/*
 * Copyright (C) 2007 Google Inc.
 *
 * 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
 *
 * http://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 ca.odell.glazedlists.impl;

/**
 * Simple static methods to be called at the start of your own methods to verify
 * correct arguments and state. This allows constructs such as
 * <pre>
 *     if (count <= 0) {
 *       throw new IllegalArgumentException("must be positive: " + count);
 *     }</pre>
 * <p/>
 * to be replaced with the more compact
 * <pre>
 *     checkArgument(count > 0, "must be positive: %s", count);</pre>
 * <p/>
 *
 * <p>This class contains modifications by Jesse Wilson to include it in the
 * Glazed Lists project. The original, unmodified version of this class can be
 * found <a href="http://google-collections.googlecode.com/svn/trunk/src/com/google/common/base/Preconditions.java">here</a>.
 *
 * @author Kevin Bourrillion
 * @author <a href="mailto:jesse@swank.ca">Jesse Wilson</a>
 */
public final class Preconditions {
    private Preconditions() {
    }

    /**
     * Ensures the truth of an expression involving one or more parameters to the
     * calling method.
     */
    public static void checkArgument(boolean expression) {
        if (!expression) {
            throw new IllegalArgumentException();
        }
    }

    /**
     * Ensures the truth of an expression involving one or more parameters to the
     * calling method.
     */
    public static void checkArgument(boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalArgumentException(String.valueOf(errorMessage));
        }
    }

    /**
     * Ensures the truth of an expression involving one or more parameters to the
     * calling method.
     */
    public static void checkArgument(boolean expression, String errorMessageTemplate, Object... errorMessageArgs) {
        if (!expression) {
            throw new IllegalArgumentException(format(errorMessageTemplate, errorMessageArgs));
        }
    }

    /**
     * Ensures the truth of an expression involving the state of the calling
     * instance, but not involving any parameters to the calling method.
     */
    public static void checkState(boolean expression) {
        if (!expression) {
            throw new IllegalStateException();
        }
    }

    /**
     * Ensures the truth of an expression involving the state of the calling
     * instance, but not involving any parameters to the calling method.
     */
    public static void checkState(boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalStateException(String.valueOf(errorMessage));
        }
    }

    /**
     * Ensures the truth of an expression involving the state of the calling
     * instance, but not involving any parameters to the calling method.
     */
    public static void checkState(boolean expression, String errorMessageTemplate, Object... errorMessageArgs) {
        if (!expression) {
            throw new IllegalStateException(format(errorMessageTemplate, errorMessageArgs));
        }
    }

    /**
     * Ensures that an object reference passed as a parameter to the calling
     * method is not null.
     */
    public static <T> T checkNotNull(T reference) {
        if (reference == null) {
            throw new NullPointerException();
        }
        return reference;
    }

    /**
     * Ensures that an object reference passed as a parameter to the calling
     * method is not null.
     */
    public static <T> T checkNotNull(T reference, Object errorMessage) {
        if (reference == null) {
            throw new NullPointerException(String.valueOf(errorMessage));
        }
        return reference;
    }

    /**
     * Ensures that an object reference passed as a parameter to the calling
     * method is not null.
     */
    public static <T> T checkNotNull(T reference, String errorMessageTemplate, Object... errorMessageArgs) {
        if (reference == null) {
            // If either of these parameters is null, the right thing happens anyway
            throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
        }
        return reference;
    }

    /**
     * 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.
     */
    // VisibleForTesting
    static String format(String template, Object... args) {
        // 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();
    }
}