/*

 * Copyright (c) 2015, 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.javac.code;

import java.io.IOException;

import java.util.Arrays;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.NoSuchElementException;

import java.util.Set;

import java.util.function.Function;

import javax.tools.JavaFileManager;

import javax.tools.JavaFileManager.Location;

import javax.tools.JavaFileObject;

import javax.tools.JavaFileObject.Kind;

import javax.tools.StandardLocation;

import com.sun.tools.javac.code.Symbol.Completer;

import com.sun.tools.javac.code.Symbol.CompletionFailure;

import com.sun.tools.javac.code.Symbol.ModuleSymbol;

import com.sun.tools.javac.jvm.ModuleNameReader;

import com.sun.tools.javac.jvm.ModuleNameReader.BadClassFile;

import com.sun.tools.javac.resources.CompilerProperties.Errors;

import com.sun.tools.javac.resources.CompilerProperties.Fragments;

import com.sun.tools.javac.util.Assert;

import com.sun.tools.javac.util.Context;

import com.sun.tools.javac.util.JCDiagnostic;

import com.sun.tools.javac.util.JCDiagnostic.Fragment;

import com.sun.tools.javac.util.List;

import com.sun.tools.javac.util.ListBuffer;

import com.sun.tools.javac.util.Log;

import com.sun.tools.javac.util.Name;

import com.sun.tools.javac.util.Names;

import static com.sun.tools.javac.code.Kinds.Kind.*;

/**

 *  This class provides operations to locate module definitions

 *  from the source and class files on the paths provided to javac.

 *

 *  <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>

 */

public class ModuleFinder {

    /** The context key for the module finder. */

    protected static final Context.Key<ModuleFinder> moduleFinderKey = new Context.Key<>();

    /** The log to use for verbose output. */

    private final Log log;

    /** The symbol table. */

    private final Symtab syms;

    /** The name table. */

    private final Names names;

    private final ClassFinder classFinder;

    /** Access to files

     */

    private final JavaFileManager fileManager;

    private final JCDiagnostic.Factory diags;

    private ModuleNameReader moduleNameReader;

    public ModuleInfoSourceFileCompleter sourceFileCompleter;

    /** Get the ModuleFinder instance for this invocation. */

    public static ModuleFinder instance(Context context) {

        ModuleFinder instance = context.get(moduleFinderKey);

        if (instance == null)

            instance = new ModuleFinder(context);

        return instance;

    }

    /** Construct a new module finder. */

    protected ModuleFinder(Context context) {

        context.put(moduleFinderKey, this);

        names = Names.instance(context);

        syms = Symtab.instance(context);

        fileManager = context.get(JavaFileManager.class);

        log = Log.instance(context);

        classFinder = ClassFinder.instance(context);

        diags = JCDiagnostic.Factory.instance(context);

    }

    class ModuleLocationIterator implements Iterator<Set<Location>> {

        StandardLocation outer;

        Set<Location> next = null;

        Iterator<StandardLocation> outerIter = Arrays.asList(

                StandardLocation.MODULE_SOURCE_PATH,

                StandardLocation.UPGRADE_MODULE_PATH,

                StandardLocation.SYSTEM_MODULES,

                StandardLocation.MODULE_PATH

        ).iterator();

        Iterator<Set<Location>> innerIter = null;

        @Override

        public boolean hasNext() {

            while (next == null) {

                while (innerIter == null || !innerIter.hasNext()) {

                    if (outerIter.hasNext()) {

                        outer = outerIter.next();

                        try {

                            innerIter = fileManager.listLocationsForModules(outer).iterator();

                        } catch (IOException e) {

                            System.err.println("error listing module locations for " + outer + ": " + e);  // FIXME

                        }

                    } else

                        return false;

                }

                if (innerIter.hasNext())

                    next = innerIter.next();

            }

            return true;

        }

        @Override

        public Set<Location> next() {

            hasNext();

            if (next != null) {

                Set<Location> result = next;

                next = null;

                return result;

            }

            throw new NoSuchElementException();

        }

    }

    ModuleLocationIterator moduleLocationIterator = new ModuleLocationIterator();

    public ModuleSymbol findModule(Name name) {

        return findModule(syms.enterModule(name));

    }

    public ModuleSymbol findModule(ModuleSymbol msym) {

        if (msym.kind != ERR && msym.sourceLocation == null && msym.classLocation == null) {

            // fill in location

            List<ModuleSymbol> list = scanModulePath(msym);

            if (list.isEmpty()) {

                msym.kind = ERR;

            }

        }

        if (msym.kind != ERR && msym.module_info.sourcefile == null && msym.module_info.classfile == null) {

            // fill in module-info

            findModuleInfo(msym);

        }

        return msym;

    }

    public List<ModuleSymbol> findAllModules() {

        List<ModuleSymbol> list = scanModulePath(null);

        for (ModuleSymbol msym: list) {

            if (msym.kind != ERR && msym.module_info.sourcefile == null && msym.module_info.classfile == null) {

                // fill in module-info

                findModuleInfo(msym);

            }

        }

        return list;

    }

    private boolean inFindSingleModule;

    public ModuleSymbol findSingleModule() {

        try {

            JavaFileObject src_fo = getModuleInfoFromLocation(StandardLocation.SOURCE_PATH, Kind.SOURCE);

            JavaFileObject class_fo = getModuleInfoFromLocation(StandardLocation.CLASS_OUTPUT, Kind.CLASS);

            JavaFileObject fo = (src_fo == null) ? class_fo

                    : (class_fo == null) ? src_fo

                            : classFinder.preferredFileObject(src_fo, class_fo);

            ModuleSymbol msym;

            if (fo == null) {

                msym = syms.unnamedModule;

