//
// Swiftfin is subject to the terms of the Mozilla Public
// License, v2.0. If a copy of the MPL was not distributed with this
// file, you can obtain one at https://mozilla.org/MPL/2.0/.
//
// Copyright (c) 2022 Jellyfin & Jellyfin Contributors
//

import SwiftUI

struct TruncatedTextView: View {

    @State
    private var truncated: Bool = false
    @State
    private var shrinkText: String
    private var text: String
    let font: UIFont
    let lineLimit: Int
    let seeMoreAction: () -> Void

    private var moreLessText: String {
        if !truncated {
            return ""
        } else {
            return L10n.seeMore
        }
    }

    init(
        _ text: String,
        lineLimit: Int,
        font: UIFont = UIFont.preferredFont(forTextStyle: UIFont.TextStyle.body),
        seeMoreAction: @escaping () -> Void
    ) {
        self.text = text
        self.lineLimit = lineLimit
        _shrinkText = State(wrappedValue: text)
        self.font = font
        self.seeMoreAction = seeMoreAction
    }

    var body: some View {
        VStack(alignment: .center) {
            Group {
                Text(shrinkText)
                    .overlay {
                        if truncated {
                            LinearGradient(
                                stops: [
                                    .init(color: .systemBackground.opacity(0), location: 0.5),
                                    .init(color: .systemBackground.opacity(0.8), location: 0.7),
                                    .init(color: .systemBackground, location: 1),
                                ],
                                startPoint: .top,
                                endPoint: .bottom
                            )
                        }
                    }
            }
            .lineLimit(lineLimit)
            .background {
                // Render the limited text and measure its size
                Text(text)
                    .lineLimit(lineLimit + 2)
                    .background {
                        GeometryReader { visibleTextGeometry in
                            Color.clear
                                .onAppear {
                                    let size = CGSize(width: visibleTextGeometry.size.width, height: .greatestFiniteMagnitude)
                                    let attributes: [NSAttributedString.Key: Any] = [NSAttributedString.Key.font: font]
                                    var low = 0
                                    var heigh = shrinkText.count
                                    var mid = heigh
                                    while (heigh - low) > 1 {
                                        let attributedText = NSAttributedString(string: shrinkText, attributes: attributes)
                                        let boundingRect = attributedText.boundingRect(
                                            with: size,
                                            options: NSStringDrawingOptions
                                                .usesLineFragmentOrigin,
                                            context: nil
                                        )
                                        if boundingRect.size.height > visibleTextGeometry.size.height {
                                            truncated = true
                                            heigh = mid
                                            mid = (heigh + low) / 2

                                        } else {
                                            if mid == text.count {
                                                break
                                            } else {
                                                low = mid
                                                mid = (low + heigh) / 2
                                            }
                                        }
                                        shrinkText = String(text.prefix(mid))
                                    }

                                    if truncated {
                                        shrinkText = String(shrinkText.prefix(shrinkText.count - 2))
                                    }
                                }
                        }
                    }
                    .hidden()
            }
            .font(Font(font))

            if truncated {
                Button {
                    seeMoreAction()
                } label: {
                    Text(moreLessText)
                }
            }
        }
    }
}