// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:meta/meta.dart' show immutable;

import 'types.dart';

/// Cap that can be applied at the start or end vertex of a [Polyline].
@immutable
class Cap {
  const Cap._(this._json);

  /// Cap that is squared off exactly at the start or end vertex of a [Polyline]
  /// with solid stroke pattern, equivalent to having no additional cap beyond
  /// the start or end vertex.
  ///
  /// This is the default cap type at start and end vertices of Polylines with
  /// solid stroke pattern.
  static const Cap buttCap = Cap._(<Object>['buttCap']);

  /// Cap that is a semicircle with radius equal to half the stroke width,
  /// centered at the start or end vertex of a [Polyline] with solid stroke
  /// pattern.
  static const Cap roundCap = Cap._(<Object>['roundCap']);

  /// Cap that is squared off after extending half the stroke width beyond the
  /// start or end vertex of a [Polyline] with solid stroke pattern.
  static const Cap squareCap = Cap._(<Object>['squareCap']);

  /// Constructs a new CustomCap with a bitmap overlay centered at the start or
  /// end vertex of a [Polyline], orientated according to the direction of the line's
  /// first or last edge and scaled with respect to the line's stroke width.
  ///
  /// CustomCap can be applied to [Polyline] with any stroke pattern.
  ///
  /// [bitmapDescriptor] must not be null.
  ///
  /// [refWidth] is the reference stroke width (in pixels) - the stroke width for which
  /// the cap bitmap at its native dimension is designed. Must be positive. Default value
  /// is 10 pixels.
  static Cap customCapFromBitmap(
    BitmapDescriptor bitmapDescriptor, {
    double refWidth = 10,
  }) {
    assert(bitmapDescriptor != null);
    assert(refWidth > 0.0);
    return Cap._(<Object>['customCap', bitmapDescriptor.toJson(), refWidth]);
  }

  final Object _json;

  /// Converts this object to something serializable in JSON.
  Object toJson() => _json;
}