/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.text;

import java.text.Format;
import java.text.MessageFormat;
import java.text.ParsePosition;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Locale;
import java.util.Locale.Category;
import java.util.Map;
import java.util.Objects;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.text.matcher.StringMatcherFactory;

/**
 * Extends {@code java.text.MessageFormat} to allow pluggable/additional formatting
 * options for embedded format elements.  Client code should specify a registry
 * of {@code FormatFactory} instances associated with {@code String}
 * format names.  This registry will be consulted when the format elements are
 * parsed from the message pattern.  In this way custom patterns can be specified,
 * and the formats supported by {@code java.text.MessageFormat} can be overridden
 * at the format and/or format style level (see MessageFormat).  A "format element"
 * embedded in the message pattern is specified (<b>()?</b> signifies optionality):<br>
 * {@code {}<i>argument-number</i><b>(</b>{@code ,}<i>format-name</i><b>
 * (</b>{@code ,}<i>format-style</i><b>)?)?</b>{@code }}
 *
 * <p>
 * <i>format-name</i> and <i>format-style</i> values are trimmed of surrounding whitespace
 * in the manner of {@code java.text.MessageFormat}.  If <i>format-name</i> denotes
 * {@code FormatFactory formatFactoryInstance} in {@code registry}, a {@code Format}
 * matching <i>format-name</i> and <i>format-style</i> is requested from
 * {@code formatFactoryInstance}.  If this is successful, the {@code Format}
 * found is used for this format element.
 * </p>
 *
 * <p><b>NOTICE:</b> The various subformat mutator methods are considered unnecessary; they exist on the parent
 * class to allow the type of customization which it is the job of this class to provide in
 * a configurable fashion.  These methods have thus been disabled and will throw
 * {@code UnsupportedOperationException} if called.
 * </p>
 *
 * <p>Limitations inherited from {@code java.text.MessageFormat}:</p>
 * <ul>
 * <li>When using "choice" subformats, support for nested formatting instructions is limited
 *     to that provided by the base class.</li>
 * <li>Thread-safety of {@code Format}s, including {@code MessageFormat} and thus
 *     {@code ExtendedMessageFormat}, is not guaranteed.</li>
 * </ul>
 *
 * @since 1.0
 */
public class ExtendedMessageFormat extends MessageFormat {

    /**
     * Serializable Object.
     */
    private static final long serialVersionUID = -2362048321261811743L;

    /**
     * Our initial seed value for calculating hashes.
     */
    private static final int HASH_SEED = 31;

    /**
     * The empty string.
     */
    private static final String DUMMY_PATTERN = StringUtils.EMPTY;

    /**
     * A comma.
     */
    private static final char START_FMT = ',';

    /**
     * A right side squiggly brace.
     */
    private static final char END_FE = '}';

    /**
     * A left side squiggly brace.
     */
    private static final char START_FE = '{';

    /**
     * A properly escaped character representing a single quote.
     */
    private static final char QUOTE = '\'';

    /**
     * To pattern string.
     */
    private String toPattern;

    /**
     * Our registry of FormatFactory.
     */
    private final Map<String, ? extends FormatFactory> registry;

    /**
     * Constructs a new ExtendedMessageFormat for the default locale.
     *
     * @param pattern  the pattern to use, not null
     * @throws IllegalArgumentException in case of a bad pattern.
     */
    public ExtendedMessageFormat(final String pattern) {
        this(pattern, Locale.getDefault(Category.FORMAT));
    }

    /**
     * Constructs a new ExtendedMessageFormat.
     *
     * @param pattern  the pattern to use, not null
     * @param locale  the locale to use, not null
     * @throws IllegalArgumentException in case of a bad pattern.
     */
    public ExtendedMessageFormat(final String pattern, final Locale locale) {
        this(pattern, locale, null);
    }

