import SwiftUI

struct ContentView: View {
    @StateObject private var game = ShikakuGame(size: 5)
    @State private var mode: DrawingMode = .draw
    @State private var zoom: CGFloat = 1.0
    @State private var pinchStartZoom: CGFloat?
    @State private var isShowingSeedSheet = false
    @State private var seedInput = ""
    @State private var seedError: String?

    private let zoomMinimum: CGFloat = 0.5
    private let zoomMaximum: CGFloat = 3.0
    private let zoomStep: CGFloat = 0.15

    var body: some View {
        VStack(spacing: 12) {
            header
            sizePicker
            modePicker
            boardViewport
            zoomControls
            controls
            statusText
        }
        .padding(.top, 18)
        .padding(.bottom, 20)
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .background(ShikakuTheme.background.ignoresSafeArea())
        .sheet(isPresented: $isShowingSeedSheet) {
            seedSheet
        }
    }

    private var header: some View {
        HStack {
            Text("SHIKAKU")
                .font(.system(size: 24, weight: .black, design: .rounded))
                .foregroundStyle(ShikakuTheme.primaryText)

            Spacer()

            TimelineView(.periodic(from: .now, by: 1)) { timeline in
                Text(game.formattedElapsed(at: timeline.date))
                    .font(.system(size: 18, weight: .semibold, design: .monospaced))
                    .foregroundStyle(ShikakuTheme.mutedText)
                    .monospacedDigit()
            }
        }
        .padding(.horizontal, 20)
    }

    private var sizePicker: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 8) {
                ForEach(ShikakuGame.supportedSizes, id: \.self) { size in
                    Button {
                        guard size != game.size else {
                            return
                        }

                        game.newPuzzle(size: size)
                        mode = .draw
                        resetZoom()
                    } label: {
                        Text("\(size)x\(size)")
                            .font(.system(size: 13, weight: .semibold, design: .rounded))
                            .monospacedDigit()
                            .frame(minWidth: 56)
                    }
                    .buttonStyle(.bordered)
                    .tint(size == game.size ? ShikakuTheme.accent : ShikakuTheme.mutedText)
                }
            }
            .padding(.horizontal, 20)
        }
    }

    private var modePicker: some View {
        Picker("Mode", selection: $mode) {
            ForEach(DrawingMode.allCases) { mode in
                Label(mode.title, systemImage: mode.symbolName).tag(mode)
            }
        }
        .pickerStyle(.segmented)
        .padding(.horizontal, 20)
    }

    private var boardViewport: some View {
        GeometryReader { proxy in
            let currentBoardSide = boardSide
            let contentWidth = max(currentBoardSide + 32, proxy.size.width)
            let contentHeight = max(currentBoardSide + 32, proxy.size.height)

            ScrollView([.horizontal, .vertical]) {
                ZStack {
                    ShikakuGridView(game: game, mode: mode, side: currentBoardSide)
                }
                .frame(width: contentWidth, height: contentHeight, alignment: .center)
            }
            .scrollIndicators(.visible)
            .background(ShikakuTheme.panel)
            .clipShape(RoundedRectangle(cornerRadius: 8, style: .continuous))
            .simultaneousGesture(pinchZoomGesture)
        }
        .padding(.horizontal, 12)
        .frame(maxHeight: .infinity)
    }

    private var zoomControls: some View {
        HStack(spacing: 12) {
            Button {
                updateZoom(by: -zoomStep)
            } label: {
                Image(systemName: "minus.magnifyingglass")
                    .frame(width: 34, height: 34)
            }
            .buttonStyle(.bordered)
            .disabled(zoom <= zoomMinimum)

            Text("\(Int((zoom * 100).rounded()))%")
                .font(.system(size: 14, weight: .semibold, design: .monospaced))
                .foregroundStyle(ShikakuTheme.mutedText)
                .monospacedDigit()
                .frame(width: 58)

            Button {
                updateZoom(by: zoomStep)
            } label: {
                Image(systemName: "plus.magnifyingglass")
                    .frame(width: 34, height: 34)
            }
            .buttonStyle(.bordered)
            .disabled(zoom >= zoomMaximum)

            Button {
                resetZoom()
            } label: {
                Label("100%", systemImage: "arrow.counterclockwise")
            }
            .buttonStyle(.bordered)
            .tint(ShikakuTheme.mutedText)
        }
        .font(.system(size: 14, weight: .semibold, design: .rounded))
        .padding(.horizontal, 20)
    }

    private var controls: some View {
        LazyVGrid(columns: [GridItem(.flexible()), GridItem(.flexible())], spacing: 10) {
            Button {
                game.newPuzzle()
                mode = .draw
            } label: {
                Label("New", systemImage: "arrow.clockwise")
                    .frame(maxWidth: .infinity)
            }
            .buttonStyle(.borderedProminent)
            .tint(ShikakuTheme.accent)

