/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.nifi.serialization.record.field;

import org.apache.nifi.serialization.record.util.IllegalTypeConversionException;

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.util.Date;
import java.util.Optional;

/**
 * Convert Object to java.time.LocalDateTime using instanceof evaluation and optional format pattern for DateTimeFormatter
 */
class ObjectLocalDateTimeFieldConverter implements FieldConverter<Object, LocalDateTime> {
    private static final long YEAR_TEN_THOUSAND = 253_402_300_800_000L;

    /**
     * Convert Object field to java.sql.Timestamp using optional format supported in DateTimeFormatter
     *
     * @param field Field can be null or a supported input type
     * @param pattern Format pattern optional for parsing
     * @param name Field name for tracking
     * @return Timestamp or null when input field is null or empty string
     * @throws IllegalTypeConversionException Thrown on parsing failures or unsupported types of input fields
     */
    @Override
    public LocalDateTime convertField(final Object field, final Optional<String> pattern, final String name) {
        if (field == null) {
            return null;
        }
        if (field instanceof LocalDateTime) {
            return (LocalDateTime) field;
        }
        if (field instanceof Date date) {
            final Instant instant = Instant.ofEpochMilli(date.getTime());
            return ofInstant(instant);
        }
        if (field instanceof final Number number) {
            // If value is a floating point number, we consider it as seconds since epoch plus a decimal part for fractions of a second.
            if (field instanceof Double || field instanceof Float) {
                return toLocalDateTime(number.doubleValue());
            }

            return toLocalDateTime(number.longValue());
        }
        if (field instanceof String) {
            final String string = field.toString().trim();
            if (string.isEmpty()) {
                return null;
            }

            if (pattern.isPresent()) {
                final DateTimeFormatter formatter = DateTimeFormatterRegistry.getDateTimeFormatter(pattern.get());
                try {
                    return LocalDateTime.parse(string, formatter);
                } catch (final DateTimeParseException e) {
                    return tryParseAsNumber(string, name);
                }
            } else {
                return tryParseAsNumber(string, name);
            }
        }

        throw new FieldConversionException(LocalDateTime.class, field, name);
    }

    private LocalDateTime tryParseAsNumber(final String value, final String fieldName) {
        try {
            // If decimal, treat as a double and convert to seconds and nanoseconds.
            if (value.contains(".")) {
                final double number = Double.parseDouble(value);
                return toLocalDateTime(number);
            }

            // attempt to parse as a long value
            final long number = Long.parseLong(value);
            return toLocalDateTime(number);
        } catch (final NumberFormatException e) {
            throw new FieldConversionException(LocalDateTime.class, value, fieldName, e);
        }
    }

    private LocalDateTime toLocalDateTime(final double secondsSinceEpoch) {
        // Determine the number of micros past the second by subtracting the number of seconds from the decimal value and multiplying by 1 million.
        final double micros = 1_000_000 * (secondsSinceEpoch - (long) secondsSinceEpoch);
        // Convert micros to nanos. Note that we perform this as a separate operation, rather than multiplying by 1_000,000,000 in order to avoid
        // issues that occur with rounding at high precision.
        final long nanos = (long) micros * 1000L;

        return toLocalDateTime((long) secondsSinceEpoch, nanos);
    }

    private LocalDateTime toLocalDateTime(final long epochSeconds, final long nanosPastSecond) {
        final Instant instant = Instant.ofEpochSecond(epochSeconds).plusNanos(nanosPastSecond);
        return ofInstant(instant);
    }

    private LocalDateTime toLocalDateTime(final long value) {
        if (value > YEAR_TEN_THOUSAND) {
            // Value is too large. Assume microseconds instead of milliseconds.
            final Instant microsInstant = Instant.ofEpochSecond(value / 1_000_000, (value % 1_000_000) * 1_000);
            return ofInstant(microsInstant);
        }

        final Instant instant = Instant.ofEpochMilli(value);
        final LocalDateTime localDateTime = ofInstant(instant);

        return localDateTime;
    }

    private LocalDateTime ofInstant(final Instant instant) {
        return LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
    }
}
