// TextInput.swift
// iOS UI Components - Form Components
//
// Text input field with validation and states (iOS only)

#if canImport(UIKit)
import SwiftUI
import UIKit
import LilithDesignTokens

/// Text input field
///
/// Styled text field with label, placeholder, validation, and error states.
///
/// Example:
/// ```swift
/// @State private var email = ""
/// @State private var emailError: String?
///
/// TextInput(
///     "Email",
///     text: $email,
///     placeholder: "you@example.com",
///     errorMessage: emailError,
///     keyboardType: .emailAddress
/// )
/// ```
@available(iOS 13.0, *)
public struct TextInput: View {
    // MARK: - Properties

    private let label: String
    @Binding private var text: String
    private let placeholder: String
    private let errorMessage: String?
    private let helperText: String?
    private let keyboardType: UIKeyboardType
    private let autocapitalization: TextInputAutocapitalization
    private let isDisabled: Bool
    private let icon: Image?
    private let onCommit: (() -> Void)?

    // MARK: - Focus State

    @FocusState private var isFocused: Bool

    // MARK: - Initialization

    /// Create a text input
    /// - Parameters:
    ///   - label: Input label
    ///   - text: Binding to text value
    ///   - placeholder: Placeholder text
    ///   - errorMessage: Error message to display
    ///   - helperText: Helper text below input
    ///   - keyboardType: Keyboard type
    ///   - autocapitalization: Autocapitalization behavior
    ///   - isDisabled: Disable input
    ///   - icon: Optional leading icon
    ///   - onCommit: Action when return is pressed
    public init(
        _ label: String,
        text: Binding<String>,
        placeholder: String = "",
        errorMessage: String? = nil,
        helperText: String? = nil,
        keyboardType: UIKeyboardType = .default,
        autocapitalization: TextInputAutocapitalization = .sentences,
        isDisabled: Bool = false,
        icon: Image? = nil,
        onCommit: (() -> Void)? = nil
    ) {
        self.label = label
        self._text = text
        self.placeholder = placeholder
        self.errorMessage = errorMessage
        self.helperText = helperText
        self.keyboardType = keyboardType
        self.autocapitalization = autocapitalization
        self.isDisabled = isDisabled
        self.icon = icon
        self.onCommit = onCommit
    }

    // MARK: - Body

    public var body: some View {
        VStack(alignment: .leading, spacing: AppSpacing.xs) {
            // Label
            Text(label)
                .font(AppTypography.label(weight: .medium))
                .foregroundColor(labelColor)

            // Input container
            HStack(spacing: AppSpacing.sm) {
                if let icon = icon {
                    icon
                        .font(.system(size: AppTypography.FontSize.base))
                        .foregroundColor(iconColor)
                }

                TextField(placeholder, text: $text)
                    .font(AppTypography.body())
                    .foregroundColor(AppColors.textPrimary)
                    .keyboardType(keyboardType)
                    .textInputAutocapitalization(autocapitalization)
                    .disabled(isDisabled)
                    .focused($isFocused)
                    .onSubmit {
                        onCommit?()
                    }

                // Clear button
                if !text.isEmpty && isFocused {
                    Button(action: { text = "" }) {
                        Image(systemName: "xmark.circle.fill")
                            .font(.system(size: AppTypography.FontSize.base))
                            .foregroundColor(AppColors.textTertiary)
                    }
                }
            }
            .padding(.horizontal, AppSpacing.md)
            .padding(.vertical, AppSpacing.sm)
            .background(backgroundColor)
            .overlay(
                RoundedRectangle(cornerRadius: AppRadius.input)
                    .stroke(borderColor, lineWidth: isFocused ? 2 : 1)
            )
            .clipShape(RoundedRectangle(cornerRadius: AppRadius.input))

            // Helper or error text
            if let errorMessage = errorMessage {
                Text(errorMessage)
                    .font(AppTypography.caption())
                    .foregroundColor(AppColors.Semantic.error)
            } else if let helperText = helperText {
                Text(helperText)
                    .font(AppTypography.caption())
                    .foregroundColor(AppColors.textSecondary)
            }
        }
        .animation(AppAnimations.fast, value: isFocused)
        .animation(AppAnimations.fast, value: errorMessage)
    }

    // MARK: - Computed Properties

    private var labelColor: Color {
        if isDisabled {
            return AppColors.textTertiary
        }
        if errorMessage != nil {
            return AppColors.Semantic.error
        }
        if isFocused {
            return AppColors.primary
        }
        return AppColors.textSecondary
    }

    private var borderColor: Color {
        if isDisabled {
            return AppColors.Gray.gray700
        }
        if errorMessage != nil {
            return AppColors.Semantic.error
        }
        if isFocused {
            return AppColors.primary
        }
        return AppColors.border
    }

    private var backgroundColor: Color {
        isDisabled ? AppColors.Gray.gray800 : AppColors.surface
    }

    private var iconColor: Color {
        if isDisabled {
            return AppColors.textTertiary
        }
        if isFocused {
            return AppColors.primary
        }
        return AppColors.textSecondary
    }
}

// MARK: - Preview Provider

#if DEBUG
struct TextInput_Previews: PreviewProvider {
    static var previews: some View {
        VStack(spacing: AppSpacing.xl) {
            // Default state
            TextInput("Email", text: .constant(""), placeholder: "you@example.com")

            // With value
            TextInput("Name", text: .constant("John Doe"))

            // With icon
            TextInput(
                "Email",
                text: .constant(""),
                placeholder: "you@example.com",
                icon: Image(systemName: "envelope")
            )

            // With helper text
            TextInput(
                "Username",
                text: .constant(""),
                placeholder: "Choose a username",
                helperText: "Must be unique and 3-20 characters"
            )

            // With error
            TextInput(
                "Email",
                text: .constant("invalid"),
                placeholder: "you@example.com",
                errorMessage: "Please enter a valid email address"
            )

            // Disabled
            TextInput(
                "Locked Field",
                text: .constant("Cannot edit"),
                isDisabled: true
            )
        }
        .padding()
        .background(AppColors.background)
        .previewDisplayName("Text Input States")
    }
}
#endif
#endif