Top-N and bottom-N reporting over a movie ratings table

topn_movies.cell

// Top-N and bottom-N reporting over a movie ratings table.
// Demonstrates top/bottom after sort_by, select for projection, avg_by for a
// summary stat, and filter_by chaining to build a "critically acclaimed" list.

cell MovieCharts {
    on movies() {
        return list(
            map("title", "Dunes",      "rating", 88, "votes", 12000, "year", 2021),
            map("title", "Neon City",  "rating", 72, "votes", 8400,  "year", 2019),
            map("title", "Quiet Lake", "rating", 95, "votes", 3100,  "year", 2022),
            map("title", "Fast Track", "rating", 61, "votes", 22000, "year", 2020),
            map("title", "Old Roads",  "rating", 90, "votes", 1500,  "year", 2018),
            map("title", "Sky Burn",   "rating", 55, "votes", 30000, "year", 2023),
            map("title", "Greywater",  "rating", 83, "votes", 6700,  "year", 2021)
        )
    }

    on best() { return movies() |> sort_by("rating", "desc") |> top(3) |> select("title", "rating") }

    on worst() { return movies() |> sort_by("rating", "desc") |> bottom(2) |> select("title", "rating") }

    on most_popular() { return movies() |> sort_by("votes", "desc") |> top(1) }

    on avg_rating() { return movies() |> avg_by("rating") }

    // Acclaimed: rating >= 85 AND a real audience (votes >= 3000).
    on acclaimed() {
        return movies()
            |> filter_by("rating", ">=", 85)
            |> filter_by("votes", ">=", 3000)
            |> pluck("title")
    }

    on run() {
        let names = best() |> pluck("title")
        print("Best: {names}")
        print("Avg rating: {avg_rating()}")
        return acclaimed()
    }
}

cell test MovieChartsTests {
    rules {
        // top-rated is Quiet Lake (95)
        assert best()[0].title == "Quiet Lake"
        assert best()[0].rating == 95
        // 3 in the best list
        assert len(best()) == 3
        // worst keeps the 2 lowest: Sky Burn (55), Fast Track (61)
        assert worst()[1].title == "Sky Burn"
        // most popular by votes is Sky Burn (30000)
        assert most_popular()[0].title == "Sky Burn"
        // acclaimed: Dunes(88,12000) and Greywater(83 -> no). Quiet Lake 95 but 3100>=3000 yes.
        // rating>=85: Quiet Lake(95,3100), Old Roads(90,1500), Dunes(88,12000)
        // votes>=3000: Quiet Lake, Dunes -> 2 titles
        assert len(acclaimed()) == 2
    }
}