/*
 * For license please see accompanying LICENSE.txt file (available also at http://www.xmlpull.org/).
 * According to www.xmlpull.org, this code is in the public domain.
 */

package de.schildbach.pte.util;

import java.io.IOException;

import javax.annotation.Nullable;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;

/**
 * Handy functions that combines XmlPull API into higher level functionality.
 */
public final class XmlPullUtil {
    public static boolean test(final XmlPullParser pp, final String tagName)
            throws XmlPullParserException, IOException {
        skipWhitespace(pp);

        return pp.getEventType() == XmlPullParser.START_TAG && pp.getName().equals(tagName);
    }

    public static void require(final XmlPullParser pp, final String tagName)
            throws XmlPullParserException, IOException {
        skipWhitespace(pp);

        pp.require(XmlPullParser.START_TAG, null, tagName);
    }

    public static void enter(final XmlPullParser pp) throws XmlPullParserException, IOException {
        skipWhitespace(pp);

        if (pp.getEventType() != XmlPullParser.START_TAG)
            throw new IllegalStateException("expecting start tag to enter");
        if (pp.isEmptyElementTag())
            throw new IllegalStateException("cannot enter empty tag");

        pp.next();
    }

    public static void enter(final XmlPullParser pp, final String tagName) throws XmlPullParserException, IOException {
        skipWhitespace(pp);

        pp.require(XmlPullParser.START_TAG, null, tagName);
        enter(pp);
    }

    public static void skipExit(final XmlPullParser pp) throws XmlPullParserException, IOException {
        skipToEnd(pp);

        if (pp.getEventType() != XmlPullParser.END_TAG)
            throw new IllegalStateException("expecting end tag to exit");

        pp.next();
    }

    public static void skipExit(final XmlPullParser pp, final String tagName)
            throws XmlPullParserException, IOException {
        skipToEnd(pp);

        pp.require(XmlPullParser.END_TAG, null, tagName);
        pp.next();
    }

    public static void exit(final XmlPullParser pp, final String tagName) throws XmlPullParserException, IOException {
        pp.require(XmlPullParser.END_TAG, null, tagName);
        pp.next();
    }

    private static void skipToEnd(final XmlPullParser pp) throws XmlPullParserException, IOException {
        while (pp.getEventType() != XmlPullParser.END_TAG) {
            if (pp.getEventType() == XmlPullParser.START_TAG)
                next(pp);
            else if (pp.getEventType() == XmlPullParser.TEXT)
                pp.next();
            else
                throw new IllegalStateException();
        }
    }

    private static void skipWhitespace(final XmlPullParser pp) throws XmlPullParserException, IOException {
        if (pp.getEventType() == XmlPullParser.START_DOCUMENT)
            pp.next();
        if (pp.getEventType() == XmlPullParser.TEXT && pp.isWhitespace())
            pp.next();
    }

    public static void requireSkip(final XmlPullParser pp, final String tagName)
            throws XmlPullParserException, IOException {
        require(pp, tagName);

        if (!pp.isEmptyElementTag()) {
            enter(pp, tagName);
            skipExit(pp, tagName);
        } else {
            next(pp);
        }
    }

    public static void optSkip(final XmlPullParser pp, final String tagName)
            throws XmlPullParserException, IOException {
        if (test(pp, tagName))
            requireSkip(pp, tagName);
    }

    public static void optSkipMultiple(final XmlPullParser pp, final String tagName)
            throws XmlPullParserException, IOException {
        while (test(pp, tagName))
            requireSkip(pp, tagName);
    }

    public static void next(final XmlPullParser pp) throws XmlPullParserException, IOException {
        skipSubTree(pp);
        pp.next();
    }

    public static String attr(final XmlPullParser pp, final String attrName) {
        final String attr = optAttr(pp, attrName, null);

        if (attr != null)
            return attr;
        else
            throw new IllegalStateException("expecting attribute: " + attrName);
    }

