package org.embulk.spi.util;

import java.util.List;
import com.google.common.collect.ImmutableList;
import org.embulk.config.TaskSource;
import org.embulk.config.ConfigSource;
import org.embulk.plugin.PluginType;
import org.embulk.spi.ExecSession;
import org.embulk.spi.FileInput;
import org.embulk.spi.DecoderPlugin;

public abstract class Decoders
{
    private Decoders() { }

    public static List<DecoderPlugin> newDecoderPlugins(ExecSession exec, List<ConfigSource> configs)
    {
        ImmutableList.Builder<DecoderPlugin> builder = ImmutableList.builder();
        for (ConfigSource config : configs) {
            builder.add(exec.newPlugin(DecoderPlugin.class, config.get(PluginType.class, "type")));
        }
        return builder.build();
    }

    public interface Control
    {
        public void run(List<TaskSource> taskSources);
    }

    public static void transaction(List<DecoderPlugin> plugins, List<ConfigSource> configs,
            Decoders.Control control)
    {
        new RecursiveControl(plugins, configs, control).transaction();
    }

    public static FileInput open(List<DecoderPlugin> plugins, List<TaskSource> taskSources,
            FileInput input)
    {
        FileInput in = input;
        int pos = 0;
        while (pos < plugins.size()) {
            in = plugins.get(pos).open(taskSources.get(pos), in);
            pos++;
        }
        return in;
    }

    private static class RecursiveControl
    {
        private final List<DecoderPlugin> plugins;
        private final List<ConfigSource> configs;
        private final Decoders.Control finalControl;
        private final ImmutableList.Builder<TaskSource> taskSources;
        private int pos;

        RecursiveControl(List<DecoderPlugin> plugins, List<ConfigSource> configs,
                Decoders.Control finalControl)
        {
            this.plugins = plugins;
            this.configs = configs;
            this.finalControl = finalControl;
            this.taskSources = ImmutableList.builder();
        }

        public void transaction()
        {
            if (pos < plugins.size()) {
                plugins.get(pos).transaction(configs.get(pos), new DecoderPlugin.Control() {
                    public void run(TaskSource taskSource)
                    {
                        taskSources.add(taskSource);
                        pos++;
                        transaction();
                    }
                });
            } else {
                finalControl.run(taskSources.build());
            }
        }
    }
}