90 lines
3.0 KiB
Swift
90 lines
3.0 KiB
Swift
//
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// Copyright (c) 2017 Touch Instinct
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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//
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import RxSwift
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/// Paging cursor implementation with enclosed cursor for fetching results
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public class FixedPageCursor<Cursor: CursorType>: CursorType, RxDataSource {
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public typealias ResultType = [Element]
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fileprivate let cursor: Cursor
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fileprivate let pageSize: Int
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/// Initializer with enclosed cursor
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///
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/// - Parameters:
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/// - cursor: enclosed cursor
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/// - pageSize: number of items loaded at once
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public init(cursor: Cursor, pageSize: Int) {
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self.cursor = cursor
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self.pageSize = pageSize
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}
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public var exhausted: Bool {
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cursor.exhausted && cursor.count == count
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}
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public private(set) var count: Int = 0
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public subscript(index: Int) -> Cursor.Element {
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cursor[index]
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}
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public func loadNextBatch() -> Single<[Cursor.Element]> {
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Single.deferred {
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if self.exhausted {
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return .error(CursorError.exhausted)
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}
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let restOfLoaded = self.cursor.count - self.count
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if restOfLoaded >= self.pageSize || self.cursor.exhausted {
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let startIndex = self.count
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self.count += min(restOfLoaded, self.pageSize)
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return .just(self.cursor[startIndex..<self.count])
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}
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return self.cursor.loadNextBatch()
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.flatMap { _ in
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self.loadNextBatch()
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}
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}
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}
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}
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/// FixedPageCursor subclass with implementation of ResettableType
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public class ResettableFixedPageCursor<Cursor: ResettableCursorType>: FixedPageCursor<Cursor>, ResettableType {
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public typealias ResultType = [Element]
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public override init(cursor: Cursor, pageSize: Int) {
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super.init(cursor: cursor, pageSize: pageSize)
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}
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public required init(resetFrom other: ResettableFixedPageCursor) {
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super.init(cursor: other.cursor.reset(), pageSize: other.pageSize)
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}
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}
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