package org.unix4j.builder;

import java.io.File;
import java.io.OutputStream;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;

import org.unix4j.command.Command;
import org.unix4j.command.ExitValueException;
import org.unix4j.command.NoOp;
import org.unix4j.context.DefaultExecutionContext;
import org.unix4j.context.ExecutionContextFactory;
import org.unix4j.io.BufferedOutput;
import org.unix4j.io.FileOutput;
import org.unix4j.io.NullOutput;
import org.unix4j.io.Output;
import org.unix4j.io.StdOutput;
import org.unix4j.io.StreamOutput;
import org.unix4j.io.StringOutput;
import org.unix4j.io.WriterOutput;
import org.unix4j.line.Line;
import org.unix4j.operation.LineOperation;
import org.unix4j.operation.AdHocCommand;

/**
 * Default implementation for a {@link CommandBuilder}. Builds a {@link NoOp}
 * command if no command is {@link #join(Command) joined} to the command chain
 * of this builder.
 */
public class DefaultCommandBuilder implements CommandBuilder {

        private final ExecutionContextFactory contextFactory;
        private Command<?> command = NoOp.INSTANCE;

        /**
         * Default constructor initialized to build a {@link NoOp} command if no
         * command is {@link #join(Command) joined} to this builder's command chain.
         * Uses a {@link DefaultExecutionContext} to execute commands.
         */
        public DefaultCommandBuilder() {
                this(DefaultExecutionContext.FACTORY);
        }

        /**
         * Constructor using the specified factory to create contexts for command
         * execution. The builder is initialized with a {@link NoOp} command which
         * will be replaced by the first command {@link #join(Command) joined} to 
         * this builder's command chain. 
         * 
         * @param contextFactory
         *            the factory used to create execution contexts that are passed
         *            to the execute method when a command is executed
         */
        public DefaultCommandBuilder(ExecutionContextFactory contextFactory) {
                this.contextFactory = contextFactory;
        }

        /**
         * Returns the context factory used to create contexts for command
         * execution. The returned factory has usually been passed to the
         * constructor of this builder.
         * 
         * @return the factory used to create execution contexts that are passed to
         *         the execute method when a command is executed
         */
        public ExecutionContextFactory getContextFactory() {
                return contextFactory;
        }

        @Override
        public CommandBuilder join(Command<?> command) {
                if (command == null) {
                        throw new NullPointerException("command argument cannot be null");
                }
                this.command = this.command.join(command);
                return this;
        }
        
        @Override
        public CommandBuilder apply(LineOperation operation) {
                return join(new AdHocCommand(operation));
        }

        @Override
        public CommandBuilder reset() {
                command = NoOp.INSTANCE;
                return this;
        }

        @Override
        public Command<?> build() {
                return command;
        }

        @Override
        public String toString() {
                return command.toString();
        }

        @Override
        public void toStdOut() {
                toOutput(new StdOutput());
        }

        @Override
        public List<Line> toLineList() {
                final List<Line> lines = new ArrayList<Line>();
                toOutput(new BufferedOutput(lines));
                return lines;
        }

        @Override
        public List<String> toStringList() {
                final List<String> lines = new ArrayList<String>();
                toOutput(new Output() {
                        @Override
                        public boolean processLine(Line line) {
                                lines.add(line.getContent());
                                return true;// we want more lines
                        }

                        @Override
                        public void finish() {
                                // no op
                        }
                });
                return lines;
        }

        @Override
        public void toOutput(Output output) {
                final Command<?> command = build();
                command.execute(getContextFactory().createExecutionContext(), output).finish();
        }

        @Override
        public void toFile(String file) {
                toFile(new File(file));
        }

        @Override
        public void toFile(File file) {
                toOutput(new FileOutput(file));
        }

        @Override
        public void toOutputStream(OutputStream stream) {
                toOutput(new StreamOutput(stream));
        }

        @Override
        public void toWriter(Writer writer) {
                toOutput(new WriterOutput(writer));
        }

        @Override
        public void toDevNull() {
                toOutput(NullOutput.DEFAULT);
        }

        @Override
        public String toStringResult() {
                final StringOutput out = new StringOutput();
                toOutput(out);
                return out.toString();
        }

        @Override
        public int toExitValue() {
                try {
                        toDevNull();
                        return 0;
                } catch (ExitValueException e) {
                        return e.getExitValue();
                }
        }
}