// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Code to save/load the dep-graph from files.

use rustc::dep_graph::{DepNode, WorkProductId};
use rustc::hir::def_id::DefId;
use rustc::hir::svh::Svh;
use rustc::session::Session;
use rustc::ty::TyCtxt;
use rustc_data_structures::fx::{FxHashSet, FxHashMap};
use rustc_serialize::Decodable as RustcDecodable;
use rustc_serialize::opaque::Decoder;
use std::path::{Path};
use std::sync::Arc;

use IncrementalHashesMap;
use ich::Fingerprint;
use super::data::*;
use super::directory::*;
use super::dirty_clean;
use super::hash::*;
use super::fs::*;
use super::file_format;
use super::work_product;

// The key is a dirty node. The value is **some** base-input that we
// can blame it on.
pub type DirtyNodes = FxHashMap<DepNode<DefPathIndex>, DepNode<DefPathIndex>>;

/// If we are in incremental mode, and a previous dep-graph exists,
/// then load up those nodes/edges that are still valid into the
/// dep-graph for this session. (This is assumed to be running very
/// early in compilation, before we've really done any work, but
/// actually it doesn't matter all that much.) See `README.md` for
/// more general overview.
pub fn load_dep_graph<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                incremental_hashes_map: &IncrementalHashesMap) {
    if tcx.sess.opts.incremental.is_none() {
        return;
    }

    match prepare_session_directory(tcx) {
        Ok(true) => {
            // We successfully allocated a session directory and there is
            // something in it to load, so continue
        }
        Ok(false) => {
            // We successfully allocated a session directory, but there is no
            // dep-graph data in it to load (because this is the first
            // compilation session with this incr. comp. dir.)
            return
        }
        Err(()) => {
            // Something went wrong while trying to allocate the session
            // directory. Don't try to use it any further.
            return
        }
    }

    let _ignore = tcx.dep_graph.in_ignore();
    load_dep_graph_if_exists(tcx, incremental_hashes_map);
}

fn load_dep_graph_if_exists<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                      incremental_hashes_map: &IncrementalHashesMap) {
    let dep_graph_path = dep_graph_path(tcx.sess);
    let dep_graph_data = match load_data(tcx.sess, &dep_graph_path) {
        Some(p) => p,
        None => return // no file
    };

    let work_products_path = work_products_path(tcx.sess);
    let work_products_data = match load_data(tcx.sess, &work_products_path) {
        Some(p) => p,
        None => return // no file
    };

    match decode_dep_graph(tcx, incremental_hashes_map, &dep_graph_data, &work_products_data) {
        Ok(dirty_nodes) => dirty_nodes,
        Err(err) => {
            tcx.sess.warn(
                &format!("decoding error in dep-graph from `{}` and `{}`: {}",
                         dep_graph_path.display(),
                         work_products_path.display(),
                         err));
        }
    }
}

fn load_data(sess: &Session, path: &Path) -> Option<Vec<u8>> {
    match file_format::read_file(sess, path) {
        Ok(Some(data)) => return Some(data),
        Ok(None) => {
            // The file either didn't exist or was produced by an incompatible
            // compiler version. Neither is an error.
        }
        Err(err) => {
            sess.err(
                &format!("could not load dep-graph from `{}`: {}",
                         path.display(), err));
        }
    }

    if let Err(err) = delete_all_session_dir_contents(sess) {
        sess.err(&format!("could not clear incompatible incremental \
                           compilation session directory `{}`: {}",
                          path.display(), err));
    }

    None
}

/// Decode the dep graph and load the edges/nodes that are still clean
/// into `tcx.dep_graph`.
pub fn decode_dep_graph<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                  incremental_hashes_map: &IncrementalHashesMap,
                                  dep_graph_data: &[u8],
                                  work_products_data: &[u8])
                                  -> Result<(), String>
{
    // Decode the list of work_products
    let mut work_product_decoder = Decoder::new(work_products_data, 0);
    let work_products = <Vec<SerializedWorkProduct>>::decode(&mut work_product_decoder)?;