            Button {
                game.checkSolution()
            } label: {
                Label("Check", systemImage: "checkmark.circle")
                    .frame(maxWidth: .infinity)
            }
            .buttonStyle(.bordered)
            .tint(ShikakuTheme.primaryText)

            Button(role: .destructive) {
                game.clear()
                mode = .draw
            } label: {
                Label("Clear", systemImage: "trash")
                    .frame(maxWidth: .infinity)
            }
            .buttonStyle(.bordered)

            Button {
                seedInput = ""
                seedError = nil
                isShowingSeedSheet = true
            } label: {
                Label("Seed", systemImage: "number")
                    .frame(maxWidth: .infinity)
            }
            .buttonStyle(.bordered)
            .tint(ShikakuTheme.primaryText)
        }
        .font(.system(size: 15, weight: .semibold, design: .rounded))
        .padding(.horizontal, 20)
    }

    private var statusText: some View {
        Text(game.message)
            .font(.system(size: 14, weight: .medium, design: .rounded))
            .foregroundStyle(statusColor)
            .frame(height: 20)
            .lineLimit(1)
            .minimumScaleFactor(0.75)
            .padding(.horizontal, 20)
    }

    private var statusColor: Color {
        switch game.status {
        case .playing:
            return ShikakuTheme.mutedText
        case .solved:
            return ShikakuTheme.success
        case .error:
            return ShikakuTheme.error
        }
    }

    private var seedSheet: some View {
        VStack(alignment: .leading, spacing: 16) {
            Text("CURRENT SEED")
                .font(.system(size: 12, weight: .bold, design: .rounded))
                .foregroundStyle(ShikakuTheme.mutedText)

            Text("\(game.currentSeed)")
                .font(.system(size: 22, weight: .bold, design: .monospaced))
                .foregroundStyle(ShikakuTheme.primaryText)
                .textSelection(.enabled)

            Divider()

            TextField("e.g. 123456789", text: $seedInput)
                .font(.system(size: 18, weight: .semibold, design: .monospaced))
                .keyboardType(.numbersAndPunctuation)
                .submitLabel(.go)
                .onSubmit(startPuzzleFromSeed)
                .textFieldStyle(.roundedBorder)

            if let seedError {
                Text(seedError)
                    .font(.system(size: 13, weight: .medium, design: .rounded))
                    .foregroundStyle(ShikakuTheme.error)
            }

            Spacer(minLength: 0)

            HStack {
                Button("Cancel") {
                    isShowingSeedSheet = false
                }
                .buttonStyle(.bordered)

                Spacer()

                Button {
                    startPuzzleFromSeed()
                } label: {
                    Label("Start Puzzle", systemImage: "play.fill")
                }
                .buttonStyle(.borderedProminent)
                .tint(ShikakuTheme.accent)
            }
        }
        .padding(24)
        .presentationDetents([.height(320)])
        .presentationDragIndicator(.visible)
        .background(ShikakuTheme.background)
    }

    private var boardSide: CGFloat {
        CGFloat(game.size) * baseCellSide(for: game.size) * zoom
    }

    private var pinchZoomGesture: some Gesture {
        MagnificationGesture()
            .onChanged { value in
                if pinchStartZoom == nil {
                    pinchStartZoom = zoom
                }

                zoom = clampedZoom((pinchStartZoom ?? zoom) * value)
            }
            .onEnded { _ in
                pinchStartZoom = nil
            }
    }

    private func baseCellSide(for size: Int) -> CGFloat {
        switch size {
        case 5:
            return 56
        case 7:
            return 52
        case 10:
            return 46
        case 15:
            return 36
        case 20:
            return 28
        case 25:
            return 24
        default:
            return 40
        }
    }

    private func updateZoom(by delta: CGFloat) {
        zoom = clampedZoom(zoom + delta)
    }

    private func resetZoom() {
        zoom = 1.0
        pinchStartZoom = nil
    }

    private func clampedZoom(_ value: CGFloat) -> CGFloat {
        min(zoomMaximum, max(zoomMinimum, value))
    }

    private func startPuzzleFromSeed() {
        let trimmed = seedInput.trimmingCharacters(in: .whitespacesAndNewlines)
        guard let seed = UInt64(trimmed) else {
            seedError = "Enter a whole-number seed."
            return
        }

        game.newPuzzle(seed: seed)
        mode = .draw
        resetZoom()
        isShowingSeedSheet = false
    }
}