56 lines
2.3 KiB
Go
56 lines
2.3 KiB
Go
package search
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import (
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"fmt"
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"github.com/ganigeorgiev/fexpr"
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)
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var TokenFunctions = map[string]func(
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argTokenResolverFunc func(fexpr.Token) (*ResolverResult, error),
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args ...fexpr.Token,
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) (*ResolverResult, error){
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// geoDistance(lonA, latA, lonB, latB) calculates the Haversine
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// distance between 2 points in kilometres (https://www.movable-type.co.uk/scripts/latlong.html).
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//
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// The accepted arguments at the moment could be either a plain number or a column identifier (including NULL).
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// If the column identifier cannot be resolved and converted to a numeric value, it resolves to NULL.
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//
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// Similar to the built-in SQLite functions, geoDistance doesn't apply
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// a "match-all" constraints in case there are multiple relation fields arguments.
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// Or in other words, if a collection has "orgs" multiple relation field pointing to "orgs" collection that has "office" as "geoPoint" field,
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// then the filter: `geoDistance(orgs.office.lon, orgs.office.lat, 1, 2) < 200`
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// will evaluate to true if for at-least-one of the "orgs.office" records the function result in a value satisfying the condition (aka. "result < 200").
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"geoDistance": func(argTokenResolverFunc func(fexpr.Token) (*ResolverResult, error), args ...fexpr.Token) (*ResolverResult, error) {
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if len(args) != 4 {
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return nil, fmt.Errorf("[geoDistance] expected 4 arguments, got %d", len(args))
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}
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resolvedArgs := make([]*ResolverResult, 4)
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for i, arg := range args {
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if arg.Type != fexpr.TokenIdentifier && arg.Type != fexpr.TokenNumber {
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return nil, fmt.Errorf("[geoDistance] argument %d must be an identifier or number", i)
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}
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resolved, err := argTokenResolverFunc(arg)
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if err != nil {
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return nil, fmt.Errorf("[geoDistance] failed to resolve argument %d: %w", i, err)
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}
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resolvedArgs[i] = resolved
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}
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lonA := resolvedArgs[0].Identifier
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latA := resolvedArgs[1].Identifier
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lonB := resolvedArgs[2].Identifier
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latB := resolvedArgs[3].Identifier
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return &ResolverResult{
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NoCoalesce: true,
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Identifier: `(6371 * acos(` +
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`cos(radians(` + latA + `)) * cos(radians(` + latB + `)) * ` +
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`cos(radians(` + lonB + `) - radians(` + lonA + `)) + ` +
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`sin(radians(` + latA + `)) * sin(radians(` + latB + `))` +
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`))`,
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Params: mergeParams(resolvedArgs[0].Params, resolvedArgs[1].Params, resolvedArgs[2].Params, resolvedArgs[3].Params),
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}, nil
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},
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}
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