/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * See LICENSE.txt included in this distribution for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at LICENSE.txt.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved.
 */

package org.opensolaris.opengrok.web;

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.opensolaris.opengrok.logger.LoggerFactory;

/**
 * An Extremely Fast Tagged Attribute Read-only File System
 * Created on October 12, 2005
 *
 * A Eftar File has the following format
 * FILE --> Record  ( Record | tagString ) *
 * Record --> 64bit:Hash 16bit:childrenOffset  16bit:(numberChildren|lenthOfTag) 16bit:tagOffset
 *
 * It is a tree of tagged names,
 * doing binary search in sorted list of children
 *
 * @author Chandan
 */
public class EftarFile {

    private static final Logger LOGGER = LoggerFactory.getLogger(EftarFile.class);

    public static final int RECORD_LENGTH = 14;
    private long offset;

    class Node {

        public long hash;
        public String tag;
        public Map<Long, Node> children;
        public long tagOffset;
        public long childOffset;
        public long myOffset;

        public Node(long hash, String tag) {
            this.hash = hash;
            this.tag = tag;
            children = new TreeMap<>();
        }

        public Node put(long hash, String desc) {
            if (children.get(hash) == null) {
                children.put(hash, new Node(hash, desc));
            }
            return children.get(hash);
        }

        public Node get(long hash) {
            return children.get(hash);
        }
    }

    class FNode {

        public long offset;
        public long hash;
        public int childOffset;
        public int numChildren;
        public int tagOffset;

        public FNode(RandomAccessFile f) throws Throwable {
            offset = f.getFilePointer();
            hash = f.readLong();
            childOffset = f.readUnsignedShort();
            numChildren = f.readUnsignedShort();
            tagOffset = f.readUnsignedShort();
        }

        public FNode(long hash, long offset, int childOffset, int num, int tagOffset) {
            this.hash = hash;
            this.offset = offset;
            this.childOffset = childOffset;
            this.numChildren = num;
            this.tagOffset = tagOffset;
        }

        public FNode get(long hash, RandomAccessFile f) throws Throwable {
            if (childOffset == 0) {
                return null;
            }
            return sbinSearch(offset + childOffset, numChildren, hash, f);
        }

        private FNode sbinSearch(long start, int len, long hash, RandomAccessFile f) throws Throwable {
            int b = 0;
            int e = len;
            while (b <= e) {
                int m = (b + e) / 2;
                f.seek(start + m * RECORD_LENGTH);
                long mhash = f.readLong();
                if (hash > mhash) {
                    b = m + 1;
                } else if (hash < mhash) {
                    e = m - 1;
                } else {
                    return new FNode(mhash, f.getFilePointer() - 8l, f.readUnsignedShort(), f.readUnsignedShort(), f.readUnsignedShort());
                }
            }
            return null;
        }
    }

    public static long myHash(String name) {
        if (name == null || name.length() == 0) {
            return 0;
        }
        long hash = 2861;
        int n = name.length();
        if (n > 100) {
            n = 100;
        }
        for (int i = 0; i < n; i++) {
            hash = (hash * 641 + name.charAt(i) * 2969 + hash << 6) % 9322397;
        }
        return hash;
    }

    private void write(Node n, DataOutputStream out) throws IOException {
        if (n.tag != null) {
            out.write(n.tag.getBytes());
            offset += n.tag.length();
        }
        for (Node childnode : n.children.values()) {
            out.writeLong(childnode.hash);
            if (childnode.children.size() > 0) {
                out.writeShort((short) (childnode.childOffset - offset));
                out.writeShort((short) childnode.children.size());
            } else {
                out.writeShort(0);
                if (childnode.tag == null) {
                    out.writeShort((short) 0);
                } else {
                    out.writeShort((short) childnode.tag.length());
                }
            }
            if (childnode.tag == null) {
                out.writeShort(0);
            } else {
                out.writeShort((short) (childnode.tagOffset - offset));
            }
            offset += RECORD_LENGTH;
        }
        for (Node childnode : n.children.values()) {
            write(childnode, out);
        }
    }

    private void traverse(Node n) {
        if (n.tag == null) {
            n.tagOffset = 0;
        } else {
            n.tagOffset = offset;
            offset += n.tag.length();
        }
        if (n.children.size() > 0) {
            n.childOffset = offset;
            offset += (RECORD_LENGTH * n.children.size());
        } else {
            n.childOffset = 0;
        }
        for (Node childnode : n.children.values()) {
            traverse(childnode);
        }
    }
    private Node root;

    public void readInput(String tagsPath) throws IOException {
        try (BufferedReader r = new BufferedReader(new FileReader(tagsPath))) {
            readInput(r);
        }
    }

    private void readInput(BufferedReader r) throws IOException {
        if (root == null) {
            root = new Node(1, null);
        }
        String line;
        while ((line = r.readLine()) != null) {
            int tab = line.indexOf('\t');
            if (tab > 0) {
                String path = line.substring(0, tab);
                String desc = line.substring(tab + 1);
                StringTokenizer toks = new StringTokenizer(path, "\\/");
                Node n = root;
                while (toks.hasMoreTokens()) {
                    n = n.put(myHash(toks.nextToken()), null);
                }
                n.tag = desc;
            }
        }
    }

    public void write(String outPath) throws FileNotFoundException, IOException {
        offset = RECORD_LENGTH;
        traverse(root);
        try (DataOutputStream out = new DataOutputStream(
                new BufferedOutputStream(new FileOutputStream(outPath)))) {
            out.writeLong(0x5e33);
            out.writeShort(RECORD_LENGTH);
            out.writeShort(root.children.size());
            out.writeShort(0);
            offset = RECORD_LENGTH;
            write(root, out);
        }
    }

    public void create(String[] args) throws IOException, FileNotFoundException {
        for (int i = 0; i < args.length - 1; i++) {
            readInput(args[i]);
        }
        write(args[args.length - 1]);
    }

    /**
     * Main method is used to generate eftar file from the path description
     * file in the run scripts.
     *
     * @param args Input files and output file
     */
    @SuppressWarnings("PMD.SystemPrintln")
    public static void main(String[] args) {
        if (args.length < 2) {
            System.err.println("Usage inputFile [inputFile ...] outputFile");
            System.exit(1);
        }

        try {
            EftarFile ef = new EftarFile();
            ef.create(args);
        } catch (IOException e) {
            LOGGER.log(Level.WARNING, "EftarFile error", e);
        }
    }

}