Add initial version

Author: coderworld10

.gitignore

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+# Jetbrain IDE
+.idea

README.md

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+# Candy
+
+Simple 2D multi-player online game.
+
+## Prerequisites
+
+- [Go v1.15.6](https://golang.org/doc/install)
+
+## Getting Started
+
+```bash
+go run main.go
+```
+
+![](docs/preview.png)
+
+## Usage
+
+| Action | Function | 
+| ------ | -------- |
+| Up arrow key | Move player upward |
+| Donw arrow key | Move player downward |
+| Left arrow key| Move player to the left |
+| Right arrow key| Move player to the right |
+
+## Testing
+
+```bash
+go test ./...
+```
+
+## Tools
+
+### Format code
+
+```bash
+goimports -w .
+```
+
+## Author
+
+- Harry - *Initial works*
+
+## Contributors
+
+## License
+
+This project is maintained under MIT license.

assets.sketch

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+package assets
+
+import (
+	"image"
+	_ "image/png"
+	"os"
+	"path/filepath"
+)
+
+var images = []string{
+	"map/default.png",
+	"sprite_sheet.png",
+}
+
+type Assets struct {
+	imageMap map[string]image.Image
+}
+
+func (a Assets) GetImage(imageName string) image.Image {
+	return a.imageMap[imageName]
+}
+
+func LoadAssets(assetRootDir string) (Assets, error) {
+	imageMap := make(map[string]image.Image)
+
+	for _, imgPath := range images {
+		file, err := os.Open(filepath.Join(assetRootDir, imgPath))
+		if err != nil {
+			return Assets{}, err
+		}
+
+		img, _, err := image.Decode(file)
+		if err != nil {
+			_ = file.Close()
+			return Assets{}, err
+		}
+		_ = file.Close()
+		imageMap[imgPath] = img
+	}
+
+	return Assets{imageMap: imageMap}, nil
+}

assets/assets.go

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+package cell
+
+import (
+	"fmt"
+)
+
+type Cell struct {
+	Row int
+	Col int
+}
+
+func (c Cell) String() string {
+	return fmt.Sprintf("[Row:%d,Col:%d]", c.Row, c.Col)
+}

assets/map/default.png

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+package cell
+
+import (
+	"fmt"
+)
+
+type CornerCells struct {
+	TopLeft     Cell
+	TopRight    Cell
+	BottomLeft  Cell
+	BottomRight Cell
+}
+
+func (c CornerCells) String() string {
+	return fmt.Sprintf("[TopLeft:%v,TopRight:%v,BottomLeft:%v,BottomRight:%v]", c.TopLeft, c.TopRight, c.BottomLeft, c.BottomRight)
+}
+
+// Detailed analysis: https://docs.google.com/document/d/1FF49lQrCCNLEuqInmXRPnbl-jvDLLtqor6Q4OgGUIy4/edit
+func GetCornerCells(
+	bottomLeftX int,
+	bottomLeftY int,
+	objectWidth int,
+	objectHeight int,
+	cellWidth int,
+	cellHeight int,
+) CornerCells {
+	topLeft := getTopLeftCell(bottomLeftX, bottomLeftY, objectHeight, cellWidth, cellHeight)
+	topRight := getTopRightCell(bottomLeftX, bottomLeftY, objectWidth, objectHeight, cellWidth, cellHeight)
+	bottomLeft := Cell{
+		Row: bottomLeftY / cellHeight,
+		Col: bottomLeftX / cellWidth,
+	}
+	bottomRight := getBottomRightCell(bottomLeftX, bottomLeftY, objectWidth, cellWidth, cellHeight)
+	return CornerCells{
+		TopLeft:     topLeft,
+		TopRight:    topRight,
+		BottomLeft:  bottomLeft,
+		BottomRight: bottomRight,
+	}
+}
+
+func getTopLeftCell(bottomLeftX int, bottomLeftY int, objectHeight int, cellWidth int, cellHeight int) Cell {
+	topY := bottomLeftY + objectHeight
+	row := topY / cellHeight
+	if topY%cellHeight == 0 {
+		row--
+	}
+	column := bottomLeftX / cellWidth
+	return Cell{
+		Row: row,
+		Col: column,
+	}
+}
+
+func getTopRightCell(bottomLeftX int, bottomLeftY int, objectWidth int, objectHeight int, cellWidth int, cellHeight int) Cell {
+	topY := bottomLeftY + objectHeight
+	row := topY / cellHeight
+	if topY%cellHeight == 0 {
+		row--
+	}
+	rightX := bottomLeftX + objectWidth
+	column := rightX / cellWidth
+	if rightX%cellWidth == 0 {
+		column--
+	}
+	return Cell{
+		Row: row,
+		Col: column,
+	}
+}
+
+func getBottomRightCell(bottomLeftX int, bottomLeftY int, objectWidth int, cellWidth int, cellHeight int) Cell {
+	row := bottomLeftY / cellHeight
+	rightX := bottomLeftX + objectWidth
+	column := rightX / cellWidth
+	if rightX%cellWidth == 0 {
+		column--
+	}
+	return Cell{
+		Row: row,
+		Col: column,
+	}
+}

