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package com.sap.hcp.cf.log4j2.layout;

import static com.sap.hcp.cf.logging.common.PatternUtils.JSON_FIELD;

import com.sap.hcp.cf.logging.common.Defaults;
import com.sap.hcp.cf.logging.common.Fields;

/**
 * Defines the "built-in" layout pattern for our JSON encoder.
 *
 */
public final class LayoutPatterns {

    public enum PATTERN_KEY {
                             APPLICATION, EXCEPTION, REQUEST
    }

    /*
     * -- this is the common prefix to all variants. -- the final line will add
     * non-predefined context parameters from the MDC -- as this list may be
     * empty, we use "replace" to at a colon if it's not
     */
    private static final String COMMON_PREFIX_PATTERN = "{ " + JSON_FIELD(Fields.WRITTEN_AT,
                                                                          "%d{yyyy-MM-dd'T'HH:mm:ss.SSSX}{UTC}", true,
                                                                          true) + JSON_FIELD(Fields.WRITTEN_TS,
                                                                                             "%tstamp", false, false) +
                                                        "%replace{%ctxp}{(.+)}{,$1},";

    /*
     * -- all layout patterns end like this
     */
    private static final String COMMON_POSTFIX_PATTERN = "}%n";

    /*
     * -- for standard application log messages we always add these fields. --
     * note the last line where we make sure that the original message string --
     * is quoted and properly escaped and that "custom fields" are added
     */
    private static final String APP_PREFIX_PATTERN = JSON_FIELD(Fields.TYPE, Defaults.TYPE_LOG, true, true) +
                                                     JSON_FIELD(Fields.LOGGER, "%logger", true, true) + JSON_FIELD(
                                                                                                                   Fields.THREAD, "%thread", true, true) +
                                                     JSON_FIELD(Fields.LEVEL, "%p", true, true) + JSON_FIELD(
                                                                                                             Fields.CATEGORIES,
                                                                                                             "%categories",
                                                                                                             false,
                                                                                                             true) +
                                                     JSON_FIELD(Fields.MSG,
                                                                "%jsonmsg{escape}%replace{%args{custom_fields}}{(.+)}{,$1}",
                                                                false, false);

    /*
     * -- a simple application log message does not include exception/stack
     * trace info
     */
    private static final String APP_LOG_PATTERN = COMMON_PREFIX_PATTERN + APP_PREFIX_PATTERN + "%ex{0} " +
                                                  COMMON_POSTFIX_PATTERN;

    /*
     * -- if the application log was written including stack trace info, write
     * it out! -- to avoid any trouble with our event processing pipeline that
     * expect a single -- line message, make sure newlines and tabs are escaped.
     * -- newlines are actually escaped with additional surrounding spaces to
     * make the -- standard ES tokenizer work
     */
    private static final String APP_EX_LOG_PATTERN = COMMON_PREFIX_PATTERN + APP_PREFIX_PATTERN + "," + JSON_FIELD(
                                                                                                                   Fields.STACKTRACE,
                                                                                                                   "%stacktrace",
                                                                                                                   false,
                                                                                                                   false) +
                                                     COMMON_POSTFIX_PATTERN;
    /*
     * -- if we write a request log/"beat" all we want/need is already in the
     * message (object), but -- we need to flatten it as we don't want nested
     * JSON objects.
     */

    private static final String REQUEST_METRICS_PATTERN = COMMON_PREFIX_PATTERN + JSON_FIELD(Fields.TYPE,
                                                                                             Defaults.TYPE_REQUEST,
                                                                                             true, true) +
                                                          "%jsonmsg{flatten}%ex{0}" + COMMON_POSTFIX_PATTERN;

    public static String getPattern(PATTERN_KEY key) {
        switch (key) {
        case REQUEST:
            return REQUEST_METRICS_PATTERN;

        case EXCEPTION:
            return APP_EX_LOG_PATTERN;

        case APPLICATION:
        default:
            return APP_LOG_PATTERN;
        }
    }
}