    // Deserialize the directory and dep-graph.
    let mut dep_graph_decoder = Decoder::new(dep_graph_data, 0);
    let prev_commandline_args_hash = u64::decode(&mut dep_graph_decoder)?;

    if prev_commandline_args_hash != tcx.sess.opts.dep_tracking_hash() {
        if tcx.sess.opts.debugging_opts.incremental_info {
            println!("incremental: completely ignoring cache because of \
                      differing commandline arguments");
        }
        // We can't reuse the cache, purge it.
        debug!("decode_dep_graph: differing commandline arg hashes");
        for swp in work_products {
            delete_dirty_work_product(tcx, swp);
        }

        // No need to do any further work
        return Ok(());
    }

    let directory = DefIdDirectory::decode(&mut dep_graph_decoder)?;
    let serialized_dep_graph = SerializedDepGraph::decode(&mut dep_graph_decoder)?;

    let edge_map: FxHashMap<_, _> = serialized_dep_graph.edges
                                                        .into_iter()
                                                        .map(|s| (s.source, s.targets))
                                                        .collect();

    // Retrace the paths in the directory to find their current location (if any).
    let retraced = directory.retrace(tcx);

    // Compute the set of nodes from the old graph where some input
    // has changed or been removed. These are "raw" source nodes,
    // which means that they still use the original `DefPathIndex`
    // values from the encoding, rather than having been retraced to a
    // `DefId`. The reason for this is that this way we can include
    // nodes that have been removed (which no longer have a `DefId` in
    // the current compilation).
    let dirty_raw_nodes = initial_dirty_nodes(tcx,
                                              incremental_hashes_map,
                                              &serialized_dep_graph.hashes,
                                              &retraced);
    let dirty_raw_nodes = transitive_dirty_nodes(&edge_map, dirty_raw_nodes);

    // Recreate the edges in the graph that are still clean.
    let mut clean_work_products = FxHashSet();
    let mut dirty_work_products = FxHashSet(); // incomplete; just used to suppress debug output
    let mut extra_edges = vec![];
    for (source, targets) in &edge_map {
        for target in targets {
            process_edges(tcx, source, target, &edge_map, &directory, &retraced, &dirty_raw_nodes,
                          &mut clean_work_products, &mut dirty_work_products, &mut extra_edges);
        }
    }

    // Subtle. Sometimes we have intermediate nodes that we can't recreate in the new graph.
    // This is pretty unusual but it arises in a scenario like this:
    //
    //     Hir(X) -> Foo(Y) -> Bar
    //
    // Note that the `Hir(Y)` is not an input to `Foo(Y)` -- this
    // almost never happens, but can happen in some obscure
    // scenarios. In that case, if `Y` is removed, then we can't
    // recreate `Foo(Y)` (the def-id `Y` no longer exists); what we do
    // then is to push the edge `Hir(X) -> Bar` onto `extra_edges`
    // (along with any other targets of `Foo(Y)`). We will then add
    // the edge from `Hir(X)` to `Bar` (or, if `Bar` itself cannot be
    // recreated, to the targets of `Bar`).
    while let Some((source, target)) = extra_edges.pop() {
        process_edges(tcx, source, target, &edge_map, &directory, &retraced, &dirty_raw_nodes,
                      &mut clean_work_products, &mut dirty_work_products, &mut extra_edges);
    }

    // Add in work-products that are still clean, and delete those that are
    // dirty.
    reconcile_work_products(tcx, work_products, &clean_work_products);

    dirty_clean::check_dirty_clean_annotations(tcx, &dirty_raw_nodes, &retraced);

    load_prev_metadata_hashes(tcx,
                              &retraced,
                              &mut *incremental_hashes_map.prev_metadata_hashes.borrow_mut());
    Ok(())
}

/// Computes which of the original set of def-ids are dirty. Stored in
/// a bit vector where the index is the DefPathIndex.
fn initial_dirty_nodes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                 incremental_hashes_map: &IncrementalHashesMap,
                                 serialized_hashes: &[SerializedHash],
                                 retraced: &RetracedDefIdDirectory)
                                 -> DirtyNodes {
    let mut hcx = HashContext::new(tcx, incremental_hashes_map);
    let mut dirty_nodes = FxHashMap();