    /**
     * Constructs a new ExtendedMessageFormat.
     *
     * @param pattern  the pattern to use, not null
     * @param locale  the locale to use, not null
     * @param registry  the registry of format factories, may be null
     * @throws IllegalArgumentException in case of a bad pattern.
     */
    public ExtendedMessageFormat(final String pattern,
                                 final Locale locale,
                                 final Map<String, ? extends FormatFactory> registry) {
        super(DUMMY_PATTERN);
        setLocale(locale);
        this.registry = registry != null
                ? Collections.unmodifiableMap(new HashMap<>(registry))
                : null;
        applyPattern(pattern);
    }

    /**
     * Constructs a new ExtendedMessageFormat for the default locale.
     *
     * @param pattern  the pattern to use, not null
     * @param registry  the registry of format factories, may be null
     * @throws IllegalArgumentException in case of a bad pattern.
     */
    public ExtendedMessageFormat(final String pattern,
                                 final Map<String, ? extends FormatFactory> registry) {
        this(pattern, Locale.getDefault(Category.FORMAT), registry);
    }

    /**
     * Consumes a quoted string, adding it to {@code appendTo} if
     * specified.
     *
     * @param pattern pattern to parse
     * @param pos current parse position
     * @param appendTo optional StringBuilder to append
     */
    private void appendQuotedString(final String pattern, final ParsePosition pos,
            final StringBuilder appendTo) {
        assert pattern.toCharArray()[pos.getIndex()] == QUOTE
                : "Quoted string must start with quote character";

        // handle quote character at the beginning of the string
        if (appendTo != null) {
            appendTo.append(QUOTE);
        }
        next(pos);

        final int start = pos.getIndex();
        final char[] c = pattern.toCharArray();
        for (int i = pos.getIndex(); i < pattern.length(); i++) {
            switch (c[pos.getIndex()]) {
            case QUOTE:
                next(pos);
                if (appendTo != null) {
                    appendTo.append(c, start, pos.getIndex() - start);
                }
                return;
            default:
                next(pos);
            }
        }
        throw new IllegalArgumentException(
                "Unterminated quoted string at position " + start);
    }

    /**
     * Applies the specified pattern.
     *
     * @param pattern String
     */
    @Override
    public final void applyPattern(final String pattern) {
        if (registry == null) {
            super.applyPattern(pattern);
            toPattern = super.toPattern();
            return;
        }
        final ArrayList<Format> foundFormats = new ArrayList<>();
        final ArrayList<String> foundDescriptions = new ArrayList<>();
        final StringBuilder stripCustom = new StringBuilder(pattern.length());

        final ParsePosition pos = new ParsePosition(0);
        final char[] c = pattern.toCharArray();
        int fmtCount = 0;
        while (pos.getIndex() < pattern.length()) {
            switch (c[pos.getIndex()]) {
            case QUOTE:
                appendQuotedString(pattern, pos, stripCustom);
                break;
            case START_FE:
                fmtCount++;
                seekNonWs(pattern, pos);
                final int start = pos.getIndex();
                final int index = readArgumentIndex(pattern, next(pos));
                stripCustom.append(START_FE).append(index);
                seekNonWs(pattern, pos);
                Format format = null;
                String formatDescription = null;
                if (c[pos.getIndex()] == START_FMT) {
                    formatDescription = parseFormatDescription(pattern,
                            next(pos));
                    format = getFormat(formatDescription);
                    if (format == null) {
                        stripCustom.append(START_FMT).append(formatDescription);
                    }
                }
                foundFormats.add(format);
                foundDescriptions.add(format == null ? null : formatDescription);
                if (foundFormats.size() != fmtCount) {
                    throw new IllegalArgumentException("The validated expression is false");
                }
                if (foundDescriptions.size() != fmtCount) {
                    throw new IllegalArgumentException("The validated expression is false");
                }
                if (c[pos.getIndex()] != END_FE) {
                    throw new IllegalArgumentException(
                            "Unreadable format element at position " + start);
                }
                //$FALL-THROUGH$
            default:
                stripCustom.append(c[pos.getIndex()]);
                next(pos);
            }
        }
        super.applyPattern(stripCustom.toString());
        toPattern = insertFormats(super.toPattern(), foundDescriptions);
        if (containsElements(foundFormats)) {
            final Format[] origFormats = getFormats();
            // only loop over what we know we have, as MessageFormat on Java 1.3
            // seems to provide an extra format element:
            int i = 0;
            for (final Format f : foundFormats) {
                if (f != null) {
                    origFormats[i] = f;
                }
                i++;
            }
            super.setFormats(origFormats);
        }
    }

