/*
 * Copyright 2002-2019 the original author or authors.
 *
 * 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
 *
 *      https://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.paypal.heapdumptool.sanitizer;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.Validate;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A data size, such as '12MB'.
 *
 * <p>This class models data size in terms of bytes and is immutable and thread-safe.
 *
 * <p>The terms and units used in this class are based on
 * <a href="https://en.wikipedia.org/wiki/Binary_prefix">binary prefixes</a>
 * indicating multiplication by powers of 2. Consult the following table and
 * the Javadoc for {@link DataUnit} for details.
 * </p>
 * @author Stephane Nicoll
 * @author Sam Brannen
 * @since 5.1
 * @see DataUnit
 */
public final class DataSize implements Comparable<DataSize> {

    /**
     * The pattern for parsing.
     */
    private static final Pattern PATTERN = Pattern.compile("^([+\\-]?\\d+)([a-zA-Z]{0,2})$");

    /**
     * Bytes per Kilobyte.
     */
    private static final long BYTES_PER_KB = 1024;

    /**
     * Bytes per Megabyte.
     */
    private static final long BYTES_PER_MB = BYTES_PER_KB * 1024;

    /**
     * Bytes per Gigabyte.
     */
    private static final long BYTES_PER_GB = BYTES_PER_MB * 1024;

    /**
     * Bytes per Terabyte.
     */
    private static final long BYTES_PER_TB = BYTES_PER_GB * 1024;

    private final long bytes;

    private DataSize(final long bytes) {
        this.bytes = bytes;
    }

    /**
     * Obtain a {@link DataSize} representing the specified number of bytes.
     * @param bytes the number of bytes, positive or negative
     * @return a {@link DataSize}
     */
    public static DataSize ofBytes(final long bytes) {
        return new DataSize(bytes);
    }

    /**
     * Obtain a {@link DataSize} representing the specified number of kilobytes.
     * @param kilobytes the number of kilobytes, positive or negative
     * @return a {@link DataSize}
     */
    public static DataSize ofKilobytes(final long kilobytes) {
        return new DataSize(Math.multiplyExact(kilobytes, BYTES_PER_KB));
    }

    /**
     * Obtain a {@link DataSize} representing the specified number of megabytes.
     * @param megabytes the number of megabytes, positive or negative
     * @return a {@link DataSize}
     */
    public static DataSize ofMegabytes(final long megabytes) {
        return new DataSize(Math.multiplyExact(megabytes, BYTES_PER_MB));
    }

    /**
     * Obtain a {@link DataSize} representing the specified number of gigabytes.
     * @param gigabytes the number of gigabytes, positive or negative
     * @return a {@link DataSize}
     */
    public static DataSize ofGigabytes(final long gigabytes) {
        return new DataSize(Math.multiplyExact(gigabytes, BYTES_PER_GB));
    }

    /**
     * Obtain a {@link DataSize} representing the specified number of terabytes.
     * @param terabytes the number of terabytes, positive or negative
     * @return a {@link DataSize}
     */
    public static DataSize ofTerabytes(final long terabytes) {
        return new DataSize(Math.multiplyExact(terabytes, BYTES_PER_TB));
    }

    /**
     * Obtain a {@link DataSize} representing an amount in the specified {@link DataUnit}.
     * @param amount the amount of the size, measured in terms of the unit,
     * positive or negative
     * @return a corresponding {@link DataSize}
     */
    public static DataSize of(final long amount, final DataUnit unit) {
        Validate.notNull(unit, "Unit must not be null");
        return new DataSize(Math.multiplyExact(amount, unit.size().toBytes()));
    }

    /**
     * Obtain a {@link DataSize} from a text string such as {@code 12MB} using
     * {@link DataUnit#BYTES} if no unit is specified.
     * <p>
     * Examples:
     * <pre>
     * "12KB" -- parses as "12 kilobytes"
     * "5MB"  -- parses as "5 megabytes"
     * "20"   -- parses as "20 bytes"
     * </pre>
     * @param text the text to parse
     * @return the parsed {@link DataSize}
     * @see #parse(CharSequence, DataUnit)
     */
    public static DataSize parse(final CharSequence text) {
        return parse(text, null);
    }

    /**
     * Obtain a {@link DataSize} from a text string such as {@code 12MB} using
     * the specified default {@link DataUnit} if no unit is specified.
     * <p>
     * The string starts with a number followed optionally by a unit matching one of the
     * supported {@linkplain DataUnit suffixes}.
     * <p>
     * Examples:
     * <pre>
     * "12KB" -- parses as "12 kilobytes"
     * "5MB"  -- parses as "5 megabytes"
     * "20"   -- parses as "20 kilobytes" (where the {@code defaultUnit} is {@link DataUnit#KILOBYTES})
     * </pre>
     * @param text the text to parse
     * @return the parsed {@link DataSize}
     */
    public static DataSize parse(final CharSequence text, final DataUnit defaultUnit) {
        Validate.notNull(text, "Text must not be null");
        try {
            final Matcher matcher = PATTERN.matcher(text);
            Validate.isTrue(matcher.matches(), "Does not match data size pattern");
            final DataUnit unit = determineDataUnit(matcher.group(2), defaultUnit);
            final long amount = Long.parseLong(matcher.group(1));
            return DataSize.of(amount, unit);
        } catch (final Exception ex) {
            throw new IllegalArgumentException("'" + text + "' is not a valid data size", ex);
        }
    }

    private static DataUnit determineDataUnit(final String suffix, final DataUnit defaultUnit) {
        final DataUnit defaultUnitToUse = (defaultUnit != null ? defaultUnit : DataUnit.BYTES);
        return (StringUtils.isNotEmpty(suffix) ? DataUnit.fromSuffix(suffix) : defaultUnitToUse);
    }

    /**
     * Checks if this size is negative, excluding zero.
     * @return true if this size has a size less than zero bytes
     */
    public boolean isNegative() {
        return this.bytes < 0;
    }

    /**
     * Return the number of bytes in this instance.
     * @return the number of bytes
     */
    public long toBytes() {
        return this.bytes;
    }

    /**
     * Return the number of kilobytes in this instance.
     * @return the number of kilobytes
     */
    public long toKilobytes() {
        return this.bytes / BYTES_PER_KB;
    }

    /**
     * Return the number of megabytes in this instance.
     * @return the number of megabytes
     */
    public long toMegabytes() {
        return this.bytes / BYTES_PER_MB;
    }

    /**
     * Return the number of gigabytes in this instance.
     * @return the number of gigabytes
     */
    public long toGigabytes() {
        return this.bytes / BYTES_PER_GB;
    }

    /**
     * Return the number of terabytes in this instance.
     * @return the number of terabytes
     */
    public long toTerabytes() {
        return this.bytes / BYTES_PER_TB;
    }

    @Override
    public int compareTo(final DataSize other) {
        return Long.compare(this.bytes, other.bytes);
    }

    @Override
    public String toString() {
        return String.format("%dB", this.bytes);
    }

    @Override
    public boolean equals(final Object other) {
        if (this == other) {
            return true;
        }
        if (other == null || getClass() != other.getClass()) {
            return false;
        }
        final DataSize otherSize = (DataSize) other;
        return (this.bytes == otherSize.bytes);
    }

    @Override
    public int hashCode() {
        return Long.hashCode(this.bytes);
    }

}