    public static String optAttr(final XmlPullParser pp, final String attrName, final @Nullable String defaultValue) {
        final String attr = pp.getAttributeValue(null, attrName);

        if (attr != null) {
            final String trimmedAttr = attr.trim();

            if (trimmedAttr.length() > 0)
                return trimmedAttr;
        }

        return defaultValue;
    }

    public static int intAttr(final XmlPullParser pp, final String attrName) {
        return Integer.parseInt(attr(pp, attrName));
    }

    public static int optIntAttr(final XmlPullParser pp, final String attrName, final int defaultValue) {
        final String attr = optAttr(pp, attrName, null);
        if (attr != null)
            return Integer.parseInt(attr);
        else
            return defaultValue;
    }

    public static double floatAttr(final XmlPullParser pp, final String attrName) {
        return Double.parseDouble(attr(pp, attrName));
    }

    public static double optFloatAttr(final XmlPullParser pp, final String attrName, final float defaultValue) {
        final String attr = optAttr(pp, attrName, null);
        if (attr != null)
            return Double.parseDouble(attr);
        else
            return defaultValue;
    }

    public static void requireAttr(final XmlPullParser pp, final String attrName, final String requiredValue) {
        if (!requiredValue.equals(attr(pp, attrName)))
            throw new IllegalStateException("cannot find " + attrName + "=\"" + requiredValue + "\" />");
    }

    public static String valueTag(final XmlPullParser pp, final String tagName)
            throws XmlPullParserException, IOException {
        XmlPullUtil.enter(pp, tagName);
        final String value = pp.getText();
        XmlPullUtil.skipExit(pp, tagName);

        return value != null ? value.trim() : null;
    }

    public static String optValueTag(final XmlPullParser pp, final String tagName, final @Nullable String defaultValue)
            throws XmlPullParserException, IOException {
        if (XmlPullUtil.test(pp, tagName)) {
            if (!pp.isEmptyElementTag()) {
                return valueTag(pp, tagName);
            } else {
                pp.next();
                return defaultValue;
            }
        } else {
            return defaultValue;
        }
    }

    /**
     * Skip sub tree that is currently parser positioned on. <br>
     * NOTE: parser must be on START_TAG and when function returns parser will be positioned on corresponding
     * END_TAG
     */
    public static void skipSubTree(final XmlPullParser pp) throws XmlPullParserException, IOException {
        pp.require(XmlPullParser.START_TAG, null, null);

        int level = 1;
        while (level > 0) {
            final int eventType = pp.next();
            if (eventType == XmlPullParser.END_TAG)
                --level;
            else if (eventType == XmlPullParser.START_TAG)
                ++level;
        }
    }

    public static void skipUntil(final XmlPullParser pp, final String tagName)
            throws XmlPullParserException, IOException {
        while (!XmlPullUtil.test(pp, tagName)) {
            if (!pp.isEmptyElementTag()) {
                XmlPullUtil.enter(pp);
                XmlPullUtil.skipExit(pp);
            } else {
                XmlPullUtil.next(pp);
            }
        }
    }

    /**
     * Read text content of element ith given namespace and name (use null namespace do indicate that namespace
     * should not be checked)
     */

    public static String nextText(final XmlPullParser pp, final String namespace, final String name)
            throws IOException, XmlPullParserException {
        pp.require(XmlPullParser.START_TAG, namespace, name);
        final String text = pp.nextText();

        // work around http://code.google.com/p/android/issues/detail?id=21425
        if (pp.getEventType() != XmlPullParser.END_TAG)
            pp.nextTag();

        pp.require(XmlPullParser.END_TAG, namespace, name);

        return text;
    }

    public static void requireEndDocument(final XmlPullParser pp) throws XmlPullParserException, IOException {
        skipWhitespace(pp);

        if (pp.getEventType() != XmlPullParser.END_DOCUMENT)
            throw new IllegalStateException("expecting end of document: " + pp.getPositionDescription());
    }
}