import Foundation
import WebKit

class IndexItem: Encodable {
    let name: String
    var index = [UInt16: UInt64]()
    var dates = [UInt16]()
    init(_ name: String) {
        self.name = name
    }

    private enum CodingKeys: String, CodingKey {
        case name
        case dates
    }
}

class Logs: NSObject, WKScriptMessageHandler {
    let fm = FileManager.default;
    let baseDir = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first!
    var buffer = UnsafeMutableRawPointer.allocate(bytes: 51000, alignedTo: 1)
    var logDir: URL!
    var index: [String: IndexItem]!

    func userContentController(_ controller: WKUserContentController, didReceive message: WKScriptMessage) {
        let data = message.body as! [String: AnyObject]
        let key = data["_id"] as! String
        do {
            var result: String?
            switch(data["_type"] as! String) {
            case "init":
                result = try initCharacter(data["character"] as! String)
            case "logMessage":
                try logMessage(data["key"] as! String, data["conversation"] as! NSString, (data["time"] as! NSNumber).uint32Value, (data["type"] as! NSNumber).uint8Value, data["sender"] as! NSString, data["message"] as! NSString)
            case "getBacklog":
                result = try getBacklog(data["key"] as! String)
            case "readString":
                result = try getLogs(data["key"] as! String, (data["date"] as! NSNumber).uint16Value)
            default:
                message.webView!.evaluateJavaScript("nativeError('\(key)',new Error('Unknown message type'))")
                return
            }
            let output = result == nil ? "undefined" : result!;
            message.webView!.evaluateJavaScript("nativeMessage('\(key)',\(output))")
        } catch(let error) {
            message.webView!.evaluateJavaScript("nativeError('\(key)',new Error('File-\(data["_type"]!): \(error.localizedDescription)'))")
        }
    }

    func initCharacter(_ name: String) throws -> String {
        logDir = baseDir.appendingPathComponent("\(name)/logs", isDirectory: true)
        index = [String: IndexItem]()
        try fm.createDirectory(at: logDir, withIntermediateDirectories: true, attributes: nil)
        let files = try fm.contentsOfDirectory(at: logDir, includingPropertiesForKeys: nil, options: [.skipsHiddenFiles])
        for file in files {
            if(!file.lastPathComponent.hasSuffix(".idx")) { continue }
            let data = NSData(contentsOf: file)!
            var nameLength = 0
            data.getBytes(&nameLength, length: 1)
            let name = String(data: data.subdata(with: NSMakeRange(1, nameLength)), encoding: .utf8)!
            var offset = nameLength + 1
            let indexItem = IndexItem(name)
            while offset < data.length {
                var date: UInt16 = 0
                data.getBytes(&date, range: NSMakeRange(offset, 2))
                indexItem.dates.append(date)
                var o: UInt64 = 0
                data.getBytes(&o, range: NSMakeRange(offset + 2, 5))
                indexItem.index[date] = o
                offset += 7
            }
            index[file.deletingPathExtension().lastPathComponent] = indexItem
        }
        return String(data: try JSONEncoder().encode(index), encoding: .utf8)!
    }

    func logMessage(_ key: String, _ conversation: NSString, _ time: UInt32, _ type: UInt8, _ sender: NSString, _ text: NSString) throws {
        var time = time
        var type = type
        var day = UInt16(time / 86400)
        let url = logDir.appendingPathComponent(key, isDirectory: false);
        var indexItem = index[key]
        if(indexItem == nil) { fm.createFile(atPath: url.path, contents: nil) }
        let fd = try FileHandle(forWritingTo: url)
        fd.seekToEndOfFile()
        if(indexItem?.index[day] == nil) {
            let indexFile = url.appendingPathExtension("idx")
            if(indexItem == nil) { fm.createFile(atPath: indexFile.path, contents: nil) }
            let indexFd = try FileHandle(forWritingTo: indexFile)
            indexFd.seekToEndOfFile()
            if(indexItem == nil) {
                indexItem = IndexItem(conversation as String)
                index[key] = indexItem
                let cstring = conversation.utf8String
                var length = strlen(cstring)
                write(indexFd.fileDescriptor, &length, 1)
                write(indexFd.fileDescriptor, cstring, length)
            }
            write(indexFd.fileDescriptor, &day, 2)
            var offset = fd.offsetInFile
            write(indexFd.fileDescriptor, &offset, 5)
            indexItem!.index[day] = offset
            indexItem!.dates.append(day)
        }
        let start = fd.offsetInFile
        write(fd.fileDescriptor, &time, 4)
        write(fd.fileDescriptor, &type, 1)
        var cstring = sender.utf8String
        var length = strlen(cstring)
        write(fd.fileDescriptor, &length, 1)
        write(fd.fileDescriptor, cstring, length)
        cstring = text.utf8String
        length = strlen(cstring)
        write(fd.fileDescriptor, &length, 2)
        write(fd.fileDescriptor, cstring, length)
        var size = fd.offsetInFile - start
        write(fd.fileDescriptor, &size, 2)
    }

    func getBacklog(_ key: String) throws -> String {
        let url = logDir.appendingPathComponent(key, isDirectory: false)
        if(!fm.fileExists(atPath: url.path)) { return "[]" }
        let file = try FileHandle(forReadingFrom: url)
        file.seekToEndOfFile()
        var strings = [String]()
        strings.reserveCapacity(20)
        while file.offsetInFile > 0 && strings.count < 20 {
            file.seek(toFileOffset: file.offsetInFile - 2)
            read(file.fileDescriptor, buffer, 2)
            let length = buffer.load(as: UInt16.self)
            let newOffset = file.offsetInFile - UInt64(length + 2)
            file.seek(toFileOffset: newOffset)
            read(file.fileDescriptor, buffer, Int(length))
            strings.append(deserializeMessage().0)
            file.seek(toFileOffset: newOffset)
        }
        return "[" + strings.reversed().joined(separator: ",") + "]"
    }

    func getLogs(_ key: String, _ date: UInt16) throws -> String {
        guard let offset = index[key]?.index[date] else { return "[]" }
        let url = logDir.appendingPathComponent(key, isDirectory: false)
        let file = try FileHandle(forReadingFrom: url)
        let size = file.seekToEndOfFile()
        file.seek(toFileOffset: offset)
        var json = "["
        while file.offsetInFile < size {
            read(file.fileDescriptor, buffer, 51000)
            let deserialized = deserializeMessage(date)
            if(deserialized.1 == 0) { break }
            json += deserialized.0 + ","
            file.seek(toFileOffset: file.offsetInFile + UInt64(deserialized.1 + 2))
        }
        return json + "]"
    }

    func deserializeMessage(_ checkDate: UInt16 = 0) -> (String, Int) {
        let date = buffer.load(as: UInt32.self)
        if(checkDate != 0 && date / 86400 != checkDate) { return ("", 0) }
        let type = buffer.load(fromByteOffset: 4, as: UInt8.self)
        let senderLength = Int(buffer.load(fromByteOffset: 5, as: UInt8.self))
        let sender = String(bytesNoCopy: buffer.advanced(by: 6), length: senderLength, encoding: .utf8, freeWhenDone: false)!
        let textLength = Int(buffer.advanced(by: 6 + senderLength).bindMemory(to: UInt16.self, capacity: 1).pointee)
        let text = String(bytesNoCopy: buffer.advanced(by: 6 + senderLength + 2), length: textLength, encoding: .utf8, freeWhenDone: false)!
        return ("{\"time\":\(date),\"type\":\(type),\"sender\":\(File.escape(sender)),\"text\":\(File.escape(text))}", senderLength + textLength + 8)
    }
}