1 files changed, 246 insertions, 0 deletions
diff --git a/mcmap/region.go b/mcmap/region.go
new file mode 100644
index 0000000..cbb9f58
--- /dev/null
+++ b/mcmap/region.go
@@ -0,0 +1,246 @@
+package mcmap
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+var (
+	NotAvailable = errors.New("Chunk or Superchunk not available")
+)
+
+type superchunk struct {
+	preChunks map[XZPos]*preChunk
+	chunks    map[XZPos]*Chunk
+	modified  bool
+}
+
+type Region struct {
+	path             string
+	superchunksAvail map[XZPos]bool
+
+	superchunks map[XZPos]*superchunk
+}
+
+var mcaRegex = regexp.MustCompile(`^r\.([0-9-]+)\.([0-9-]+)\.mca$`)
+
+// OpenRegion opens a region directory.
+func OpenRegion(path string) (*Region, error) {
+	rv := &Region{
+		path:             path,
+		superchunksAvail: make(map[XZPos]bool),
+		superchunks:      make(map[XZPos]*superchunk),
+	}
+
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	fi, err := f.Stat()
+	if err != nil {
+		return nil, err
+	}
+
+	if !fi.IsDir() {
+		return nil, fmt.Errorf("%s is not a directory", path)
+	}
+
+	names, err := f.Readdirnames(-1)
+	if err != nil {
+		return nil, err
+	}
+	for _, name := range names {
+		match := mcaRegex.FindStringSubmatch(name)
+		if len(match) == 3 {
+			// We ignore the error here. The Regexp already ensures that the inputs are numbers.
+			x, _ := strconv.ParseInt(match[1], 10, 32)
+			z, _ := strconv.ParseInt(match[2], 10, 32)
+
+			rv.superchunksAvail[XZPos{int(x), int(z)}] = true
+		}
+	}
+
+	return rv, nil
+}
+
+// MaxDims calculates the approximate maximum x, z dimensions of this region in number of chunks. The actual maximum dimensions might be a bit smaller.
+func (reg *Region) MaxDims() (xmin, xmax, zmin, zmax int) {
+	if len(reg.superchunksAvail) == 0 {
+		return 0, 0, 0, 0
+	}
+
+	xmin = math.MaxInt32
+	zmin = math.MaxInt32
+	xmax = math.MinInt32
+	zmax = math.MinInt32
+
+	for pos := range reg.superchunksAvail {
+		if pos.X < xmin {
+			xmin = pos.X
+		}
+		if pos.Z < zmin {
+			zmin = pos.Z
+		}
+		if pos.X > xmax {
+			xmax = pos.X
+		}
+		if pos.Z > zmax {
+			zmax = pos.Z
+		}
+	}
+
+	xmax++
+	zmax++
+	xmin *= 16
+	xmax *= 16
+	zmin *= 16
+	zmax *= 16
+	return
+}
+
+func chunkToSuperchunk(cx, cz int) (scx, scz, rx, rz int) {
+	scx = cx >> 5
+	scz = cz >> 5
+	rx = ((cx % 32) + 32) % 32
+	rz = ((cz % 32) + 32) % 32
+	return
+}
+
+func superchunkToChunk(scx, scz, rx, rz int) (cx, cz int) {
+	cx = scx*32 + rx
+	cz = scz*32 + rz
+	return
+}
+
+func (reg *Region) loadSuperchunk(pos XZPos) error {
+	if !reg.superchunksAvail[pos] {
+		return NotAvailable
+	}
+	fname := fmt.Sprintf("%s%cr.%d.%d.mca", reg.path, os.PathSeparator, pos.X, pos.Z)
+
+	f, err := os.Open(fname)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	pcs, err := readRegionFile(f)
+	if err != nil {
+		return err
+	}
+
+	reg.superchunks[pos] = &superchunk{
+		preChunks: pcs,
+		chunks:    make(map[XZPos]*Chunk),
+	}
+	return nil
+}
+
+func (reg *Region) cleanSuperchunks() error {
+	del := make(map[XZPos]bool)
+
+	for scPos, sc := range reg.superchunks {
+		if len(sc.chunks) > 0 {
+			return nil
+		}
+
+		if sc.modified {
+			// TODO: Save superchunk to region file
+		}
+
+		del[scPos] = true
+	}
+
+	for scPos, _ := range del {
+		delete(reg.superchunks, scPos)
+	}
+
+	return nil
+}
+
+func (reg *Region) Chunk(x, z int) (*Chunk, error) {
+	scx, scz, cx, cz := chunkToSuperchunk(x, z)
+	scPos := XZPos{scx, scz}
+	cPos := XZPos{cx, cz}
+
+	sc, ok := reg.superchunks[scPos]
+	if !ok {
+		if err := reg.loadSuperchunk(scPos); err != nil {
+			return nil, err
+		}
+		sc = reg.superchunks[scPos]
+	}
+
+	chunk, ok := sc.chunks[cPos]
+	if !ok {
+		pc, ok := sc.preChunks[cPos]
+		if !ok {
+			return nil, NotAvailable
+		}
+
+		var err error
+		if chunk, err = pc.toChunk(); err != nil {
+			return nil, err
+		}
+		sc.chunks[cPos] = chunk
+	}
+
+	if err := reg.cleanSuperchunks(); err != nil {
+		return nil, err
+	}
+
+	return chunk, nil
+}
+
+// UnloadChunk marks a chunk as unused. If all chunks of a superchunk are marked as unused, the superchunk will be unloaded and saved (if needed).
+func (reg *Region) UnloadChunk(x, z int) {
+	scx, scz, cx, cz := chunkToSuperchunk(x, z)
+	scPos := XZPos{scx, scz}
+	cPos := XZPos{cx, cz}
+
+	sc, ok := reg.superchunks[scPos]
+	if !ok {
+		return
+	}
+
+	chunk, ok := sc.chunks[cPos]
+	if !ok {
+		return
+	}
+
+	if chunk.modified {
+		// TODO: Save to prechunks
+
+		chunk.modified = false
+		sc.modified = true
+	}
+
+	delete(sc.chunks, cPos)
+}
+
+// AllChunks returns a channel that will give you the positions of all possibly available chunks in an efficient order.
+//
+// Note the "possibly available", you still have to check, if the chunk could actually be loaded.
+func (reg *Region) AllChunks() <-chan XZPos {
+	ch := make(chan XZPos)
+	go func(ch chan<- XZPos) {
+		for spos, _ := range reg.superchunksAvail {
+			scx, scz := spos.X, spos.Z
+			for rx := 0; rx < 16; rx++ {
+				for rz := 0; rz < 16; rz++ {
+					cx, cz := superchunkToChunk(scx, scz, rx, rz)
+					ch <- XZPos{cx, cz}
+				}
+			}
+		}
+		close(ch)
+	}(ch)
+
+	return ch
+}