/*
 * Copyright  2000-2004 The Apache Software Foundation
 *
 *  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 org.apache.tools.ant.taskdefs;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;
import java.util.Enumeration;
import java.util.Properties;
import java.util.Vector;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.DirectoryScanner;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.util.FileUtils;
import org.apache.tools.ant.util.StringUtils;

/**
 * Replaces all occurrences of one or more string tokens with given
 * values in the indicated files. Each value can be either a string
 * or the value of a property available in a designated property file.
 * If you want to replace a text that crosses line boundaries, you
 * must use a nested <code><replacetoken></code> element.
 *
 * @since Ant 1.1
 *
 * @ant.task category="filesystem"
 */
public class Replace extends MatchingTask {

    private File src = null;
    private NestedString token = null;
    private NestedString value = new NestedString();

    private File propertyFile = null;
    private File replaceFilterFile = null;
    private Properties properties = null;
    private Vector replacefilters = new Vector();

    private File dir = null;

    private int fileCount;
    private int replaceCount;
    private boolean summary = false;

    /** The encoding used to read and write files - if null, uses default */
    private String encoding = null;

    private FileUtils fileUtils = FileUtils.newFileUtils();

    /**
     * an inline string to use as the replacement text
     */
    public class NestedString {

        private StringBuffer buf = new StringBuffer();

        /**
         * the text of the element
         *
         * @param val the string to add
         */
        public void addText(String val) {
            buf.append(val);
        }

        /**
         * @return the text
         */
        public String getText() {
            return buf.substring(0);
        }
    }

    /**
     * A filter to apply.
     */
    public class Replacefilter {
        private String token;
        private String value;
        private String property;

        /**
         * validate the filter's configuration
         * @throws BuildException if any part is invalid
         */
        public void validate() throws BuildException {
            //Validate mandatory attributes
            if (token == null) {
                String message = "token is a mandatory attribute "
                    + "of replacefilter.";
                throw new BuildException(message);
            }

            if ("".equals(token)) {
                String message = "The token attribute must not be an empty "
                    + "string.";
                throw new BuildException(message);
            }

            //value and property are mutually exclusive attributes
            if ((value != null) && (property != null)) {
                String message = "Either value or property "
                    + "can be specified, but a replacefilter "
                    + "element cannot have both.";
                throw new BuildException(message);
            }

            if ((property != null)) {
                //the property attribute must have access to a property file
                if (propertyFile == null) {
                    String message = "The replacefilter's property attribute "
                        + "can only be used with the replacetask's "
                        + "propertyFile attribute.";
                    throw new BuildException(message);
                }

                //Make sure property exists in property file
                if (properties == null
                    || properties.getProperty(property) == null) {
                    String message = "property \"" + property
                        + "\" was not found in " + propertyFile.getPath();
                    throw new BuildException(message);
                }
            }
        }

        /**
         * Get the replacement value for this filter token.
         * @return the replacement value
         */
        public String getReplaceValue() {
            if (property != null) {
                return properties.getProperty(property);
            } else if (value != null) {
                return value;
            } else if (Replace.this.value != null) {
                return Replace.this.value.getText();
            } else {
                //Default is empty string
                return new String("");
            }
        }

        /**
         * Set the token to replace
         * @param token token
         */
        public void setToken(String token) {
            this.token = token;
        }

        /**
         * Get the string to search for
         * @return current token
         */
        public String getToken() {
            return token;
        }

        /**
         * The replacement string; required if <code>property<code>
         * is not set
         * @param value value to replace
         */
        public void setValue(String value) {
            this.value = value;
        }

        /**
         * Get replacements string
         * @return replacement or null
         */
        public String getValue() {
            return value;
        }

        /**
         * Set the name of the property whose value is to serve as
         * the replacement value; required if <code>value</code> is not set.
         * @param property propname
         */
        public void setProperty(String property) {
            this.property = property;
        }

        /**
         * Get the name of the property whose value is to serve as
         * the replacement value;
         * @return property or null
         */
        public String getProperty() {
            return property;
        }
    }

    /**
     * Do the execution.
     * @throws BuildException if we cant build
     */
    public void execute() throws BuildException {