    /**
     * Tests whether the specified Collection contains non-null elements.
     * @param coll to check
     * @return {@code true} if some Object was found, {@code false} otherwise.
     */
    private boolean containsElements(final Collection<?> coll) {
        if (coll == null || coll.isEmpty()) {
            return false;
        }
        return coll.stream().anyMatch(Objects::nonNull);
    }

    /**
     * Tests if this extended message format is equal to another object.
     *
     * @param obj the object to compare to
     * @return true if this object equals the other, otherwise false
     */
    @Override
    public boolean equals(final Object obj) {
        if (obj == this) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (!Objects.equals(getClass(), obj.getClass())) {
          return false;
        }
        final ExtendedMessageFormat rhs = (ExtendedMessageFormat) obj;
        if (!Objects.equals(toPattern, rhs.toPattern)) {
            return false;
        }
        if (!super.equals(obj)) {
            return false;
        }
        return Objects.equals(registry, rhs.registry);
    }

    /**
     * Gets a custom format from a format description.
     *
     * @param desc String
     * @return Format
     */
    private Format getFormat(final String desc) {
        if (registry != null) {
            String name = desc;
            String args = null;
            final int i = desc.indexOf(START_FMT);
            if (i > 0) {
                name = desc.substring(0, i).trim();
                args = desc.substring(i + 1).trim();
            }
            final FormatFactory factory = registry.get(name);
            if (factory != null) {
                return factory.getFormat(name, args, getLocale());
            }
        }
        return null;
    }

    /**
     * Consumes quoted string only.
     *
     * @param pattern pattern to parse
     * @param pos current parse position
     */
    private void getQuotedString(final String pattern, final ParsePosition pos) {
        appendQuotedString(pattern, pos, null);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode() {
        int result = super.hashCode();
        result = HASH_SEED * result + Objects.hashCode(registry);
        result = HASH_SEED * result + Objects.hashCode(toPattern);
        return result;
    }

    /**
     * Inserts formats back into the pattern for toPattern() support.
     *
     * @param pattern source
     * @param customPatterns The custom patterns to re-insert, if any
     * @return full pattern
     */
    private String insertFormats(final String pattern, final ArrayList<String> customPatterns) {
        if (!containsElements(customPatterns)) {
            return pattern;
        }
        final StringBuilder sb = new StringBuilder(pattern.length() * 2);
        final ParsePosition pos = new ParsePosition(0);
        int fe = -1;
        int depth = 0;
        while (pos.getIndex() < pattern.length()) {
            final char c = pattern.charAt(pos.getIndex());
            switch (c) {
            case QUOTE:
                appendQuotedString(pattern, pos, sb);
                break;
            case START_FE:
                depth++;
                sb.append(START_FE).append(readArgumentIndex(pattern, next(pos)));
                // do not look for custom patterns when they are embedded, e.g. in a choice
                if (depth == 1) {
                    fe++;
                    final String customPattern = customPatterns.get(fe);
                    if (customPattern != null) {
                        sb.append(START_FMT).append(customPattern);
                    }
                }
                break;
            case END_FE:
                depth--;
                //$FALL-THROUGH$
            default:
                sb.append(c);
                next(pos);
            }
        }
        return sb.toString();
    }

    /**
     * Advances parse position by 1.
     *
     * @param pos ParsePosition
     * @return {@code pos}
     */
    private ParsePosition next(final ParsePosition pos) {
        pos.setIndex(pos.getIndex() + 1);
        return pos;
    }

