//! This pass is only used for UNIT TESTS related to incremental
//! compilation. It tests whether a particular `.o` file will be re-used
//! from a previous compilation or whether it must be regenerated.
//!
//! The user adds annotations to the crate of the following form:
//!
//! ```
//! # #![feature(rustc_attrs)]
//! # #![allow(internal_features)]
//! #![rustc_partition_reused(module="spike", cfg="rpass2")]
//! #![rustc_partition_codegened(module="spike-x", cfg="rpass2")]
//! ```
//!
//! The first indicates (in the cfg `rpass2`) that `spike.o` will be
//! reused, the second that `spike-x.o` will be recreated. If these
//! annotations are inaccurate, errors are reported.
//!
//! The reason that we use `cfg=...` and not `#[cfg_attr]` is so that
//! the HIR doesn't change as a result of the annotations, which might
//! perturb the reuse results.
//!
//! `#![rustc_expected_cgu_reuse(module="spike", cfg="rpass2", kind="post-lto")]`
//! allows for doing a more fine-grained check to see if pre- or post-lto data
//! was re-used.

use crate::errors;
use rustc_ast as ast;
use rustc_data_structures::unord::UnordSet;
use rustc_hir::def_id::LOCAL_CRATE;
use rustc_middle::mir::mono::CodegenUnitNameBuilder;
use rustc_middle::ty::TyCtxt;
use rustc_session::cgu_reuse_tracker::*;
use rustc_span::symbol::{sym, Symbol};
use thin_vec::ThinVec;

#[allow(missing_docs)]
pub fn assert_module_sources(tcx: TyCtxt<'_>) {
    tcx.dep_graph.with_ignore(|| {
        if tcx.sess.opts.incremental.is_none() {
            return;
        }

        let available_cgus =
            tcx.collect_and_partition_mono_items(()).1.iter().map(|cgu| cgu.name()).collect();

        let ams = AssertModuleSource { tcx, available_cgus };

        for attr in tcx.hir().attrs(rustc_hir::CRATE_HIR_ID) {
            ams.check_attr(attr);
        }
    })
}

struct AssertModuleSource<'tcx> {
    tcx: TyCtxt<'tcx>,
    available_cgus: UnordSet<Symbol>,
}

impl<'tcx> AssertModuleSource<'tcx> {
    fn check_attr(&self, attr: &ast::Attribute) {
        let (expected_reuse, comp_kind) = if attr.has_name(sym::rustc_partition_reused) {
            (CguReuse::PreLto, ComparisonKind::AtLeast)
        } else if attr.has_name(sym::rustc_partition_codegened) {
            (CguReuse::No, ComparisonKind::Exact)
        } else if attr.has_name(sym::rustc_expected_cgu_reuse) {
            match self.field(attr, sym::kind) {
                sym::no => (CguReuse::No, ComparisonKind::Exact),
                sym::pre_dash_lto => (CguReuse::PreLto, ComparisonKind::Exact),
                sym::post_dash_lto => (CguReuse::PostLto, ComparisonKind::Exact),
                sym::any => (CguReuse::PreLto, ComparisonKind::AtLeast),
                other => {
                    self.tcx
                        .sess
                        .emit_fatal(errors::UnknownReuseKind { span: attr.span, kind: other });
                }
            }
        } else {
            return;
        };

        if !self.tcx.sess.opts.unstable_opts.query_dep_graph {
            self.tcx.sess.emit_fatal(errors::MissingQueryDepGraph { span: attr.span });
        }

        if !self.check_config(attr) {
            debug!("check_attr: config does not match, ignoring attr");
            return;
        }

        let user_path = self.field(attr, sym::module).to_string();
        let crate_name = self.tcx.crate_name(LOCAL_CRATE).to_string();

        if !user_path.starts_with(&crate_name) {
            self.tcx.sess.emit_fatal(errors::MalformedCguName {
                span: attr.span,
                user_path,
                crate_name,
            });
        }

        // Split of the "special suffix" if there is one.
        let (user_path, cgu_special_suffix) = if let Some(index) = user_path.rfind('.') {
            (&user_path[..index], Some(&user_path[index + 1..]))
        } else {
            (&user_path[..], None)
        };

        let mut iter = user_path.split('-');

        // Remove the crate name
        assert_eq!(iter.next().unwrap(), crate_name);

        let cgu_path_components = iter.collect::<Vec<_>>();

        let cgu_name_builder = &mut CodegenUnitNameBuilder::new(self.tcx);
        let cgu_name =
            cgu_name_builder.build_cgu_name(LOCAL_CRATE, cgu_path_components, cgu_special_suffix);

        debug!("mapping '{}' to cgu name '{}'", self.field(attr, sym::module), cgu_name);

        if !self.available_cgus.contains(&cgu_name) {
            let cgu_names: Vec<&str> =
                self.available_cgus.items().map(|cgu| cgu.as_str()).into_sorted_stable_ord();
            self.tcx.sess.emit_err(errors::NoModuleNamed {
                span: attr.span,
                user_path,
                cgu_name,
                cgu_names: cgu_names.join(", "),
            });
        }

        self.tcx.sess.cgu_reuse_tracker.set_expectation(
            cgu_name,
            &user_path,
            attr.span,
            expected_reuse,
            comp_kind,
        );
    }

    fn field(&self, attr: &ast::Attribute, name: Symbol) -> Symbol {
        for item in attr.meta_item_list().unwrap_or_else(ThinVec::new) {
            if item.has_name(name) {
                if let Some(value) = item.value_str() {
                    return value;
                } else {
                    self.tcx.sess.emit_fatal(errors::FieldAssociatedValueExpected {
                        span: item.span(),
                        name,
                    });
                }
            }
        }

        self.tcx.sess.emit_fatal(errors::NoField { span: attr.span, name });
    }

    /// Scan for a `cfg="foo"` attribute and check whether we have a
    /// cfg flag called `foo`.
    fn check_config(&self, attr: &ast::Attribute) -> bool {
        let config = &self.tcx.sess.parse_sess.config;
        let value = self.field(attr, sym::cfg);
        debug!("check_config(config={:?}, value={:?})", config, value);
        if config.iter().any(|&(name, _)| name == value) {
            debug!("check_config: matched");
            return true;
        }
        debug!("check_config: no match found");
        false
    }
}