//
//  GraphicCodesReader.swift
//  pmd
//
//  Created by Tomasz Kiszka on 24/05/2017.
//  Copyright © 2017 EARP. All rights reserved.
//

import UIKit
import AVFoundation

protocol GraphicCodesReaderDelegate: class {

    func didCaptureCodes(_ codes: [GraphicCodeType]) -> Bool
    func didFailInitializingCaptureSession(error: Error)
}

struct GraphicCodeType {

    let code: String
    let type: String
}

class GraphicCodesReader: NSObject {

    weak var delegate: GraphicCodesReaderDelegate?

    fileprivate var cameraFrameView: UIView?
    fileprivate(set) var captureSession: AVCaptureSession?
    fileprivate var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    fileprivate var metadataObjectTypes: [String]

    init(metadataObjectTypes: [String]? = nil) {
        if let objectTypes = metadataObjectTypes {
            self.metadataObjectTypes = objectTypes
        }
        else {
            // If none provided, let's make it all possible objects
            self.metadataObjectTypes = [AVMetadataObjectTypeQRCode,
                                        AVMetadataObjectTypeUPCECode,
                                        AVMetadataObjectTypeCode39Code,
                                        AVMetadataObjectTypeCode39Mod43Code,
                                        AVMetadataObjectTypeEAN13Code,
                                        AVMetadataObjectTypeEAN8Code,
                                        AVMetadataObjectTypeCode93Code,
                                        AVMetadataObjectTypeCode128Code,
                                        AVMetadataObjectTypePDF417Code,
                                        AVMetadataObjectTypeAztecCode]
        }
    }

    func prepareCaptureSession(cameraFrameView: UIView) {
        self.cameraFrameView = cameraFrameView
        let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
        do {
            let input = try AVCaptureDeviceInput(device: captureDevice)
            captureSession = AVCaptureSession()
            captureSession?.addInput(input)
        }
        catch {
            delegate?.didFailInitializingCaptureSession(error: error)
            return
        }
        let captureMetadataOutput = AVCaptureMetadataOutput()
        captureSession?.addOutput(captureMetadataOutput)
        captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
        captureMetadataOutput.metadataObjectTypes = metadataObjectTypes

        videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
        videoPreviewLayer?.frame = cameraFrameView.layer.bounds
        cameraFrameView.layer.addSublayer(videoPreviewLayer!)

        captureSession?.startRunning()
    }

    func resumeCaptureSession() {
        captureSession?.startRunning()
    }

    func pauseCaptureSession() {
        captureSession?.stopRunning()
    }
}

extension GraphicCodesReader: AVCaptureMetadataOutputObjectsDelegate {

    func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
        let codes = metadataObjects
            .map { (object) -> GraphicCodeType? in
                guard let readableCodeObject = object as? AVMetadataMachineReadableCodeObject else { return nil }
                return GraphicCodeType(code: readableCodeObject.stringValue, type: readableCodeObject.type)
            }
            .flatMap { $0 }
        let shouldStopRunning = delegate?.didCaptureCodes(codes) ?? false
        if  shouldStopRunning {
            captureSession?.stopRunning()
        }
    }
}