//
// Copyright 2019 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only
//

import Foundation

@objc
public class Batching: NSObject {
    @objc
    public static let kDefaultBatchSize: UInt = 1000

    // Break loop cycles into batches, releasing stale objects
    // after each batch to avoid out of memory errors.
    //
    // If batchSize == 0, no batching is done and no
    // autoreleasepool is used.
    public static func loop(batchSize: UInt,
                            loopBlock: (UnsafeMutablePointer<ObjCBool>) throws -> Void) rethrows {
        var stop: ObjCBool = false
        guard batchSize > 0 else {
            // No batching.
            while !stop.boolValue {
                try loopBlock(&stop)
            }
            return
        }

        // With batching.
        while !stop.boolValue {
            try autoreleasepool {
                for _ in 0..<batchSize {
                    guard !stop.boolValue else {
                        return
                    }
                    try loopBlock(&stop)
                }
            }
        }
    }

    @objc
    public static func loopObjc(batchSize: UInt,
                                loopBlock: (UnsafeMutablePointer<ObjCBool>) -> Void) {
        var stop: ObjCBool = false
        guard batchSize > 0 else {
            // No batching.
            while !stop.boolValue {
                loopBlock(&stop)
            }
            return
        }

        // With batching.
        var batchIndex = 0
        while !stop.boolValue {
            autoreleasepool {
                for _ in 0..<batchSize {
                    guard !stop.boolValue else {
                        return
                    }
                    loopBlock(&stop)
                }
            }
            batchIndex += 1
        }
    }
}