import AppKit
import ConjureKit
import Security

@MainActor
final class TranslationController: NSViewController, NSTextFieldDelegate {
    private let keyField = NSSecureTextField()
    private let provider = NSPopUpButton()
    private let credentials = NSStackView()
    private var usesMyMemory: Bool { provider.indexOfSelectedItem == 0 }
    private let output = NSTextView()
    private let disclosure = NSTextField(wrappingLabelWithString: "")
    private let status = NSTextField(wrappingLabelWithString: "")
    private let translateButton = NSButton(title: "Translate", target: nil, action: nil)
    private var task: Task<Void, Never>?
    var input: (() -> String)?
    var closed: (() -> Void)?
    private let defaults: UserDefaults
    private let credentialsStore: Credentials
    private let myMemory: @MainActor (String) async throws -> String
    private let openAI: @MainActor (String, String) async throws -> String

    init(
        defaults: UserDefaults = .standard,
        credentials: Credentials = .keychain,
        myMemory: @escaping @MainActor (String) async throws -> String = { try await MyMemoryAPI.translate($0) },
        openAI: @escaping @MainActor (String, String) async throws -> String = { try await TranslationAPI.translate($0, apiKey: $1) }
    ) {
        self.defaults = defaults
        self.credentialsStore = credentials
        self.myMemory = myMemory
        self.openAI = openAI
        super.init(nibName: nil, bundle: nil)
    }

    required init?(coder: NSCoder) { fatalError("Conjure creates Translate programmatically") }

    override func loadView() {
        view = NSView()
        let title = NSTextField(labelWithString: "Conjure Translate · English → Japanese")
        title.font = .systemFont(ofSize: 13, weight: .semibold)
        title.textColor = SunsetPalette.text
        provider.addItems(withTitles: ["MyMemory (no key)", "OpenAI · gpt-6-luna"])
        provider.selectItem(at: defaults.string(forKey: "translationProvider") == "openai" ? 1 : 0)
        provider.setAccessibilityLabel("Translation provider")
        provider.target = self
        provider.action = #selector(providerChanged)
        keyField.placeholderString = "OpenAI API key (saved in Keychain)"
        keyField.setAccessibilityLabel("OpenAI API key")
        keyField.delegate = self
        keyField.widthAnchor.constraint(greaterThanOrEqualToConstant: 220).isActive = true
        let save = NSButton(title: "Save Key", target: self, action: #selector(saveKey))
        let forget = NSButton(title: "Forget Key", target: self, action: #selector(forgetKey))
        for control in [keyField, save, forget] { credentials.addArrangedSubview(control) }
        credentials.distribution = .fill
        translateButton.target = self
        translateButton.action = #selector(translate)
        translateButton.keyEquivalent = "\r"
        translateButton.isBordered = false
        translateButton.font = .systemFont(ofSize: 12, weight: .medium)
        translateButton.contentTintColor = SunsetPalette.text
        translateButton.toolTip = "Translate the English input (Return). Escape dismisses Conjure."
        let returnKey = ShortcutIndicator("↵")
        let actionPill = NSView()
        actionPill.wantsLayer = true
        actionPill.layer?.cornerRadius = 18
        actionPill.layer?.borderWidth = 0.5
        actionPill.layer?.borderColor = SunsetPalette.accent.withAlphaComponent(0.35).cgColor
        actionPill.layer?.backgroundColor = SunsetPalette.background.withAlphaComponent(0.25).cgColor
        for control in [translateButton, returnKey] {
            control.translatesAutoresizingMaskIntoConstraints = false
            actionPill.addSubview(control)
        }
        NSLayoutConstraint.activate([
            actionPill.heightAnchor.constraint(equalToConstant: 36),
            translateButton.leadingAnchor.constraint(equalTo: actionPill.leadingAnchor, constant: 14),
            translateButton.centerYAnchor.constraint(equalTo: actionPill.centerYAnchor),
            returnKey.leadingAnchor.constraint(equalTo: translateButton.trailingAnchor, constant: 8),
            returnKey.centerYAnchor.constraint(equalTo: actionPill.centerYAnchor),
            returnKey.trailingAnchor.constraint(equalTo: actionPill.trailingAnchor, constant: -12),
        ])
        let footer = NSStackView(views: [status, NSView(), actionPill])
        footer.orientation = .horizontal
        footer.alignment = .centerY
        footer.spacing = 12
        footer.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(footer)
        output.isEditable = false
        output.isSelectable = true
        output.drawsBackground = false
        output.textColor = SunsetPalette.text
        output.font = .systemFont(ofSize: 20)
        output.setAccessibilityLabel("Japanese translation")
        let scroll = NSScrollView()
        scroll.documentView = output
        scroll.hasVerticalScroller = true
        scroll.drawsBackground = false
        output.isVerticallyResizable = true
        output.autoresizingMask = [.width]
        output.textContainer?.widthTracksTextView = true
        disclosure.textColor = SunsetPalette.secondaryText
        disclosure.font = .systemFont(ofSize: 12)
        disclosure.setAccessibilityLabel("Translation provider, privacy, and limits")
        status.font = .systemFont(ofSize: 12)
        status.setAccessibilityLabel("Translation status and errors")
        status.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        let stack = NSStackView(views: [title, provider, disclosure, credentials, scroll])
        stack.orientation = .vertical
        stack.alignment = .leading
        stack.spacing = 12
        stack.setCustomSpacing(4, after: provider)
        stack.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(stack)
        NSLayoutConstraint.activate([
            stack.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16),
            stack.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -16),
            stack.topAnchor.constraint(equalTo: view.topAnchor),
            stack.bottomAnchor.constraint(equalTo: footer.topAnchor, constant: -12),
            footer.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16),
            footer.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -8),
            footer.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -8),
            footer.heightAnchor.constraint(equalToConstant: 36),
            credentials.widthAnchor.constraint(equalTo: stack.widthAnchor),
            disclosure.widthAnchor.constraint(equalTo: stack.widthAnchor),
            scroll.widthAnchor.constraint(equalTo: stack.widthAnchor),
            scroll.heightAnchor.constraint(greaterThanOrEqualToConstant: 100),
        ])
        updateProvider()
    }