    for hash in serialized_hashes {
        if let Some(dep_node) = retraced.map(&hash.dep_node) {
            let current_hash = hcx.hash(&dep_node).unwrap();
            if current_hash == hash.hash {
                debug!("initial_dirty_nodes: {:?} is clean (hash={:?})",
                   dep_node.map_def(|&def_id| Some(tcx.def_path(def_id))).unwrap(),
                   current_hash);
                continue;
            }

            if tcx.sess.opts.debugging_opts.incremental_dump_hash {
                println!("node {:?} is dirty as hash is {:?} was {:?}",
                         dep_node.map_def(|&def_id| Some(tcx.def_path(def_id))).unwrap(),
                         current_hash,
                         hash.hash);
            }

            debug!("initial_dirty_nodes: {:?} is dirty as hash is {:?}, was {:?}",
                   dep_node.map_def(|&def_id| Some(tcx.def_path(def_id))).unwrap(),
                   current_hash,
                   hash.hash);
        } else {
            if tcx.sess.opts.debugging_opts.incremental_dump_hash {
                println!("node {:?} is dirty as it was removed",
                         hash.dep_node);
            }

            debug!("initial_dirty_nodes: {:?} is dirty as it was removed",
                   hash.dep_node);
        }

        dirty_nodes.insert(hash.dep_node.clone(), hash.dep_node.clone());
    }

    dirty_nodes
}

fn transitive_dirty_nodes(edge_map: &FxHashMap<DepNode<DefPathIndex>, Vec<DepNode<DefPathIndex>>>,
                          mut dirty_nodes: DirtyNodes)
                          -> DirtyNodes
{
    let mut stack: Vec<(DepNode<DefPathIndex>, DepNode<DefPathIndex>)> = vec![];
    stack.extend(dirty_nodes.iter().map(|(s, b)| (s.clone(), b.clone())));
    while let Some((source, blame)) = stack.pop() {
        // we know the source is dirty (because of the node `blame`)...
        assert!(dirty_nodes.contains_key(&source));

        // ...so we dirty all the targets (with the same blame)
        if let Some(targets) = edge_map.get(&source) {
            for target in targets {
                if !dirty_nodes.contains_key(target) {
                    dirty_nodes.insert(target.clone(), blame.clone());
                    stack.push((target.clone(), blame.clone()));
                }
            }
        }
    }
    dirty_nodes
}

/// Go through the list of work-products produced in the previous run.
/// Delete any whose nodes have been found to be dirty or which are
/// otherwise no longer applicable.
fn reconcile_work_products<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                     work_products: Vec<SerializedWorkProduct>,
                                     clean_work_products: &FxHashSet<Arc<WorkProductId>>) {
    debug!("reconcile_work_products({:?})", work_products);
    for swp in work_products {
        if !clean_work_products.contains(&swp.id) {
            debug!("reconcile_work_products: dep-node for {:?} is dirty", swp);
            delete_dirty_work_product(tcx, swp);
        } else {
            let mut all_files_exist = true;
            for &(_, ref file_name) in swp.work_product.saved_files.iter() {
                let path = in_incr_comp_dir_sess(tcx.sess, file_name);
                if !path.exists() {
                    all_files_exist = false;

                    if tcx.sess.opts.debugging_opts.incremental_info {
                        println!("incremental: could not find file for up-to-date work product: {}",
                                 path.display());
                    }
                }
            }

            if all_files_exist {
                debug!("reconcile_work_products: all files for {:?} exist", swp);
                tcx.dep_graph.insert_previous_work_product(&swp.id, swp.work_product);
            } else {
                debug!("reconcile_work_products: some file for {:?} does not exist", swp);
                delete_dirty_work_product(tcx, swp);
            }
        }
    }
}

fn delete_dirty_work_product(tcx: TyCtxt,
                             swp: SerializedWorkProduct) {
    debug!("delete_dirty_work_product({:?})", swp);
    work_product::delete_workproduct_files(tcx.sess, &swp.work_product);
}

fn load_prev_metadata_hashes(tcx: TyCtxt,
                             retraced: &RetracedDefIdDirectory,
                             output: &mut FxHashMap<DefId, Fingerprint>) {
    if !tcx.sess.opts.debugging_opts.query_dep_graph {
        return
    }

    debug!("load_prev_metadata_hashes() - Loading previous metadata hashes");

    let file_path = metadata_hash_export_path(tcx.sess);

