import UIKit

/// The page's keyboard, natively.
///
/// Feedly's set, which is what ipx uses: a letter to move through items or feeds, g and a letter
/// to go somewhere, ? to list them. None fire with Ctrl, Alt or Command held, so the system's own
/// shortcuts still work.
///
/// UIKeyCommand rather than SwiftUI's onKeyPress, which is iOS 17 and this still runs on 16.
enum Keys {
    /// What a key asks for. The controller decides how to do it.
    enum Action: Equatable {
        case nextItem, previousItem
        case nextFeed, previousFeed
        case play, toggleRead, togglePin, openOriginal
        case readAll, refresh, toggleSidebar, shortcuts
        case playPause, back15, forward30
        case go(Go)
        case startPair
    }

    enum Go: Equatable { case all, directory, popular, listening, settings }

    /// Single keys, and the ones that only mean something after g.
    static let single: [String: Action] = [
        "j": .nextItem, "n": .nextItem, "k": .previousItem, "p": .previousItem,
        "J": .nextFeed, "K": .previousFeed,
        "o": .play, "m": .toggleRead, "s": .togglePin, "v": .openOriginal,
        "A": .readAll, "r": .refresh, "[": .toggleSidebar, "?": .shortcuts,
        "g": .startPair,
    ]

    static let paired: [String: Go] = [
        "a": .all, "d": .directory, "p": .popular, "l": .listening, "s": .settings,
    ]

    /// Every key the app answers to, for UIResponder.keyCommands. Space and the arrows are
    /// listed separately because their input is not a letter.
    static func commands(_ selector: Selector) -> [UIKeyCommand] {
        var all = single.keys.map { UIKeyCommand(input: $0, modifierFlags: [], action: selector) }
        all.append(UIKeyCommand(input: " ", modifierFlags: [], action: selector))
        all.append(UIKeyCommand(input: UIKeyCommand.inputLeftArrow, modifierFlags: [], action: selector))
        all.append(UIKeyCommand(input: UIKeyCommand.inputRightArrow, modifierFlags: [], action: selector))
        // The second key of a g pair: only these, and only just after a g.
        for key in paired.keys where single[key] == nil {
            all.append(UIKeyCommand(input: key, modifierFlags: [], action: selector))
        }
        for command in all { command.wantsPriorityOverSystemBehavior = true }
        return all
    }

    /// How long after g the second key still counts, matching the page.
    static let pairWindow: TimeInterval = 1.5

    /// What a key press means, given whether a g is still warm.
    static func action(for input: String, afterG: Bool) -> Action? {
        if afterG, let go = paired[input] { return .go(go) }
        switch input {
        case " ": return .playPause
        case UIKeyCommand.inputLeftArrow: return .back15
        case UIKeyCommand.inputRightArrow: return .forward30
        default: return single[input]
        }
    }

    /// The list ? shows, grouped as the page groups it.
    static let listing: [(String, [(String, String)])] = [
        ("Go to", [("g a", "All Subscriptions"), ("g d", "Directory"), ("g p", "Popular"),
                   ("g l", "Currently Listening"), ("g s", "Settings"),
                   ("⇧ J", "Next feed"), ("⇧ K", "Previous feed"),
                   ("r", "Refresh"), ("[", "Show or hide the feed list")]),
        ("Items", [("j or n", "Next item"), ("k or p", "Previous item"),
                   ("⇧ A", "Mark all read")]),
        ("The selected item", [("o", "Play it"), ("m", "Mark it read or unread"),
                               ("s", "Pin it, or unpin it"), ("v", "Open the original")]),
        ("The player", [("Space", "Play or pause"), ("← →", "Back 15 seconds, forward 30")]),
        ("Anywhere", [("?", "This list")]),
    ]
}