    func controlTextDidChange(_ notification: Notification) { inputChanged() }

    @objc func goBack() {
        cancelRequest()
        closed?()
    }

    func inputChanged() {
        cancelRequest()
        output.string = ""
        setStatus("Press Return to translate.")
    }

    @objc private func providerChanged() {
        defaults.set(usesMyMemory ? "mymemory" : "openai", forKey: "translationProvider")
        keyField.stringValue = ""
        updateProvider()
    }

    private func updateProvider() {
        credentials.isHidden = usesMyMemory
        disclosure.stringValue = usesMyMemory
            ? "MyMemory · No key · 500 bytes/request · 5,000 characters/day. Text is sent to MyMemory; avoid sensitive content."
            : "OpenAI · gpt-6-luna · Text is sent to OpenAI only when you translate."
        inputChanged()
    }

    @objc private func saveKey() {
        let key = keyField.stringValue.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !key.isEmpty, !key.contains(where: { $0.isNewline }) else {
            setStatus("Enter a valid API key before saving.", isError: true)
            return
        }
        do {
            try credentialsStore.save(key)
            keyField.stringValue = ""
            setStatus("API key saved in Keychain. Press Return to translate.")
        } catch { setStatus(error.localizedDescription, isError: true) }
    }

    @objc private func forgetKey() {
        cancelRequest()
        do {
            try credentialsStore.forget()
            keyField.stringValue = ""
            setStatus("API key removed.")
        } catch { setStatus(error.localizedDescription, isError: true) }
    }

    private func cancelRequest() {
        task?.cancel()
        task = nil
        translateButton.isEnabled = true
    }

    private func setStatus(_ message: String, isError: Bool = false) {
        status.stringValue = message
        status.textColor = isError ? .systemRed : SunsetPalette.secondaryText
    }

    @objc func translate() {
        guard task == nil else { return }
        let text = input?() ?? ""
        guard !text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty else {
            setStatus("Enter English text in the search bar.", isError: true)
            return
        }
        let myMemory = usesMyMemory
        var key = ""
        if !myMemory {
            if !keyField.stringValue.isEmpty { saveKey(); guard keyField.stringValue.isEmpty else { return } }
            do {
                guard let savedKey = try credentialsStore.load() else {
                    setStatus("Enter and save your OpenAI API key first.", isError: true)
                    return
                }
                key = savedKey
            } catch {
                setStatus(error.localizedDescription, isError: true)
                return
            }
        }
        output.string = ""
        setStatus("Translating…")
        translateButton.isEnabled = false
        let myMemoryTranslate = self.myMemory
        let openAITranslate = self.openAI
        task = Task { [weak self] in
            do {
                let translation = try await myMemory
                    ? myMemoryTranslate(text)
                    : openAITranslate(text, key)
                guard !Task.isCancelled, let self else { return }
                self.output.string = translation
                self.setStatus("Japanese · Select text to copy (⌘C).")
            } catch {
                guard !Task.isCancelled, let self else { return }
                self.setStatus("Translation failed: \(error.localizedDescription)", isError: true)
            }
            guard let self else { return }
            self.task = nil
            self.translateButton.isEnabled = true
        }
    }

    @MainActor
    struct Credentials {
        var save: (String) throws -> Void
        var load: () throws -> String?
        var forget: () throws -> Void

        private static var query: [String: Any] {
            [kSecClass as String: kSecClassGenericPassword,
             kSecAttrService as String: "Conjure.OpenAI",
             kSecAttrAccount as String: "translation"]
        }

        static let keychain = Credentials(
            save: { key in
                let data = Data(key.utf8)
                var result = SecItemUpdate(query as CFDictionary, [kSecValueData as String: data] as CFDictionary)
                if result == errSecItemNotFound {
                    var item = query
                    item[kSecValueData as String] = data
                    item[kSecAttrAccessible as String] = kSecAttrAccessibleWhenUnlockedThisDeviceOnly
                    result = SecItemAdd(item as CFDictionary, nil)
                }
                guard result == errSecSuccess else { throw KeychainError(code: result) }
            },
            load: {
                var query = Self.query
                query[kSecReturnData as String] = true
                var item: CFTypeRef?
                let result = SecItemCopyMatching(query as CFDictionary, &item)
                if result == errSecItemNotFound { return nil }
                guard result == errSecSuccess, let data = item as? Data,
                      let key = String(data: data, encoding: .utf8) else { throw KeychainError(code: result) }
                return key
            },
            forget: {
                let result = SecItemDelete(query as CFDictionary)
                guard result == errSecSuccess || result == errSecItemNotFound else { throw KeychainError(code: result) }
            }
        )
    }

    private struct KeychainError: LocalizedError {
        let code: OSStatus
        var errorDescription: String? {
            "Keychain error: \(SecCopyErrorMessageString(code, nil) as String? ?? String(code))"
        }
    }
}