1 | import { Observable, EventData } from '../../data/observable';
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2 | import { ImageSource } from '../../image-source';
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3 |
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4 | /**
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5 | * Represents a single download request.
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6 | */
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7 | export interface DownloadRequest {
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8 | /**
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9 | * The url of the image.
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10 | */
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11 | url: string;
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12 | /**
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13 | * The key used to cache the image.
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14 | */
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15 | key: string;
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16 | /**
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17 | * An optional function to be called when the download is complete.
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18 | */
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19 | completed?: (image: any, key: string) => void;
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20 | /**
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21 | * An optional function to be called if the download errors.
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22 | */
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23 | error?: (key: string) => void;
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24 | }
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25 |
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26 | /**
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27 | * Represents a class that stores handles image download requests and caches the already downloaded images.
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28 | */
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29 | export class Cache extends Observable {
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30 | /**
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31 | * String value used when hooking to downloaded event.
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32 | */
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33 | public static downloadedEvent: string;
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34 | /**
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35 | * String value used when hooking to download error event.
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36 | */
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37 | public static downloadErrorEvent: string;
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38 | /**
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39 | * The image to be used to notify for a pending download request - e.g. loading indicator.
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40 | */
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41 | placeholder: ImageSource;
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42 | /**
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43 | * The maximum number of simultaneous download requests. Defaults to 5.
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44 | */
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45 | maxRequests: number;
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46 |
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47 | /**
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48 | * Enables previously suspended download requests.
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49 | */
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50 | enableDownload(): void;
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51 | /**
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52 | * Temporary disables download requests.
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53 | */
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54 | disableDownload(): void;
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55 |
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56 | /**
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57 | * Adds a new download request at the top of the download queue. This will be the next immediate download to start.
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58 | */
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59 | push(request: DownloadRequest);
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60 | /**
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61 | * Adds a new download request at the end of the download queue. This will be the last download to start.
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62 | */
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63 | enqueue(request: DownloadRequest);
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64 |
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65 | /**
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66 | * Gets the image for the specified key. May be undefined if the key is not present in the cache.
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67 | */
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68 | get(key: string): any;
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69 | /**
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70 | * Sets the image for the specified key.
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71 | */
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72 | set(key: string, image: any): void;
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73 | /**
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74 | * Removes the cache for the specified key.
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75 | */
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76 | remove(key: string): void;
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77 | /**
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78 | * Removes all the previously cached images.
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79 | */
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80 | clear(): void;
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81 |
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82 | /**
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83 | * A basic method signature to hook an event listener (shortcut alias to the addEventListener method).
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84 | * @param eventNames - String corresponding to events (e.g. "propertyChange"). Optionally could be used more events separated by `,` (e.g. "propertyChange", "change").
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85 | * @param callback - Callback function which will be executed when event is raised.
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86 | * @param thisArg - An optional parameter which will be used as `this` context for callback execution.
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87 | */
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88 | on(eventNames: string, callback: (args: EventData) => void, thisArg?: any): void;
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89 |
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90 | /**
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91 | * Raised when the image has been downloaded.
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92 | */
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93 | on(event: 'downloaded', callback: (args: DownloadedData) => void, thisArg?: any): void;
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94 |
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95 | /**
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96 | * Raised if the image download errors.
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97 | */
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98 | on(event: 'downloadError', callback: (args: DownloadError) => void, thisArg?: any): void;
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99 |
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100 | //@private
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101 | /**
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102 | * @private
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103 | */
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104 | _downloadCore(request: DownloadRequest);
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105 | /**
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106 | * @private
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107 | */
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108 | _onDownloadCompleted(key: string, image: any);
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109 | //@endprivate
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110 | /**
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111 | * @private
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112 | */
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113 | _onDownloadError(key: string, err: Error);
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114 | //@endprivate
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115 | }
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116 |
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117 | /**
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118 | * Provides data for downloaded event.
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119 | */
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120 | export interface DownloadedData extends EventData {
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121 | /**
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122 | * A string indentifier of the cached image.
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123 | */
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124 | key: string;
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125 | /**
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126 | * Gets the cached image.
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127 | */
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128 | image: ImageSource;
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129 | }
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130 |
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131 | /**
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132 | * Provides data for download error.
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133 | */
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134 | export interface DownloadError extends EventData {
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135 | /**
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136 | * A string indentifier of the cached image.
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137 | */
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138 | key: string;
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139 | /**
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140 | * Gets the error.
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141 | */
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142 | error: Error;
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143 | }
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