support multi-module (#4)

* add multimodule
* re-package modules

server/internal/generator/plotter/plotter.go

@@ -0,0 +1,76 @@
+package plotter
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"math/rand"
+
+	"github.com/iliadenisov/galaxy/server/internal/bitmap"
+)
+
+type Plotter struct {
+	factor              float64
+	clearFn             func()
+	circleFn            func(x, y int, r float64)
+	freeCountFn         func() int
+	freeNumberToCoordFn func(int) (int, int, error)
+}
+
+func NewPlotter(width, height uint32, factor float64) (Plotter, error) {
+	return NewBitmapPlotter(NewBitmap(width, height, factor), factor)
+}
+
+func NewBitmap(width, height uint32, factor float64) bitmap.Bitmap {
+	return bitmap.NewBitmap(AsPlotterSize(width, height, factor))
+}
+
+func NewBitmapPlotter(bm bitmap.Bitmap, factor float64) (Plotter, error) {
+	if factor > 1 || factor <= 0 {
+		return Plotter{}, fmt.Errorf("factor should be: 0 > F <= 1")
+	}
+	return Plotter{
+		factor:              factor,
+		clearFn:             bm.Clear,
+		circleFn:            func(x, y int, r float64) { bm.Circle(x, y, r, true) },
+		freeCountFn:         bm.FreeCount,
+		freeNumberToCoordFn: bm.GetFreeN,
+	}, nil
+}
+
+func (p Plotter) RandomFreePoint(deadZoneRaduis float64) (float64, float64, error) {
+	fsCount := p.freeCountFn()
+	if fsCount == 0 {
+		return 0, 0, errors.New("RandomFreePoint: no free space left")
+	}
+	next := rand.Intn(fsCount)
+	x, y, err := p.freeNumberToCoordFn(next)
+	if err != nil {
+		return 0, 0, fmt.Errorf("RandomFreePoint: freeNumberToCoordFn: %s", err)
+	}
+	if deadZoneRaduis > 0 {
+		p.plotDeadZone(x, y, deadZoneRaduis)
+	}
+	planetX := float64(x)*p.factor + rand.Float64()*p.factor
+	planetY := float64(y)*p.factor + rand.Float64()*p.factor
+	return planetX, planetY, nil
+}
+
+func (p Plotter) MarkDeadZone(x, y float64, radius float64) {
+	p.plotDeadZone(int(x/p.factor), int(y/p.factor), radius)
+}
+
+func (p Plotter) plotDeadZone(x, y int, radius float64) {
+	// Adding extra 'pixel' to avoid radius became less than deadZoneRaduis
+	// after division by factor due to floating-point operations specifics
+	p.circleFn(x, y, (radius+p.factor)/p.factor)
+}
+
+func (p Plotter) Clear() { p.clearFn() }
+
+func AsPlotterSize(width, height uint32, factor float64) (uint32, uint32) {
+	if factor > 1 || factor <= 0 {
+		return width, height
+	}
+	return uint32(math.Ceil(float64(width) / float64(factor))), uint32(math.Ceil(float64(height) / float64(factor)))
+}