/**
 * This class holds all info about paths, their FIDs, and their QIDs.
 */
class PathInfo() {
    private val paths: MutableSet<Path> = mutableSetOf()

    /**
     * Information about a path. Each FID maps to one path but not all paths have FIDs (injective). On the other hand,
     * one QID can be shared with different paths and FIDs.
     *
     * FIDs are optional because some R-messages only return QIDs for certain files (e.g. walk).
     *
     * @param path The path.
     * @param fid The optional FID associated with the path.
     * @param qid The QID associated with the path.
     */
    data class Path(val path: List<String>, val fid: UInt?, val qid: QID)

    /**
     * Add a path.
     */
    fun addPath(path: Path) {
        this.paths.add(path)
    }

    /**
     * Find the FID associated with a path.
     *
     * @param path The path to find the FID of.
     * @return The FID if [path] has an associated FID, or null otherwise.
     */
    fun findFIDByPath(path: List<String>): UInt? {
        return this.paths.find { x -> x.path == path }?.fid
    }                                                                

    /**
     * Find the QID associated to a path.
     *
     * @param path The path to find the QID of.
     * @return The QID if [path] could be found, or null otherwise.
     */
    fun findQIDByPath(path: List<String>): QID? {
        return this.paths.find { x -> x.path == path }?.qid
    }

    /**
     * Find the path associated to a FID.
     *
     * @param fid The FID to find the path of.
     * @return The path if [fid] could be found, or null otherwise.
     */
    fun findPathByFID(fid: UInt): List<String>? {
        return this.paths.find { x -> x.fid == fid }?.path
    }

    /**
     * Retrieve all paths
     */
    fun getAllPaths(): Set<Path> {
        return this.paths.toSet()
    }
}