/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.ide.common.resources;

import static com.android.SdkConstants.AMP_ENTITY;
import static com.android.SdkConstants.LT_ENTITY;

import com.android.annotations.Nullable;
import com.android.annotations.VisibleForTesting;
import com.android.ide.common.rendering.api.AttrResourceValue;
import com.android.ide.common.rendering.api.DeclareStyleableResourceValue;
import com.android.ide.common.rendering.api.ResourceValue;
import com.android.ide.common.rendering.api.StyleResourceValue;
import com.android.resources.ResourceType;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * SAX handler to parser value resource files.
 */
public final class ValueResourceParser extends DefaultHandler {

    // TODO: reuse definitions from somewhere else.
    private final static String NODE_RESOURCES = "resources";
    private final static String NODE_ITEM = "item";
    private final static String ATTR_NAME = "name";
    private final static String ATTR_TYPE = "type";
    private final static String ATTR_PARENT = "parent";
    private final static String ATTR_VALUE = "value";

    private final static String DEFAULT_NS_PREFIX = "android:";
    private final static int DEFAULT_NS_PREFIX_LEN = DEFAULT_NS_PREFIX.length();

    public interface IValueResourceRepository {
        void addResourceValue(ResourceValue value);
        boolean hasResourceValue(ResourceType type, String name);
    }

    private boolean inResources = false;
    private int mDepth = 0;
    private ResourceValue mCurrentValue = null;
    private StyleResourceValue mCurrentStyle = null;
    private DeclareStyleableResourceValue mCurrentDeclareStyleable = null;
    private AttrResourceValue mCurrentAttr;
    private IValueResourceRepository mRepository;
    private final boolean mIsFramework;

    public ValueResourceParser(IValueResourceRepository repository, boolean isFramework) {
        mRepository = repository;
        mIsFramework = isFramework;
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if (mCurrentValue != null) {
            mCurrentValue.setValue(unescapeResourceString(mCurrentValue.getValue(), false, true));
        }

        if (inResources && qName.equals(NODE_RESOURCES)) {
            inResources = false;
        } else if (mDepth == 2) {
            mCurrentValue = null;
            mCurrentStyle = null;
            mCurrentDeclareStyleable = null;
            mCurrentAttr = null;
        } else if (mDepth == 3) {
            mCurrentValue = null;
            if (mCurrentDeclareStyleable != null) {
                mCurrentAttr = null;
            }
        }

        mDepth--;
        super.endElement(uri, localName, qName);
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes)
            throws SAXException {
        try {
            mDepth++;
            if (inResources == false && mDepth == 1) {
                if (qName.equals(NODE_RESOURCES)) {
                    inResources = true;
                }
            } else if (mDepth == 2 && inResources == true) {
                ResourceType type = getType(qName, attributes);

                if (type != null) {
                    // get the resource name
                    String name = attributes.getValue(ATTR_NAME);
                    if (name != null) {
                        switch (type) {
                            case STYLE:
                                String parent = attributes.getValue(ATTR_PARENT);
                                mCurrentStyle = new StyleResourceValue(type, name, parent,
                                        mIsFramework);
                                mRepository.addResourceValue(mCurrentStyle);
                                break;
                            case DECLARE_STYLEABLE:
                                mCurrentDeclareStyleable = new DeclareStyleableResourceValue(
                                        type, name, mIsFramework);
                                mRepository.addResourceValue(mCurrentDeclareStyleable);
                                break;
                            case ATTR:
                                mCurrentAttr = new AttrResourceValue(type, name, mIsFramework);
                                mRepository.addResourceValue(mCurrentAttr);
                                break;
                            default:
                                mCurrentValue = new ResourceValue(type, name, mIsFramework);
                                mRepository.addResourceValue(mCurrentValue);
                                break;
                        }
                    }
                }
            } else if (mDepth == 3) {
                // get the resource name
                String name = attributes.getValue(ATTR_NAME);
                if (name != null) {

                    if (mCurrentStyle != null) {
                        // is the attribute in the android namespace?
                        boolean isFrameworkAttr = mIsFramework;
                        if (name.startsWith(DEFAULT_NS_PREFIX)) {
                            name = name.substring(DEFAULT_NS_PREFIX_LEN);
                            isFrameworkAttr = true;
                        }

                        mCurrentValue = new ResourceValue(null, name, mIsFramework);
                        mCurrentStyle.addValue(mCurrentValue, isFrameworkAttr);
                    } else if (mCurrentDeclareStyleable != null) {
                        // is the attribute in the android namespace?
                        boolean isFramework = mIsFramework;
                        if (name.startsWith(DEFAULT_NS_PREFIX)) {
                            name = name.substring(DEFAULT_NS_PREFIX_LEN);
                            isFramework = true;
                        }

