FlopRest - Stripe-style REST parameters for Flop

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Hey folks!

I built FlopRest, a small library that transforms Stripe-style query parameters into Flop format.

The Problem

Flop is excellent for filtering, sorting, and paginating Ecto queries. But when building JSON APIs, its native format creates friction:

?filters[0][field]=status&filters[0][op]==&filters[0][value]=published&filters[1][field]=starts_at&filters[1][op]=>=&filters[1][value]=2024-01-01&order_by[0]=starts_at&order_directions[0]=desc&first=20

Frontend developers expect something like Stripe or GitHub:

?status=published&starts_at[gte]=2024-01-01&sort=-starts_at&limit=20

Same query. FlopRest bridges that gap—same Flop power underneath, better DX on top.

Usage

def index(conn, params) do
  flop_params = FlopRest.normalize(params)

  with {:ok, {events, meta}} <- Flop.validate_and_run(Event, flop_params, for: Event) do
    json(conn, %{
      data: events,
      links: %{
        self: FlopRest.build_path(conn.request_path, meta.flop),
        next: meta.has_next_page? && FlopRest.build_path(conn.request_path, meta.next_flop),
        prev: meta.has_previous_page? && FlopRest.build_path(conn.request_path, meta.previous_flop)
      }
    })
  end
end

What It Supports

  • Filters: status=published, amount[gte]=100
  • Sorting: sort=-created_at,name (minus for desc)
  • Pagination: Cursor (limit + starting_after), page-based, and offset-based
  • Pagination links: build_path/2 generates next/prev URLs from Flop meta

All 21 Flop operators are supported.

When to Use It

Building a LiveView/HTML app? Flop Phoenix already handles the UI side.

Building a JSON API consumed by React/Vue/Svelte/mobile apps? FlopRest makes your API feel native to frontend developers—standard URLSearchParams just works, no custom serialization needed.

Design

Pure transformation layer. Invalid params pass through for Flop to validate.

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