BitTorrentSwift/BitTorrent/Models/TorrentMetaInfo.swift

//
//  TorrentMetaInfo.swift
//  BitTorrent
//
//  Created by Ben Davis on 25/03/2016.
//  Copyright © 2016 Ben Davis. All rights reserved.
//

import Foundation
import class BEncode.BEncoder

class TorrentMetaInfo {
    
    var infoHash : NSData // this is the original bencoded dictionary, hashed

    var info: TorrentInfoDictionary
//    var announce: String
//    var announceList: [String]?
//    var creationDate: NSDate?
//    var comment: String?
//    var createdBy: String?

    init?(data: NSData) {
        self.infoHash = try! BEncoder.decodeDictionaryKeysOnly(data)["info"]!.sha1()
        let decodedMetainfo = try! BEncoder.decodeStringKeyedDictionary(data)
        if let info = TorrentInfoDictionary(decodedMetainfo["info"] as! [String : AnyObject]) {
            self.info = info
        } else {
            return nil
        }
    }
    
}

class TorrentInfoDictionary {
    
    let name : String
    let pieceLength : Int
    let isPrivate : Bool
    let files: [TorrentFileInfo]
    let pieces : [NSData]?
    let length: Int

    init?(_ dictionary: [String : AnyObject]) {
        
        if let nameData = dictionary["name"] as? NSData, name = String(asciiData: nameData) {
            self.name = name
        } else {
            return nil
        }
        
        if let pieceLength = dictionary["piece length"] as? Int {
            self.pieceLength = pieceLength
        } else {
            return nil
        }
        
        if let pieces = dictionary["pieces"] as? NSData, piecesArray = TorrentInfoDictionary.seperatePieces(pieces) {
            self.pieces = piecesArray
        } else {
            return nil
        }
        
        if let tuple = TorrentInfoDictionary.parseFilesAndLengthFromDictionary(dictionary, parsedName: name) {
            self.files = tuple.files
            self.length = tuple.totalLength
        } else {
            return nil
        }
        
        if let isPrivate = dictionary["private"] as? Int {
            self.isPrivate = (isPrivate == 1)
        } else {
            self.isPrivate = false
        }
        
    }
    
    private class func parseFilesAndLengthFromDictionary(dictionary: [ String : AnyObject ],
                                                         parsedName name: String)
        -> (files: [TorrentFileInfo], totalLength: Int)? {
            
            if let files = dictionary["files"] as? [ [ String : AnyObject ] ] {
                
                return TorrentInfoDictionary.parseFilesDictionaries(files)
                
            } else if let length = dictionary["length"] as? Int {
                
                return TorrentInfoDictionary.parseSingleFileFromInfoDictionary(dictionary,
                                                                               parsedName: name,
                                                                               parsedLength: length)
                
            } else {
                
                return nil
                
            }
    }
    
    private class func parseSingleFileFromInfoDictionary(dictionary: [ String : AnyObject ],
                                                         parsedName name: String,
                                                         parsedLength length: Int) -> ([TorrentFileInfo], Int) {
        
        let md5sumData = dictionary["md5sum"] as? NSData
        let md5sum = String(asciiData: md5sumData)
        let files = [ TorrentFileInfo(path: name, length: length, md5sum: md5sum) ]
        
        return (files, length)
    }
    
    private class func parseFilesDictionaries(files: [ [ String : AnyObject ] ]) -> ([TorrentFileInfo], Int)? {
        
        var totalLength = 0
        var result: [TorrentFileInfo] = []
        
        for fileDictionary in files {
            
            if let file = TorrentFileInfo(dictionary: fileDictionary) {
                
                totalLength += file.length
                result.append(file)
                
            } else {
                return nil
            }
            
        }
        
        return (files: result, totalLength: totalLength)
    }
    
    private class func seperatePieces(pieces: NSData) -> [NSData]? {
        if pieces.length % 20 != 0 {
            return nil
        }
        
        var result: [NSData] = []
        for index in 0.stride(to:pieces.length, by: 20) {
            result.append(pieces.subdataWithRange(NSMakeRange(index, 20)))
        }
        return result
    }
}

class TorrentFileInfo {
    let path: String
    let length: Int
    let md5sum: String?

    init(path: String, length: Int, md5sum: String?) {
        self.path = path
        self.length = length
        self.md5sum = md5sum
    }
    
    convenience init?(dictionary: [ String : AnyObject ]) {
        
        let pathData = dictionary["path"] as? NSData
        let path = String(asciiData: pathData)
        
        let length = dictionary["length"] as? Int
        
        if let length = length, path = path {
            
            let md5sumData = dictionary["md5sum"] as? NSData
            let md5sum = String(asciiData: md5sumData)
            
            self.init(path: path, length: length, md5sum: md5sum)
            
        } else {
            return nil
        }
    }
}