import Foundation

public struct RDEPUBTextPositionConverter {

    public let book: RDEPUBTextBook

    public init(book: RDEPUBTextBook) {
        self.book = book
    }

    public var totalCharacterCount: Int {
        book.indexTable.totalCharacterCount
    }

    public func globalIndex(for anchor: RDEPUBTextAnchor) -> Int {
        book.indexTable.globalIndex(for: anchor)
    }

    public func globalRange(for rangeAnchor: RDEPUBTextRangeAnchor) -> NSRange {
        book.indexTable.globalRange(for: rangeAnchor)
    }

    public func fileIndex(forCharacterPosition index: Int) -> Int? {
        book.indexTable.fileIndex(forCharacterPosition: index)
    }

    public func localOffsetInFile(at fileIndex: Int, forGlobalPosition index: Int) -> Int? {
        book.indexTable.localOffsetInFile(at: fileIndex, forGlobalPosition: index)
    }

    public func anchor(forCharacterPosition index: Int) -> RDEPUBTextAnchor? {
        book.indexTable.anchor(forGlobalIndex: index)
    }

    public func anchor(for location: RDEPUBLocation) -> RDEPUBTextAnchor? {
        book.indexTable.anchor(for: location)
    }

    public func pageNumber(for anchor: RDEPUBTextAnchor) -> Int? {
        book.indexTable.pageNumber(for: anchor, in: book).map { $0 + 1 }
    }

    public func pageNumber(forCharacterPosition index: Int) -> Int? {
        guard let anchor = anchor(forCharacterPosition: index) else {
            return nil
        }
        return pageNumber(for: anchor)
    }

    public func location(
        for anchor: RDEPUBTextAnchor,
        bookIdentifier: String?
    ) -> RDEPUBLocation? {
        guard let chapter = book.chapters.first(where: { $0.spineIndex == anchor.fileIndex }) else {
            return nil
        }
        return book.indexTable.location(for: anchor, in: chapter, bookIdentifier: bookIdentifier)
    }

    public func location(
        for rangeAnchor: RDEPUBTextRangeAnchor,
        bookIdentifier: String?
    ) -> RDEPUBLocation? {
        guard let chapter = book.chapters.first(where: { $0.spineIndex == rangeAnchor.start.fileIndex }) else {
            return nil
        }
        return book.indexTable.location(for: rangeAnchor, in: chapter, bookIdentifier: bookIdentifier)
    }
}