MapOSMatic remote rendering API
===============================
Hartmut Holzgraefe <hartmut@php.net>
:toc:
:toclevels: 2
:source-highlighter: coderay
:data-uri:
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v1, September 16th 2018 (Work in progress)

MapOSMatic is a web frontend for the OCitySMap renderer, which uses
the Mapnik map rendering libary, Python and the CairoGraphics library
to create decorated single page maps and multi page atlas-like booklets.

Originally this was a pure user centric web GUI, but recently a wish
for using the infrastructure with different web frontends did come up.

So this HTTP API provides an alternative way to submit map rendering
requests, and to retrieve additional data that may be needed on the
way.

Requests and results are submitted as JSON documents, with the
optional possibility to attach extra data files, like GPX tracks
or Umap user created maps.

This documentation begins with describing the helper calls that
provide lists of possible choices for different data fields,
followed by the actual map rendering call and how to retrieve
rendering status and results, and ends with example programs
to access the API from different programming languages.

API calls
---------

Paper Formats
~~~~~~~~~~~~~

Request URL
^^^^^^^^^^^

----
https://api.get-map.org/apis/paper_formats
----

Example result
^^^^^^^^^^^^^^

----
{
    "Best fit": {
        "height": null,
        "width": null
    },
    "Din A4": {
        "height": 297,
        "width": 210
    },
    "US letter": {
        "height": 279,
        "width": 216
    }
}
----




Layouts
~~~~~~~

Request URL
^^^^^^^^^^^

----
https://api.get-map.org/apis/layouts
----

Example result
^^^^^^^^^^^^^^

----
{
    "multi_page": {
        "description": "A multi-page layout.",
        "preview_url": "https://api.get-map.org/media/img/layout/multi_page.png"
    },
    "plain": {
        "description": "Full-page layout without index.",
        "preview_url": "https://api.get-map.org/media/img/layout/plain.png"
    },
    "single_page_index_bottom": {
        "description": "Full-page layout with the index at the bottom.",
        "preview_url": "https://api.get-map.org/media/img/layout/single_page_index_bottom.png"
    },
    "single_page_index_side": {
        "description": "Full-page layout with the index on the side.",
        "preview_url": "https://api.get-map.org/media/img/layout/single_page_index_side.png"
    }
}
----



Base Styles
~~~~~~~~~~~

Request URL
^^^^^^^^^^^

----
https://api.get-map.org/apis/styles
----

Example output
^^^^^^^^^^^^^^

----
{
    "CartoOSM": {
        "annotation": "OpenStreetMap Carto standard style",
        "description": "CartoCSS OSM standard style",
        "preview_url": "https://api.get-map.org/media/img/style/CartoOSM.png"
    },
    "GermanCartoOSM": {
        "annotation": "German OSM style based on OSM Carto",
        "description": "German OSM style",
        "preview_url": "https://api.get-map.org/media/img/style/GermanCartoOSM.png"
    }
}
----


Overlay Styles
~~~~~~~~~~~~~~

Request URL
^^^^^^^^^^^

----
https://api.get-map.org/apis/overlays
----


Example output
^^^^^^^^^^^^^^

----
{
    "OpenRailwayMap_Overlay": {
        "annotation": "OpenRailwayMap overlay",
        "description": "OpenRailwayMap rail line overlay",
        "preview_url": "https://api.get-map.org/media/img/style/OpenRailwayMap_Overlay.jpg"
    },
    "Scale_Bar_overlay": {
        "annotation": "",
        "description": "Map scale bar"
        "preview_url": "https://api.get-map.org/media/img/style/Scale_Bar_overlay.jpg"
    }
 }
----


Job Stati
~~~~~~~~~

Request URL
^^^^^^^^^^^

----
https://api.get-map.org/apis/job_stati/
----

Example result
^^^^^^^^^^^^^^

----
{
    "0": "Submitted",
    "1": "In progress",
    "2": "Done",
    "3": "Done w/o files",
    "4": "Cancelled"
}
----


Submitting a Job
~~~~~~~~~~~~~~~~

Request URL
^^^^^^^^^^^

----
POST https://api.get-map.org/apis/jobs/
----


Expects render job named parameters as a JSON collection.

Possible parameters:

osmid:: ID of an object in the osm2pgsql
bbox_top:: 
bbox_bottom:: 
bbox_left:: 
bbox_right:: Render area min. bounding box, may be extended to fit paper format
title:: Text to put into the title box (default: "Untitled API Request")
language:: locale to use for rendering (default: "en_US.UTF-8")
layout:: Map layout to use (default: "plain")
style:: Map base style to use (default: "CartoOSM")
overlays:: List of overlays to put on top of base style (default: None)
paper_size:: Paper size to use (default: "Din A4" 210x297mm²)
orientation:: Paper orientation: "portrait" or "landscape" (default: "portrait")
track_url:: URL pointing to a GPX track to download and print
umap_url:: URL pointing to an Umap export file do download and print

It is also possible to upload GPX and Umap files directly using a multipart/form-data
POST request. In this case you have to submit the actual API JSON as a post parameter
named "json", and add file fields named "track" for a GPX track, or "umap" for an
Umap JSON export.

After successfully submitting a request you can either poll the job result API every
once in a while until it either returns the "200 OK" status, or a 4xx error code.
Or you can redirect a web client to the human readable result page listed in the
returned "interactive" job parameter.

