From 069d03004dd1f7321aee8d097d95bf2427c697be Mon Sep 17 00:00:00 2001
From: Brian Buller <brian@bullercodeworks.com>
Date: Sun, 20 Dec 2020 14:25:28 -0600
Subject: [PATCH] Forgot a file

---
 2020/day20/tile.go | 94 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 2020/day20/tile.go

diff --git a/2020/day20/tile.go b/2020/day20/tile.go
new file mode 100644
index 0000000..10d81c9
--- /dev/null
+++ b/2020/day20/tile.go
@@ -0,0 +1,94 @@
+package main
+
+import (
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+type Tile struct {
+	Num       int
+	Data      [][]bool
+	Neighbors map[h.Coordinate]*Tile
+}
+
+func NewTile(num int, lines []string) *Tile {
+	t := Tile{
+		Num:       num,
+		Neighbors: make(map[h.Coordinate]*Tile),
+	}
+	for y := range lines {
+		var lineData []bool
+		for x := range lines[y] {
+			lineData = append(lineData, lines[y][x] == '#')
+		}
+		t.Data = append(t.Data, lineData)
+	}
+	return &t
+}
+
+func (t *Tile) Rotate() {
+	t.Data = RotateMap(t.Data)
+}
+
+func (t *Tile) Flip() {
+	t.Data = FlipMap(t.Data)
+}
+
+func (t *Tile) IsEastNeighbor(wrk *Tile) bool {
+	size := len(t.Data)
+	for y := range t.Data {
+		if t.Data[y][size-1] != wrk.Data[y][0] {
+			return false
+		}
+	}
+	return true
+}
+
+func (t *Tile) IsSouthNeighbor(wrk *Tile) bool {
+	size := len(t.Data)
+	for x := range t.Data[size-1] {
+		if t.Data[size-1][x] != wrk.Data[0][x] {
+			return false
+		}
+	}
+	return true
+}
+
+func (t *Tile) IsNeighbor(wrk *Tile, canChange bool) bool {
+	for _, c := range []h.Coordinate{N, E, S, W} {
+		if _, ok := t.Neighbors[c]; ok {
+			continue
+		}
+		for i := 0; i < 8; i++ {
+			if c == E && t.IsEastNeighbor(wrk) {
+				t.Neighbors[E] = wrk
+				wrk.Neighbors[W] = t
+				return true
+			}
+			if c == W && wrk.IsEastNeighbor(t) {
+				t.Neighbors[W] = wrk
+				wrk.Neighbors[E] = t
+				return true
+			}
+			if c == S && t.IsSouthNeighbor(wrk) {
+				t.Neighbors[S] = wrk
+				wrk.Neighbors[N] = t
+				return true
+			}
+			if c == N && wrk.IsSouthNeighbor(t) {
+				t.Neighbors[N] = wrk
+				wrk.Neighbors[S] = t
+				return true
+			}
+			if !canChange {
+				break
+			}
+			if i&1 == 0 {
+				wrk.Flip()
+			} else {
+				wrk.Flip()
+				wrk.Rotate()
+			}
+		}
+	}
+	return false
+}