    /**
     * Parses the format component of a format element.
     *
     * @param pattern string to parse
     * @param pos current parse position
     * @return Format description String
     */
    private String parseFormatDescription(final String pattern, final ParsePosition pos) {
        final int start = pos.getIndex();
        seekNonWs(pattern, pos);
        final int text = pos.getIndex();
        int depth = 1;
        while (pos.getIndex() < pattern.length()) {
            switch (pattern.charAt(pos.getIndex())) {
            case START_FE:
                depth++;
                next(pos);
                break;
            case END_FE:
                depth--;
                if (depth == 0) {
                    return pattern.substring(text, pos.getIndex());
                }
                next(pos);
                break;
            case QUOTE:
                getQuotedString(pattern, pos);
                break;
            default:
                next(pos);
                break;
            }
        }
        throw new IllegalArgumentException(
                "Unterminated format element at position " + start);
    }

    /**
     * Reads the argument index from the current format element.
     *
     * @param pattern pattern to parse
     * @param pos current parse position
     * @return argument index
     */
    private int readArgumentIndex(final String pattern, final ParsePosition pos) {
        final int start = pos.getIndex();
        seekNonWs(pattern, pos);
        final StringBuilder result = new StringBuilder();
        boolean error = false;
        for (; !error && pos.getIndex() < pattern.length(); next(pos)) {
            char c = pattern.charAt(pos.getIndex());
            if (Character.isWhitespace(c)) {
                seekNonWs(pattern, pos);
                c = pattern.charAt(pos.getIndex());
                if (c != START_FMT && c != END_FE) {
                    error = true;
                    continue;
                }
            }
            if ((c == START_FMT || c == END_FE) && result.length() > 0) {
                try {
                    return Integer.parseInt(result.toString());
                } catch (final NumberFormatException e) { // NOPMD
                    // we've already ensured only digits, so unless something
                    // outlandishly large was specified we should be okay.
                }
            }
            error = !Character.isDigit(c);
            result.append(c);
        }
        if (error) {
            throw new IllegalArgumentException(
                    "Invalid format argument index at position " + start + ": "
                            + pattern.substring(start, pos.getIndex()));
        }
        throw new IllegalArgumentException(
                "Unterminated format element at position " + start);
    }

    /**
     * Consumes whitespace from the current parse position.
     *
     * @param pattern String to read
     * @param pos current position
     */
    private void seekNonWs(final String pattern, final ParsePosition pos) {
        int len = 0;
        final char[] buffer = pattern.toCharArray();
        do {
            len = StringMatcherFactory.INSTANCE.splitMatcher().isMatch(buffer, pos.getIndex(), 0, buffer.length);
            pos.setIndex(pos.getIndex() + len);
        } while (len > 0 && pos.getIndex() < pattern.length());
    }

    /**
     * Throws UnsupportedOperationException - see class Javadoc for details.
     *
     * @param formatElementIndex format element index
     * @param newFormat the new format
     * @throws UnsupportedOperationException always thrown since this isn't
     *                                       supported by ExtendMessageFormat
     */
    @Override
    public void setFormat(final int formatElementIndex, final Format newFormat) {
        throw new UnsupportedOperationException();
    }

    /**
     * Throws UnsupportedOperationException - see class Javadoc for details.
     *
     * @param argumentIndex argument index
     * @param newFormat the new format
     * @throws UnsupportedOperationException always thrown since this isn't
     *                                       supported by ExtendMessageFormat
     */
    @Override
    public void setFormatByArgumentIndex(final int argumentIndex,
                                         final Format newFormat) {
        throw new UnsupportedOperationException();
    }

    /**
     * Throws UnsupportedOperationException - see class Javadoc for details.
     *
     * @param newFormats new formats
     * @throws UnsupportedOperationException always thrown since this isn't
     *                                       supported by ExtendMessageFormat
     */
    @Override
    public void setFormats(final Format[] newFormats) {
        throw new UnsupportedOperationException();
    }

    /**
     * Throws UnsupportedOperationException - see class Javadoc for details.
     *
     * @param newFormats new formats
     * @throws UnsupportedOperationException always thrown since this isn't
     *                                       supported by ExtendMessageFormat
     */
    @Override
    public void setFormatsByArgumentIndex(final Format[] newFormats) {
        throw new UnsupportedOperationException();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toPattern() {
        return toPattern;
    }
}