/**
 * Copyright (C) 2022 The Android Open Source Project
 *
 * 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 com.android.healthconnect.controller.autodelete

import com.android.healthconnect.controller.utils.TimeSource
import java.time.Instant
import java.time.LocalDateTime

/**
 * Specifies the range of auto-deletion, where data wil be automatically deleted from (no data gets
 * deleted in case of [AutoDeleteRange.AUTO_DELETE_RANGE_NEVER]).
 *
 * @param numberOfMonths: number of months used to retention the data.
 */
enum class AutoDeleteRange(val numberOfMonths: Int) {
    AUTO_DELETE_RANGE_NEVER(0),
    AUTO_DELETE_RANGE_THREE_MONTHS(3),
    AUTO_DELETE_RANGE_EIGHTEEN_MONTHS(18)
}

/**
 * Returns [AutoDeleteRange] corresponding to the given number of months or throws in case of
 * unsupported number of months.
 */
fun fromNumberOfMonths(numberOfMonths: Int): AutoDeleteRange {
    AutoDeleteRange.values().forEach { range ->
        if (range.numberOfMonths == numberOfMonths) {
            return range
        }
    }
    throw UnsupportedOperationException("Number of months is not supported: $numberOfMonths")
}

/** Returns the [Instant] that is the start of the [AutoDeleteRange]. */
fun autoDeleteRangeStart(): Instant {
    return Instant.EPOCH
}

/**
 * Returns the [Instant] that is the end of the [AutoDeleteRange] or throws in case of
 * [AutoDeleteRange.AUTO_DELETE_RANGE_NEVER].
 */
fun autoDeleteRangeEnd(timeSource: TimeSource, range: AutoDeleteRange): Instant {
    val localDateTimeNow: LocalDateTime = timeSource.currentLocalDateTime()
    when (range) {
        AutoDeleteRange.AUTO_DELETE_RANGE_THREE_MONTHS,
        AutoDeleteRange.AUTO_DELETE_RANGE_EIGHTEEN_MONTHS -> {
            val exactlyXMonthsAgo: LocalDateTime =
                localDateTimeNow.minusMonths(range.numberOfMonths.toLong())
            return exactlyXMonthsAgo
                .toLocalDate()
                .atStartOfDay(timeSource.deviceZoneOffset())
                .toInstant()
        }
        AutoDeleteRange.AUTO_DELETE_RANGE_NEVER -> {
            throw UnsupportedOperationException("Invalid auto-delete range to delete data.")
        }
    }
}