maze-solver-go/io/reader/text.go

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package reader
import (
"bufio"
"fmt"
"maze-solver/maze"
"os"
)
type TextReader struct {
PathChar, WallChar byte
}
func (r *TextReader) Read(filename string) (*maze.Maze, error) {
nodesByCoord := make(map[maze.Coordinates]*maze.Node)
var lines []string
ret := &maze.Maze{}
if _, err := os.Stat(filename); err != nil {
return nil, err
}
file, err := os.Open(filename)
if err != nil {
return nil, err
}
scanner := bufio.NewScanner(file)
scanner.Split(bufio.ScanLines)
y := 0
var line string
for scanner.Scan() {
line = scanner.Text()
if len(lines) == 0 {
lines = make([]string, 0, len(line))
}
for x := 1; x < len(line)-1; x++ {
char := line[x]
var left_char, right_char, above_char byte
if y > 0 {
left_char = line[x-1]
right_char = line[x+1]
above_char = lines[y-1][x]
}
// Parse first line to get entrance
if y == 0 && char == r.PathChar {
coords := maze.Coordinates{X: x, Y: y}
node := maze.NewNode(coords)
ret.Nodes = append(ret.Nodes, node)
nodesByCoord[coords] = node
continue
}
// Parse middle of the maze
if y > 0 && char == r.PathChar &&
(left_char == r.WallChar && right_char == r.PathChar ||
left_char == r.PathChar && right_char == r.WallChar ||
above_char == r.PathChar && (left_char == r.PathChar || right_char == r.PathChar)) {
coords := maze.Coordinates{X: x, Y: y}
node := maze.NewNode(coords)
ret.Nodes = append(ret.Nodes, node)
nodesByCoord[coords] = node
r.lookupNeighbourAbove(&lines, node, &nodesByCoord)
if left_char == r.PathChar && right_char == r.WallChar ||
above_char == r.PathChar && (left_char == r.PathChar || right_char == r.PathChar) {
r.lookupNeighbourLeft(&line, node, &nodesByCoord)
}
}
}
lines = append(lines, line)
y++
}
y--
// Parse last line to get exit
for x, rune := range line {
char := byte(rune)
if char == r.PathChar {
coords := maze.Coordinates{X: x, Y: y}
node := maze.NewNode(coords)
r.lookupNeighbourAbove(&lines, node, &nodesByCoord)
ret.Nodes = append(ret.Nodes, node)
break
}
}
return ret, nil
}
func (r *TextReader) lookupNeighbourAbove(lines *[]string, node *maze.Node, nodesByCoord *map[maze.Coordinates]*maze.Node) {
for y := node.Coords.Y - 1; y >= 0; y-- {
if (*lines)[y][node.Coords.X] == r.WallChar {
break
}
neighbour, ok := (*nodesByCoord)[maze.Coordinates{X: node.Coords.X, Y: y}]
if ok {
node.Up = neighbour
neighbour.Down = node
}
}
}
func (r *TextReader) lookupNeighbourLeft(line *string, node *maze.Node, nodesByCoord *map[maze.Coordinates]*maze.Node) {
for x := node.Coords.X - 1; x > 0; x-- {
if (*line)[x] == r.WallChar {
panic(fmt.Sprintf("Found no node before wall while looking to the left at neighbours of node %v", node))
}
neighbour, ok := (*nodesByCoord)[maze.Coordinates{X: x, Y: node.Coords.Y}]
if ok {
node.Left = neighbour
neighbour.Right = node
break
}
}
}