import SwiftUI

// MARK: - 通用验证组件
struct ValidationView: View {
    let validationState: ValidationState
    let message: String?
    let showIcon: Bool
    
    init(
        validationState: ValidationState,
        message: String? = nil,
        showIcon: Bool = true
    ) {
        self.validationState = validationState
        self.message = message
        self.showIcon = showIcon
    }
    
    var body: some View {
        if validationState != .none {
            HStack(spacing: 6) {
                if showIcon {
                    Image(systemName: iconName)
                        .font(.caption)
                        .foregroundColor(iconColor)
                }
                
                if let message = message {
                    Text(message)
                        .font(.caption)
                        .foregroundColor(textColor)
                }
                
                Spacer()
            }
            .padding(.horizontal, 12)
            .padding(.vertical, 6)
            .background(
                RoundedRectangle(cornerRadius: 6)
                    .fill(backgroundColor)
            )
        }
    }
    
    private var iconName: String {
        switch validationState {
        case .none:
            return ""
        case .valid:
            return "checkmark.circle"
        case .warning:
            return "exclamationmark.triangle"
        case .error:
            return "xmark.circle"
        case .info:
            return "info.circle"
        }
    }
    
    private var iconColor: Color {
        switch validationState {
        case .none:
            return .clear
        case .valid:
            return .green
        case .warning:
            return .orange
        case .error:
            return .red
        case .info:
            return .blue
        }
    }
    
    private var textColor: Color {
        switch validationState {
        case .none:
            return .clear
        case .valid:
            return .green
        case .warning:
            return .orange
        case .error:
            return .red
        case .info:
            return .blue
        }
    }
    
    private var backgroundColor: Color {
        switch validationState {
        case .none:
            return .clear
        case .valid:
            return .green.opacity(0.1)
        case .warning:
            return .orange.opacity(0.1)
        case .error:
            return .red.opacity(0.1)
        case .info:
            return .blue.opacity(0.1)
        }
    }
}

// MARK: - 验证状态枚举
enum ValidationState {
    case none
    case valid
    case warning
    case error
    case info
}

// MARK: - 预定义的验证样式
extension ValidationView {
    static func success(message: String, showIcon: Bool = true) -> ValidationView {
        ValidationView(
            validationState: .valid,
            message: message,
            showIcon: showIcon
        )
    }
    
    static func warning(message: String, showIcon: Bool = true) -> ValidationView {
        ValidationView(
            validationState: .warning,
            message: message,
            showIcon: showIcon
        )
    }
    
    static func error(message: String, showIcon: Bool = true) -> ValidationView {
        ValidationView(
            validationState: .error,
            message: message,
            showIcon: showIcon
        )
    }
    
    static func info(message: String, showIcon: Bool = true) -> ValidationView {
        ValidationView(
            validationState: .info,
            message: message,
            showIcon: showIcon
        )
    }
}

// MARK: - 字符计数验证
struct CharacterCountValidation: View {
    let currentCount: Int
    let maxCount: Int
    let warningThreshold: Double
    
    init(
        currentCount: Int,
        maxCount: Int,
        warningThreshold: Double = 0.9
    ) {
        self.currentCount = currentCount
        self.maxCount = maxCount
        self.warningThreshold = warningThreshold
    }
    
    var body: some View {
        HStack {
            Spacer()
            
            if currentCount >= maxCount {
                ValidationView.error(message: "已达到最大字符数")
            } else if currentCount >= Int(Double(maxCount) * warningThreshold) {
                ValidationView.warning(message: "接近字符限制")
            } else {
                Text("\(currentCount)/\(maxCount)")
                    .font(.caption)
                    .foregroundColor(.secondary)
            }
        }
    }
}

// MARK: - 必填字段验证
struct RequiredFieldValidation: View {
    let fieldName: String
    let isEmpty: Bool
    
    var body: some View {
        if isEmpty {
            ValidationView.error(message: "\(fieldName)为必填项")
        }
    }
}

// MARK: - 格式验证
struct FormatValidation: View {
    let fieldName: String
    let isValid: Bool
    let errorMessage: String?
    
    init(
        fieldName: String,
        isValid: Bool,
        errorMessage: String? = nil
    ) {
        self.fieldName = fieldName
        self.isValid = isValid
        self.errorMessage = errorMessage
    }
    
    var body: some View {
        if !isValid {
            ValidationView.error(
                message: errorMessage ?? "\(fieldName)格式不正确"
            )
        }
    }
}

#Preview {
    VStack(spacing: 16) {
        ValidationView.success(message: "验证成功！")
        ValidationView.warning(message: "这是一个警告")
        ValidationView.error(message: "这是一个错误")
        ValidationView.info(message: "这是一个提示")
        
        CharacterCountValidation(currentCount: 95, maxCount: 100)
        CharacterCountValidation(currentCount: 100, maxCount: 100)
        
        RequiredFieldValidation(fieldName: "用户名", isEmpty: true)
        RequiredFieldValidation(fieldName: "邮箱", isEmpty: false)
        
        FormatValidation(fieldName: "邮箱地址", isValid: false)
        FormatValidation(fieldName: "电话号码", isValid: true)
    }
    .padding()
}