//
//  LNImagePreviewController.swift
//  Lanu
//
//  Created by OneeChan on 2025/12/11.
//

import Foundation
import UIKit
import SnapKit


extension UIView {
    func presentImagePreview(_ urls: [String], _ targetIndex: Int) {
        let vc = LNImagePreviewController()
        vc.loadImages(urls: urls, targetIndex: targetIndex)
        vc.modalPresentationStyle = .overFullScreen
        viewController?.present(vc, animated: true)
    }
}


class LNImagePreviewController: LNViewController {
    private var imageURLs: [String] = []
    private var curIndex: Int = 0 {
        didSet {
            titleLabel.text = "\(curIndex + 1)/\(imageURLs.count)"
        }
    }
    
    private var collectionView: UICollectionView?
    
    private let fakeBar = LNFakeNaviBar()
    private let titleLabel = UILabel()
    
    func loadImages(urls: [String], targetIndex: Int) {
        imageURLs = urls
        curIndex = targetIndex
        
        collectionView?.reloadData()
        runOnMain { [weak self] in
            guard let self else { return }
            collectionView?.scrollToItem(
                at: .init(row: curIndex, section: 0),
                at: .centeredHorizontally,
                animated: false)
        }
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        showNavigationBar = false
        setupViews()
    }
}

extension LNImagePreviewController: LNImagePreviewCellDelegate {
    func onImagePreviewCellDragToDismiss(cell: LNImagePreviewCell) {
        dismiss(animated: false)
    }
}

extension LNImagePreviewController: UICollectionViewDataSource, UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        imageURLs.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: LNImagePreviewCell.className, for: indexPath) as! LNImagePreviewCell
        cell.update(url: imageURLs[indexPath.row])
        cell.delegate = self
        return cell
    }
    
    func collectionView(_ collectionView: UICollectionView, didEndDisplaying cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
        let previewCell = cell as! LNImagePreviewCell
        previewCell.resetZoom()
    }
    
    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        curIndex = Int(scrollView.contentOffset.x / scrollView.bounds.width)
    }
    
    func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
        curIndex = Int(scrollView.contentOffset.x / scrollView.bounds.width)
    }
}

extension LNImagePreviewController {
    private func setupViews() {
        view.backgroundColor = .clear
        
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .horizontal
        layout.itemSize = view.bounds.size
        layout.minimumLineSpacing = 0
        layout.minimumInteritemSpacing = 0
        
        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
        collectionView.isPagingEnabled = true
        collectionView.showsHorizontalScrollIndicator = false
        collectionView.backgroundColor = .black
        collectionView.register(LNImagePreviewCell.self, forCellWithReuseIdentifier: LNImagePreviewCell.className)
        collectionView.dataSource = self
        collectionView.delegate = self
        view.addSubview(collectionView)
        collectionView.snp.makeConstraints { make in
            make.edges.equalToSuperview()
        }
        self.collectionView = collectionView
        
        let fakeBar = buildFakeNavBar()
        view.addSubview(fakeBar)
        fakeBar.snp.makeConstraints { make in
            make.horizontalEdges.equalToSuperview()
            make.top.equalToSuperview()
        }
    }
    
    private func buildFakeNavBar() -> UIView {
        fakeBar.showBackButton { [weak self] in
            guard let self else { return }
            dismiss(animated: true)
        }
        fakeBar.backButton?.setImage(.init(systemName: "chevron.backward")?.withRenderingMode(.alwaysTemplate), for: .normal)
        fakeBar.backButton?.tintColor = .fill
        
        titleLabel.font = .body_l
        titleLabel.textColor = .text_1
        fakeBar.actionView.addSubview(titleLabel)
        titleLabel.snp.makeConstraints { make in
            make.center.equalToSuperview()
        }
        
        return fakeBar
    }
}