any_specified = false;

        for arg in args {
            if arg.is_word()
                && let Some(ident) = arg.ident()
            {
                if values_specified {
                    error!("`cfg()` names cannot be after values");
                }

                if ident.is_path_segment_keyword() {
                    error!("malformed `cfg` input, expected a valid identifier");
                }

                names.push(ident);
            } else if let Some(boolean) = arg.boolean_literal() {
                if values_specified {
                    error!("`cfg()` names cannot be after values");
                }
                names.push(rustc_span::Ident::new(
                    if boolean { rustc_span::kw::True } else { rustc_span::kw::False },
                    arg.span(),
                ));
            } else if arg.has_name(sym::any)
                && let Some(args) = arg.meta_item_list()
            {
                if any_specified {
                    error!("`any()` cannot be specified multiple times");
                }
                any_specified = true;
                if !args.is_empty() {
                    error!(in arg, "`any()` takes no argument");
                }
            } else if arg.has_name(sym::values)
                && let Some(args) = arg.meta_item_list()
            {
                if names.is_empty() {
                    error!("`values()` cannot be specified before the names");
                } else if values_specified {
                    error!("`values()` cannot be specified multiple times");
                }
                values_specified = true;

                for arg in args {
                    if let Some(LitKind::Str(s, _)) = arg.lit().map(|lit| &lit.kind) {
                        values.insert(Some(*s));
                    } else if arg.has_name(sym::any)
                        && let Some(args) = arg.meta_item_list()
                    {
                        if values_any_specified {
                            error!(in arg, "`any()` in `values()` cannot be specified multiple times");
                        }
                        values_any_specified = true;
                        if !args.is_empty() {
                            error!(in arg, "`any()` in `values()` takes no argument");
                        }
                    } else if arg.has_name(sym::none)
                        && let Some(args) = arg.meta_item_list()
                    {
                        values.insert(None);
                        if !args.is_empty() {
                            error!(in arg, "`none()` in `values()` takes no argument");
                        }
                    } else {
                        error!(in arg, "`values()` arguments must be string literals, `none()` or `any()`");
                    }
                }
            } else {
                error!(in arg, "`cfg()` arguments must be simple identifiers, `any()` or `values(...)`");
            }
        }

        if !values_specified && !any_specified {
            // `cfg(name)` is equivalent to `cfg(name, values(none()))` so add
            // an implicit `none()`
            values.insert(None);
        } else if !values.is_empty() && values_any_specified {
            error!(
                "`values()` arguments cannot specify string literals and `any()` at the same time"
            );
        }

        if any_specified {
            if names.is_empty() && values.is_empty() && !values_specified && !values_any_specified {
                check_cfg.exhaustive_names = false;
            } else {
                error!("`cfg(any())` can only be provided in isolation");
            }
        } else {
            for name in names {
                check_cfg
                    .expecteds
                    .entry(name.name)
                    .and_modify(|v| match v {
                        ExpectedValues::Some(v) if !values_any_specified =>
                        {
                            #[allow(rustc::potential_query_instability)]
                            v.extend(values.clone())
                        }
                        ExpectedValues::Some(_) => *v = ExpectedValues::Any,
                        ExpectedValues::Any => {}
                    })
                    .or_insert_with(|| {
                        if values_any_specified {
                            ExpectedValues::Any
                        } else {
                            ExpectedValues::Some(values.clone())
                        }
                    });
            }
        }
    }

    check_cfg
}

/// The compiler configuration
pub struct Config {
    /// Command line options
    pub opts: config::Options,

    /// Unparsed cfg! configuration in addition to the default ones.
    pub crate_cfg: Vec<String>,
    pub crate_check_cfg: Vec<String>,

    pub input: Input,
    pub output_dir: Option<PathBuf>,
    pub output_file: Option<OutFileName>,
    pub ice_file: Option<PathBuf>,
    /// Load files from sources other than the file system.
    ///
    /// Has no uses within this repository, but may be used in the future by
    /// bjorn3 for "hooking rust-analyzer's VFS into rustc at some point for
    /// running rustc without having to save". (See #102759.)
    pub file_loader: Option<Box<dyn FileLoader + Send + Sync>>,

    pub lint_caps: FxHashMap<lint::LintId, lint::Level>,

    /// This is a callback from the driver that is called when [`ParseSess`] is created.
    pub psess_created: Option<Box<dyn FnOnce(&mut ParseSess) + Send>>,

