import UIKit

/// Debug-only automation (`--demo-settings-flip`) that replays the user
/// gesture sequence suspected of producing stale page tables: open the
/// settings panel, change the line height, close the panel, flip pages —
/// with several timing variants aimed at the preview-repagination and
/// in-flight chapter build races. Combine with
/// `--demo-pagination-validate` to detect any resulting metric mismatch.
enum RDEPUBSettingsFlipAutomation {

    static let isEnabled = ProcessInfo.processInfo.arguments.contains("--demo-settings-flip")

    private(set) static var hasStarted = false

    static func startIfNeeded(controller: RDEPUBReaderController) {
        guard isEnabled, !hasStarted else { return }
        hasStarted = true
        print("[SETTINGS-FLIP] scheduled")

        // Pass 1 starts while progressive pagination of the freshly opened
        // book is still running, so prefetch builds are in flight.
        run(after: 2.0) { [weak controller] in
            guard let controller else { return }
            pass(controller: controller, index: 1, lineHeight: 1.8, changeToCloseDelay: 1.2) {
                pass(controller: controller, index: 2, lineHeight: 1.6, changeToCloseDelay: 0.05) {
                    pass(controller: controller, index: 3, lineHeight: 1.8, changeToCloseDelay: 0.3) {
                        print("[SETTINGS-FLIP] finished all passes")
                    }
                }
            }
        }
    }

    /// One panel round-trip: present → change line height → close after
    /// `changeToCloseDelay` → flip pages forward and back.
    private static func pass(
        controller: RDEPUBReaderController,
        index: Int,
        lineHeight: CGFloat,
        changeToCloseDelay: TimeInterval,
        completion: @escaping () -> Void
    ) {
        print("[SETTINGS-FLIP] pass \(index) present panel")
        controller.presentSettings()

        run(after: 0.7) { [weak controller] in
            guard let controller else { return }
            print("[SETTINGS-FLIP] pass \(index) set lineHeightMultiple=\(lineHeight)")
            controller.updateConfiguration { $0.lineHeightMultiple = lineHeight }

            run(after: changeToCloseDelay) { [weak controller] in
                guard let controller else { return }
                print("[SETTINGS-FLIP] pass \(index) close panel")
                controller.dismiss(animated: true) { [weak controller] in
                    controller?.runtime.settingsPanelDidDisappear()
                    run(after: 1.0) { [weak controller] in
                        guard let controller else { return }
                        flipPages(controller: controller, index: index, completion: completion)
                    }
                }
            }
        }
    }

    private static func flipPages(
        controller: RDEPUBReaderController,
        index: Int,
        completion: @escaping () -> Void
    ) {
        let startPage = controller.readerView.currentPage + 1
        let offsets = [1, 2, 3, 2, 1, 0]
        print("[SETTINGS-FLIP] pass \(index) flip pages from \(startPage)")
        for (step, offset) in offsets.enumerated() {
            run(after: 0.6 * Double(step + 1)) { [weak controller] in
                _ = controller?.go(toPageNumber: startPage + offset, animated: false)
            }
        }
        run(after: 0.6 * Double(offsets.count + 1) + 0.5, block: completion)
    }

    private static func run(after delay: TimeInterval, block: @escaping () -> Void) {
        DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: block)
    }
}