//
//  ContentViewModel.swift
//  MSRecognition
//
//  Created by Prismetric tech on 22/02/22.
//

import UIKit
import ShazamKit

class ContentViewModel: NSObject, ObservableObject {
    
    @Published private(set) var songMatch: SongMatch? = nil
    private let session = SHSession()
   private let audioFileURL = Bundle.main.url(forResource: "songname", withExtension: "mp3")
    @Published private(set) var isMatching = false

    
    override init() {
        super.init()
        session.delegate = self
    }

    
    private func buffer(audioFile: AVAudioFile, outputFormat: AVAudioFormat) -> AVAudioPCMBuffer? {
        
        let frameCount = AVAudioFrameCount((1024 * 64) / (audioFile.processingFormat.streamDescription.pointee.mBytesPerFrame))
        let outputFrameCapacity = AVAudioFrameCount(12 * audioFile.fileFormat.sampleRate)
            
        guard let inputBuffer = AVAudioPCMBuffer(pcmFormat: audioFile.processingFormat, frameCapacity: frameCount),
            let outputBuffer = AVAudioPCMBuffer(pcmFormat: outputFormat, frameCapacity: outputFrameCapacity),
            let converter = AVAudioConverter(from: audioFile.processingFormat, to: outputFormat) else { return nil }

        while true {
            let status = converter.convert(to: outputBuffer, error: nil) { inNumPackets, outStatus in
                do {
                    try audioFile.read(into: inputBuffer)
                    outStatus.pointee = .haveData
                    return inputBuffer
                } catch {
                    if audioFile.framePosition >= audioFile.length {
                        outStatus.pointee = .endOfStream
                        return nil
                    } else {
                        outStatus.pointee = .noDataNow
                        return nil
                    }
                }
            }
            switch status {
            case .endOfStream, .error: return nil
            default: return outputBuffer
            }
        }
        
    }
    private func signature() -> SHSignature? {
        
        // Create the buffer from the audio file.
        guard let audioFileURL = audioFileURL,
            let audioFile = try? AVAudioFile(forReading: audioFileURL),
            let audioFormat = AVAudioFormat(standardFormatWithSampleRate: 44100, channels: 1),
            let buffer = buffer(audioFile: audioFile, outputFormat: audioFormat) else { return nil }
        
        // Initialise the generator and append the buffer to it.
        let signatureGenerator = SHSignatureGenerator()
        try? signatureGenerator.append(buffer, at: nil)
        
        // Return the generated signature.
        return signatureGenerator.signature()
        
    }
    
    func startMatching() {

        // Verify if the signature is not nil,
        // and if the session not already searching for a match.
        guard let signature = signature(), isMatching == false else { return }
        isMatching = true
        
        // Search for a match.
        session.match(signature)
        
    }
    
    
    
}

extension ContentViewModel: SHSessionDelegate {
    
    func session(_ session: SHSession, didFind match: SHMatch) {
        
        // Get the matched media item if it exists.
        guard let matchedMediaItem = match.mediaItems.first else { return }
        
        // Set isMatching to false,
        // and set the songMatch property with the matched media's metadata.
        DispatchQueue.main.async { [weak self] in
            self?.isMatching = false
            print(matchedMediaItem.title ?? "title")
            print(matchedMediaItem.artist ?? "artist")
            print(matchedMediaItem.artworkURL?.absoluteString ?? "artworkurl")
            self?.songMatch = SongMatch(appleMusicURL: matchedMediaItem.appleMusicURL,
                                        artist: matchedMediaItem.artist,
                                        artworkURL: matchedMediaItem.artworkURL,
                                        title: matchedMediaItem.title)
        
        }
    }
    
}
struct SongMatch {
    let appleMusicURL: URL?
    let artist: String?
    let artworkURL: URL?
    let title: String?
}