/*
 * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.tools.sjavac;

import java.io.File;
import java.net.URI;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

import com.sun.tools.javac.main.Main.Result;
import com.sun.tools.sjavac.comp.CompilationService;
import com.sun.tools.sjavac.options.Options;
import com.sun.tools.sjavac.pubapi.PubApi;
import com.sun.tools.sjavac.server.CompilationSubResult;
import com.sun.tools.sjavac.server.SysInfo;

This transform compiles a set of packages containing Java sources.
The compile request is divided into separate sets of source files.
For each set a separate request thread is dispatched to a javac server
and the meta data is accumulated. The number of sets correspond more or
less to the number of cores. Less so now, than it will in the future.
This is NOT part of any supported API.
If you write code that depends on this, you do so at your own
risk.  This code and its internal interfaces are subject to change
or deletion without notice.
/**
 * This transform compiles a set of packages containing Java sources.
 * The compile request is divided into separate sets of source files.
 * For each set a separate request thread is dispatched to a javac server
 * and the meta data is accumulated. The number of sets correspond more or
 * less to the number of cores. Less so now, than it will in the future.
 *
 * <p><b>This is NOT part of any supported API.
 * If you write code that depends on this, you do so at your own
 * risk.  This code and its internal interfaces are subject to change
 * or deletion without notice.</b></p>
 */
public class CompileJavaPackages implements Transformer {

    // The current limited sharing of data between concurrent JavaCompilers
    // in the server will not give speedups above 3 cores. Thus this limit.
    // We hope to improve this in the future.
    final static int limitOnConcurrency = 3;

    Options args;

    public void setExtra(String e) {
    }

    public void setExtra(Options a) {
        args = a;
    }

    public boolean transform(final CompilationService sjavac,
                             Map<String,Set<URI>> pkgSrcs,
                             final Set<URI>             visibleSources,
                             Map<String,Set<String>> oldPackageDependents,
                             URI destRoot,
                             final Map<String,Set<URI>>    packageArtifacts,
                             final Map<String,Map<String, Set<String>>> packageDependencies,
                             final Map<String,Map<String, Set<String>>> packageCpDependencies,
                             final Map<String, PubApi> packagePubapis,
                             final Map<String, PubApi> dependencyPubapis,
                             int debugLevel,
                             boolean incremental,
                             int numCores) {

        Log.debug("Performing CompileJavaPackages transform...");

        boolean rc = true;
        boolean concurrentCompiles = true;

        // Fetch the id.
        final String id = String.valueOf(new Random().nextInt());
        // Only keep portfile and sjavac settings..
        //String psServerSettings = Util.cleanSubOptions(Util.set("portfile","sjavac","background","keepalive"), sjavac.serverSettings());

        SysInfo sysinfo = sjavac.getSysInfo();
        int numMBytes = (int)(sysinfo.maxMemory / ((long)(1024*1024)));
        Log.debug("Server reports "+numMBytes+"MiB of memory and "+sysinfo.numCores+" cores");

        if (numCores <= 0) {
            // Set the requested number of cores to the number of cores on the server.
            numCores = sysinfo.numCores;
            Log.debug("Number of jobs not explicitly set, defaulting to "+sysinfo.numCores);
        } else if (sysinfo.numCores < numCores) {
            // Set the requested number of cores to the number of cores on the server.
            Log.debug("Limiting jobs from explicitly set "+numCores+" to cores available on server: "+sysinfo.numCores);
            numCores = sysinfo.numCores;
        } else {
            Log.debug("Number of jobs explicitly set to "+numCores);
        }
        // More than three concurrent cores does not currently give a speedup, at least for compiling the jdk
        // in the OpenJDK. This will change in the future.
        int numCompiles = numCores;
        if (numCores > limitOnConcurrency) numCompiles = limitOnConcurrency;
        // Split the work up in chunks to compiled.

        int numSources = 0;
        for (String s : pkgSrcs.keySet()) {
            Set<URI> ss = pkgSrcs.get(s);
            numSources += ss.size();
        }

        int sourcesPerCompile = numSources / numCompiles;

