import AppKit

// Capture reads the current selection by simulating Cmd+C, watching the
// pasteboard change count, then restoring the previous clipboard contents so
// the user's own clipboard is untouched. Requires Accessibility permission
// for the synthesized events to be delivered.
enum Capture {
    static func captureSelectionIntoStore() {
        let sourceApp = NSWorkspace.shared.frontmostApplication?.localizedName
        guard let text = captureSelection() else { return }
        let trimmed = text.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else { return }
        Task { @MainActor in
            Store.shared.addText(text, sourceApp: sourceApp)
            PanelController.shared.show()
        }
    }

    static func captureSelection() -> String? {
        let pasteboard = NSPasteboard.general
        let backup = backupPasteboard(pasteboard)
        let oldChangeCount = pasteboard.changeCount

        simulateCopy()

        let deadline = Date().addingTimeInterval(0.5)
        var result: String?
        while Date() < deadline {
            if pasteboard.changeCount != oldChangeCount {
                result = pasteboard.string(forType: .string)
                break
            }
            usleep(10_000)
        }

        restorePasteboard(pasteboard, backup: backup)
        return result
    }

    private static func simulateCopy() {
        let source = CGEventSource(stateID: .hidSystemState)
        let keyCodeC: CGKeyCode = 8 // kVK_ANSI_C
        let keyDown = CGEvent(keyboardEventSource: source, virtualKey: keyCodeC, keyDown: true)
        keyDown?.flags = .maskCommand
        keyDown?.post(tap: .cghidEventTap)
        let keyUp = CGEvent(keyboardEventSource: source, virtualKey: keyCodeC, keyDown: false)
        keyUp?.flags = .maskCommand
        keyUp?.post(tap: .cghidEventTap)
    }

    private static func backupPasteboard(_ pasteboard: NSPasteboard) -> [[String: Data]] {
        var backup: [[String: Data]] = []
        for item in pasteboard.pasteboardItems ?? [] {
            var entry: [String: Data] = [:]
            for type in item.types {
                if let data = item.data(forType: type) {
                    entry[type.rawValue] = data
                }
            }
            backup.append(entry)
        }
        return backup
    }

    private static func restorePasteboard(_ pasteboard: NSPasteboard, backup: [[String: Data]]) {
        pasteboard.clearContents()
        let items = backup.map { entry -> NSPasteboardItem in
            let item = NSPasteboardItem()
            for (type, data) in entry {
                item.setData(data, forType: NSPasteboard.PasteboardType(type))
            }
            return item
        }
        if !items.isEmpty {
            pasteboard.writeObjects(items)
        }
    }
}