import SwiftUI

/// Modal sheet for server-backed account login and registration.
struct AuthModalView: View {
    @Environment(\.dismiss) private var dismiss
    @ObservedObject var authManager: AuthManager = .shared
    var guidanceMessage: String? = nil
    
    @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?
    @State private var isSubmitting = false
    @FocusState private var focusedField: AuthField?
    
    enum AuthTab {
        case login
        case register
    }

    private enum AuthField: Hashable {
        case username
        case identifier
        case password
        case confirmPassword
    }
    
    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(
                        guidanceMessage
                            ?? (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,
                            field: .username,
                            contentType: .nickname,
                            keyboardType: .default,
                            submitLabel: .next
                        )
                    }
                    
                    inputField(
                        icon: "envelope",
                        placeholder: "手机号或电子邮箱",
                        text: $identifierInput,
                        field: .identifier,
                        contentType: .username,
                        submitLabel: .next
                    )
                    
                    inputField(
                        icon: "lock",
                        placeholder: "密码 (至少 6 位)",
                        text: $passwordInput,
                        field: .password,
                        isSecure: true,
                        contentType: selectedTab == .login ? .password : .newPassword,
                        submitLabel: selectedTab == .login ? .go : .next
                    )
                    
                    if selectedTab == .register {
                        inputField(
                            icon: "lock.shield",
                            placeholder: "再次确认密码",
                            text: $confirmPasswordInput,
                            field: .confirmPassword,
                            isSecure: true,
                            contentType: .newPassword,
                            submitLabel: .go
                        )
                    }
                    
                    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: {
                    HStack(spacing: 8) {
                        if isSubmitting {
                            ProgressView()
                                .tint(Color.spaceBlack)
                        }
                        Text(submitButtonTitle)
                            .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(isSubmitting)
            }
        }
        .interactiveDismissDisabled(isSubmitting)
    }
    
    private func tabButton(title: String, tab: AuthTab) -> some View {
        Button {
            withAnimation(.snappy) {
                selectedTab = tab
                errorMessage = nil
                focusedField = 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>,
        field: AuthField,
        isSecure: Bool = false,
        contentType: UITextContentType?,
        keyboardType: UIKeyboardType = .asciiCapable,
        submitLabel: SubmitLabel
    ) -> 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))
                    .textContentType(contentType)
                    .keyboardType(keyboardType)
                    .textInputAutocapitalization(.never)
                    .autocorrectionDisabled()
                    .focused($focusedField, equals: field)
                    .submitLabel(submitLabel)
                    .onSubmit { handleSubmit(from: field) }
            } else {
                TextField(placeholder, text: text)
                    .font(.system(size: 14))
                    .textContentType(contentType)
                    .keyboardType(keyboardType)
                    .textInputAutocapitalization(.never)
                    .autocorrectionDisabled()
                    .focused($focusedField, equals: field)
                    .submitLabel(submitLabel)
                    .onSubmit { handleSubmit(from: field) }
            }
        }
        .padding(.horizontal, 14)
        .padding(.vertical, 12)
        .background(Color.cardBackground.opacity(0.3))
        .businessBorder(cornerRadius: 8)
    }

    private var submitButtonTitle: String {
        if isSubmitting {
            return selectedTab == .login ? "正在登录…" : "正在注册…"
        }
        return selectedTab == .login ? "安全登录" : "注册并自动登录"
    }

    private func handleSubmit(from field: AuthField) {
        switch field {
        case .username:
            focusedField = .identifier
        case .identifier:
            focusedField = .password
        case .password where selectedTab == .register:
            focusedField = .confirmPassword
        case .password, .confirmPassword:
            handleAuthSubmit()
        }
    }
    
    private func handleAuthSubmit() {
        guard !isSubmitting else { return }
        errorMessage = nil
        
        if selectedTab == .login {
            let identifier = identifierInput.trimmingCharacters(in: .whitespacesAndNewlines)
            guard !identifier.isEmpty else {
                errorMessage = "请输入手机号或邮箱"
                focusedField = .identifier
                return
            }
            guard passwordInput.count >= 6 else {
                errorMessage = "密码不能少于 6 位"
                focusedField = .password
                return
            }
            
            focusedField = nil
            isSubmitting = true
            authManager.login(identifier: identifier, password: passwordInput) { success, err in
                isSubmitting = false
                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"
                focusedField = .username
                return
            }
            let identifier = identifierInput.trimmingCharacters(in: .whitespacesAndNewlines)
            guard !identifier.isEmpty else {
                errorMessage = "请输入注册手机号或邮箱"
                focusedField = .identifier
                return
            }
            guard passwordInput.count >= 6 else {
                errorMessage = "密码不能少于 6 位"
                focusedField = .password
                return
            }
            guard passwordInput == confirmPasswordInput else {
                errorMessage = "两次输入的密码不一致"
                focusedField = .confirmPassword
                return
            }
            
            focusedField = nil
            isSubmitting = true
            authManager.register(username: name, identifier: identifier, password: passwordInput) { success, err in
                isSubmitting = false
                if success {
                    dismiss()
                } else {
                    errorMessage = err ?? "注册失败"
                }
            }
        }
    }
}

#Preview {
    AuthModalView()
}