Game leaderboard: rank players by score, award medals, compute gaps

leaderboard.cell

// Game leaderboard: rank players by score, award medals, compute gaps.
// Demonstrates sort_by("score","desc") -> top, pluck, max_by/min_by, and
// per-row derived fields via map(... with ...). Records built with map().

cell Leaderboard {
    on players() {
        return list(
            map("name", "nova",   "score", 4200, "wins", 31, "country", "PT"),
            map("name", "blaze",  "score", 5100, "wins", 44, "country", "BR"),
            map("name", "kira",   "score", 3800, "wins", 22, "country", "JP"),
            map("name", "echo",   "score", 5100, "wins", 39, "country", "US"),
            map("name", "vex",    "score", 2900, "wins", 17, "country", "DE"),
            map("name", "rune",   "score", 4750, "wins", 28, "country", "PT")
        )
    }

    // Ranked descending; ties keep stable order.
    on ranked() { return players() |> sort_by("score", "desc") }

    on podium() { return ranked() |> top(3) |> pluck("name") }

    on champion() { return max_by(players(), "score") }

    // Attach a rank index 1..n as a new field on each row.
    on with_ranks() {
        let rows = ranked()
        let out = list()
        let i = 0
        while i < len(rows) {
            out = out.push(rows[i] |> with("rank", i + 1))
            i += 1
        }
        return out
    }

    on run() {
        for r in with_ranks() {
            print("#{r.rank} {r.name} - {r.score}")
        }
        return podium()
    }
}

cell test LeaderboardTests {
    rules {
        // highest score is 5100, appears twice; max_by returns one of them
        assert champion().score == 5100
        // podium is a list of names; top-ranked name is blaze or echo (tie at 5100)
        assert ranked()[0].score == 5100
        assert len(podium()) == 3
        // lowest scorer is vex
        assert min_by(players(), "score").name == "vex"
        // rank #1 has the top score
        assert with_ranks()[0].rank == 1
        assert with_ranks()[5].rank == 6
        // there are 6 players
        assert len(players()) == 6
    }
}