package day23

import (
	"fmt"
	"os"
	"strings"
)

type Coord struct {
	Row, Col int
}

type CellType rune

const (
	Path       CellType = '.'
	Tree       CellType = '#'
	SlideDown  CellType = 'v'
	SlideUp    CellType = '^'
	SlideLeft  CellType = '<'
	SlideRight CellType = '>'
)

type Field struct {
	MaxRow, MaxCol   int
	Cells            map[Coord]CellType
	StartCol, EndCol int
}

func (f *Field) EndCoord() Coord {
	return Coord{Row: f.MaxRow, Col: f.EndCol}
}

func (f *Field) NeighborsPart2(c Coord) (neighbors []Coord) {
	symb, exists := f.Cells[c]
	if !exists {
		panic(fmt.Sprintf("coord %+v not found in field", c))
	}

	var coords []Coord
	switch symb {
	case Tree:
		panic(fmt.Sprintf("attempting to get neighbors of a tree at %+v", c))
	default:
		coords = []Coord{
			{Row: c.Row + 1, Col: c.Col},
			{Row: c.Row - 1, Col: c.Col},
			{Row: c.Row, Col: c.Col + 1},
			{Row: c.Row, Col: c.Col - 1},
		}
	}

	for _, coord := range coords {
		neighborSymb, found := f.Cells[coord]
		if !found || neighborSymb == Tree {
			continue
		}
		neighbors = append(neighbors, coord)
	}
	return
}

func (f *Field) Neighbors(c Coord) (neighbors []Coord) {
	symb, exists := f.Cells[c]
	if !exists {
		panic(fmt.Sprintf("coord %+v not found in field", c))
	}

	var coords []Coord
	switch symb {
	case Path:
		coords = []Coord{
			{Row: c.Row + 1, Col: c.Col},
			{Row: c.Row - 1, Col: c.Col},
			{Row: c.Row, Col: c.Col + 1},
			{Row: c.Row, Col: c.Col - 1},
		}
	case Tree:
		panic(fmt.Sprintf("attempting to get neighbors of a tree at %+v", c))
	case SlideDown:
		coords = []Coord{{Row: c.Row + 1, Col: c.Col}}
	case SlideUp:
		coords = []Coord{{Row: c.Row - 1, Col: c.Col}}
	case SlideLeft:
		coords = []Coord{{Row: c.Row, Col: c.Col - 1}}
	case SlideRight:
		coords = []Coord{{Row: c.Row, Col: c.Col + 1}}
	}

	for _, coord := range coords {
		neighborSymb, found := f.Cells[coord]
		if !found || neighborSymb == Tree {
			continue
		}
		neighbors = append(neighbors, coord)
	}
	return
}

func (f *Field) String() (result string) {
	result += "\n"
	for row := 0; row <= f.MaxRow; row++ {
		for col := 0; col <= f.MaxCol; col++ {
			if row == 0 && col == f.StartCol {
				result += "S"
				continue
			}
			if row == f.MaxRow && col == f.EndCol {
				result += "E"
				continue
			}

			symb := f.Cells[Coord{Row: row, Col: col}]
			result += string(symb)
		}
		result += "\n"
	}
	return
}

func ReadField(filename string) (result Field) {
	bytes, err := os.ReadFile(filename)
	if err != nil {
		panic(err)
	}
	lines := strings.Split(strings.TrimSpace(string(bytes)), "\n")
	result.MaxRow = len(lines) - 1
	result.MaxCol = len(lines[0]) - 1
	rows := make(map[Coord]CellType)

	for rowNum, row := range lines {
		for colNum, symb := range row {
			rows[Coord{Row: rowNum, Col: colNum}] = CellType(symb)
			if rowNum == 0 && symb == rune(Path) {
				result.StartCol = colNum
			}
			if rowNum == result.MaxRow && symb == rune(Path) {
				result.EndCol = colNum
			}
		}
	}
	result.Cells = rows

	return
}