swift-forms/Sources/LilithForms/Checkbox.swift

// Checkbox.swift
// iOS UI Components - Form Components
//
// Checkbox with label and indeterminate state

import SwiftUI
import LilithDesignTokens

/// Checkbox control
///
/// Checkbox with optional label and indeterminate state support.
///
/// Example:
/// ```swift
/// @State private var isAgreed = false
///
/// Checkbox(
///     "I agree to the terms",
///     isChecked: $isAgreed
/// )
/// ```
public struct Checkbox: View {
    // MARK: - CheckboxState

    public enum CheckboxState {
        case unchecked
        case checked
        case indeterminate
    }

    // MARK: - Properties

    private let label: String?
    @Binding private var isChecked: Bool
    private let isIndeterminate: Bool
    private let isDisabled: Bool
    private let onChange: ((Bool) -> Void)?

    // MARK: - State

    @State private var isPressed = false

    // MARK: - Initialization

    /// Create a checkbox
    /// - Parameters:
    ///   - label: Optional label text
    ///   - isChecked: Binding to checked state
    ///   - isIndeterminate: Show indeterminate state
    ///   - isDisabled: Disable interaction
    ///   - onChange: Callback when checked state changes
    public init(
        _ label: String? = nil,
        isChecked: Binding<Bool>,
        isIndeterminate: Bool = false,
        isDisabled: Bool = false,
        onChange: ((Bool) -> Void)? = nil
    ) {
        self.label = label
        self._isChecked = isChecked
        self.isIndeterminate = isIndeterminate
        self.isDisabled = isDisabled
        self.onChange = onChange
    }

    // MARK: - Body

    public var body: some View {
        Button(action: handleTap) {
            HStack(spacing: AppSpacing.sm) {
                // Checkbox box
                ZStack {
                    RoundedRectangle(cornerRadius: AppRadius.xs)
                        .fill(boxBackgroundColor)
                        .frame(width: 24, height: 24)

                    RoundedRectangle(cornerRadius: AppRadius.xs)
                        .stroke(borderColor, lineWidth: 2)
                        .frame(width: 24, height: 24)

                    // Checkmark or dash
                    if isIndeterminate {
                        Rectangle()
                            .fill(checkmarkColor)
                            .frame(width: 12, height: 2)
                    } else if isChecked {
                        Image(systemName: "checkmark")
                            .font(.system(size: 14, weight: .bold))
                            .foregroundColor(checkmarkColor)
                    }
                }
                .scaleEffect(isPressed ? 0.9 : 1.0)
                .animation(AppAnimations.buttonPress, value: isPressed)

                // Label
                if let label = label {
                    Text(label)
                        .font(AppTypography.body())
                        .foregroundColor(labelColor)
                        .multilineTextAlignment(.leading)
                }
            }
        }
        .disabled(isDisabled)
        .buttonStyle(PlainButtonStyle())
        .accessibilityElement(children: .combine)
        .accessibilityLabel(label ?? "Checkbox")
        .accessibilityAddTraits(isChecked ? [.isSelected] : [])
        .accessibilityHint("Double tap to \(isChecked ? "uncheck" : "check")")
        .onLongPressGesture(minimumDuration: .infinity, maximumDistance: .infinity, pressing: { pressing in
            if !isDisabled {
                isPressed = pressing
            }
        }, perform: {})
    }

    // MARK: - Computed Properties

    private var state: CheckboxState {
        if isIndeterminate {
            return .indeterminate
        }
        return isChecked ? .checked : .unchecked
    }

    private var boxBackgroundColor: Color {
        if isDisabled {
            return AppColors.Gray.gray800
        }
        if isChecked || isIndeterminate {
            return AppColors.primary
        }
        return AppColors.surface
    }

    private var borderColor: Color {
        if isDisabled {
            return AppColors.Gray.gray600
        }
        if isChecked || isIndeterminate {
            return AppColors.primary
        }
        return AppColors.border
    }

    private var checkmarkColor: Color {
        .white
    }

    private var labelColor: Color {
        isDisabled ? AppColors.textTertiary : AppColors.textPrimary
    }

    // MARK: - Methods

    private func handleTap() {
        guard !isDisabled else { return }

        isChecked.toggle()

        // Light haptic feedback
#if canImport(UIKit)
        let generator = UIImpactFeedbackGenerator(style: .light)
        generator.impactOccurred()
#endif

        onChange?(isChecked)
    }
}

// MARK: - Preview Provider

#if DEBUG
struct Checkbox_Previews: PreviewProvider {
    static var previews: some View {
        VStack(alignment: .leading, spacing: AppSpacing.xl) {
            // Unchecked
            Checkbox("Unchecked", isChecked: .constant(false))

            // Checked
            Checkbox("Checked", isChecked: .constant(true))

            // Indeterminate
            Checkbox("Indeterminate", isChecked: .constant(false), isIndeterminate: true)

            // Disabled unchecked
            Checkbox("Disabled Unchecked", isChecked: .constant(false), isDisabled: true)

            // Disabled checked
            Checkbox("Disabled Checked", isChecked: .constant(true), isDisabled: true)

            // Without label
            HStack {
                Checkbox(isChecked: .constant(false))
                Checkbox(isChecked: .constant(true))
                Checkbox(isChecked: .constant(false), isIndeterminate: true)
            }

            Divider()

            // In context - Settings form
            VStack(alignment: .leading, spacing: AppSpacing.md) {
                Text("Notification Settings")
                    .font(AppTypography.h3())
                    .foregroundColor(AppColors.textPrimary)

                Checkbox("Email notifications", isChecked: .constant(true))
                Checkbox("Push notifications", isChecked: .constant(true))
                Checkbox("SMS notifications", isChecked: .constant(false))
                Checkbox("Marketing emails", isChecked: .constant(false), isDisabled: true)
            }
            .padding()
            .background(AppColors.surface)
            .clipShape(RoundedRectangle(cornerRadius: AppRadius.card))

            Divider()

            // In context - Terms agreement
            HStack(alignment: .top, spacing: AppSpacing.sm) {
                Checkbox(isChecked: .constant(false))

                VStack(alignment: .leading, spacing: AppSpacing.xs) {
                    Text("I agree to the Terms of Service and Privacy Policy")
                        .font(AppTypography.body())
                        .foregroundColor(AppColors.textPrimary)

                    Text("Required to create an account")
                        .font(AppTypography.caption())
                        .foregroundColor(AppColors.textSecondary)
                }
            }
            .padding()
            .background(AppColors.surface)
            .clipShape(RoundedRectangle(cornerRadius: AppRadius.card))
        }
        .padding()
        .background(AppColors.background)
        .previewDisplayName("Checkbox States")
    }
}
#endif