assets/sprite_sheet.png

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+package cell
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetCornerCells(t *testing.T) {
+	testCases := []struct {
+		name                string
+		bottomLeftX         int
+		bottomLeftY         int
+		objectWidth         int
+		objectHeight        int
+		cellWidth           int
+		cellHeight          int
+		expectedCornerCells CornerCells
+	}{
+		{
+			name:        "Object corners overlap with grid corners",
+			bottomLeftX: 4, bottomLeftY: 2, objectWidth: 2, objectHeight: 2,
+			cellWidth: 2, cellHeight: 2,
+			expectedCornerCells: CornerCells{
+				TopLeft:     Cell{Row: 1, Col: 2},
+				TopRight:    Cell{Row: 1, Col: 2},
+				BottomLeft:  Cell{Row: 1, Col: 2},
+				BottomRight: Cell{Row: 1, Col: 2},
+			},
+		},
+		{
+			name:        "Object corners on vertical grid lines",
+			bottomLeftX: 8, bottomLeftY: 3, objectWidth: 2, objectHeight: 2,
+			cellWidth: 2, cellHeight: 2,
+			expectedCornerCells: CornerCells{
+				TopLeft:     Cell{Row: 2, Col: 4},
+				TopRight:    Cell{Row: 2, Col: 4},
+				BottomLeft:  Cell{Row: 1, Col: 4},
+				BottomRight: Cell{Row: 1, Col: 4},
+			},
+		},
+		{
+			name:        "Object corners on horizontal grid lines",
+			bottomLeftX: 5, bottomLeftY: 2, objectWidth: 2, objectHeight: 2,
+			cellWidth: 2, cellHeight: 2,
+			expectedCornerCells: CornerCells{
+				TopLeft:     Cell{Row: 1, Col: 2},
+				TopRight:    Cell{Row: 1, Col: 3},
+				BottomLeft:  Cell{Row: 1, Col: 2},
+				BottomRight: Cell{Row: 1, Col: 3},
+			},
+		},
+		{
+			name:        "Object corners not on grid lines",
+			bottomLeftX: 9, bottomLeftY: 3, objectWidth: 2, objectHeight: 2,
+			cellWidth: 2, cellHeight: 2,
+			expectedCornerCells: CornerCells{
+				TopLeft:     Cell{Row: 2, Col: 4},
+				TopRight:    Cell{Row: 2, Col: 5},
+				BottomLeft:  Cell{Row: 1, Col: 4},
+				BottomRight: Cell{Row: 1, Col: 5},
+			},
+		},
+		{
+			name:        "Object width occupy multiple columns and height occupy multiple columns",
+			bottomLeftX: 4, bottomLeftY: 2, objectWidth: 4, objectHeight: 6,
+			cellWidth: 2, cellHeight: 2,
+			expectedCornerCells: CornerCells{
+				TopLeft:     Cell{Row: 3, Col: 2},
+				TopRight:    Cell{Row: 3, Col: 3},
+				BottomLeft:  Cell{Row: 1, Col: 2},
+				BottomRight: Cell{Row: 1, Col: 3},
+			},
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			cornerCells := GetCornerCells(
+				testCase.bottomLeftX, testCase.bottomLeftY, testCase.objectWidth, testCase.objectHeight,
+				testCase.cellWidth, testCase.cellHeight,
+			)
+			assert.Equal(t, testCase.expectedCornerCells, cornerCells)
+		})
+	}
+}

collison.sketch

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+package cell
+
+func GetLeftNeighborCells(cornerCells CornerCells, minCol int) []Cell {
+	neighborCells := make([]Cell, 0)
+	if cornerCells.TopLeft.Col-1 >= minCol {
+		// Add left col
+		for row := cornerCells.BottomLeft.Row; row <= cornerCells.TopLeft.Row; row++ {
+			cell := Cell{
+				Row: row,
+				Col: cornerCells.TopLeft.Col - 1,
+			}
+			neighborCells = append(neighborCells, cell)
+		}
+	}
+	return neighborCells
+}
+
+func GetRightNeighborCells(cornerCells CornerCells, maxCol int) []Cell {
+	neighborCells := make([]Cell, 0)
+	if cornerCells.BottomRight.Col+1 <= maxCol {
+		// Add right col
+		for row := cornerCells.BottomLeft.Row; row <= cornerCells.TopLeft.Row; row++ {
+			cell := Cell{
+				Row: row,
+				Col: cornerCells.BottomRight.Col + 1,
+			}
+			neighborCells = append(neighborCells, cell)
+		}
+	}
+	return neighborCells
+}
+
+func GetTopNeighborCells(cornerCells CornerCells, maxRow int) []Cell {
+	neighborCells := make([]Cell, 0)
+	if cornerCells.TopLeft.Row+1 <= maxRow {
+		// Add top row
+		for col := cornerCells.TopLeft.Col; col <= cornerCells.TopRight.Col; col++ {
+			cell := Cell{
+				Row: cornerCells.TopLeft.Row + 1,
+				Col: col,
+			}
+			neighborCells = append(neighborCells, cell)
+		}
+	}
+	return neighborCells
+}
+
+func GetBottomNeighborCells(cornerCells CornerCells, minRow int) []Cell {
+	neighborCells := make([]Cell, 0)
+	if cornerCells.BottomRight.Row-1 >= minRow {
+		// Add bottom row
+		for col := cornerCells.BottomLeft.Col; col <= cornerCells.BottomRight.Col; col++ {
+			cell := Cell{
+				Row: cornerCells.BottomRight.Row - 1,
+				Col: col,
+			}
+			neighborCells = append(neighborCells, cell)
+		}
+	}
+	return neighborCells
+}

docs/preview.png

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+package direction
+
+type Direction int
+
+const (
+	Up Direction = iota
+	Right
+	Left
+	Down
+)