import Foundation

struct RDEPUBChapterOffsetMap {
    let fragmentOffsets: [String: Int]
    let pageStartOffsets: [Int]
    let pageEndOffsets: [Int]

    /// fragmentID -> 章内字符偏移
    func chapterOffset(forFragmentID fragmentID: String) -> Int? {
        return fragmentOffsets[fragmentID]
    }

    /// 章内字符偏移 -> 章内页码（从 0 开始）
    func pageIndex(forChapterOffset offset: Int) -> Int? {
        for i in 0..<pageStartOffsets.count {
            if offset >= pageStartOffsets[i] && offset <= pageEndOffsets[i] {
                return i
            }
        }
        return nil
    }
}