package main

import (
	"fmt"
	"math"

	h "git.bullercodeworks.com/brian/adventofcode/helpers"
)

func main() {
	inp := h.StdinToStringSlice()
	part1(inp)
	fmt.Println()
	part2(inp)
}

func part1(inp []string) {
	m := h.StringSliceToCoordByteMap(inp)
	start, _ := m.FindFirst('S')
	m.Put(start, 'a')
	end, _ := m.FindFirst('E')
	m.Put(end, 'z')

	fmt.Println("# Part 1")
	fmt.Println("Steps:", bfs(m, start, end))
}

func part2(inp []string) {
	m := h.StringSliceToCoordByteMap(inp)
	starts := m.FindAll('a')
	if s, err := m.FindFirst('S'); err == nil {
		m.Put(s, 'a')
		starts = append(starts, s)
	}
	end, _ := m.FindFirst('E')
	m.Put(end, 'z')

	minSteps := math.MaxInt
	for _, start := range starts {
		curSteps := bfs(m, start, end)
		if minSteps > curSteps {
			minSteps = curSteps
		}
	}
	fmt.Println("# Part 2")
	fmt.Println("Steps:", minSteps)
}

func bfs(m h.CoordByteMap, start, end h.Coordinate) int {
	seen := make(map[h.Coordinate]bool)
	seen[start] = true
	queue := []h.Coordinate{start}
	steps := 0
	found := false
	// BFS Search
SEARCH:
	for len(queue) > 0 {
		k := len(queue)
		for i := 0; i < k; i++ {
			curr := queue[0]
			currVal := m.Get(curr)
			queue = queue[1:]
			if end.Equals(curr) {
				found = true
				break SEARCH
			}
			for _, dir := range curr.GetOrthNeighbors() {
				if !m.ContainsCoord(dir) || seen[dir] {
					continue
				}
				newVal := m.Get(dir)
				greater := m.Get(dir) > currVal
				if greater && newVal-currVal > 1 {
					continue
				}
				seen[dir] = true
				queue = append(queue, dir)
			}
		}
		steps++
	}
	if !found {
		//fmt.Println("Path from", start, "to", end, "not found!")
		return math.MaxInt
	}
	return steps
}