/*
 * Copyright 2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.gradle.language.swift.tasks;

import org.gradle.api.Action;
import org.gradle.api.DefaultTask;
import org.gradle.api.Incubating;
import org.gradle.api.file.ConfigurableFileCollection;
import org.gradle.api.file.DirectoryProperty;
import org.gradle.api.file.FileCollection;
import org.gradle.api.tasks.CacheableTask;
import org.gradle.api.tasks.InputFiles;
import org.gradle.api.tasks.Internal;
import org.gradle.api.tasks.OutputDirectory;
import org.gradle.api.tasks.PathSensitive;
import org.gradle.api.tasks.PathSensitivity;
import org.gradle.api.tasks.SkipWhenEmpty;
import org.gradle.api.tasks.TaskAction;
import org.gradle.internal.os.OperatingSystem;
import org.gradle.internal.UncheckedException;
import org.gradle.language.swift.tasks.internal.SymbolHider;
import org.gradle.process.ExecSpec;

import java.io.File;
import java.io.IOException;

/**
 * Unexports the <code>main</code> entry point symbol in an object file, so the object file can be linked with an executable.
 *
 * @since 4.4
 */
@Incubating
@CacheableTask
public class UnexportMainSymbol extends DefaultTask {
    private final ConfigurableFileCollection source = getProject().files();
    private final DirectoryProperty outputDirectory = getProject().getObjects().directoryProperty();

    /**
     * The object files to relocate.
     *
     * @since 4.5
     */
    @InputFiles
    @PathSensitive(PathSensitivity.NAME_ONLY)
    @SkipWhenEmpty
    public ConfigurableFileCollection getObjects() {
        return source;
    }

    /**
     * Collection of modified object files.
     *
     * @since 4.8
     */
    @Internal
    public FileCollection getRelocatedObjects() {
        return outputDirectory.getAsFileTree();
    }

    /**
     * Location of modified object files.
     *
     * @since 4.5
     */
    @OutputDirectory
    public DirectoryProperty getOutputDirectory() {
        return outputDirectory;
    }

    @TaskAction
    public void unexport() {
        for (final File file: source) {
            final File relocatedObject = outputDirectory.file(file.getName()).get().getAsFile();
            if (OperatingSystem.current().isWindows()) {       
                try {
                    final SymbolHider symbolHider = new SymbolHider(file);
                    symbolHider.hideSymbol("main");     // 64 bit
                    symbolHider.hideSymbol("_main");    // 32 bit
                    symbolHider.saveTo(relocatedObject);
                } catch (IOException e) {
                    throw UncheckedException.throwAsUncheckedException(e);
                }   
            } else {
                getProject().exec(new Action<ExecSpec>() {
                    @Override
                    public void execute(ExecSpec execSpec) {
                        // TODO: should use target platform to make this decision
                        if (OperatingSystem.current().isMacOsX()) {
                            execSpec.executable("ld"); // TODO: Locate this tool from a tool provider
                            execSpec.args(file);
                            execSpec.args("-o", relocatedObject);
                            execSpec.args("-r"); // relink, produce another object file
                            execSpec.args("-unexported_symbol", "_main"); // hide _main symbol
                        } else if (OperatingSystem.current().isLinux()) {
                            execSpec.executable("objcopy"); // TODO: Locate this tool from a tool provider
                            execSpec.args("-L", "main"); // hide main symbol
                            execSpec.args(file);
                            execSpec.args(relocatedObject);
                        } else {
                            throw new IllegalStateException("Do not know how to unexport a main symbol on " + OperatingSystem.current());
                        }
                    }
                });
            }
        }
    }
}