    if !file_path.exists() {
        debug!("load_prev_metadata_hashes() - Couldn't find file containing \
                hashes at `{}`", file_path.display());
        return
    }

    debug!("load_prev_metadata_hashes() - File: {}", file_path.display());

    let data = match file_format::read_file(tcx.sess, &file_path) {
        Ok(Some(data)) => data,
        Ok(None) => {
            debug!("load_prev_metadata_hashes() - File produced by incompatible \
                    compiler version: {}", file_path.display());
            return
        }
        Err(err) => {
            debug!("load_prev_metadata_hashes() - Error reading file `{}`: {}",
                   file_path.display(), err);
            return
        }
    };

    debug!("load_prev_metadata_hashes() - Decoding hashes");
    let mut decoder = Decoder::new(&data, 0);
    let _ = Svh::decode(&mut decoder).unwrap();
    let serialized_hashes = SerializedMetadataHashes::decode(&mut decoder).unwrap();

    debug!("load_prev_metadata_hashes() - Mapping DefIds");

    assert_eq!(serialized_hashes.index_map.len(), serialized_hashes.hashes.len());
    for serialized_hash in serialized_hashes.hashes {
        let def_path_index = serialized_hashes.index_map[&serialized_hash.def_index];
        if let Some(def_id) = retraced.def_id(def_path_index) {
            let old = output.insert(def_id, serialized_hash.hash);
            assert!(old.is_none(), "already have hash for {:?}", def_id);
        }
    }

    debug!("load_prev_metadata_hashes() - successfully loaded {} hashes",
           serialized_hashes.index_map.len());
}

fn process_edges<'a, 'tcx, 'edges>(
    tcx: TyCtxt<'a, 'tcx, 'tcx>,
    source: &'edges DepNode<DefPathIndex>,
    target: &'edges DepNode<DefPathIndex>,
    edges: &'edges FxHashMap<DepNode<DefPathIndex>, Vec<DepNode<DefPathIndex>>>,
    directory: &DefIdDirectory,
    retraced: &RetracedDefIdDirectory,
    dirty_raw_nodes: &DirtyNodes,
    clean_work_products: &mut FxHashSet<Arc<WorkProductId>>,
    dirty_work_products: &mut FxHashSet<Arc<WorkProductId>>,
    extra_edges: &mut Vec<(&'edges DepNode<DefPathIndex>, &'edges DepNode<DefPathIndex>)>)
{
    // If the target is dirty, skip the edge. If this is an edge
    // that targets a work-product, we can print the blame
    // information now.
    if let Some(blame) = dirty_raw_nodes.get(target) {
        if let DepNode::WorkProduct(ref wp) = *target {
            if tcx.sess.opts.debugging_opts.incremental_info {
                if dirty_work_products.insert(wp.clone()) {
                    // It'd be nice to pretty-print these paths better than just
                    // using the `Debug` impls, but wev.
                    println!("incremental: module {:?} is dirty because {:?} \
                              changed or was removed",
                             wp,
                             blame.map_def(|&index| {
                                 Some(directory.def_path_string(tcx, index))
                             }).unwrap());
                }
            }
        }
        return;
    }

    // If the source is dirty, the target will be dirty.
    assert!(!dirty_raw_nodes.contains_key(source));

    // Retrace the source -> target edges to def-ids and then create
    // an edge in the graph. Retracing may yield none if some of the
    // data happens to have been removed.
    if let Some(source_node) = retraced.map(source) {
        if let Some(target_node) = retraced.map(target) {
            let _task = tcx.dep_graph.in_task(target_node);
            tcx.dep_graph.read(source_node);
            if let DepNode::WorkProduct(ref wp) = *target {
                clean_work_products.insert(wp.clone());
            }
        } else {
            // As discussed in `decode_dep_graph` above, sometimes the
            // target cannot be recreated again, in which case we add
            // edges to go from `source` to the targets of `target`.
            extra_edges.extend(
                edges[target].iter().map(|t| (source, t)));
        }
    } else {
        // It's also possible that the source can't be created! But we
        // can ignore such cases, because (a) if `source` is a HIR
        // node, it would be considered dirty; and (b) in other cases,
        // there must be some input to this node that is clean, and so
        // we'll re-create the edges over in the case where target is
        // undefined.
    }
}

