A library for fetching data from paginated JSON REST APIs.

Motivation

This library is built to handle fetching data from a JSON REST API that paginates its results. It inspects response headers, and will prepare subsequent requests when additional pages of results remain.

Given a JSON decoder for the data type returned in the paginated collection, it will return a data structure containing the results fetched, and a new request object for fetching additional records from the next page if more are available.

It is expected that the paginated REST API will provide a link for the next page of results in the Link header, e.g.:

Link: <https://api.example.com/search?q=abc&page=2>; rel="next"

Absence of a link with rel="next" in the response headers is assumed to mean the final page of results has been reached.

Example Usage

import Http
import Json.Decode exposing (string)
import Paginated exposing (Response(..))

type alias Model =
    { results : Maybe (Paginated.Response String) }

type Msg
    = Search
    | Results (Result Http.Error (Paginated.Response String))

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        Search ->
            ( model, doSearch )

        Results (Ok response) ->
            case response of
                Partial request results ->
                    ( { model
                        | results =
                            Maybe.map (\x -> Paginated.update x response)
                                model.results
                      }
                    , Paginated.send Results request
                    )

                Complete results ->
                    ( { model
                        | results =
                            Maybe.map (\x -> Paginated.update x response)
                                model.results
                      }
                    , Cmd.none
                    )

        Results (Err _) ->
            ( model, Cmd.none )

doSearch : Cmd Msg
doSearch =
    Paginated.send Results <|
        Paginated.get "http://example.com/items" string