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package io.github.mike10004.containment.lifecycle;

import javax.annotation.Nullable;

class Preconditions {

    private Preconditions() {}

    /**
     * Substitutes each {@code %s} in {@code template} with an argument. These are matched by
     * position: the first {@code %s} gets {@code args[0]}, etc.  If there are more arguments than
     * placeholders, the unmatched arguments will be appended to the end of the formatted message in
     * square braces.
     *
     * @param template a non-null string containing 0 or more {@code %s} placeholders.
     * @param args the arguments to be substituted into the message template. Arguments are converted
     *     to strings using {@link String#valueOf(Object)}. Arguments can be null.
     */
    // Note that this is somewhat-improperly used from Verify.java as well.
    static String format(String template, @Nullable Object... args) {
        template = String.valueOf(template); // null -> "null"
        if (args == null) {
            return template;
        }
        // start substituting the arguments into the '%s' placeholders
        StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
        int templateStart = 0;
        int i = 0;
        while (i < args.length) {
            int placeholderStart = template.indexOf("%s", templateStart);
            if (placeholderStart == -1) {
                break;
            }
            builder.append(template.substring(templateStart, placeholderStart));
            builder.append(args[i++]);
            templateStart = placeholderStart + 2;
        }
        builder.append(template.substring(templateStart));

        // if we run out of placeholders, append the extra args in square braces
        if (i < args.length) {
            builder.append(" [");
            builder.append(args[i++]);
            while (i < args.length) {
                builder.append(", ");
                builder.append(args[i++]);
            }
            builder.append(']');
        }

        return builder.toString();
    }

}