Adding upstream version 0.28.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tools/search/token_functions.go

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