                        mCurrentAttr = new AttrResourceValue(ResourceType.ATTR, name, isFramework);
                        mCurrentDeclareStyleable.addValue(mCurrentAttr);

                        // also add it to the repository.
                        mRepository.addResourceValue(mCurrentAttr);

                    } else if (mCurrentAttr != null) {
                        // get the enum/flag value
                        String value = attributes.getValue(ATTR_VALUE);

                        try {
                            // Integer.decode/parseInt can't deal with hex value > 0x7FFFFFFF so we
                            // use Long.decode instead.
                            mCurrentAttr.addValue(name, (int)(long)Long.decode(value));
                        } catch (NumberFormatException e) {
                            // pass, we'll just ignore this value
                        }

                    }
                }
            } else if (mDepth == 4 && mCurrentAttr != null) {
                // get the enum/flag name
                String name = attributes.getValue(ATTR_NAME);
                String value = attributes.getValue(ATTR_VALUE);

                try {
                    // Integer.decode/parseInt can't deal with hex value > 0x7FFFFFFF so we
                    // use Long.decode instead.
                    mCurrentAttr.addValue(name, (int)(long)Long.decode(value));
                } catch (NumberFormatException e) {
                    // pass, we'll just ignore this value
                }
            }
        } finally {
            super.startElement(uri, localName, qName, attributes);
        }
    }

    private ResourceType getType(String qName, Attributes attributes) {
        String typeValue;

        // if the node is <item>, we get the type from the attribute "type"
        if (NODE_ITEM.equals(qName)) {
            typeValue = attributes.getValue(ATTR_TYPE);
        } else {
            // the type is the name of the node.
            typeValue = qName;
        }

        ResourceType type = ResourceType.getEnum(typeValue);
        return type;
    }


    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        if (mCurrentValue != null) {
            String value = mCurrentValue.getValue();
            if (value == null) {
                mCurrentValue.setValue(new String(ch, start, length));
            } else {
                mCurrentValue.setValue(value + new String(ch, start, length));
            }
        }
    }

    /**
     * Replaces escapes in an XML resource string with the actual characters,
     * performing unicode substitutions (replacing any {@code \\uNNNN} references in the
     * given string with the corresponding unicode characters), etc.
     *
     *
     *
     * @param s the string to unescape
     * @param escapeEntities XML entities
     * @param trim whether surrounding space and quotes should be trimmed
     * @return the string with the escape characters removed and expanded
     */
    @Nullable
    public static String unescapeResourceString(
            @Nullable String s,
            boolean escapeEntities, boolean trim) {
        if (s == null) {
            return null;
        }

        // Trim space surrounding optional quotes
        int i = 0;
        int n = s.length();
        if (trim) {
            while (i < n) {
                char c = s.charAt(i);
                if (!Character.isWhitespace(c)) {
                    break;
                }
                i++;
            }
            while (n > i) {
                char c = s.charAt(n - 1);
                if (!Character.isWhitespace(c)) {
                    //See if this was a \, and if so, see whether it was escaped
                    if (n < s.length() && isEscaped(s, n)) {
                        n++;
                    }
                    break;
                }
                n--;
            }

            // Trim surrounding quotes. Note that there can be *any* number of these, and
            // the left side and right side do not have to match; e.g. you can have
            //    """"f"" => f
            int quoteStart = i;
            int quoteEnd = n;
            while (i < n) {
                char c = s.charAt(i);
                if (c != '"') {
                    break;
                }
                i++;
            }
            // Searching backwards is slightly more complicated; make sure we don't trim
            // quotes that have been escaped.
            while (n > i) {
                char c = s.charAt(n - 1);
                if (c != '"') {
                    if (n < s.length() && isEscaped(s, n)) {
                        n++;
                    }
                    break;
                }
                n--;
            }
            if (n == i) {
                return ""; //$NON-NLS-1$
            }

            // Only trim leading spaces if we didn't already process a leading quote:
            if (i == quoteStart) {
                while (i < n) {
                    char c = s.charAt(i);
                    if (!Character.isWhitespace(c)) {
                        break;
                    }
                    i++;
                }
            }
            // Only trim trailing spaces if we didn't already process a trailing quote:
            if (n == quoteEnd) {
                while (n > i) {
                    char c = s.charAt(n - 1);
                    if (!Character.isWhitespace(c)) {
                        //See if this was a \, and if so, see whether it was escaped
                        if (n < s.length() && isEscaped(s, n)) {
                            n++;
                        }
                        break;
                    }
                    n--;
                }
            }
            if (n == i) {
                return ""; //$NON-NLS-1$
            }
        }

