DSP-1002 Update standoff link value

[tobiasschweizer]

resolves DSP-1002

When adding an internal link to a text value, Knora creates a corresponding standoff link value.
When clicking on or hovering over a standoff link, this information can be used to emit the ReadLinkValue. Since this requires access to the standoff link value from the text value, @Input() propArray: PropertyInfoValues[]; was added to DisplayEditComponent.

[tobiasschweizer]

@mdelez Since updating the standoff link value is a bit complex, I think I should mention it in the design docs. But please go ahead with the review.

[tobiasschweizer]

@mdelez Feel free to correct the English in 192a732

[mdelez]

Nice! Just a little comment/question :)

[mdelez]

should this throw an error?

[tobiasschweizer]

That should actually never occur: if the user is able to click on a standoff link, then the resource must have been initialised before in resource-view comp.

I added a comment in 76e251a

However, this is an easy way to know that this.resource.id won't cause an error and that no malformed query will be sent to Knora.

If the method is left immediately, then simply the standoff link value would not be updated.

I implemented DisplayEditComponent._getStandoffLinkValueForResource so it would not fail if it cannot find the standoff link value, see:

dsp-ui-lib/projects/dsp-ui/src/lib/viewer/operations/display-edit/display-edit.component.ts

Lines 157 to 191 in 81b1e43

	/**
	* Given a resource Iri, finds the corresponding standoff link value.
	* Returns an empty array if the standoff link cannot be found.
	*
	* @param resIri the Iri of the resource.
	*/
	private _getStandoffLinkValueForResource(resIri: string): ReadLinkValue[] {
	// find the PropertyInfoValues for the standoff link value
	const standoffLinkPropInfoVals: PropertyInfoValues[] = this.propArray.filter(
	resPropInfoVal => {
	return resPropInfoVal.propDef.id === "http://api.knora.org/ontology/knora-api/v2#hasStandoffLinkToValue";
	}
	);
	if (standoffLinkPropInfoVals.length === 1) {
	// find the corresponding standoff link value
	const referredResStandoffLinkVal: ReadValue[] = standoffLinkPropInfoVals[0].values.filter(
	(standoffLinkVal: ReadValue) => {
	return standoffLinkVal instanceof ReadLinkValue
	&& (standoffLinkVal as ReadLinkValue).linkedResourceIri === resIri;
	}
	);
	// if no corresponding standoff link value was found,
	// this array is empty
	return referredResStandoffLinkVal as ReadLinkValue[];
	} else {
	// this should actually never happen
	// because all resource types have a cardinality for a standoff link value
	return [];
	}
	}

Now if it cannot find a corresponding standoff link value, there will simply be no event emitted:

dsp-ui-lib/projects/dsp-ui/src/lib/viewer/operations/display-edit/display-edit.component.ts

Lines 193 to 224 in 81b1e43

	/**
	* React when a standoff link in a text has received a click event.
	*
	* @param resIri the Iri of the resource the standoff link refers to.
	*/
	standoffLinkClicked(resIri: string): void {
	// find the corresponding standoff link value
	const referredResStandoffLinkVal: ReadLinkValue[] = this._getStandoffLinkValueForResource(resIri);
	// only emit an event if the corresponding standoff link value could be found
	if (referredResStandoffLinkVal.length === 1) {
	this.referredResourceClicked.emit(referredResStandoffLinkVal[0]);
	}
	}
	/**
	* React when a standoff link in a text has received a hover event.
	*
	* @param resIri the Iri of the resource the standoff link refers to.
	*/
	standoffLinkHovered(resIri: string): void {
	// find the corresponding standoff link value
	const referredResStandoffLinkVal: ReadLinkValue[] = this._getStandoffLinkValueForResource(resIri);
	// only emit an event if the corresponding standoff link value could be found
	if (referredResStandoffLinkVal.length === 1) {
	this.referredResourceHovered.emit(referredResStandoffLinkVal[0]);
	}
	}

This could be the case because of timing. The standoff link values are only queried after the values have been updated, and it is also async. And it that case the user would just click again and by then the values should be there.

[tobiasschweizer]

I will write a test that makes sure that display-edit does not break when there is no corresponding standoff link value

[tobiasschweizer]

@mdelez I added two tests in 3812be6

[mdelez]

same as above comment

[tobiasschweizer]

this should never happen since the Optional is used: also if there is no standoff link value, the resource should be returned. However, being paranoid res.resources[0] without an assertion seems dangerous to me.

[tobiasschweizer]

let's discus the whole flow of data together today or tomorrow to make sure I did not make an error in reasoning.

[tobiasschweizer]

@mdelez I actually found the test for "non reacting" to be too weak and improved them in 112bf76

I set the init value of the parent comp. to "init" so I can check that no undefined was emitted by mistake (if the code would accidentally access the first entry of an empty array).