purchases-ios/Sources/FoundationExtensions/Array+Extensions.swift

//
//  Copyright RevenueCat Inc. All Rights Reserved.
//
//  Licensed under the MIT License (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//      https://opensource.org/licenses/MIT
//
//  Array+Extensions.swift
//
//  Created by Nacho Soto on 2/17/22.

import Foundation

extension Array {

    /// Equivalent to `removeFirst()` but it returns `Optional` if the collection is empty.
    mutating func popFirst() -> Element? {
        guard !self.isEmpty else { return nil }

        return self.removeFirst()
    }

}

extension Collection {

    /// - Returns: an element if and only if it's the only one in the collection
    var onlyElement: Element? {
        guard self.count == 1, let first = self.first else {
            return nil
        }

        return first
    }

    /// Returns the element at the specified index if it exists, otherwise nil.
    subscript(safe index: Index) -> Element? {
        return self.indices.contains(index) ? self[index] : nil
    }

}

extension Sequence where Element: AdditiveArithmetic {

    /// - Returns: the sum of the elements in the sequence.
    func sum() -> Element {
        return reduce(.zero, +)
    }

}

extension Sequence where Element: Hashable {

    /// Returns the sequence's unique elements, preserving each element's first occurrence.
    func deduplicated() -> [Element] {
        var seen: Set<Element> = []

        return self.filter { seen.insert($0).inserted }
    }

}