/*
 * 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.
 */

/* $Id: AdvancedMessageFormat.java 1805177 2017-08-16 11:02:44Z ssteiner $ */

package org.apache.fop.util.text;

import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;

import org.apache.xmlgraphics.util.Service;


Formats messages based on a template and with a set of named parameters. This is similar to MessageFormat but uses named parameters and supports conditional sub-groups. 

Example:

Missing field "{fieldName}"[ at location: {location}]!

  
Curly brackets ("{}") are used for fields.
  
Square brackets ("[]") are used to delimit conditional sub-groups. A sub-group is
    conditional when all fields inside the sub-group have a null value. In the case, everything
    between the brackets is skipped.

/**
 * Formats messages based on a template and with a set of named parameters. This is similar to
 * {@link java.text.MessageFormat} but uses named parameters and supports conditional sub-groups.
 * <p>
 * Example:
 * </p>
 * <p><code>Missing field "{fieldName}"[ at location: {location}]!</code></p>
 * <ul>
 *   <li>Curly brackets ("{}") are used for fields.</li>
 *   <li>Square brackets ("[]") are used to delimit conditional sub-groups. A sub-group is
 *     conditional when all fields inside the sub-group have a null value. In the case, everything
 *     between the brackets is skipped.</li>
 * </ul>
 */
public class AdvancedMessageFormat {

    
Regex that matches "," but not "\," (escaped comma) /** Regex that matches "," but not "\," (escaped comma) */
    static final Pattern COMMA_SEPARATOR_REGEX = Pattern.compile("(?<!\\\\),");

    private static final Map<String, PartFactory> PART_FACTORIES
        = new java.util.HashMap<String, PartFactory>();
    private static final List<ObjectFormatter> OBJECT_FORMATTERS
        = new java.util.ArrayList<ObjectFormatter>();
    private static final Map<Object, Function> FUNCTIONS
        = new java.util.HashMap<Object, Function>();

    private CompositePart rootPart;

    static {
        Iterator<Object> iter;
        iter = Service.providers(PartFactory.class);
        while (iter.hasNext()) {
            PartFactory factory = (PartFactory)iter.next();
            PART_FACTORIES.put(factory.getFormat(), factory);
        }
        iter = Service.providers(ObjectFormatter.class);
        while (iter.hasNext()) {
            OBJECT_FORMATTERS.add((ObjectFormatter)iter.next());
        }
        iter = Service.providers(Function.class);
        while (iter.hasNext()) {
            Function function = (Function)iter.next();
            FUNCTIONS.put(function.getName(), function);
        }
    }

    
Construct a new message format.
Params:
pattern – the message format pattern./**
     * Construct a new message format.
     * @param pattern the message format pattern.
     */
    public AdvancedMessageFormat(CharSequence pattern) {
        parsePattern(pattern);
    }

    private void parsePattern(CharSequence pattern) {
        rootPart = new CompositePart(false);
        StringBuffer sb = new StringBuffer();
        parseInnerPattern(pattern, rootPart, sb, 0);
    }

    private int parseInnerPattern(CharSequence pattern, CompositePart parent,
            StringBuffer sb, int start) {
        assert sb.length() == 0;
        int i = start;
        int len = pattern.length();
        loop:
        while (i < len) {
            char ch = pattern.charAt(i);
            switch (ch) {
            case '{':
                if (sb.length() > 0) {
                    parent.addChild(new TextPart(sb.toString()));
                    sb.setLength(0);
                }
                i++;
                int nesting = 1;
                while (i < len) {
                    ch = pattern.charAt(i);
                    if (ch == '{') {
                        nesting++;
                    } else if (ch == '}') {
                        nesting--;
                        if (nesting == 0) {
                            i++;
                            break;
                        }
                    }
                    sb.append(ch);
                    i++;
                }
                parent.addChild(parseField(sb.toString()));
                sb.setLength(0);
                break;
            case ']':
                i++;
                break loop; //Current composite is finished
            case '[':
                if (sb.length() > 0) {
                    parent.addChild(new TextPart(sb.toString()));
                    sb.setLength(0);
                }
                i++;
                CompositePart composite = new CompositePart(true);
                parent.addChild(composite);
                i += parseInnerPattern(pattern, composite, sb, i);
                break;
            case '|':
                if (sb.length() > 0) {
                    parent.addChild(new TextPart(sb.toString()));
                    sb.setLength(0);
                }
                parent.newSection();
                i++;
                break;
            case '\\':
                if (i < len - 1) {
                    i++;
                    ch = pattern.charAt(i);
                }
                sb.append(ch);
                i++;
                break;
            default:
                sb.append(ch);
                i++;
                break;
            }
        }
        if (sb.length() > 0) {
            parent.addChild(new TextPart(sb.toString()));
            sb.setLength(0);
        }
        return i - start;
    }

