PagerView.swift

//
//  PagerView.swift
//  Lucify (iOS)
//
//  Created by Patrick Elfert on 26.06.22.
//

import SwiftUI

struct PagerView<Content: View>: View {
    let pageCount: Int
    @Binding var currentIndex: Int
    let content: Content

    @GestureState private var translation: CGFloat = 0

    init(pageCount: Int, currentIndex: Binding<Int>, @ViewBuilder content: () -> Content) {
        self.pageCount = pageCount
        _currentIndex = currentIndex
        self.content = content()
    }

    var body: some View {
        GeometryReader { geometry in
            HStack(spacing: 0) {
                self.content.frame(width: geometry.size.width)
            }
            .frame(width: geometry.size.width, alignment: .leading)
            .offset(x: -CGFloat(self.currentIndex) * geometry.size.width)
            .offset(x: self.translation)
            .gesture(
                DragGesture().updating(self.$translation) { value, state, _ in
                    state = value.translation.width
                }.onEnded { value in
                    withAnimation(.interactiveSpring()) {
                        let offset = value.translation.width / geometry.size.width
                        let newIndex = (CGFloat(self.currentIndex) - offset).rounded()
                        self.currentIndex = min(max(Int(newIndex), 0), self.pageCount - 1)
                    }
                }
            )
        }
    }
}