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map.go
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map.go
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package osmx
import (
"errors"
"fmt"
"io"
"sort"
osm "github.com/glaslos/go-osm"
"github.com/golang/geo/s2"
)
// ErrNoRelations is returned on map without relations decoding/wrapping.
var ErrNoRelations = errors.New("osmx: map contains no relations")
var errNoValidRelations = errors.New("osmx: map contains no valid relations")
// Map wraps osm.Map.
type Map struct {
*osm.Map
rel osm.Relation
}
// Decode decodes a Map.
func Decode(r io.Reader) (*Map, error) {
parent, err := osm.Decode(r)
if err != nil {
return nil, err
}
return WrapMap(parent)
}
// WrapMap initialises Map and sorts indexes
// for further processing.
func WrapMap(parent *osm.Map) (*Map, error) {
if len(parent.Relations) == 0 {
return nil, ErrNoRelations
}
// Get first relation that has ways
var m *Map
for ri := range parent.Relations {
rel := parent.Relations[ri]
for mi := range rel.Members {
mem := rel.Members[mi]
if mem.Type == "way" {
m = &Map{Map: parent, rel: rel}
break
}
}
}
if m == nil {
return nil, errNoValidRelations
}
sort.Slice(m.Nodes, func(i, j int) bool { return m.Nodes[i].ID < m.Nodes[j].ID })
sort.Slice(m.Ways, func(i, j int) bool { return m.Ways[i].ID < m.Ways[j].ID })
return m, nil
}
// Tag returns the value if a particular tag.
func (m *Map) Tag(key string) string {
for i := range m.rel.Tags {
if tag := m.rel.Tags[i]; tag.Key == key {
return tag.Value
}
}
return ""
}
// Rel returns the primary relation in Map.
func (m *Map) Rel() *osm.Relation {
return &m.rel
}
// FindNode finds and returns a node by its ID.
func (m *Map) FindNode(id int64) (*osm.Node, error) {
if pos := sort.Search(len(m.Nodes), func(i int) bool { return m.Nodes[i].ID >= id }); pos < len(m.Nodes) && m.Nodes[pos].ID == id {
node := m.Nodes[pos]
return &node, nil
}
return nil, fmt.Errorf("osmx: node #%d not found", id)
}
// FindWay finds and returns a way by its ID.
func (m *Map) FindWay(id int64) (*osm.Way, error) {
if pos := sort.Search(len(m.Ways), func(i int) bool { return m.Ways[i].ID >= id }); pos < len(m.Ways) && m.Ways[pos].ID == id {
if way := m.Ways[pos]; len(way.Nds) != 0 {
return &way, nil
}
}
return nil, fmt.Errorf("osmx: way #%d not found", id)
}
// ExtractLoops extracts and generates (outer) loops from the map.
func (m *Map) ExtractLoops() ([]*s2.Loop, error) {
ways, err := m.extractWays()
if err != nil {
return nil, err
}
loops := make([]*s2.Loop, 0, len(ways))
for _, line := range ways {
loop, err := line.Loop()
if err != nil {
return nil, err
}
loops = append(loops, loop)
}
return loops, nil
}
// --------------------------------------------------------------------
func (m *Map) extractWays() (waySlice, error) {
ways := make(waySlice, 0, len(m.rel.Members))
for _, osmMember := range m.rel.Members {
if osmMember.Type != "way" {
continue
}
osmWay, err := m.FindWay(osmMember.Ref)
if err != nil {
return nil, err
}
way := &wayPath{
Role: osmMember.Role,
Path: make([]*osm.Node, 0, len(osmWay.Nds)),
}
for _, nodeRef := range osmWay.Nds {
osmNode, err := m.FindNode(nodeRef.ID)
if err != nil {
return nil, err
}
way.Path = append(way.Path, osmNode)
}
if way.IsValid() {
ways = append(ways, way)
}
}
return ways.Reduce(), nil
}