    /// This is a callback to track otherwise untracked state used by the caller.
    ///
    /// You can write to `sess.env_depinfo` and `sess.file_depinfo` to track env vars and files.
    pub track_state: Option<Box<dyn FnOnce(&Session) + Send>>,

    /// This is a callback from the driver that is called when we're registering lints;
    /// it is called during lint loading when we have the LintStore in a non-shared state.
    ///
    /// Note that if you find a Some here you probably want to call that function in the new
    /// function being registered.
    pub register_lints: Option<Box<dyn Fn(&Session, &mut LintStore) + Send + Sync>>,

    /// This is a callback from the driver that is called just after we have populated
    /// the list of queries.
    pub override_queries: Option<fn(&Session, &mut Providers)>,

    /// An extra set of symbols to add to the symbol interner, the symbol indices
    /// will start at [`PREDEFINED_SYMBOLS_COUNT`](rustc_span::symbol::PREDEFINED_SYMBOLS_COUNT)
    pub extra_symbols: Vec<&'static str>,

    /// This is a callback from the driver that is called to create a codegen backend.
    ///
    /// Has no uses within this repository, but is used by bjorn3 for "the
    /// hotswapping branch of cg_clif" for "setting the codegen backend from a
    /// custom driver where the custom codegen backend has arbitrary data."
    /// (See #102759.)
    pub make_codegen_backend: Option<Box<dyn FnOnce(&Session) -> Box<dyn CodegenBackend> + Send>>,

    /// The inner atomic value is set to true when a feature marked as `internal` is
    /// enabled. Makes it so that "please report a bug" is hidden, as ICEs with
    /// internal features are wontfix, and they are usually the cause of the ICEs.
    pub using_internal_features: &'static std::sync::atomic::AtomicBool,
}

// JUSTIFICATION: before session exists, only config
#[allow(rustc::bad_opt_access)]
pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Send) -> R {
    trace!("run_compiler");

    // Set parallel mode before thread pool creation, which will create `Lock`s.
    rustc_data_structures::sync::set_dyn_thread_safe_mode(config.opts.jobs.frontend.is_some());

    // Initialize jobserver as early as possible.
    let early_dcx = EarlyDiagCtxt::new(config.opts.error_format);
    let jobs = config.opts.jobs;
    if let Some(limit) = jobs.frontend.max(jobs.backend).max(jobs.linker.limit()) {
        jobserver::initialize(limit.get(), |err| {
            let note = "the build environment is likely misconfigured";
            early_dcx.early_struct_warn(err).with_note(note).emit()
        });
    }

    crate::callbacks::setup_callbacks();

    let target = config::build_target_config(
        &early_dcx,
        &config.opts.target_triple,
        config.opts.sysroot.path(),
        config.opts.unstable_opts.unstable_options,
    );
    let file_loader = config.file_loader.unwrap_or_else(|| Box::new(RealFileLoader));
    let path_mapping = config.opts.file_path_mapping();
    let hash_kind = config.opts.unstable_opts.src_hash_algorithm(&target);
    let checksum_hash_kind = config.opts.unstable_opts.checksum_hash_algorithm();

    util::run_in_thread_pool_with_globals(
        &early_dcx,
        config.opts.edition,
        jobs,
        &config.extra_symbols,
        SourceMapInputs { file_loader, path_mapping, hash_kind, checksum_hash_kind },
        |current_gcx| {
            // The previous `early_dcx` can't be reused here because it doesn't
            // impl `Send`. Creating a new one is fine.
            let early_dcx = EarlyDiagCtxt::new(config.opts.error_format);

            let temps_dir = config.opts.unstable_opts.temps_dir.as_deref().map(PathBuf::from);

            let mut sess = rustc_session::build_session(
                config.opts,
                CompilerIO {
                    input: config.input,
                    output_dir: config.output_dir,
                    output_file: config.output_file,
                    temps_dir,
                },
                config.lint_caps,
                target,
                util::rustc_version_str().unwrap_or("unknown"),
                config.ice_file,
                config.using_internal_features,
            );

