Chart
=====

Generic Highcharts wrapper. ``<chart>`` is the underlying
chart primitive other components can reach for instead of
mounting Highcharts directly. Renders either as a Highstock
chart (the default, suitable for time-series with the built-in
range selector and navigator) or as a plain Highcharts chart
when ``isStock`` is set to ``false``.

The component accepts two data-supply modes:

* ``url`` -- fetch the data from a JSON endpoint. The endpoint
  must return ``{"status": true, "data": [...]}``. The
  ``<loading>`` overlay is started for the duration of the
  request.
* ``series`` -- pass the data inline as a prop. No fetch is
  performed; the chart renders straight from the prop.

Re-rendering destroys the previous chart instance before the
new one is constructed, so the component is safe to drive from
reactive parents.

Default exporting buttons
-------------------------

For chart types other than ``pie`` and ``column``, the wrapper
adds three Highcharts exporting buttons:

* ``-`` -- reset data grouping (turns ``dataGrouping`` off).
* ``G:W`` -- group by week (forced, averaging approximation).
* ``G:M`` -- group by month (forced, averaging approximation).

Component accepts following params:

* ``name`` (required) -- unique identifier used as the DOM ID
  of the chart container (``chart-{name}``).
* ``height`` (required) -- height in pixels.
* ``url`` -- JSON endpoint that returns
  ``{"status": ..., "data": ...}``. Mutually exclusive with
  ``series``.
* ``series`` -- inline Highcharts series array. Mutually
  exclusive with ``url``.
* ``type`` -- Highcharts chart type (default ``"line"``).
* ``isStock`` -- Boolean flag; ``true`` (default) renders via
  ``Highcharts.StockChart``, ``false`` via
  ``Highcharts.Chart``.
* ``isCoin`` -- Boolean flag; when ``true``, the tooltip uses
  ``settings.COINS_MAX_PRECISION`` decimals, otherwise
  ``settings.MAX_PRECISION``.
* ``options`` -- additional Highcharts options as a string
  expression; ``eval``-ed and deep-merged into the defaults.