import Foundation

public enum RDEPUBCFIGenerator {

    public static func makeOffsetCFI(
        href: String,
        fileIndex: Int,
        chapterOffset: Int,
        fragmentID: String? = nil,
        sideBias: RDEPUBCFISideBias? = nil,
        textAssertion: RDEPUBCFITextAssertion? = nil,
        contentPath: RDEPUBCFIPath? = nil
    ) -> RDEPUBCFI {
        let packagePath = RDEPUBCFIPath(steps: [
            RDEPUBCFIStep(index: 6),
            RDEPUBCFIStep(index: max((fileIndex + 1) * 2, 2), idAssertion: href)
        ])
        let resolvedContentPath = contentPath ?? RDEPUBCFIPath(steps: [
            RDEPUBCFIStep(index: 4),
            RDEPUBCFIStep(index: 2, idAssertion: fragmentID)
        ])
        return RDEPUBCFI(
            packagePath: packagePath,
            contentPath: resolvedContentPath,
            characterOffset: max(chapterOffset, 0),
            sideBias: sideBias,
            textAssertion: textAssertion
        )
    }

    public static func makeCFI(
        href: String,
        fileIndex: Int,
        contentPath: RDEPUBCFIPath,
        characterOffset: Int,
        sideBias: RDEPUBCFISideBias? = nil,
        textAssertion: RDEPUBCFITextAssertion? = nil
    ) -> RDEPUBCFI {
        let packagePath = RDEPUBCFIPath(steps: [
            RDEPUBCFIStep(index: 6),
            RDEPUBCFIStep(index: max((fileIndex + 1) * 2, 2), idAssertion: href)
        ])
        return RDEPUBCFI(
            packagePath: packagePath,
            contentPath: contentPath,
            characterOffset: max(characterOffset, 0),
            sideBias: sideBias,
            textAssertion: textAssertion
        )
    }

    public static func makeOffsetRangeCFI(
        href: String,
        fileIndex: Int,
        startOffset: Int,
        endOffset: Int,
        fragmentID: String? = nil,
        startTextAssertion: RDEPUBCFITextAssertion? = nil,
        endTextAssertion: RDEPUBCFITextAssertion? = nil,
        contentPath: RDEPUBCFIPath? = nil
    ) -> RDEPUBCFIRange {
        precondition(startOffset <= endOffset, "startOffset (\(startOffset)) must be <= endOffset (\(endOffset))")
        let start = makeOffsetCFI(
            href: href,
            fileIndex: fileIndex,
            chapterOffset: startOffset,
            fragmentID: fragmentID,
            sideBias: .before,
            textAssertion: startTextAssertion,
            contentPath: contentPath
        )
        let end = makeOffsetCFI(
            href: href,
            fileIndex: fileIndex,
            chapterOffset: endOffset,
            fragmentID: fragmentID,
            sideBias: .after,
            textAssertion: endTextAssertion,
            contentPath: contentPath
        )
        let parent = RDEPUBCFI(
            packagePath: start.packagePath.commonPrefix(with: end.packagePath),
            contentPath: start.contentPath.commonPrefix(with: end.contentPath)
        )
        return RDEPUBCFIRange(parent: parent, start: start, end: end)
    }
}