        Vector savedFilters = (Vector) replacefilters.clone();
        Properties savedProperties =
            properties == null ? null : (Properties) properties.clone();

        try {
            if (replaceFilterFile != null) {
                Properties props = getProperties(replaceFilterFile);
                Enumeration e = props.keys();
                while (e.hasMoreElements()) {
                    String token =  e.nextElement().toString();
                    Replacefilter replaceFilter = createReplacefilter();
                    replaceFilter.setToken(token);
                    replaceFilter.setValue(props.getProperty(token));
                }
            }

            validateAttributes();

            if (propertyFile != null) {
                properties = getProperties(propertyFile);
            }

            validateReplacefilters();
            fileCount = 0;
            replaceCount = 0;

            if (src != null) {
                processFile(src);
            }

            if (dir != null) {
                DirectoryScanner ds = super.getDirectoryScanner(dir);
                String[] srcs = ds.getIncludedFiles();

                for (int i = 0; i < srcs.length; i++) {
                    File file = new File(dir, srcs[i]);
                    processFile(file);
                }
            }

            if (summary) {
                log("Replaced " + replaceCount + " occurrences in "
                    + fileCount + " files.", Project.MSG_INFO);
            }
        } finally {
            replacefilters = savedFilters;
            properties = savedProperties;
        } // end of finally

    }

    /**
     * Validate attributes provided for this task in .xml build file.
     *
     * @exception BuildException if any supplied attribute is invalid or any
     * mandatory attribute is missing
     */
    public void validateAttributes() throws BuildException {
        if (src == null && dir == null) {
            String message = "Either the file or the dir attribute "
                + "must be specified";
            throw new BuildException(message, getLocation());
        }
        if (propertyFile != null && !propertyFile.exists()) {
            String message = "Property file " + propertyFile.getPath()
                + " does not exist.";
            throw new BuildException(message, getLocation());
        }
        if (token == null && replacefilters.size() == 0) {
            String message = "Either token or a nested replacefilter "
                + "must be specified";
            throw new BuildException(message, getLocation());
        }
        if (token != null && "".equals(token.getText())) {
            String message = "The token attribute must not be an empty string.";
            throw new BuildException(message, getLocation());
        }
    }

    /**
     * Validate nested elements.
     *
     * @exception BuildException if any supplied attribute is invalid or any
     * mandatory attribute is missing
     */
    public void validateReplacefilters()
            throws BuildException {
        for (int i = 0; i < replacefilters.size(); i++) {
            Replacefilter element =
                (Replacefilter) replacefilters.elementAt(i);
            element.validate();
        }
    }

    /**
     * helper method to load a properties file and throw a build exception
     * if it cannot be loaded
     * @param propertyFile the file to load the properties from
     * @return loaded properties collection
     * @throws BuildException if the file could not be found or read
     */
    public Properties getProperties(File propertyFile) throws BuildException {
        Properties properties = new Properties();

        try {
            properties.load(new FileInputStream(propertyFile));
        } catch (FileNotFoundException e) {
            String message = "Property file (" + propertyFile.getPath()
                + ") not found.";
            throw new BuildException(message);
        } catch (IOException e) {
            String message = "Property file (" + propertyFile.getPath()
                + ") cannot be loaded.";
            throw new BuildException(message);
        }

        return properties;
    }

    /**
     * Perform the replacement on the given file.
     *
     * The replacement is performed on a temporary file which then
     * replaces the original file.
     *
     * @param src the source file
     */
    private void processFile(File src) throws BuildException {
        if (!src.exists()) {
            throw new BuildException("Replace: source file " + src.getPath()
                                     + " doesn't exist", getLocation());
        }

        File temp = fileUtils.createTempFile("rep", ".tmp",
                                             fileUtils.getParentFile(src));
        temp.deleteOnExit();

        Reader reader = null;
        Writer writer = null;
        try {
            reader = encoding == null ? new FileReader(src)
                : new InputStreamReader(new FileInputStream(src), encoding);
            writer = encoding == null ? new FileWriter(temp)
                : new OutputStreamWriter(new FileOutputStream(temp), encoding);

            BufferedReader br = new BufferedReader(reader);
            BufferedWriter bw = new BufferedWriter(writer);

            String buf = fileUtils.readFully(br);
            if (buf == null) {
                buf = "";
            }

            //Preserve original string (buf) so we can compare the result
            String newString = new String(buf);

            if (token != null) {
                // line separators in values and tokens are "\n"
                // in order to compare with the file contents, replace them
                // as needed
                String val = stringReplace(value.getText(), "\r\n",
                                           "\n", false);
                val = stringReplace(val, "\n",
                                           StringUtils.LINE_SEP, false);
                String tok = stringReplace(token.getText(), "\r\n",
                                            "\n", false);
                tok = stringReplace(tok, "\n",
                                           StringUtils.LINE_SEP, false);

                // for each found token, replace with value
                log("Replacing in " + src.getPath() + ": " + token.getText()
                    + " --> " + value.getText(), Project.MSG_VERBOSE);
                newString = stringReplace(newString, tok, val, true);
            }

            if (replacefilters.size() > 0) {
                newString = processReplacefilters(newString, src.getPath());
            }

            boolean changes = !newString.equals(buf);
            if (changes) {
                bw.write(newString, 0, newString.length());
                bw.flush();
            }