            let codegen_backend = match config.make_codegen_backend {
                None => util::get_codegen_backend(
                    &early_dcx,
                    &sess.opts.sysroot,
                    sess.opts.unstable_opts.codegen_backend.as_deref(),
                    &sess.target,
                ),
                Some(make_codegen_backend) => {
                    // N.B. `make_codegen_backend` takes precedence over
                    // `target.default_codegen_backend`, which is ignored in this case.
                    make_codegen_backend(&sess)
                }
            };
            codegen_backend.init(&sess);
            sess.replaced_intrinsics = FxHashSet::from_iter(codegen_backend.replaced_intrinsics());
            sess.fallback_intrinsics = FxHashSet::from_iter(codegen_backend.fallback_intrinsics());
            sess.thin_lto_supported = codegen_backend.thin_lto_supported();

            let cfg = parse_cfg(sess.dcx(), config.crate_cfg);
            let mut cfg = config::build_configuration(&sess, cfg);
            util::add_configuration(&mut cfg, &mut sess, &*codegen_backend);
            sess.config = cfg;

            let mut check_cfg = parse_check_cfg(sess.dcx(), config.crate_check_cfg);
            check_cfg.fill_well_known(&sess.target);
            sess.check_config = check_cfg;

            if let Some(psess_created) = config.psess_created {
                psess_created(&mut sess.psess);
            }

            if let Some(track_state) = config.track_state {
                track_state(&sess);
            }

            // Even though the session holds the lint store, we can't build the
            // lint store until after the session exists. And we wait until now
            // so that `register_lints` sees the fully initialized session.
            let mut lint_store = rustc_lint::new_lint_store(sess.enable_internal_lints());
            if let Some(register_lints) = config.register_lints.as_deref() {
                register_lints(&sess, &mut lint_store);
            }
            sess.lint_store = Some(Arc::new(lint_store));

            util::check_abi_required_features(&sess);

            let compiler = Compiler {
                sess,
                codegen_backend,
                override_queries: config.override_queries,
                current_gcx,
            };

            // There are two paths out of `f`.
            // - Normal exit.
            // - Panic, e.g. triggered by `abort_if_errors` or a fatal error.
            //
            // We must run `finish_diagnostics` in both cases.
            let res = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| f(&compiler)));

            compiler.sess.finish_diagnostics();

            // If error diagnostics have been emitted, we can't return an
            // error directly, because the return type of this function
            // is `R`, not `Result<R, E>`. But we need to communicate the
            // errors' existence to the caller, otherwise the caller might
            // mistakenly think that no errors occurred and return a zero
            // exit code. So we abort (panic) instead, similar to if `f`
            // had panicked.
            if res.is_ok() {
                compiler.sess.dcx().abort_if_errors();
            }

            // Also make sure to flush delayed bugs as if we panicked, the
            // bugs would be flushed by the Drop impl of DiagCtxt while
            // unwinding, which would result in an abort with
            // "panic in a destructor during cleanup".
            compiler.sess.dcx().flush_delayed();

            let res = match res {
                Ok(res) => res,
                // Resume unwinding if a panic happened.
                Err(err) => std::panic::resume_unwind(err),
            };

            let prof = compiler.sess.prof.clone();
            prof.generic_activity("drop_compiler").run(move || drop(compiler));

            res
        },
    )
}

pub fn try_print_query_stack(
    dcx: DiagCtxtHandle<'_>,
    limit_frames: Option<usize>,
    file: Option<std::fs::File>,
) {
    eprintln!("query stack during panic:");

    // Be careful relying on global state here: this code is called from
    // a panic hook, which means that the global `DiagCtxt` may be in a weird
    // state if it was responsible for triggering the panic.
    let all_frames = ty::tls::with_context_opt(|icx| {
        if let Some(icx) = icx {
            ty::print::with_no_queries!(print_query_stack(
                icx.tcx,
                icx.query,
                dcx,
                limit_frames,
                file,
            ))
        } else {
            0
        }
    });

    if let Some(limit_frames) = limit_frames
        && all_frames > limit_frames
    {
        eprintln!(
            "... and {} other queries... use `env RUST_BACKTRACE=1` to see the full query stack",
            all_frames - limit_frames
        );
    } else {
        eprintln!("end of query stack");
    }
}