ReadViewSDK/Sources/RDReaderView/EPUBCore/CFI/RDEPUBCFIPath.swift

import Foundation

public struct RDEPUBCFIPath: Codable, Equatable, Hashable {

    public var steps: [RDEPUBCFIStep]

    public init(steps: [RDEPUBCFIStep] = []) {
        self.steps = steps
    }

    public func commonPrefix(with other: RDEPUBCFIPath) -> RDEPUBCFIPath {
        var prefix: [RDEPUBCFIStep] = []
        let upperBound = min(steps.count, other.steps.count)
        for index in 0..<upperBound {
            guard steps[index] == other.steps[index] else { break }
            prefix.append(steps[index])
        }
        return RDEPUBCFIPath(steps: prefix)
    }

    public func droppingPrefix(_ prefix: RDEPUBCFIPath) -> RDEPUBCFIPath {
        guard prefix.steps.count <= steps.count else { return self }
        let candidate = Array(steps.prefix(prefix.steps.count))
        guard candidate == prefix.steps else { return self }
        return RDEPUBCFIPath(steps: Array(steps.dropFirst(prefix.steps.count)))
    }
}

public struct RDEPUBCFIStep: Codable, Equatable, Hashable {

    public var index: Int

    public var idAssertion: String?

    public init(index: Int, idAssertion: String? = nil) {
        self.index = index
        self.idAssertion = idAssertion?.nilIfEmpty
    }
}