/*
 * Copyright 2002-2023 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 org.springframework.util.unit;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import java.io.Serializable;
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>
 * <table border="1">
 * <tr><th>Term</th><th>Data Size</th><th>Size in Bytes</th></tr>
 * <tr><td>byte</td><td>1B</td><td>1</td></tr>
 * <tr><td>kilobyte</td><td>1KB</td><td>1,024</td></tr>
 * <tr><td>megabyte</td><td>1MB</td><td>1,048,576</td></tr>
 * <tr><td>gigabyte</td><td>1GB</td><td>1,073,741,824</td></tr>
 * <tr><td>terabyte</td><td>1TB</td><td>1,099,511,627,776</td></tr>
 * </table>
 *
 * @author Stephane Nicoll
 * @author Sam Brannen
 * @since 5.1
 * @see DataUnit
 */

public final class DataSize implements Comparable<DataSize>, Serializable {

    /**
     * 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(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 {@code DataSize}
     */
    public static DataSize ofBytes(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 {@code DataSize}
     */
    public static DataSize ofKilobytes(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 {@code DataSize}
     */
    public static DataSize ofMegabytes(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 {@code DataSize}
     */
    public static DataSize ofGigabytes(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 {@code DataSize}
     */
    public static DataSize ofTerabytes(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 {@code DataSize}
     */
    public static DataSize of(long amount, @NonNull DataUnit unit) {
        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 {@code DataSize}
     * @see #parse(CharSequence, DataUnit)
     */
    public static DataSize parse(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>If neither a unit nor a default {@code DataUnit} is specified,
     * {@link DataUnit#BYTES} will be inferred.
     * <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})
     * "20"   -- parses as "20 bytes" (if the {@code defaultUnit} is {@code null})
     * </pre>
     * @param text the text to parse
     * @param defaultUnit the default {@code DataUnit} to use
     * @return the parsed {@code DataSize}
     */
    public static DataSize parse(@NonNull CharSequence text, @Nullable DataUnit defaultUnit) {
        try {
            CharSequence trimmedText = text.toString().trim();
            Matcher matcher = DataSizeUtils.PATTERN.matcher(trimmedText);
            if (!matcher.matches())
                throw new IllegalStateException("'" + text + "' does not match data size pattern");
            DataUnit unit = DataSizeUtils.determineDataUnit(matcher.group(2), defaultUnit);
            final String formattedStr = matcher.group(1).replace(',','.');
            final float value = Float.parseFloat(formattedStr);
            final long amount = (long)(unit.size().toBytes() * value);
            return DataSize.ofBytes(amount);
        }
        catch (Exception ex) {
            throw new IllegalArgumentException("'" + text + "' is not a valid data size", ex);
        }
    }

    /**
     * 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(DataSize other) {
        return Long.compare(this.bytes, other.bytes);
    }

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

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

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


    /**
     * Static nested class to support lazy loading of the {@link #PATTERN}
     * @since 5.3.21
     */
    private static class DataSizeUtils {

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

        private static DataUnit determineDataUnit(String suffix, @Nullable DataUnit defaultUnit) {
            DataUnit defaultUnitToUse = (defaultUnit != null ? defaultUnit : DataUnit.BYTES);
            return ((suffix != null && !suffix.isEmpty()) ? DataUnit.fromSuffix(suffix.toUpperCase()) : defaultUnitToUse);
        }

    }

}