import Foundation

final class RDEPUBPageCountCache {
    private var storage: [RDEPUBChapterCacheKey: RDEPUBRuntimePageCount] = [:]
    private let lock = NSLock()

    subscript(key: RDEPUBChapterCacheKey) -> RDEPUBRuntimePageCount? {
        get {
            lock.lock()
            defer { lock.unlock() }
            return storage[key]
        }
        set {
            lock.lock()
            defer { lock.unlock() }
            storage[key] = newValue
        }
    }

    func entriesForSpineIndex(_ spineIndex: Int) -> [(RDEPUBChapterCacheKey, RDEPUBRuntimePageCount)] {
        lock.lock()
        defer { lock.unlock() }
        return storage.filter { $0.value.spineIndex == spineIndex }.map { ($0.key, $0.value) }
    }

    func remove(forSpineIndex spineIndex: Int) {
        lock.lock()
        defer { lock.unlock() }
        storage = storage.filter { $0.value.spineIndex != spineIndex }
    }

    func removeAll() {
        lock.lock()
        defer { lock.unlock() }
        storage.removeAll()
    }
}