import SwiftUI

/// Modal sheet for server-backed account login and registration.
struct AuthModalView: View {
    @Environment(\.dismiss) private var dismiss
    @ObservedObject var authManager: AuthManager = .shared
    
    @State private var selectedTab: AuthTab = .login
    @State private var usernameInput: String = ""
    @State private var identifierInput: String = ""
    @State private var passwordInput: String = ""
    @State private var confirmPasswordInput: String = ""
    @State private var errorMessage: String?
    
    enum AuthTab {
        case login
        case register
    }
    
    var body: some View {
        ZStack {
            Color.spaceBlack.ignoresSafeArea()
            
            VStack(spacing: 20) {
                // Header
                HStack {
                    Spacer()
                    Button {
                        dismiss()
                    } label: {
                        Image(systemName: "xmark.circle.fill")
                            .font(.system(size: 22))
                            .foregroundStyle(Color.secondary.opacity(0.6))
                    }
                }
                .padding(.horizontal, 16)
                .padding(.top, 16)
                
                // Title
                VStack(spacing: 6) {
                    Text(selectedTab == .login ? "账号登录" : "创建新账号")
                        .font(.system(size: 22, weight: .bold))
                        .foregroundStyle(Color.primary)
                    
                    Text(selectedTab == .login ? "登录以同步录音并管理专属设备" : "注册后可将本机记录安全同步至云端")
                        .font(.system(size: 12))
                        .foregroundStyle(Color.secondary)
                        .multilineTextAlignment(.center)
                }
                .padding(.horizontal, 24)
                
                // Tab Picker
                HStack(spacing: 0) {
                    tabButton(title: "登录", tab: .login)
                    tabButton(title: "注册账号", tab: .register)
                }
                .background(Color.cardBackground.opacity(0.4))
                .cornerRadius(8)
                .padding(.horizontal, 24)
                .padding(.top, 8)
                
                // Input Fields
                VStack(spacing: 14) {
                    if selectedTab == .register {
                        inputField(
                            icon: "person",
                            placeholder: "设置昵称 (如: 星痕探索者)",
                            text: $usernameInput
                        )
                    }
                    
                    inputField(
                        icon: "envelope",
                        placeholder: "手机号或电子邮箱",
                        text: $identifierInput
                    )
                    
                    inputField(
                        icon: "lock",
                        placeholder: "密码 (至少 6 位)",
                        text: $passwordInput,
                        isSecure: true
                    )
                    
                    if selectedTab == .register {
                        inputField(
                            icon: "lock.shield",
                            placeholder: "再次确认密码",
                            text: $confirmPasswordInput,
                            isSecure: true
                        )
                    }
                    
                    if let error = errorMessage {
                        Text(error)
                            .font(.system(size: 12))
                            .foregroundStyle(Color.recordingRed)
                            .frame(maxWidth: .infinity, alignment: .leading)
                            .padding(.horizontal, 4)
                    }
                }
                .padding(.horizontal, 24)
                .padding(.top, 12)
                
                Spacer()
                
                // Submit Button
                Button {
                    handleAuthSubmit()
                } label: {
                    if authManager.isProcessing {
                        ProgressView()
                            .tint(Color.spaceBlack)
                    } else {
                        Text(selectedTab == .login ? "安全登录" : "注册并自动登录")
                            .font(.system(size: 15, weight: .semibold))
                            .foregroundStyle(Color.spaceBlack)
                    }
                }
                .frame(maxWidth: .infinity)
                .padding(.vertical, 14)
                .background(Color.primary)
                .cornerRadius(8)
                .padding(.horizontal, 24)
                .padding(.bottom, 32)
                .disabled(authManager.isProcessing)
            }
        }
    }
    
    private func tabButton(title: String, tab: AuthTab) -> some View {
        Button {
            withAnimation(.snappy) {
                selectedTab = tab
                errorMessage = nil
            }
        } label: {
            Text(title)
                .font(.system(size: 14, weight: selectedTab == tab ? .semibold : .regular))
                .foregroundStyle(selectedTab == tab ? Color.primary : Color.secondary)
                .frame(maxWidth: .infinity)
                .padding(.vertical, 10)
                .background(
                    selectedTab == tab ? Color.cardBackground : Color.clear
                )
                .cornerRadius(6)
                .padding(2)
        }
    }
    
    private func inputField(icon: String, placeholder: String, text: Binding<String>, isSecure: Bool = false) -> some View {
        HStack(spacing: 12) {
            Image(systemName: icon)
                .font(.system(size: 14))
                .foregroundStyle(Color.secondary)
                .frame(width: 20)
            
            if isSecure {
                SecureField(placeholder, text: text)
                    .font(.system(size: 14))
            } else {
                TextField(placeholder, text: text)
                    .font(.system(size: 14))
                    .autocapitalization(.none)
                    .disableAutocorrection(true)
            }
        }
        .padding(.horizontal, 14)
        .padding(.vertical, 12)
        .background(Color.cardBackground.opacity(0.3))
        .businessBorder(cornerRadius: 8)
    }
    
    private func handleAuthSubmit() {
        errorMessage = nil
        
        if selectedTab == .login {
            guard !identifierInput.trimmingCharacters(in: .whitespaces).isEmpty else {
                errorMessage = "请输入手机号或邮箱"
                return
            }
            guard passwordInput.count >= 6 else {
                errorMessage = "密码不能少于 6 位"
                return
            }
            
            authManager.login(identifier: identifierInput, password: passwordInput) { success, err in
                if success {
                    dismiss()
                } else {
                    errorMessage = err ?? "登录失败"
                }
            }
        } else {
            let name = usernameInput.trimmingCharacters(in: .whitespaces)
            guard !name.isEmpty else {
                errorMessage = "请输入用户昵称"
                return
            }
            guard !identifierInput.trimmingCharacters(in: .whitespaces).isEmpty else {
                errorMessage = "请输入注册手机号或邮箱"
                return
            }
            guard passwordInput.count >= 6 else {
                errorMessage = "密码不能少于 6 位"
                return
            }
            guard passwordInput == confirmPasswordInput else {
                errorMessage = "两次输入的密码不一致"
                return
            }
            
            authManager.register(username: name, identifier: identifierInput, password: passwordInput) { success, err in
                if success {
                    dismiss()
                } else {
                    errorMessage = err ?? "注册失败"
                }
            }
        }
    }
}

#Preview {
    AuthModalView()
}