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package org.jsoftware.utils.chain;


/**
 * Chain responsibility pattern implementation.
 * @author m-szalik
 * @param  invocation context type
 */
public class Chain {
    private final ChainCommandHolder first;

    public Chain(ChainCommand... commands) {
        if (commands != null && commands.length > 0) {
            ChainCommandHolder prev = null;
            for (int i = commands.length -1; i >= 0; i--) {
                ChainCommand command = commands[i];
                ChainCommandHolder current = new ChainCommandHolder<>(command, prev);
                prev = current;
            }
            first = prev;
        } else {
            first = null;
        }
    }

    public void execute(C context) throws Exception {
        if (first != null) {
            first.execute(context);
        }
    }
}

/**
 * Holds command and it's successor
 * @param  Invocation context type
 */
class ChainCommandHolder implements DoChain {
    private final ChainCommand command;
    private final ChainCommandHolder next;

    public ChainCommandHolder(ChainCommand command, ChainCommandHolder next) {
        this.command = command;
        this.next = next;
    }

    @Override
    public void doContinue(C context) throws Exception {
        if (next != null) {
            next.execute(context);
        }
    }

    void execute(C context) throws Exception {
        command.execute(context, this);
    }
}