MapComplete/Logic/MetaTagging.ts

import SimpleMetaTagger from "./SimpleMetaTagger";
import {ExtraFuncParams, ExtraFunctions} from "./ExtraFunctions";
import LayerConfig from "../Models/ThemeConfig/LayerConfig";
import State from "../State";


/**
 * Metatagging adds various tags to the elements, e.g. lat, lon, surface area, ...
 *
 * All metatags start with an underscore
 */
export default class MetaTagging {


    private static errorPrintCount = 0;
    private static readonly stopErrorOutputAt = 10;

    /**
     * This method (re)calculates all metatags and calculated tags on every given object.
     * The given features should be part of the given layer
     *
     * Returns true if at least one feature has changed properties
     */
    public static addMetatags(features: { feature: any; freshness: Date }[],
                              params: ExtraFuncParams,
                              layer: LayerConfig,
                              options?: {
                                  includeDates?: true | boolean,
                                  includeNonDates?: true | boolean
                              }): boolean {

        if (features === undefined || features.length === 0) {
            return;
        }


        const metatagsToApply: SimpleMetaTagger [] = []
        for (const metatag of SimpleMetaTagger.metatags) {
            if (metatag.includesDates) {
                if (options.includeDates ?? true) {
                    metatagsToApply.push(metatag)
                }
            } else {
                if (options.includeNonDates ?? true) {
                    metatagsToApply.push(metatag)
                }
            }
        }

        // The calculated functions - per layer - which add the new keys
        const layerFuncs = this.createRetaggingFunc(layer)

        let atLeastOneFeatureChanged = false;

        for (let i = 0; i < features.length; i++) {
            const ff = features[i];
            const feature = ff.feature
            const freshness = ff.freshness
            let somethingChanged = false
            for (const metatag of metatagsToApply) {
                try {
                    if (!metatag.keys.some(key => feature.properties[key] === undefined)) {
                        // All keys are already defined, we probably already ran this one
                        continue
                    }

                    if (metatag.isLazy) {
                        somethingChanged = true;

                        metatag.applyMetaTagsOnFeature(feature, freshness, layer)

                    } else {


                        const newValueAdded = metatag.applyMetaTagsOnFeature(feature, freshness, layer)
                        /* Note that the expression:
                        * `somethingChanged = newValueAdded || metatag.applyMetaTagsOnFeature(feature, freshness)`
                        * Is WRONG
                        * 
                        * IF something changed is `true` due to an earlier run, it will short-circuit and _not_ evaluate the right hand of the OR, 
                        * thus not running an update!
                        */
                        somethingChanged = newValueAdded || somethingChanged
                    }
                } catch (e) {
                    console.error("Could not calculate metatag for ", metatag.keys.join(","), ":", e, e.stack)
                }
            }

            if (layerFuncs !== undefined) {
                try {
                    layerFuncs(params, feature)
                } catch (e) {
                    console.error(e)
                }
                somethingChanged = true
            }

            if (somethingChanged) {
                State.state?.allElements?.getEventSourceById(feature.properties.id)?.ping()
                atLeastOneFeatureChanged = true
            }
        }
        return atLeastOneFeatureChanged
    }


    public static createFunctionsForFeature(layerId: string, calculatedTags: [string, string][]): ((feature: any) => void)[] {
        const functions: ((feature: any) => void)[] = [];
        for (const entry of calculatedTags) {
            const key = entry[0]
            const code = entry[1];
            if (code === undefined) {
                continue;
            }

            const func = new Function("feat", "return " + code + ";");

            const f = (feature: any) => {
                delete feature.properties[key]

                Object.defineProperty(feature.properties, key, {
                    configurable: true,
                    enumerable: false, // By setting this as not enumerable, the localTileSaver will _not_ calculate this
                    get: function () {
                        try {
                            // Lazyness for the win!
                            let result = func(feature);

                            if (result === "") {
                                result === undefined
                            }
                            if (result !== undefined && typeof result !== "string") {
                                // Make sure it is a string!
                                result = JSON.stringify(result);
                            }
                            delete feature.properties[key]
                            feature.properties[key] = result;
                            return result;
                        } catch (e) {
                            if (MetaTagging.errorPrintCount < MetaTagging.stopErrorOutputAt) {
                                console.warn("Could not calculate a calculated tag for key "+key+" defined by " + code + " (in layer"+layerId+") due to \n" + e + "\n. Are you the theme creator? Doublecheck your code. Note that the metatags might not be stable on new features", e, e.stack)
                                MetaTagging.errorPrintCount++;
                                if (MetaTagging.errorPrintCount == MetaTagging.stopErrorOutputAt) {
                                    console.error("Got ", MetaTagging.stopErrorOutputAt, " errors calculating this metatagging - stopping output now")
                                }
                            }
                        }

                    }
                })

            }


            functions.push(f)
        }
        return functions;
    }

    private static createRetaggingFunc(layer: LayerConfig):
        ((params: ExtraFuncParams, feature: any) => void) {

        const calculatedTags: [string, string][] = layer.calculatedTags;
        if (calculatedTags === undefined || calculatedTags.length === 0) {
            return undefined;
        }

        return (params: ExtraFuncParams, feature) => {
            const tags = feature.properties
            if (tags === undefined) {
                return;
            }

            try {
                const functions = MetaTagging.createFunctionsForFeature(layer.id, calculatedTags)


                ExtraFunctions.FullPatchFeature(params, feature);
                for (const f of functions) {
                    f(feature);
                }
                State.state?.allElements?.getEventSourceById(feature.properties.id)?.ping();
            } catch (e) {
                console.error("Invalid syntax in calculated tags or some other error: ", e)
            }
        }
    }


}