import Foundation
import UniformTypeIdentifiers

/// A helper class for creating Spotlight importer plug-ins.
///
/// Any `CFPlugIn`, and that includes a Spotlight plug-in, has a single entry
/// point with the C prototype:
///
/// ```
/// extern void * myPlugInEntryPoint(CFAllocatorRef allocator, CFUUIDRef typeUUID)
/// ```
///
/// To create a Spotlight plug-in:
///
/// 1. Run the `uuidgen` command-line tool to generate a factory UUID for your
///    plug-in. This UUID identifies your specific plug-in, so you need a new
///    one each time you start a new Spotlight plug-in project.
///
/// 2. Subclass this class.
///
/// 3. Implement the `importFrom(_:type:updating:)` method, declared below.
///
/// 4. Write an entry point function with the prototype above that calls through
///    to the `class makeInstance(factoryID:)` method, passing in the factory
///    UUID from step 1.
///
/// 5. Configure your `Info.plist` with the factory UUID from step 1 and the
///    name of your plug-in entry point from step 4.

open class QSpotlightPlugIn: QCFPlugIn {

    /// Plug-in entry point.
    /// 
    /// Call this method from your plug-in’s entry point, passing in the factory
    /// UUID that identifiers your specific plug-in.
    /// 
    /// - important: This factory UUID needs to match that in your `Info.plist`
    /// (it actually shows up twice, once in `CFPlugInFactories` and again in
    /// `CFPlugInTypes).
    /// 
    /// - Parameter factoryID: The factory UUID for this plug-in.

    final class func makeInstance(factoryID: UUID) -> UnsafeMutableRawPointer? {
        // `kMDImporterTypeID` is defined by a complicated macro that Swift is
        // unable to import, so I’ve just copied the value here.  This should
        // be safe because the value can’t reasonably change because it’s are
        // baked into a bazillion shipping Spotlight importer plug-ins.
        let kMDImporterTypeID = UUID(uuid: (0x8B, 0x08, 0xC4, 0xBF, 0x41, 0x5B, 0x11, 0xD8, 0xB3, 0xF9, 0x00, 0x03, 0x93, 0x67, 0x26, 0xFC))
        return self.makeInstance(factoryID: factoryID, typeID: kMDImporterTypeID, typeVTableSize: MemoryLayout.size)
    }

    final public override func setupVTable(_ vtable: UnsafeMutableRawPointer, for interfaceID: UUID) -> Bool {
        // I’ve hard-coded `kMDImporterURLInterfaceID` much like I did for
        // `kMDImporterTypeID`.
        let kMDImporterURLInterfaceID = UUID(uuid: (0x13, 0xF6, 0x0F, 0x02, 0x36, 0x22, 0x4F, 0x35, 0x98, 0x91, 0xEC, 0x10, 0xE6, 0xCD, 0x08, 0xF8))
        guard interfaceID == kMDImporterURLInterfaceID else { return false }
        let vtable = vtable.assumingMemoryBound(to: MDImporterURLInterfaceStruct.self)
        vtable.pointee.ImporterImportURLData = { interface, attributes, contentTypeUTI, urlForFile in
            let obj = QSpotlightPlugIn.object(forInstance: interface!)
            do {
                try obj.importFrom(urlForFile! as URL, type: UTType(contentTypeUTI! as String)!, updating: attributes!)
                return true
            } catch {
                return false
            }
        }
        return true
    }

    /// Import data entry point.
    /// 
    /// Implement this method to support Spotlight import.
    /// 
    /// This method corresponds to the [`ImporterImportData`][refImporterImportData]
    /// member of the `MDImporterInterfaceStruct`. The  `url`, `contentTypeUTI`,
    /// `attributes` parameters all have the same meaning as their equivalent
    /// parameters in that API.
    /// 
    /// [refImporterImportData]: 
    /// 
    /// - Parameters:
    ///   - url: Equivalent to the `pathToFile` parameter of `ImporterImportData`
    ///   - contextTypeUTI: See `ImporterImportData`.
    ///   - attributes: See `ImporterImportData`.

    open func importFrom(_ url: URL, type contextTypeUTI: UTType, updating attributes: NSMutableDictionary) throws {
        fatalError("Implement this in your factory-specific subclass.")
    }
}