    private Part parseField(String field) {
        String[] parts = COMMA_SEPARATOR_REGEX.split(field, 3);
        String fieldName = parts[0];
        if (parts.length == 1) {
            if (fieldName.startsWith("#")) {
                return new FunctionPart(fieldName.substring(1));
            } else {
                return new SimpleFieldPart(fieldName);
            }
        } else {
            String format = parts[1];
            PartFactory factory = PART_FACTORIES.get(format);
            if (factory == null) {
                throw new IllegalArgumentException(
                        "No PartFactory available under the name: " + format);
            }
            if (parts.length == 2) {
                return factory.newPart(fieldName, null);
            } else {
                return factory.newPart(fieldName, parts[2]);
            }
        }
    }

    private static Function getFunction(String functionName) {
        return FUNCTIONS.get(functionName);
    }

    
Formats a message with the given parameters.
Params:
params – a Map of named parameters (Contents: <String, Object>)
Returns:
the formatted message/**
     * Formats a message with the given parameters.
     * @param params a Map of named parameters (Contents: &lt;String, Object&gt;)
     * @return the formatted message
     */
    public String format(Map<String, Object> params) {
        StringBuffer sb = new StringBuffer();
        format(params, sb);
        return sb.toString();
    }

    
Formats a message with the given parameters.
Params:
params – a Map of named parameters (Contents: <String, Object>)
target – the target StringBuffer to write the formatted message to/**
     * Formats a message with the given parameters.
     * @param params a Map of named parameters (Contents: &lt;String, Object&gt;)
     * @param target the target StringBuffer to write the formatted message to
     */
    public void format(Map<String, Object> params, StringBuffer target) {
        rootPart.write(target, params);
    }

    
Represents a message template part. This interface is implemented by various variants of
the single curly braces pattern ({field}, {field,if,yes,no} etc.).
/**
     * Represents a message template part. This interface is implemented by various variants of
     * the single curly braces pattern ({field}, {field,if,yes,no} etc.).
     */
    public interface Part {

        
Writes the formatted part to a string buffer.
Params:
sb – the target string buffer
params – the parameters to work with/**
         * Writes the formatted part to a string buffer.
         * @param sb the target string buffer
         * @param params the parameters to work with
         */
        void write(StringBuffer sb, Map<String, Object> params);

        
Indicates whether there is any content that is generated by this message part.
Params:
params – the parameters to work with
Returns:
true if the part has content/**
         * Indicates whether there is any content that is generated by this message part.
         * @param params the parameters to work with
         * @return true if the part has content
         */
        boolean isGenerated(Map<String, Object> params);
    }

    
Implementations of this interface parse a field part and return message parts.
/**
     * Implementations of this interface parse a field part and return message parts.
     */
    public interface PartFactory {

        
Creates a new part by parsing the values parameter to configure the part.
Params:
fieldName – the field name
values – the unparsed parameter values
Returns:
the new message part/**
         * Creates a new part by parsing the values parameter to configure the part.
         * @param fieldName the field name
         * @param values the unparsed parameter values
         * @return the new message part
         */
        Part newPart(String fieldName, String values);

        
Returns the name of the message part format.
Returns:
the name of the message part format/**
         * Returns the name of the message part format.
         * @return the name of the message part format
         */
        String getFormat();
    }

    
Implementations of this interface format certain objects to strings.
/**
     * Implementations of this interface format certain objects to strings.
     */
    public interface ObjectFormatter {

        
Formats an object to a string and writes the result to a string buffer.
Params:
sb – the target string buffer
obj – the object to be formatted/**
         * Formats an object to a string and writes the result to a string buffer.
         * @param sb the target string buffer
         * @param obj the object to be formatted
         */
        void format(StringBuffer sb, Object obj);

        
Indicates whether a given object is supported.
Params:
obj – the object
Returns:
true if the object is supported by the formatter/**
         * Indicates whether a given object is supported.
         * @param obj the object
         * @return true if the object is supported by the formatter
         */
        boolean supportsObject(Object obj);
    }

    
Implementations of this interface do some computation based on the message parameters
given to it. Note: at the moment, this has to be done in a local-independent way since
there is no locale information.
/**
     * Implementations of this interface do some computation based on the message parameters
     * given to it. Note: at the moment, this has to be done in a local-independent way since
     * there is no locale information.
     */
    public interface Function {

        
Executes the function.
Params:
params – the message parameters
Returns:
the function result/**
         * Executes the function.
         * @param params the message parameters
         * @return the function result
         */
        Object evaluate(Map<String, Object> params);

