adding setter methods for points only and space optimisation

Author: Sreekanth Sivasankaran

go.mod

@@ -1,3 +1,3 @@
-module github.com/golang/geo
+module github.com/sreekanth-cb/geo
 
 go 1.12

s2/region_term_indexer.go

@@ -0,0 +1,226 @@
+// Copyright 2020 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package s2
+
+type TermType int
+
+var marker = string('$')
+
+const (
+	ANCESTOR TermType = iota + 1
+	COVERING
+)
+
+var defaultMaxCells = int(8)
+
+type Options struct {
+	maxCells      int
+	minLevel      int
+	maxLevel      int
+	levelMod      int
+	pointsOnly    bool
+	optimizeSpace bool
+}
+
+func (o *Options) MaxCells() int {
+	return o.maxCells
+}
+
+func (o *Options) SetMaxCells(mc int) {
+	o.maxCells = mc
+}
+
+func (o *Options) MinLevel() int {
+	return o.minLevel
+}
+
+func (o *Options) SetMinLevel(ml int) {
+	o.minLevel = ml
+}
+
+func (o *Options) MaxLevel() int {
+	return o.maxLevel
+}
+
+func (o *Options) SetMaxLevel(ml int) {
+	o.maxLevel = ml
+}
+
+func (o *Options) LevelMod() int {
+	return o.levelMod
+}
+
+func (o *Options) SetLevelMod(lm int) {
+	o.levelMod = lm
+}
+
+func (o *Options) SetPointsOnly(v bool) {
+	o.pointsOnly = v
+}
+
+func (o *Options) SetOptimizeSpace(v bool) {
+	o.optimizeSpace = v
+}
+
+func (o *Options) trueMaxLevel() int {
+	trueMax := o.maxLevel
+	if o.levelMod != 1 {
+		trueMax = o.maxLevel - (o.maxLevel-o.minLevel)%o.levelMod
+	}
+	return trueMax
+}
+
+type RegionTermIndexer struct {
+	options       Options
+	regionCoverer RegionCoverer
+}
+
+func NewRegionTermIndexer() *RegionTermIndexer {
+	rv := &RegionTermIndexer{
+		options: Options{
+			maxCells: 8,
+			minLevel: 4,
+			maxLevel: 16,
+			levelMod: 1,
+		},
+	}
+	return rv
+}
+
+func NewRegionTermIndexerWithOptions(option Options) *RegionTermIndexer {
+	return &RegionTermIndexer{options: option}
+}
+
+func (rti *RegionTermIndexer) GetTerm(termTyp TermType, id CellID,
+	prefix string) string {
+	if termTyp == ANCESTOR {
+		return prefix + id.ToToken()
+	}
+	return prefix + marker + id.ToToken()
+}
+
+func (rti *RegionTermIndexer) GetIndexTermsForPoint(p Point, prefix string) []string {
+	cellID := cellIDFromPoint(p)
+	var rv []string
+	for l := rti.options.minLevel; l <= rti.options.maxLevel; l += rti.options.levelMod {
+		rv = append(rv, rti.GetTerm(ANCESTOR, cellID.Parent(l), prefix))
+	}
+	return rv
+}
+
+func (rti *RegionTermIndexer) GetIndexTermsForRegion(region Region,
+	prefix string) []string {
+	rti.regionCoverer.LevelMod = rti.options.levelMod
+	rti.regionCoverer.MaxLevel = rti.options.maxLevel
+	rti.regionCoverer.MinLevel = rti.options.minLevel
+	rti.regionCoverer.MaxCells = rti.options.maxCells
+
+	covering := rti.regionCoverer.Covering(region)
+	return rti.GetIndexTermsForCanonicalCovering(covering, prefix)
+}
+
+func (rti *RegionTermIndexer) GetIndexTermsForCanonicalCovering(
+	covering CellUnion, prefix string) []string {
+	var rv []string
+	prevID := CellID(0)
+	tml := rti.options.trueMaxLevel()
+
+	for _, cellID := range covering {
+		level := cellID.Level()
+		if level < tml {
+			rv = append(rv, rti.GetTerm(COVERING, cellID, prefix))
+		}
+
+		if level == tml || !rti.options.optimizeSpace {
+			rv = append(rv, rti.GetTerm(ANCESTOR, cellID.Parent(level), prefix))
+		}
+
+		for (level - rti.options.levelMod) >= rti.options.minLevel {
+			level -= rti.options.levelMod
+			ancestorID := cellID.Parent(level)
+			if prevID != CellID(0) && prevID.Level() > level &&
+				prevID.Parent(level) == ancestorID {
+				break
+			}
+			rv = append(rv, rti.GetTerm(ANCESTOR, ancestorID, prefix))
+		}
+		prevID = cellID
+	}
+
+	return rv
+}
+
+func (rti *RegionTermIndexer) GetQueryTermsForPoint(p Point, prefix string) []string {
+	cellID := cellIDFromPoint(p)
+	var rv []string
+
+	level := rti.options.trueMaxLevel()
+	rv = append(rv, rti.GetTerm(ANCESTOR, cellID.Parent(level), prefix))
+	if rti.options.pointsOnly {
+		return rv
+	}
+
+	for level >= rti.options.minLevel {
+		rv = append(rv, rti.GetTerm(COVERING, cellID.Parent(level), prefix))
+		level -= rti.options.levelMod
+	}
+
+	return rv
+}
+
+func (rti *RegionTermIndexer) GetQueryTermsForRegion(region Region,
+	prefix string) []string {
+	rti.regionCoverer.LevelMod = rti.options.levelMod
+	rti.regionCoverer.MaxLevel = rti.options.maxLevel
+	rti.regionCoverer.MinLevel = rti.options.minLevel
+	rti.regionCoverer.MaxCells = rti.options.maxCells
+
+	covering := rti.regionCoverer.Covering(region)
+	return rti.GetQueryTermsForCanonicalCovering(covering, prefix)
+
+}
+
+func (rti *RegionTermIndexer) GetQueryTermsForCanonicalCovering(
+	covering CellUnion, prefix string) []string {
+	var rv []string
+	prevID := CellID(0)
+	tml := rti.options.trueMaxLevel()
+	for _, cellID := range covering {
+		level := cellID.Level()
+		rv = append(rv, rti.GetTerm(ANCESTOR, cellID, prefix))
+
+		if rti.options.pointsOnly {
+			continue
+		}
+
+		if rti.options.optimizeSpace && level < tml {
+			rv = append(rv, rti.GetTerm(COVERING, cellID, prefix))
+		}
+
+		for level-rti.options.levelMod >= rti.options.minLevel {
+			level -= rti.options.levelMod
+			ancestorID := cellID.Parent(level)
+			if prevID != CellID(0) && prevID.Level() > level &&
+				prevID.Parent(level) == ancestorID {
+				break
+			}
+			rv = append(rv, rti.GetTerm(COVERING, ancestorID, prefix))
+		}
+
+		prevID = cellID
+	}
+
+	return rv
+}