package com.alibaba.excel.util;

/**
 * String utils
 *
 * @author jipengfei
 */
public class StringUtils {
    private StringUtils() {}

    /**
     * A String for a space character.
     */
    public static final String SPACE = " ";

    /**
     * The empty String {@code ""}.
     */
    public static final String EMPTY = "";

    /**
     * <p>Checks if a CharSequence is empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isEmpty(null)      = true
     * StringUtils.isEmpty("")        = true
     * StringUtils.isEmpty(" ")       = false
     * StringUtils.isEmpty("bob")     = false
     * StringUtils.isEmpty("  bob  ") = false
     * </pre>
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer trims the CharSequence.
     * That functionality is available in isBlank().</p>
     *
     * @param cs the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is empty or null
     */
    public static boolean isEmpty(final CharSequence cs) {
        return cs == null || cs.length() == 0;
    }

    /**
     * <p>Checks if a CharSequence is empty (""), null or whitespace only.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.isBlank(null)      = true
     * StringUtils.isBlank("")        = true
     * StringUtils.isBlank(" ")       = true
     * StringUtils.isBlank("bob")     = false
     * StringUtils.isBlank("  bob  ") = false
     * </pre>
     *
     * @param cs the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is null, empty or whitespace only
     */
    public static boolean isBlank(final CharSequence cs) {
        int strLen;
        if (cs == null || (strLen = cs.length()) == 0) {
            return true;
        }
        for (int i = 0; i < strLen; i++) {
            if (!Character.isWhitespace(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>Checks if a CharSequence is not empty (""), not null and not whitespace only.</p>
     *
     * <p>Whitespace is defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.isNotBlank(null)      = false
     * StringUtils.isNotBlank("")        = false
     * StringUtils.isNotBlank(" ")       = false
     * StringUtils.isNotBlank("bob")     = true
     * StringUtils.isNotBlank("  bob  ") = true
     * </pre>
     *
     * @param cs the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is
     * not empty and not null and not whitespace only
     * @since 2.0
     * @since 3.0 Changed signature from isNotBlank(String) to isNotBlank(CharSequence)
     */
    public static boolean isNotBlank(final CharSequence cs) {
        return !isBlank(cs);
    }

    /**
     * <p>Compares two CharSequences, returning {@code true} if they represent
     * equal sequences of characters.</p>
     *
     * <p>{@code null}s are handled without exceptions. Two {@code null}
     * references are considered to be equal. The comparison is case sensitive.</p>
     *
     * <pre>
     * StringUtils.equals(null, null)   = true
     * StringUtils.equals(null, "abc")  = false
     * StringUtils.equals("abc", null)  = false
     * StringUtils.equals("abc", "abc") = true
     * StringUtils.equals("abc", "ABC") = false
     * </pre>
     *
     * @param cs1 the first CharSequence, may be {@code null}
     * @param cs2 the second CharSequence, may be {@code null}
     * @return {@code true} if the CharSequences are equal (case-sensitive), or both {@code null}
     * @see Object#equals(Object)
     * @since 3.0 Changed signature from equals(String, String) to equals(CharSequence, CharSequence)
     */
    public static boolean equals(final CharSequence cs1, final CharSequence cs2) {
        if (cs1 == cs2) {
            return true;
        }
        if (cs1 == null || cs2 == null) {
            return false;
        }
        if (cs1.length() != cs2.length()) {
            return false;
        }
        if (cs1 instanceof String && cs2 instanceof String) {
            return cs1.equals(cs2);
        }
        return regionMatches(cs1, false, 0, cs2, 0, cs1.length());
    }

    /**
     * Green implementation of regionMatches.
     *
     * @param cs         the {@code CharSequence} to be processed
     * @param ignoreCase whether or not to be case insensitive
     * @param thisStart  the index to start on the {@code cs} CharSequence
     * @param substring  the {@code CharSequence} to be looked for
     * @param start      the index to start on the {@code substring} CharSequence
     * @param length     character length of the region
     * @return whether the region matched
     */
    public static boolean regionMatches(final CharSequence cs, final boolean ignoreCase, final int thisStart,
        final CharSequence substring, final int start, final int length) {
        if (cs instanceof String && substring instanceof String) {
            return ((String)cs).regionMatches(ignoreCase, thisStart, (String)substring, start, length);
        }
        int index1 = thisStart;
        int index2 = start;
        int tmpLen = length;

        // Extract these first so we detect NPEs the same as the java.lang.String version
        final int srcLen = cs.length() - thisStart;
        final int otherLen = substring.length() - start;

        // Check for invalid parameters
        if (thisStart < 0 || start < 0 || length < 0) {
            return false;
        }

        // Check that the regions are long enough
        if (srcLen < length || otherLen < length) {
            return false;
        }

        while (tmpLen-- > 0) {
            final char c1 = cs.charAt(index1++);
            final char c2 = substring.charAt(index2++);

            if (c1 == c2) {
                continue;
            }

            if (!ignoreCase) {
                return false;
            }

            // The same check as in String.regionMatches():
            if (Character.toUpperCase(c1) != Character.toUpperCase(c2)
                && Character.toLowerCase(c1) != Character.toLowerCase(c2)) {
                return false;
            }
        }

        return true;
    }


    /**
     * <p>Checks if the CharSequence contains only Unicode digits.
     * A decimal point is not a Unicode digit and returns false.</p>
     *
     * <p>{@code null} will return {@code false}.
     * An empty CharSequence (length()=0) will return {@code false}.</p>
     *
     * <p>Note that the method does not allow for a leading sign, either positive or negative.
     * Also, if a String passes the numeric test, it may still generate a NumberFormatException
     * when parsed by Integer.parseInt or Long.parseLong, e.g. if the value is outside the range
     * for int or long respectively.</p>
     *
     * <pre>
     * StringUtils.isNumeric(null)   = false
     * StringUtils.isNumeric("")     = false
     * StringUtils.isNumeric("  ")   = false
     * StringUtils.isNumeric("123")  = true
     * StringUtils.isNumeric("\u0967\u0968\u0969")  = true
     * StringUtils.isNumeric("12 3") = false
     * StringUtils.isNumeric("ab2c") = false
     * StringUtils.isNumeric("12-3") = false
     * StringUtils.isNumeric("12.3") = false
     * StringUtils.isNumeric("-123") = false
     * StringUtils.isNumeric("+123") = false
     * </pre>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if only contains digits, and is non-null
     * @since 3.0 Changed signature from isNumeric(String) to isNumeric(CharSequence)
     * @since 3.0 Changed "" to return false and not true
     */
    public static boolean isNumeric(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isDigit(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }
}
