import Foundation

struct RDEPUBChapterOffsetMap {

    let fragmentOffsets: [String: Int]

    let pageStartOffsets: [Int]

    let pageEndOffsets: [Int]

    let cfiMap: RDEPUBCFIMap?

    let chapterText: String?

    func chapterOffset(forFragmentID fragmentID: String) -> Int? {
        return fragmentOffsets[fragmentID]
    }

    func chapterOffset(forCFI rawCFI: String?) -> Int? {
        guard let cfi = RDEPUBCFICompatibility.parseLossy(rawCFI) else { return nil }
        let resolved = RDEPUBCFIResolver.resolve(cfi)
        let lastOffset = max((pageEndOffsets.max() ?? 0), 0)
        return RDEPUBCFIRecoveryEngine.recover(
            cfi: cfi,
            cfiMap: cfiMap,
            chapterText: chapterText,
            fragmentOffsets: fragmentOffsets,
            fallbackOffset: resolved.chapterOffset,
            lastOffset: lastOffset
        )?.chapterOffset
    }

    func pageIndex(forChapterOffset offset: Int) -> Int? {
        for i in 0..<pageStartOffsets.count {
            if offset >= pageStartOffsets[i] && offset <= pageEndOffsets[i] {
                return i
            }
        }
        return nil
    }
}