import Foundation

@main
struct PlaybackQueueChecks {
    static func require(_ condition: @autoclosure () -> Bool, _ message: String) {
        if !condition() { fatalError("FAIL: " + message) }
    }

    static func file(_ name: String) -> URL {
        URL(fileURLWithPath: "/queue-check/" + name + ".mp4")
    }

    static func main() {
        let first = file("Episode1"), second = file("Episode2"), tenth = file("Episode10")
        var queue = PlaybackQueue()
        require(queue.items.isEmpty && queue.currentURL == nil && !queue.canPrevious && !queue.canNext,
                "empty queue has no selection or navigation")
        require(queue.advance(1) == nil && queue.advance(-1) == nil, "empty navigation is harmless")

        queue.replace([tenth, second, first])
        require(queue.items.map(\.url) == [first, second, tenth], "replace uses natural Episode2/Episode10 filename order")
        require(queue.currentURL == first && !queue.canPrevious && queue.canNext, "replace selects first item")
        let firstID = queue.currentID
        require(queue.advance(-1) == nil && queue.currentID == firstID, "previous at start does not wrap or deselect")
        require(queue.advance(1) == second && queue.canPrevious && queue.canNext, "next selects middle item")
        require(queue.advance(1) == tenth && queue.canPrevious && !queue.canNext, "next selects final item")
        let tenthID = queue.currentID
        require(queue.advance(1) == nil && queue.currentID == tenthID, "next at end stops without wrapping")
        require(queue.advance(-1) == second, "previous moves back one item")

        let selected = queue.currentID!
        queue.append([file("Episode20"), file("Episode3")])
        require(queue.items.map(\.url) == [first, second, tenth, file("Episode3"), file("Episode20")],
                "append naturally sorts the new batch without reordering existing items")
        require(queue.currentID == selected && queue.currentURL == second, "append does not interrupt selection")
        queue.move(fromOffsets: IndexSet(integer: 1), toOffset: queue.items.count)
        require(queue.items.last?.id == selected && queue.currentID == selected && queue.currentURL == second,
                "reordering preserves current item identity")
        require(queue.canPrevious && !queue.canNext, "navigation follows reordered positions")
        queue.move(fromOffsets: IndexSet([0, 1]), toOffset: queue.items.count)
        require(queue.currentID == selected && queue.currentURL == second, "moving other items preserves current")

        queue.replace([tenth, second, first])
        queue.select(queue.items[1].id)
        require(queue.currentURL == second, "explicit selection jumps to an item")
        let current = queue.currentID
        let unrelated = queue.items[0].id
        require(queue.remove(unrelated) == nil && queue.currentID == current && queue.currentURL == second,
                "removing another item does not request playback or change selection")
        require(queue.remove(current!) == tenth && queue.currentURL == tenth,
                "removing current selects the next remaining item")
        require(queue.remove(queue.currentID!) == nil && queue.currentURL == nil && queue.items.isEmpty,
                "removing final item stops and empties queue")

        queue.replace([first, second, tenth])
        queue.select(queue.items.last!.id)
        require(queue.remove(queue.currentID!) == nil && queue.currentID == nil && queue.items.count == 2,
                "removing current at end stops rather than jumping backward")
        require(!queue.canPrevious && !queue.canNext, "stopped queue has no implicit selection")
        queue.select(queue.items[0].id)
        require(queue.currentURL == first, "remaining items can be explicitly selected after stopping")
        queue.append([first])
        require(Set(queue.items.map(\.id)).count == queue.items.count, "duplicate file entries have independent identities")
        queue.replace([tenth])
        require(queue.items.map(\.url) == [tenth] && queue.currentURL == tenth && !queue.canPrevious && !queue.canNext,
                "replace discards previous queue and starts new selection")
        queue.replace([])
        require(queue.items.isEmpty && queue.currentID == nil, "empty replacement clears queue")
        print("playback queue checks passed")
    }
}