Return codes
^^^^^^^^^^^^

202:: 'Accepted' when successfully submitted, "Location:" header will contain result URL
400:: 'Bad request' on request validation errors

Example requests
^^^^^^^^^^^^^^^^

----
Content-type: application/json

{
    "title": "API Test",
    "bbox_bottom": 52.00,
    "bbox_left": 8.52,
    "bbox_right": 8.50,
    "bbox_top": 52.02
}
----

----
Content-Type: multipart/form-data; boundary=--XXXXXXXX

--XXXXXXXX
Content-Disposition: form-data; name="json"

{
    "title": "GPX Test",
    "paper_size": "Din A1"
}
--XXXXXXXX
Content-Disposition: form-data; name="track"; filename="test.gpx"
Content-Type: application/gpx+xml

<?xml version="1.0" encoding="UTF-8"?>
  
<gpx version="1.1">
  <metadata>
    <name>GPX test</name>
  </metadata>
  <trk>
    <trkseg>
      <trkpt lat="52.00" lon="8.50" />
      <trkpt lat="52.02" lon="8.52" />
    </trkseg>
  </trk>
</gpx>
--XXXXXXXX--
----

Example results
^^^^^^^^^^^^^^^

----
HTTP/1.1 202 Accepted
[...]
Location: /api/jobs/36
Content-Type: text/json

{
    "bbox_bottom": 52.01,
    "bbox_left": 8.52,
    "bbox_right": 8.50,
    "bbox_top": 52.02,
    "id": 36,
    "interactive": "https://api.get-map.org/maps/214"
    "language": "en_US.UTF-8",
    "layout": "plain",
    "paper_height_mm": 297,
    "paper_width_mm": 210,
    "status": 0,
    "styles": "CartoOSM"
    "title": "API Test",
}
----

----
HTTP/1.1 400 Bad Request
[...]
Content-Type: text/json
 
{
    "error": {
        "non_field_errors": [
            "No bounding box area or OsmID given"
        ]
    }
}
----


Checking Job results
~~~~~~~~~~~~~~~~~~~~

Request Url
^^^^^^^^^^^

----
https://api.get-map.org/apis/jobs/
----

Return codes
^^^^^^^^^^^^

200:: 'OK' when request has been processed successfully
202:: 'Accepted' when rendering is still in progress, "Location:" header will contain same URL again
410:: 'Gone' when a request had been processed successfuly in the past, but result files have since been purged to free file system space
400:: 'Bad request' when a request failed to render

Example result
^^^^^^^^^^^^^^

----
HTTP/1.1 200 OK
[...]
Content-type: application/json

{
    "bbox_bottom": 52.01,
    "bbox_left": 8.53,
    "bbox_right": 8.49,
    "bbox_top": 52.02,
    "files": 
    {
        "8bit.png": "https://api.get-map.org/results//000215_2018-09-12_23-14_GPX-test.8bit.png",
        "jpg": "https://api.get-map.org/results//000215_2018-09-12_23-14_GPX-test.jpg",
        "pdf": "https://api.get-map.org/results//000215_2018-09-12_23-14_GPX-test.pdf",
        "png": "https://api.get-map.org/results//000215_2018-09-12_23-14_GPX-test.png",
        "svgz": "https://api.get-map.org/results//000215_2018-09-12_23-14_GPX-test.svgz"
    }
    "id": 215,
    "language": "en_US.UTF-8",
    "layout": "plain",
    "paper_height_mm": 594,
    "paper_width_mm": 841,
    "queue_size": 0,
    "status": 2,
    "style": "CartoOSM",
    "title": "GPX test"
}
----



Example code
------------


PHP
~~~

All examples in this script use the `PEAR:HTTP_Request2` class for sending
HTTP requests and receiving server replies. 

Retrieve parameter choices
^^^^^^^^^^^^^^^^^^^^^^^^^^

Here we are using the `/paper_formats`, `/layouts`, `styles` and `overlays`
API calls to retrieve possible choices for all of these parameters, and
their textual description where available.

.parameters.php
[source,php]
----
include::code-snippets/parameters.php[]
----


Submitting a simple request
^^^^^^^^^^^^^^^^^^^^^^^^^^^

Now we are submitting a simple request, only setting the map title,
and the bounding box of the area to display. We do not check for
rendering to complete, but redirect the web client to the interactive
result URL given as `interactive` in the returned JSON data.

This is the same result page as when you submit a map request manually
via the standard web user interface, so this approach is suitable for
interactive web applications:

.simple-request.php
[source,php]
----
include::code-snippets/simple-request.php[]
----


Attaching a file
^^^^^^^^^^^^^^^^

Now, to make things more interesting, we are going to attach a GPX
file to our request. As the page title and the necessariy bounding
box to fit all track data can be extracted from the file, if it is
a valid GPX file, we do not need to pass any other data at all.

.file-request.php
[source,php]
----
include::code-snippets/file-request.php[]
----




Wait for rendering to complete
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To have your application check for the rendering status yourself
you need to poll the `/jobs` status page, adding the job `id`
returned by the API. Please wait at least 15 seconds between
status poll requests.

As long as the returned HTTP status is "202 Accepted" the
request is either currently being processed, or still
waiting in the job queue.

When the job has completed successfully "200 OK" will be returned,
and the `files` object in the returned JSON result will contain
a hash of produced file formats, and under what URL each of them
can be retrieved.

In the example we retrieve the PDF version, and start the users
preferred PDF viewer to present the result.

.wait-for-result.php
[source,php]
----
include::code-snippets/wait-for-result.php[]
----


Python
~~~~~~

To be done


Javascript
~~~~~~~~~~

To be done, maybe. Due to the "same origin" restrictions
this is low on my list ...
