CombinedLoadStates.kt

/*
 * Copyright 2020 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 androidx.paging

/**
 * Collection of pagination [LoadState]s for both a [PagingSource], and [RemoteMediator].
 *
 * Note: The [LoadType] [REFRESH][LoadType.REFRESH] always has [LoadState.endOfPaginationReached]
 * set to `false`.
 */
public class CombinedLoadStates(
    /**
     * Convenience for combined behavior of [REFRESH][LoadType.REFRESH] [LoadState], which
     * generally defers to [mediator] if it exists, but if previously was [LoadState.Loading],
     * awaits for both [source] and [mediator] to become [LoadState.NotLoading] to ensure the
     * remote load was applied.
     *
     * For use cases that require reacting to [LoadState] of [source] and [mediator]
     * specifically, e.g., showing cached data when network loads via [mediator] fail,
     * [LoadStates] exposed via [source] and [mediator] should be used directly.
     */
    public val refresh: LoadState,
    /**
     * Convenience for combined behavior of [PREPEND][LoadType.REFRESH] [LoadState], which
     * generally defers to [mediator] if it exists, but if previously was [LoadState.Loading],
     * awaits for both [source] and [mediator] to become [LoadState.NotLoading] to ensure the
     * remote load was applied.
     *
     * For use cases that require reacting to [LoadState] of [source] and [mediator]
     * specifically, e.g., showing cached data when network loads via [mediator] fail,
     * [LoadStates] exposed via [source] and [mediator] should be used directly.
     */
    public val prepend: LoadState,
    /**
     * Convenience for combined behavior of [APPEND][LoadType.REFRESH] [LoadState], which
     * generally defers to [mediator] if it exists, but if previously was [LoadState.Loading],
     * awaits for both [source] and [mediator] to become [LoadState.NotLoading] to ensure the
     * remote load was applied.
     *
     * For use cases that require reacting to [LoadState] of [source] and [mediator]
     * specifically, e.g., showing cached data when network loads via [mediator] fail,
     * [LoadStates] exposed via [source] and [mediator] should be used directly.
     */
    public val append: LoadState,
    /**
     * [LoadStates] corresponding to loads from a [PagingSource].
     */
    public val source: LoadStates,

    /**
     * [LoadStates] corresponding to loads from a [RemoteMediator], or `null` if [RemoteMediator]
     * not present.
     */
    public val mediator: LoadStates? = null,
) {

    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        if (javaClass != other?.javaClass) return false

        other as CombinedLoadStates

        if (refresh != other.refresh) return false
        if (prepend != other.prepend) return false
        if (append != other.append) return false
        if (source != other.source) return false
        if (mediator != other.mediator) return false

        return true
    }

    override fun hashCode(): Int {
        var result = refresh.hashCode()
        result = 31 * result + prepend.hashCode()
        result = 31 * result + append.hashCode()
        result = 31 * result + source.hashCode()
        result = 31 * result + (mediator?.hashCode() ?: 0)
        return result
    }

    override fun toString(): String {
        return "CombinedLoadStates(refresh=$refresh, prepend=$prepend, append=$append, " +
            "source=$source, mediator=$mediator)"
    }

    internal fun forEach(op: (LoadType, Boolean, LoadState) -> Unit) {
        source.forEach { type, state ->
            op(type, false, state)
        }
        mediator?.forEach { type, state ->
            op(type, true, state)
        }
    }
}