/*
 * Copyright 2010 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.configuration;

import org.gradle.api.DefaultTask;
import org.gradle.api.internal.tasks.options.OptionReader;
import org.gradle.api.tasks.TaskAction;
import org.gradle.api.tasks.options.Option;
import org.gradle.execution.TaskSelection;
import org.gradle.execution.TaskSelector;
import org.gradle.initialization.BuildClientMetaData;
import org.gradle.internal.logging.text.StyledTextOutput;
import org.gradle.internal.logging.text.StyledTextOutputFactory;
import org.gradle.util.GradleVersion;
import org.gradle.work.DisableCachingByDefault;

import javax.inject.Inject;

import static org.gradle.internal.logging.text.StyledTextOutput.Style.UserInput;

@DisableCachingByDefault(because = "Produces only non-cacheable console output")
public class Help extends DefaultTask {
    private String taskPath;

    @Inject
    protected StyledTextOutputFactory getTextOutputFactory() {
        throw new UnsupportedOperationException();
    }

    @Inject
    protected BuildClientMetaData getClientMetaData() {
        throw new UnsupportedOperationException();
    }

    @Inject
    protected TaskSelector getTaskSelector() {
        throw new UnsupportedOperationException();
    }

    @Inject
    protected OptionReader getOptionReader() {
        throw new UnsupportedOperationException();
    }

    @TaskAction
    void displayHelp() {
        StyledTextOutput output = getTextOutputFactory().create(Help.class);
        BuildClientMetaData metaData = getClientMetaData();
        if (taskPath != null) {
            printTaskHelp(output);
        } else {
            printDefaultHelp(output, metaData);
        }
    }

    private void printTaskHelp(StyledTextOutput output) {
        TaskSelector selector = getTaskSelector();
        TaskSelection selection = selector.getSelection(taskPath);
        OptionReader optionReader = getOptionReader();
        TaskDetailPrinter taskDetailPrinter = new TaskDetailPrinter(taskPath, selection, optionReader);
        taskDetailPrinter.print(output);
    }

    private void printDefaultHelp(StyledTextOutput output, BuildClientMetaData metaData) {
        output.println();
        output.formatln("Welcome to Gradle %s.", GradleVersion.current().getVersion());
        output.println();
        output.text("To run a build, run ");
        metaData.describeCommand(output.withStyle(UserInput), "<task> ...");
        output.println();
        output.println();
        output.text("To see a list of available tasks, run ");
        metaData.describeCommand(output.withStyle(UserInput), "tasks");
        output.println();
        output.println();
        output.text("To see a list of command-line options, run ");
        metaData.describeCommand(output.withStyle(UserInput), "--help");
        output.println();
        output.println();
        output.text("To see more detail about a task, run ");
        metaData.describeCommand(output.withStyle(UserInput), "help --task <task>");
        output.println();
        output.println();
        output.text("For troubleshooting, visit ");
        output.withStyle(UserInput).text("https://help.gradle.org");
        output.println();
    }

    @Option(option = "task", description = "The task to show help for.")
    public void setTaskPath(String taskPath) {
        this.taskPath = taskPath;
    }
}