        // For 64 bit Java, it seems we can compile the OpenJDK 8800 files with a 1500M of heap
        // in a single chunk, with reasonable performance.
        // For 32 bit java, it seems we need 1G of heap.
        // Number experimentally determined when compiling the OpenJDK.
        // Includes space for reasonably efficient garbage collection etc,
        // Calculating backwards gives us a requirement of
        // 1500M/8800 = 175 KiB for 64 bit platforms
        // and 1G/8800 = 119 KiB for 32 bit platform
        // for each compile.....
        int kbPerFile = 175;
        String osarch = System.getProperty("os.arch");
        String dataModel = System.getProperty("sun.arch.data.model");
        if ("32".equals(dataModel)) {
            // For 32 bit platforms, assume it is slightly smaller
            // because of smaller object headers and pointers.
            kbPerFile = 119;
        }
        int numRequiredMBytes = (kbPerFile*numSources)/1024;
        Log.debug("For os.arch "+osarch+" the empirically determined heap required per file is "+kbPerFile+"KiB");
        Log.debug("Server has "+numMBytes+"MiB of heap.");
        Log.debug("Heuristics say that we need "+numRequiredMBytes+"MiB of heap for all source files.");
        // Perform heuristics to see how many cores we can use,
        // or if we have to the work serially in smaller chunks.
        if (numMBytes < numRequiredMBytes) {
            // Ouch, cannot fit even a single compile into the heap.
            // Split it up into several serial chunks.
            concurrentCompiles = false;
            // Limit the number of sources for each compile to 500.
            if (numSources < 500) {
                numCompiles = 1;
                sourcesPerCompile = numSources;
                Log.debug("Compiling as a single source code chunk to stay within heap size limitations!");
            } else if (sourcesPerCompile > 500) {
                // This number is very low, and tuned to dealing with the OpenJDK
                // where the source is >very< circular! In normal application,
                // with less circularity the number could perhaps be increased.
                numCompiles = numSources / 500;
                sourcesPerCompile = numSources/numCompiles;
                Log.debug("Compiling source as "+numCompiles+" code chunks serially to stay within heap size limitations!");
            }
        } else {
            if (numCompiles > 1) {
                // Ok, we can fit at least one full compilation on the heap.
                float usagePerCompile = (float)numRequiredMBytes / ((float)numCompiles * (float)0.7);
                int usage = (int)(usagePerCompile * (float)numCompiles);
                Log.debug("Heuristics say that for "+numCompiles+" concurrent compiles we need "+usage+"MiB");
                if (usage > numMBytes) {
                    // Ouch it does not fit. Reduce to a single chunk.
                    numCompiles = 1;
                    sourcesPerCompile = numSources;
                    // What if the relationship betweem number of compile_chunks and num_required_mbytes
                    // is not linear? Then perhaps 2 chunks would fit where 3 does not. Well, this is
                    // something to experiment upon in the future.
                    Log.debug("Limiting compile to a single thread to stay within heap size limitations!");
                }
            }
        }

        Log.debug("Compiling sources in "+numCompiles+" chunk(s)");

        // Create the chunks to be compiled.
        final CompileChunk[] compileChunks = createCompileChunks(pkgSrcs, oldPackageDependents,
                numCompiles, sourcesPerCompile);

        if (Log.isDebugging()) {
            int cn = 1;
            for (CompileChunk cc : compileChunks) {
                Log.debug("Chunk "+cn+" for "+id+" ---------------");
                cn++;
                for (URI u : cc.srcs) {
                    Log.debug(""+u);
                }
            }
        }

        long start = System.currentTimeMillis();

        // Prepare compilation calls
        List<Callable<CompilationSubResult>> compilationCalls = new ArrayList<>();
        final Object lock = new Object();
        for (int i = 0; i < numCompiles; i++) {
            CompileChunk cc = compileChunks[i];
            if (cc.srcs.isEmpty()) {
                continue;
            }

            String chunkId = id + "-" + String.valueOf(i);
            Log log = Log.get();
            compilationCalls.add(() -> {
                Log.setLogForCurrentThread(log);
                CompilationSubResult result = sjavac.compile("n/a",
                                                             chunkId,
                                                             args.prepJavacArgs(),
                                                             Collections.emptyList(),
                                                             cc.srcs,
                                                             visibleSources);
                synchronized (lock) {
                    Util.getLines(result.stdout).forEach(Log::info);
                    Util.getLines(result.stderr).forEach(Log::error);
                }
                return result;
            });
        }

        // Perform compilations and collect results
        List<CompilationSubResult> subResults = new ArrayList<>();
        List<Future<CompilationSubResult>> futs = new ArrayList<>();
        ExecutorService exec = Executors.newFixedThreadPool(concurrentCompiles ? compilationCalls.size() : 1);
        for (Callable<CompilationSubResult> compilationCall : compilationCalls) {
            futs.add(exec.submit(compilationCall));
        }
        for (Future<CompilationSubResult> fut : futs) {
            try {
                subResults.add(fut.get());
            } catch (ExecutionException ee) {
                Log.error("Compilation failed: " + ee.getMessage());
                Log.error(ee);
            } catch (InterruptedException ie) {
                Log.error("Compilation interrupted: " + ie.getMessage());
                Log.error(ie);
                Thread.currentThread().interrupt();
            }
        }
        exec.shutdownNow();

