/*
 * Copyright (c) 2012, 2015, 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
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package com.sun.tools.sjavac;

import java.io.File;
import java.io.IOException;
import java.io.Writer;
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.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.
 *
 * <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,
                             final Map<URI,Set<String>> visibleClasses,
                             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,
                             final Writer out,
                             final Writer err) {

        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);
            compilationCalls.add(() -> {
                CompilationSubResult result = sjavac.compile("n/a",
                                                             chunkId,
                                                             args.prepJavacArgs(),
                                                             Collections.<File>emptyList(),
                                                             cc.srcs,
                                                             visibleSources);
                synchronized (lock) {
                    safeWrite(result.stdout, out);
                    safeWrite(result.stderr, err);
                }
                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());
            } catch (InterruptedException ee) {
                Log.error("Compilation interrupted: " + ee.getMessage());
                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.returnCode != 0) {
                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;
    }

    private void safeWrite(String str, Writer w) {
        if (str.length() > 0) {
            try {
                w.write(str);
            } catch (IOException e) {
                Log.error("Could not print compilation output.");
            }
        }
    }

    /**
     * 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;
    }
}