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package Torello.HTML.Tools.NewsSite;

import java.util.Vector;
import java.net.URL;

import Torello.HTML.HTMLNode;

/**
 * An exception that is thrown from inside the <CODE><B>lambda-methods</B></CODE> created by the 
 * class <CODE><B>ArticleGet</B></CODE> methods - <I>if an error occurs while retrieving a news
 * article body from inside a news web-page</I>.
 * 
 * <BR /><BR /><EMBED CLASS='external-html' DATA-FILE-ID=ARTICLE_GET_EX>
 */
public class ArticleGetException extends Exception
{
    /** <EMBED CLASS='external-html' DATA-FILE-ID=SVUIDEX>  */
    public static final long serialVersionUID = 1;

    /**
     * If the code that has generated this exception has decided to pass the HTML 
     * page-{@code Vector} as a parameter to the constructor it has used, when this exception is
     * thrown, that page will be retained in this {@code public, final} parameter.  Not all four
     * of the provided constructor's for this exception require the {@code page} and {@code url}
     * be preserved.  <I>If the throwing code has declined to provide this reference to the
     * constructor, then the value of this {@code 'page'} field will be null.</I>
     */
    public final Vector<HTMLNode> page;

    /**
     * If the code that has generated this exception has decided to pass the HTML page-{@code URL}
     * as a parameter to the constructor it has used, when this exception is thrown, that page will
     * be retained in this {@code public, final} parameter. Not all four of the provided
     * constructor's for this exception require the {@code 'page'} and {@code 'URL'} be preserved.
     * <I>If the throwing code has declined to provide this reference to the constructor, then the
     * value of this {@code 'URL'} field will be null.</I>
     */
    public final URL url;

    /**
     * Creates a new {@code ArticleGetException} that may be thrown.
     *
     * @param message An explanation of the problem encountered when using the {@code ArticleGet}
     * consumer.
     */
    public ArticleGetException(String message)
    { this(message, null, null); }

    /**
     * Creates a new {@code ArticleGetException} that may be thrown, having the given message,
     * and a "previously thrown exception" (cause) - either from another thread, or caught and
     * re-branded into an {@code ArticleGetException}
     *
     * @param message The explanation of the problem encountered when parsing an HTML page using
     * the a user-defined, or factory-created {@code ArticleGet} instance.
     *
     * @param cause This may be a "cause" exception.  It can be caused, and facilitates a
     * programmer catching a problem, and then re-naming it to {@code ArticleGetException}
     */
    public ArticleGetException(String message, Throwable cause)
    { this(message, cause, null, null); }

    /**
     * When this constructor is used, the {@code URL} and page-{@code Vector} will be preserved
     * as {@code final} (constant) fields within this class instance for future reference and
     * debugging.
     *
     * @param message The explanation of the problem encountered when parsing an HTML page using
     * the a user-defined, or factory-created {@code ArticleGet} instance.
     *
     * @param url The {@code URL} from which the original HTML page-{@code Vector} was retrieved
     *
     * @param page The HTML page (as a {@code Vector}) that could not be resolved by the
     * {@code ArticleGet} instance which threw this exception.
     */
    public ArticleGetException(String message, URL url, Vector<HTMLNode> page)
    {
        super(message);
        this.url = url;
        this.page = page;
    }

    /**
     * When this constructor is used, the {@code URL} and page-{@code Vector} will be preserved
     * as {@code final} (constant) fields within this class instance for future reference and 
     * debugging.  If there was an underlying exception that caused the article-body retrieval to
     * fail, that will be stored in the Java {@code getCause();} method available.
     *
     * @param message The explanation of the problem encountered when parsing an HTML page using
     * the a user-defined, or factory-created {@code ArticleGet} instance.
     *
     * @param cause This may be a "cause" exception.  It can be caused, and facilitates a
     * programmer catching a problem, and then re-naming it to {@code ArticleGetException}
     *
     * @param url The {@code URL} from which the original HTML page-{@code Vector} was retrieved
     *
     * @param page The HTML page (as a {@code Vector}) that could not be resolved by the
     * {@code ArticleGet} instance which threw this exception.
     */
    public ArticleGetException(String message, Throwable cause, URL url, Vector<HTMLNode> page)
    {
        super(message, cause);
        this.url = url;
        this.page = page;
    }

    /**
     * When this constructor is used, the {@code URL} and page-{@code Vector} will be preserved
     * as {@code final} (constant) fields within this class instance for future reference and
     * debugging.
     *
     * @param url The {@code URL} from which the original HTML page-{@code Vector} was retrieved
     *
     * @param page The HTML page (as a {@code Vector}) that could not be resolved by the
     * {@code ArticleGet} instance which threw this exception.
     */
    public static void check(URL url, Vector<HTMLNode> page) throws ArticleGetException
    {
        if (url == null) throw new ArticleGetException
            ("ArticleGet.apply(...) has been called with a null URL.", url, page);

        if (page == null) throw new ArticleGetException
            ("ArticleGet.apply(...) has been called with a null page-vector.", url, page);

        if (page.size() == 0) throw new ArticleGetException
            ("ArticleGet.apply(...) has been called with a zero-length page-vector.", url, page);
    }

    static final int RET_NULL = 1;
    static final int RET_EMPTY_VECTOR = 2;
    static final int GOT_EXCEPTION = 3;

    // Constructor #1
    ArticleGetException(int FLAG, String functionNameStr, Exception e)
    { this(MESSAGE(FLAG, functionNameStr), e); }

    // Constructor #2
    ArticleGetException(int FLAG, String functionNameStr)
    { this(MESSAGE(FLAG, functionNameStr)); }

    private static String MESSAGE(int FLAG, String functionNameStr)
    {
        StringBuilder sb = new StringBuilder
            ("The article or page whose content-body you have tried to retrieve using your ArticleGet ");

        switch (FLAG)
        {
            case RET_NULL:          sb.append("produced null.");
                                    break;

            case RET_EMPTY_VECTOR:  sb.append("produced a ZERO-LENGTH vector.");
                                    break;

            case GOT_EXCEPTION:     sb.append("threw an exception while parsing.  (see e.getCause().)");
                                    break;

            default:                sb.append("failed.  Unknown cause.");
                                    break;
        }

        sb.append("\nFactory-generated ArticleGet had called: " + functionNameStr);

        return sb.toString();
    }
}