package day14

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

func Run() int {
	fmt.Println("hello day 14")

	field := ReadPlatform("day14/example")
	fmt.Println(field.String())

	// fmt.Printf("> lines for field %+v\n", field.UpIndices())
	field.MoveUp(field.Height())
	fmt.Println(field.String())

	// north rock load
	return field.NorthLoad()
}

const Rock rune = 'O'
const Wall rune = '#'
const Space rune = '.'

type Platform struct {
	Rocks [][]rune
}

func (p *Platform)Height() int {
	return len(p.Rocks)
}
func (p *Platform)Width() int {
	return len(p.Rocks[0])
}

func ReadPlatform(filename string) Platform {
	bytes, err := os.ReadFile(filename)
	if err != nil {
		panic(fmt.Sprint("cannot read file: ", filename))
	}
	text := string(bytes)
	text = strings.TrimSpace(text)
	lines := strings.Split(text, "\n")

	rocks := make([][]rune, len(lines))
	for i, line := range lines {
		rocks[i] = []rune(line)
	}

	return Platform{
		Rocks: rocks,
	}
}

func (p *Platform) String() string {
	text := "\n"
	for _, row := range p.Rocks {
		text += string(row)
		text += "\n"
	}

	return text
}

type Coord struct { Row, Col int }

func (p *Platform) UpIndices() [][]Coord {
	lines := make([][]Coord,0)
	for col := 0; col < p.Width(); col++ {
		line := make([]Coord, 0)
		for row := 0; row < p.Height(); row++ {
			line = append(line, Coord{Row: row, Col: col})
		}
		lines = append(lines, line)
	}
	return lines
}

func (p *Platform) DownIndices() [][]Coord {
	lines := make([][]Coord,0)
	for col := 0; col < p.Width(); col++ {
		line := make([]Coord, 0)
		for row := p.Height() - 1; row >= 0; row-- {
			line = append(line, Coord{Row: row, Col: col})
		}
		lines = append(lines, line)
	}
	return lines
}

func (p *Platform)SymbAt(coord Coord) rune {
	return p.Rocks[coord.Row][coord.Col]
}
func (p *Platform)SetSymbAt(coord Coord, symb rune) {
	p.Rocks[coord.Row][coord.Col] = symb
}

func (p *Platform) MoveUp(n int) {
	lines := p.UpIndices()

	for _, line := range lines {
		moveSize := 0
		for i, coord := range line {
			symb := p.SymbAt(coord)
			switch symb {
			case Space:
				moveSize += 1
				if moveSize > n {
					moveSize = n
				}
			case Wall:
				moveSize = 0
			case Rock:
				if moveSize == 0 {
					continue
				}
				// get coord for moveSize back. and set that to 'o'
				// and set current to '.'
				// panic if that place is not '.' i guess
				moveTo := line[i - moveSize]
				symbAtTarget := p.SymbAt(moveTo)
				if symbAtTarget != Space {
					panic(fmt.Sprintf("attempting to move %+v to %+v, target symbol is %s, not '.'",
						coord, moveTo, string(symbAtTarget)))
				}
				p.SetSymbAt(moveTo, Rock)
				p.SetSymbAt(coord, Space)
			}
		}
	}
}

func (p *Platform)NorthLoad() int {
	total := 0
	height := p.Height()
	for i, row := range p.Rocks {
		for _, symb := range row {
			if symb == Rock {
				total += (height - i)
			}
		}
	}
	return total
}