        
Returns the name of the function.
Returns:
the name of the function/**
         * Returns the name of the function.
         * @return the name of the function
         */
        Object getName();
    }

    private static class TextPart implements Part {

        private String text;

        public TextPart(String text) {
            this.text = text;
        }

        public void write(StringBuffer sb, Map<String, Object> params) {
            sb.append(text);
        }

        public boolean isGenerated(Map<String, Object> params) {
            return true;
        }

        
{@inheritDoc} /** {@inheritDoc} */
        public String toString() {
            return this.text;
        }
    }

    private static class SimpleFieldPart implements Part {

        private String fieldName;

        public SimpleFieldPart(String fieldName) {
            this.fieldName = fieldName;
        }

        public void write(StringBuffer sb, Map<String, Object> params) {
            if (!params.containsKey(fieldName)) {
                throw new IllegalArgumentException(
                        "Message pattern contains unsupported field name: " + fieldName);
            }
            Object obj = params.get(fieldName);
            formatObject(obj, sb);
        }

        public boolean isGenerated(Map<String, Object> params) {
            Object obj = params.get(fieldName);
            return obj != null;
        }

        
{@inheritDoc} /** {@inheritDoc} */
        public String toString() {
            return "{" + this.fieldName + "}";
        }
    }

    
Formats an object to a string and writes the result to a string buffer. This method
usually uses the object's toString() method unless there is an ObjectFormatter that supports the object. ObjectFormatters are registered through the service provider mechanism defined by the JAR specification. 
Params:
obj – the object to be formatted
target – the target string buffer/**
     * Formats an object to a string and writes the result to a string buffer. This method
     * usually uses the object's <code>toString()</code> method unless there is an
     * {@link ObjectFormatter} that supports the object. {@link ObjectFormatter}s are registered
     * through the service provider mechanism defined by the JAR specification.
     * @param obj the object to be formatted
     * @param target the target string buffer
     */
    public static void formatObject(Object obj, StringBuffer target) {
        if (obj instanceof String) {
            target.append(obj);
        } else {
            boolean handled = false;
            for (ObjectFormatter formatter : OBJECT_FORMATTERS) {
                if (formatter.supportsObject(obj)) {
                    formatter.format(target, obj);
                    handled = true;
                    break;
                }
            }
            if (!handled) {
                target.append(String.valueOf(obj));
            }
        }
    }

    private static class FunctionPart implements Part {

        private Function function;

        public FunctionPart(String functionName) {
            this.function = getFunction(functionName);
            if (this.function == null) {
                throw new IllegalArgumentException("Unknown function: " + functionName);
            }
        }

        public void write(StringBuffer sb, Map<String, Object> params) {
            Object obj = this.function.evaluate(params);
            formatObject(obj, sb);
        }

        public boolean isGenerated(Map<String, Object> params) {
            Object obj = this.function.evaluate(params);
            return obj != null;
        }

        
{@inheritDoc} /** {@inheritDoc} */
        public String toString() {
            return "{#" + this.function.getName() + "}";
        }
    }

    private static class CompositePart implements Part {

        protected List<Part> parts = new java.util.ArrayList<Part>();
        private boolean conditional;
        private boolean hasSections;

        public CompositePart(boolean conditional) {
            this.conditional = conditional;
        }

        private CompositePart(List<Part> parts) {
            this.parts.addAll(parts);
            this.conditional = true;
        }

        public void addChild(Part part) {
            if (part == null) {
                throw new NullPointerException("part must not be null");
            }
            if (hasSections) {
                CompositePart composite = (CompositePart) this.parts.get(this.parts.size() - 1);
                composite.addChild(part);
            } else {
                this.parts.add(part);
            }
        }

        public void newSection() {
            if (!hasSections) {
                List<Part> p = this.parts;
                //Dropping into a different mode...
                this.parts = new java.util.ArrayList<Part>();
                this.parts.add(new CompositePart(p));
                hasSections = true;
            }
            this.parts.add(new CompositePart(true));
        }

        public void write(StringBuffer sb, Map<String, Object> params) {
            if (hasSections) {
                for (Part part : this.parts) {
                    if (part.isGenerated(params)) {
                        part.write(sb, params);
                        break;
                    }
                }
            } else {
                if (isGenerated(params)) {
                    for (Part part : this.parts) {
                        part.write(sb, params);
                    }
                }
            }
        }

        public boolean isGenerated(Map<String, Object> params) {
            if (hasSections) {
                for (Part part : this.parts) {
                    if (part.isGenerated(params)) {
                        return true;
                    }
                }
                return false;
            } else {
                if (conditional) {
                    for (Part part : this.parts) {
                        if (!part.isGenerated(params)) {
                            return false;
                        }
                    }
                }
                return true;
            }
        }

        
{@inheritDoc} /** {@inheritDoc} */
        public String toString() {
            return this.parts.toString();
        }
    }


    static String unescapeComma(String string) {
        return string.replaceAll("\\\\,", ",");
    }
}