            // cleanup
            bw.close();
            writer = null;
            br.close();
            reader = null;

            // If there were changes, move the new one to the old one;
            // otherwise, delete the new one
            if (changes) {
                ++fileCount;
                fileUtils.rename(temp, src);
                temp = null;
            }
        } catch (IOException ioe) {
            throw new BuildException("IOException in " + src + " - "
                                    + ioe.getClass().getName() + ":"
                                    + ioe.getMessage(), ioe, getLocation());
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    // ignore
                }
            }
            if (writer != null) {
                try {
                    writer.close();
                } catch (IOException e) {
                    // ignore
                }
            }
            if (temp != null) {
                temp.delete();
            }
        }

    }

    /**
     * apply all replace filters to a buffer
     * @param buffer string to filter
     * @param filename filename for logging purposes
     * @return filtered string
     */
    private String processReplacefilters(String buffer, String filename) {
        String newString = new String(buffer);

        for (int i = 0; i < replacefilters.size(); i++) {
            Replacefilter filter = (Replacefilter) replacefilters.elementAt(i);

            //for each found token, replace with value
            log("Replacing in " + filename + ": " + filter.getToken()
                + " --> " + filter.getReplaceValue(), Project.MSG_VERBOSE);
            newString = stringReplace(newString, filter.getToken(),
                                      filter.getReplaceValue(), true);
        }

        return newString;
    }


    /**
     * Set the source file; required unless <code>dir</code> is set.
     * @param file source file
     */
    public void setFile(File file) {
        this.src = file;
    }

    /**
     * Indicates whether a summary of the replace operation should be
     * produced, detailing how many token occurrences and files were
     * processed; optional, default=false
     *
     * @param summary true if you would like a summary logged of the
     * replace operation
     */
    public void setSummary(boolean summary) {
        this.summary = summary;
    }


    /**
     * Sets the name of a property file containing filters; optional.
     * Each property will be treated as a
     * replacefilter where token is the name of the property and value
     * is the value of the property.
     * @param filename file to load
     */
    public void setReplaceFilterFile(File filename) {
        replaceFilterFile = filename;
    }

    /**
     * The base directory to use when replacing a token in multiple files;
     * required if <code>file</code> is not defined.
     * @param dir base dir
     */
    public void setDir(File dir) {
        this.dir = dir;
    }

    /**
     * Set the string token to replace;
     * required unless a nested
     * <code>replacetoken</code> element or the <code>replacefilterfile</code>
     * attribute is used.
     * @param token token string
     */
    public void setToken(String token) {
        createReplaceToken().addText(token);
    }

    /**
     * Set the string value to use as token replacement;
     * optional, default is the empty string ""
     * @param value replacement value
     */
    public void setValue(String value) {
        createReplaceValue().addText(value);
    }

    /**
     * Set the file encoding to use on the files read and written by the task;
     * optional, defaults to default JVM encoding
     *
     * @param encoding the encoding to use on the files
     */
    public void setEncoding(String encoding) {
        this.encoding = encoding;
    }

    /**
     * the token to filter as the text of a nested element
     * @return nested token to configure
     */
    public NestedString createReplaceToken() {
        if (token == null) {
            token = new NestedString();
        }
        return token;
    }

    /**
     * the string to replace the token as the text of a nested element
     * @return replacement value to configure
     */
    public NestedString createReplaceValue() {
        return value;
    }

    /**
     * The name of a property file from which properties specified using
     * nested <code><replacefilter></code> elements are drawn;
     * Required only if <i>property</i> attribute of
     * <code><replacefilter></code> is used.
     * @param filename file to load
     */
    public void setPropertyFile(File filename) {
        propertyFile = filename;
    }

    /**
     * Add a nested <replacefilter> element.
     * @return a nested ReplaceFilter object to be configured
     */
    public Replacefilter createReplacefilter() {
        Replacefilter filter = new Replacefilter();
        replacefilters.addElement(filter);
        return filter;
    }

    /**
     * Replace occurrences of str1 in string str with str2
     */
    private String stringReplace(String str, String str1, String str2,
                                 boolean countReplaces) {
        StringBuffer ret = new StringBuffer();
        int start = 0;
        int found = str.indexOf(str1);
        while (found >= 0) {
            // write everything up to the found str1
            if (found > start) {
                ret.append(str.substring(start, found));
            }

            // write the replacement str2
            if (str2 != null) {
                ret.append(str2);
            }

            // search again
            start = found + str1.length();
            found = str.indexOf(str1, start);
            if (countReplaces) {
                ++replaceCount;
            }
        }

        // write the remaining characters
        if (str.length() > start) {
            ret.append(str.substring(start, str.length()));
        }

        return ret.toString();
    }

}