        // Process each sub result
        for (CompilationSubResult subResult : subResults) {
            for (String pkg : subResult.packageArtifacts.keySet()) {
                Set<URI> pkgArtifacts = subResult.packageArtifacts.get(pkg);
                packageArtifacts.merge(pkg, pkgArtifacts, Util::union);
            }

            for (String pkg : subResult.packageDependencies.keySet()) {
                packageDependencies.putIfAbsent(pkg, new HashMap<>());
                packageDependencies.get(pkg).putAll(subResult.packageDependencies.get(pkg));
            }

            for (String pkg : subResult.packageCpDependencies.keySet()) {
                packageCpDependencies.putIfAbsent(pkg, new HashMap<>());
                packageCpDependencies.get(pkg).putAll(subResult.packageCpDependencies.get(pkg));
            }

            for (String pkg : subResult.packagePubapis.keySet()) {
                packagePubapis.merge(pkg, subResult.packagePubapis.get(pkg), PubApi::mergeTypes);
            }

            for (String pkg : subResult.dependencyPubapis.keySet()) {
                dependencyPubapis.merge(pkg, subResult.dependencyPubapis.get(pkg), PubApi::mergeTypes);
            }

            // Check the return values.
            if (subResult.result != Result.OK) {
                rc = false;
            }
        }

        long duration = System.currentTimeMillis() - start;
        long minutes = duration/60000;
        long seconds = (duration-minutes*60000)/1000;
        Log.debug("Compilation of "+numSources+" source files took "+minutes+"m "+seconds+"s");

        return rc;
    }

    
Split up the sources into compile chunks. If old package dependents information
is available, sort the order of the chunks into the most dependent first!
(Typically that chunk contains the java.lang package.) In the future
we could perhaps improve the heuristics to put the sources into even more sensible chunks.
Now the package are simple sorted in alphabetical order and chunked, then the chunks
are sorted on how dependent they are.
Params:
pkgSrcs – The sources to compile.
oldPackageDependents – Old package dependents, if non-empty, used to sort the chunks.
numCompiles – The number of chunks.
sourcesPerCompile – The number of sources per chunk.
Returns:
/**
     * Split up the sources into compile chunks. If old package dependents information
     * is available, sort the order of the chunks into the most dependent first!
     * (Typically that chunk contains the java.lang package.) In the future
     * we could perhaps improve the heuristics to put the sources into even more sensible chunks.
     * Now the package are simple sorted in alphabetical order and chunked, then the chunks
     * are sorted on how dependent they are.
     *
     * @param pkgSrcs The sources to compile.
     * @param oldPackageDependents Old package dependents, if non-empty, used to sort the chunks.
     * @param numCompiles The number of chunks.
     * @param sourcesPerCompile The number of sources per chunk.
     * @return
     */
    CompileChunk[] createCompileChunks(Map<String,Set<URI>> pkgSrcs,
                                       Map<String,Set<String>> oldPackageDependents,
                                       int numCompiles,
                                       int sourcesPerCompile) {

        CompileChunk[] compileChunks = new CompileChunk[numCompiles];
        for (int i=0; i<compileChunks.length; ++i) {
            compileChunks[i] = new CompileChunk();
        }

        // Now go through the packages and spread out the source on the different chunks.
        int ci = 0;
        // Sort the packages
        String[] packageNames = pkgSrcs.keySet().toArray(new String[0]);
        Arrays.sort(packageNames);
        String from = null;
        for (String pkgName : packageNames) {
            CompileChunk cc = compileChunks[ci];
            Set<URI> s = pkgSrcs.get(pkgName);
            if (cc.srcs.size()+s.size() > sourcesPerCompile && ci < numCompiles-1) {
                from = null;
                ci++;
                cc = compileChunks[ci];
            }
            cc.numPackages++;
            cc.srcs.addAll(s);

            // Calculate nice package names to use as information when compiling.
            String justPkgName = Util.justPackageName(pkgName);
            // Fetch how many packages depend on this package from the old build state.
            Set<String> ss = oldPackageDependents.get(pkgName);
            if (ss != null) {
                // Accumulate this information onto this chunk.
                cc.numDependents += ss.size();
            }
            if (from == null || from.trim().equals("")) from = justPkgName;
            cc.pkgNames.append(justPkgName+"("+s.size()+") ");
            cc.pkgFromTos = from+" to "+justPkgName;
        }
        // If we are compiling serially, sort the chunks, so that the chunk (with the most dependents) (usually the chunk
        // containing java.lang.Object, is to be compiled first!
        // For concurrent compilation, this does not matter.
        Arrays.sort(compileChunks);
        return compileChunks;
    }
}