        // If no surrounding whitespace and no escape characters, no need to do any
        // more work
        if (i == 0 && n == s.length() && s.indexOf('\\') == -1
                && (!escapeEntities || s.indexOf('&') == -1)) {
            return s;
        }

        StringBuilder sb = new StringBuilder(n - i);
        for (; i < n; i++) {
            char c = s.charAt(i);
            if (c == '\\' && i < n - 1) {
                char next = s.charAt(i + 1);
                // Unicode escapes
                if (next == 'u' && i < n - 5) { // case sensitive
                    String hex = s.substring(i + 2, i + 6);
                    try {
                        int unicodeValue = Integer.parseInt(hex, 16);
                        sb.append((char) unicodeValue);
                        i += 5;
                        continue;
                    } catch (NumberFormatException e) {
                        // Invalid escape: Just proceed to literally transcribe it
                        sb.append(c);
                    }
                } else if (next == 'n') {
                    sb.append('\n');
                    i++;
                } else if (next == 't') {
                    sb.append('\t');
                    i++;
                } else {
                    sb.append(next);
                    i++;
                    continue;
                }
            } else {
                if (c == '&' && escapeEntities) {
                    if (s.regionMatches(true, i, LT_ENTITY, 0, LT_ENTITY.length())) {
                        sb.append('<');
                        i += LT_ENTITY.length() - 1;
                        continue;
                    } else if (s.regionMatches(true, i, AMP_ENTITY, 0, AMP_ENTITY.length())) {
                        sb.append('&');
                        i += AMP_ENTITY.length() - 1;
                        continue;
                    }
                }
                sb.append(c);
            }
        }
        s = sb.toString();

        return s;
    }

    /**
     * Returns true if the character at the given offset in the string is escaped
     * (the previous character is a \, and that character isn't itself an escaped \)
     *
     * @param s the string
     * @param index the index of the character in the string to check
     * @return true if the character is escaped
     */
    @VisibleForTesting
    static boolean isEscaped(String s, int index) {
        if (index == 0 || index == s.length()) {
            return false;
        }
        int prevPos = index - 1;
        char prev = s.charAt(prevPos);
        if (prev != '\\') {
            return false;
        }
        // The character *may* be escaped; not sure if the \ we ran into is
        // an escape character, or an escaped backslash; we have to search backwards
        // to be certain.
        int j = prevPos - 1;
        while (j >= 0) {
            if (s.charAt(j) != '\\') {
                break;
            }
            j--;
        }
        // If we passed an odd number of \'s, the space is escaped
        return (prevPos - j) % 2 == 1;
    }

    /**
     * Escape a string value to be placed in a string resource file such that it complies with
     * the escaping rules described here:
     *   http://developer.android.com/guide/topics/resources/string-resource.html
     * More examples of the escaping rules can be found here:
     *   http://androidcookbook.com/Recipe.seam?recipeId=2219&recipeFrom=ViewTOC
     * This method assumes that the String is not escaped already.
     *
     * Rules:
     * <ul>
     * <li>Double quotes are needed if string starts or ends with at least one space.
     * <li>{@code @, ?} at beginning of string have to be escaped with a backslash.
     * <li>{@code ', ", \} have to be escaped with a backslash.
     * <li>{@code <, >, &} have to be replaced by their predefined xml entity.
     * <li>{@code \n, \t} have to be replaced by a backslash and the appropriate character.
     * </ul>
     * @param s the string to be escaped
     * @return the escaped string as it would appear in the XML text in a values file
     */
    public static String escapeResourceString(String s) {
        int n = s.length();
        if (n == 0) {
            return "";
        }

        StringBuilder sb = new StringBuilder(s.length() * 2);
        boolean hasSpace = s.charAt(0) == ' ' || s.charAt(n - 1) == ' ';

        if (hasSpace) {
            sb.append('"');
        } else if (s.charAt(0) == '@' || s.charAt(0) == '?') {
            sb.append('\\');
        }

        for (int i = 0; i < n; ++i) {
            char c = s.charAt(i);
            switch (c) {
                case '\'':
                    if (!hasSpace) {
                        sb.append('\\');
                    }
                    sb.append(c);
                    break;
                case '"':
                case '\\':
                    sb.append('\\');
                    sb.append(c);
                    break;
                case '<':
                    sb.append(LT_ENTITY);
                    break;
                case '&':
                    sb.append(AMP_ENTITY);
                    break;
                case '\n':
                    sb.append("\\n"); //$NON-NLS-1$
                    break;
                case '\t':
                    sb.append("\\t"); //$NON-NLS-1$
                    break;
                default:
                    sb.append(c);
                    break;
            }
        }

        if (hasSpace) {
            sb.append('"');
        }

        return sb.toString();
    }
}