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package net.dongliu.commons.lang;

/**
 * string utils methods
 *
 * @author Dong Liu
 */
public class Strings {

    /**
     * get sub string by begin(included) and end(not included) index.
     * begin and end can be negative, will be eval as str.length() + begin/end.
     *      *     sub("test", 1, 2) returns "e"
     *     sub("test", 1, -1) returns "es"
     *     sub("test", -2, -1) returns "s"
     *     sub("test", 4, 2) returns ""
     *     sub("test", -10, 2) returns "te"
     *     sub(null, -2, -1) returns null
     * 
     *
     * @param str can be null. when str is null, always return null
     * @return subString
     */
    public static String sub(String str, int begin, int end) {
        if (str == null) {
            return null;
        }
        int len = str.length();
        if (begin < 0) {
            begin += len;
        }
        if (end < 0) {
            end += len;
        }
        begin = Math.max(begin, 0);
        begin = Math.min(begin, len);
        end = Math.max(begin, end);
        end = Math.min(end, len);
        return str.substring(begin, end);
    }

    /**
     * get sub string by begin(included) index, till the end of string.
     * begin can be negative, will be eval as str.length() + begin.
     *      *     sub("test", 1) returns "est"
     *     sub("test", -2) returns "st"
     *     sub(null, -2) returns null
     * 
     *
     * @param str can be null. when str is null, always return null
     * @return subString
     */
    public static String sub(String str, int begin) {
        return sub(str, begin, str.length());
    }

    /**
     * get sub-string between begin and end.
     *
     * @param str   if null, return null
     * @param begin the begin str, cannot be null
     * @param end   the end str, cannot be null
     * @return str between begin and end. if not exists, return null
     */
    public static String between(String str, String begin, String end) {
        if (str == null) {
            return null;
        }

        int idx = str.indexOf(begin);
        if (idx < 0) {
            return null;
        }
        idx += begin.length();
        int eidx = str.indexOf(end, idx);
        if (eidx < 0) {
            return null;
        }
        return str.substring(idx, eidx);
    }

    /**
     * format string
     * {@code
     *     Strings.format("{}, {}", 1, "test") --> "1, test"
     *     Strings.format("{}, {}", 1) --> "1, {}"
     *     Strings.format("{}, {}", null, "test") --> "null, test"
     * }
     * 
     *
     * @param format if is null, return null
     */
    public static String format(String format, Object... params) {
        if (format == null) {
            return null;
        }
        if (format.isEmpty()) {
            return "";
        }

        StringBuilder sb = new StringBuilder(format.length());
        int count = 0;
        int state = 0;
        for (int idx = 0; idx < format.length(); idx++) {
            char c = format.charAt(idx);
            switch (c) {
                case '{':
                    if (state == 0) {
                        state = 1;
                    } else {
                        sb.append('{');
                    }
                    break;
                case '}':
                    if (state == 1) {
                        if (count < params.length) {
                            Object param = params[count++];
                            sb.append(param);
                            state = 0;
                        } else {
                            sb.append("{}");
                            state = 0;
                        }
                    } else {
                        sb.append('}');
                    }
                    break;
                default:
                    sb.append(c);
            }
        }
        return sb.toString();
    }
}