1 | // Copyright 2017-2022 @polkadot/api authors & contributors
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2 | // SPDX-License-Identifier: Apache-2.0
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3 | import EventEmitter from 'eventemitter3';
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4 | export class Events {
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5 | #eventemitter = new EventEmitter();
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6 |
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7 | emit(type, ...args) {
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8 | return this.#eventemitter.emit(type, ...args);
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9 | }
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10 | /**
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11 | * @description Attach an eventemitter handler to listen to a specific event
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12 | *
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13 | * @param type The type of event to listen to. Available events are `connected`, `disconnected`, `ready` and `error`
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14 | * @param handler The callback to be called when the event fires. Depending on the event type, it could fire with additional arguments.
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15 | *
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16 | * @example
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17 | * <BR>
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18 | *
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19 | * ```javascript
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20 | * api.on('connected', (): void => {
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21 | * console.log('API has been connected to the endpoint');
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22 | * });
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23 | *
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24 | * api.on('disconnected', (): void => {
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25 | * console.log('API has been disconnected from the endpoint');
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26 | * });
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27 | * ```
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28 | */
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29 |
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30 |
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31 | on(type, handler) {
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32 | this.#eventemitter.on(type, handler);
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33 | return this;
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34 | }
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35 | /**
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36 | * @description Remove the given eventemitter handler
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37 | *
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38 | * @param type The type of event the callback was attached to. Available events are `connected`, `disconnected`, `ready` and `error`
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39 | * @param handler The callback to unregister.
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40 | *
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41 | * @example
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42 | * <BR>
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43 | *
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44 | * ```javascript
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45 | * const handler = (): void => {
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46 | * console.log('Connected !);
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47 | * };
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48 | *
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49 | * // Start listening
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50 | * api.on('connected', handler);
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51 | *
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52 | * // Stop listening
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53 | * api.off('connected', handler);
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54 | * ```
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55 | */
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56 |
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57 |
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58 | off(type, handler) {
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59 | this.#eventemitter.removeListener(type, handler);
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60 | return this;
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61 | }
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62 | /**
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63 | * @description Attach an one-time eventemitter handler to listen to a specific event
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64 | *
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65 | * @param type The type of event to listen to. Available events are `connected`, `disconnected`, `ready` and `error`
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66 | * @param handler The callback to be called when the event fires. Depending on the event type, it could fire with additional arguments.
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67 | *
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68 | * @example
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69 | * <BR>
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70 | *
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71 | * ```javascript
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72 | * api.once('connected', (): void => {
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73 | * console.log('API has been connected to the endpoint');
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74 | * });
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75 | *
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76 | * api.once('disconnected', (): void => {
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77 | * console.log('API has been disconnected from the endpoint');
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78 | * });
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79 | * ```
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80 | */
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81 |
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82 |
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83 | once(type, handler) {
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84 | this.#eventemitter.once(type, handler);
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85 | return this;
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86 | }
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87 |
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88 | } |
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