            } else {

                switch (fo.getKind()) {

                    case SOURCE:

                        if (!inFindSingleModule) {

                            try {

                                inFindSingleModule = true;

                                // Note: the following will trigger a re-entrant call to Modules.enter

                                msym = sourceFileCompleter.complete(fo);

                                msym.module_info.classfile = fo;

                            } finally {

                                inFindSingleModule = false;

                            }

                        } else {

                            //the module-info.java does not contain a module declaration,

                            //avoid infinite recursion:

                            msym = syms.unnamedModule;

                        }

                        break;

                    case CLASS:

                        Name name;

                        try {

                            name = names.fromString(readModuleName(fo));

                        } catch (BadClassFile | IOException ex) {

                            //fillIn will report proper errors:

                            name = names.error;

                        }

                        msym = syms.enterModule(name);

                        msym.module_info.classfile = fo;

                        msym.completer = Completer.NULL_COMPLETER;

                        classFinder.fillIn(msym.module_info);

                        break;

                    default:

                        Assert.error();

                        msym = syms.unnamedModule;

                        break;

                }

            }

            msym.classLocation = StandardLocation.CLASS_OUTPUT;

            return msym;

        } catch (IOException e) {

            throw new Error(e); // FIXME

        }

    }

    private String readModuleName(JavaFileObject jfo) throws IOException, ModuleNameReader.BadClassFile {

        if (moduleNameReader == null)

            moduleNameReader = new ModuleNameReader();

        return moduleNameReader.readModuleName(jfo);

    }

    private JavaFileObject getModuleInfoFromLocation(Location location, Kind kind) throws IOException {

        if (!fileManager.hasLocation(location))

            return null;

        return fileManager.getJavaFileForInput(location,

                                               names.module_info.toString(),

                                               kind);

    }

    private List<ModuleSymbol> scanModulePath(ModuleSymbol toFind) {

        ListBuffer<ModuleSymbol> results = new ListBuffer<>();

        Map<Name, Location> namesInSet = new HashMap<>();

        while (moduleLocationIterator.hasNext()) {

            Set<Location> locns = (moduleLocationIterator.next());

            namesInSet.clear();

            for (Location l: locns) {

                try {

                    Name n = names.fromString(fileManager.inferModuleName(l));

                    if (namesInSet.put(n, l) == null) {

                        ModuleSymbol msym = syms.enterModule(n);

                        if (msym.sourceLocation != null || msym.classLocation != null) {

                            // module has already been found, so ignore this instance

                            continue;

                        }

                        if (moduleLocationIterator.outer == StandardLocation.MODULE_SOURCE_PATH) {

                            msym.sourceLocation = l;

                            if (fileManager.hasLocation(StandardLocation.CLASS_OUTPUT)) {

                                msym.classLocation = fileManager.getLocationForModule(StandardLocation.CLASS_OUTPUT, msym.name.toString());

                            }

                        } else {

                            msym.classLocation = l;

                        }

                        if (moduleLocationIterator.outer == StandardLocation.SYSTEM_MODULES ||

                            moduleLocationIterator.outer == StandardLocation.UPGRADE_MODULE_PATH) {

                            msym.flags_field |= Flags.SYSTEM_MODULE;

                        }

                        if (toFind == msym || toFind == null) {

                            // Note: cannot return msym directly, because we must finish

                            // processing this set first

                            results.add(msym);

                        }

                    } else {

                        log.error(Errors.DuplicateModuleOnPath(

                                getDescription(moduleLocationIterator.outer), n));

                    }

                } catch (IOException e) {

                    // skip location for now?  log error?

                }

            }

            if (toFind != null && results.nonEmpty())

                return results.toList();

        }

        return results.toList();

    }

    private void findModuleInfo(ModuleSymbol msym) {

        try {

            JavaFileObject src_fo = (msym.sourceLocation == null) ? null

                    : fileManager.getJavaFileForInput(msym.sourceLocation,

                            names.module_info.toString(), Kind.SOURCE);

            JavaFileObject class_fo = (msym.classLocation == null) ? null

                    : fileManager.getJavaFileForInput(msym.classLocation,

                            names.module_info.toString(), Kind.CLASS);

            JavaFileObject fo = (src_fo == null) ? class_fo :

                    (class_fo == null) ? src_fo :

                    classFinder.preferredFileObject(src_fo, class_fo);

            if (fo == null) {

                String moduleName = msym.sourceLocation == null && msym.classLocation != null ?

                    fileManager.inferModuleName(msym.classLocation) : null;

                if (moduleName != null) {

                    msym.module_info.classfile = null;

                    msym.flags_field |= Flags.AUTOMATIC_MODULE;

                } else {

                    msym.kind = ERR;

                }

            } else {

                msym.module_info.classfile = fo;

                msym.module_info.completer = new Symbol.Completer() {

                    @Override

                    public void complete(Symbol sym) throws CompletionFailure {

                        classFinder.fillIn(msym.module_info);

                    }

                    @Override

                    public String toString() {

                        return "ModuleInfoCompleter";

                    }

                };

            }

        } catch (IOException e) {

            msym.kind = ERR;

        }

    }

    Fragment getDescription(StandardLocation l) {

        switch (l) {

            case MODULE_PATH: return Fragments.LocnModule_path;

            case MODULE_SOURCE_PATH: return Fragments.LocnModule_source_path;

            case SYSTEM_MODULES: return Fragments.LocnSystem_modules;

            case UPGRADE_MODULE_PATH: return Fragments.LocnUpgrade_module_path;

            default:

                throw new AssertionError();

        }

    }

    public interface ModuleInfoSourceFileCompleter {

        public ModuleSymbol complete(JavaFileObject file);

    }

}