import AppKit
import CoreGraphics

/// Enumerates on-screen windows using CGWindowListCopyWindowInfo.
enum WindowEnumerator {
    /// Returns all normal, on-screen windows excluding this app and desktop elements.
    static func enumerateWindows() -> [WindowInfo] {
        let options: CGWindowListOption = [.optionOnScreenOnly, .excludeDesktopElements]
        guard let windowList = CGWindowListCopyWindowInfo(options, kCGNullWindowID) as? [[String: Any]] else {
            return []
        }

        let ownPID = ProcessInfo.processInfo.processIdentifier

        var windows: [WindowInfo] = []
        for (_, entry) in windowList.enumerated() {
            guard let windowID = entry[kCGWindowNumber as String] as? CGWindowID,
                  let pid = entry[kCGWindowOwnerPID as String] as? pid_t,
                  let layer = entry[kCGWindowLayer as String] as? Int,
                  layer == 0, // normal windows only
                  pid != ownPID
            else { continue }

            // Skip windows with no bounds or zero-size bounds
            guard let boundsDict = entry[kCGWindowBounds as String] as? [String: Any],
                  let bounds = CGRect(dictionaryRepresentation: boundsDict as CFDictionary),
                  bounds.width > 1, bounds.height > 1
            else { continue }

            let ownerName = entry[kCGWindowOwnerName as String] as? String ?? "Unknown"
            let windowTitle = entry[kCGWindowName as String] as? String ?? ownerName

            // Look up app info from running applications
            let app = NSRunningApplication(processIdentifier: pid)
            let bundleID = app?.bundleIdentifier ?? "unknown.\(pid)"
            let appIcon = app?.icon

            let isOnScreen = (entry[kCGWindowIsOnscreen as String] as? Bool) ?? true

            let info = WindowInfo(
                windowID: windowID,
                title: windowTitle,
                appName: ownerName,
                appBundleID: bundleID,
                appIcon: appIcon,
                frame: bounds,
                pid: pid,
                isOnScreen: isOnScreen,
                thumbnail: nil
            )
            windows.append(info)
        }

        return windows
    }

    /// Group windows by application, ordered per the layout algorithm spec.
    static func groupWindows(_ windows: [WindowInfo]) -> [WindowGroup] {
        var groupMap: [String: WindowGroup] = [:]

        for (index, window) in windows.enumerated() {
            if var group = groupMap[window.appBundleID] {
                group.windows.append(window)
                group.frontmostIndex = min(group.frontmostIndex, index)
                groupMap[window.appBundleID] = group
            } else {
                groupMap[window.appBundleID] = WindowGroup(
                    appBundleID: window.appBundleID,
                    appName: window.appName,
                    appIcon: window.appIcon,
                    windows: [window],
                    frontmostIndex: index
                )
            }
        }

        // Sort windows within each group by title for stable ordering
        for key in groupMap.keys {
            groupMap[key]!.windows.sort {
                $0.title.localizedCaseInsensitiveCompare($1.title) == .orderedAscending
            }
        }

        // Sort groups alphabetically by app name
        return groupMap.values.sorted { a, b in
            a.appName.localizedCaseInsensitiveCompare(b.appName) == .orderedAscending
        }
    }
}