package days

import (
	"fmt"
	"strings"

	u "parnic.com/aoc2019/utilities"
)

type camViewCellType int
type botFacing int

const (
	cellTypeScaffold camViewCellType = iota
	cellTypeOpen
	cellTypeInvalid
)

const (
	botFacingUp botFacing = iota
	botFacingLeft
	botFacingDown
	botFacingRight

	botFacingFirst = botFacingUp
	botFacingLast  = botFacingRight
)

const (
	dirLeft  dirType = 1
	dirRight dirType = -1
)

var (
	day17AdjacentOffsets = []u.Vec2i{
		{X: -1, Y: 0},
		{X: 1, Y: 0},
		{X: 0, Y: -1},
		{X: 0, Y: 1},
	}
)

type Day17 struct {
	program      u.IntcodeProgram
	grid         [][]camViewCellType
	botLocation  u.Vec2i
	botFacingDir botFacing
	endLocation  u.Vec2i
}

func (d *Day17) Parse() {
	d.program = u.LoadIntcodeProgram("17p")
	d.grid = [][]camViewCellType{{}}
}

func (d Day17) Num() int {
	return 17
}

func (d Day17) Draw() {
	for y := range d.grid {
		for x := range d.grid[y] {
			switch d.grid[y][x] {
			case cellTypeOpen:
				fmt.Print(" ")
			case cellTypeScaffold:
				char := "█"
				color := u.ColorBlack
				if d.botLocation.X == x && d.botLocation.Y == y {
					switch d.botFacingDir {
					case botFacingUp:
						char = "^"
					case botFacingLeft:
						char = "<"
					case botFacingDown:
						char = "v"
					case botFacingRight:
						char = ">"
					}
				} else if d.endLocation.X == x && d.endLocation.Y == y {
					char = "@"
				} else {
					color = u.ColorWhite
				}
				fmt.Printf("%s%s%s%s", u.BackgroundWhite, color, char, u.TextReset)
			}
		}
		fmt.Println()
	}
}

func (d Day17) getAdjacentScaffolds(y, x int) []u.Vec2i {
	retval := make([]u.Vec2i, 0)
	for _, offset := range day17AdjacentOffsets {
		offY := y + offset.Y
		offX := x + offset.X
		if offY < 0 || offY >= len(d.grid) ||
			offX < 0 || offX >= len(d.grid[0]) {
			continue
		}

		if d.grid[offY][offX] == cellTypeScaffold {
			retval = append(retval, u.Vec2i{X: offX, Y: offY})
		}
	}

	return retval
}

func (d Day17) getNumSurroundingScaffolds(y, x int) int {
	return len(d.getAdjacentScaffolds(y, x))
}

func (d Day17) forEachCellOfType(t camViewCellType, f func(y, x int)) {
	for y := range d.grid {
		for x := range d.grid[y] {
			if d.grid[y][x] == t {
				f(y, x)
			}
		}
	}
}

func (d Day17) getNewFacingDir(currentDir botFacing, turnDir dirType) botFacing {
	currentDir += botFacing(turnDir)
	if currentDir < botFacingFirst {
		currentDir = botFacingLast
	} else if currentDir > botFacingLast {
		currentDir = botFacingFirst
	}

	return currentDir
}

func (d Day17) getCellTypeInDirection(y, x int, facingDir botFacing) (camViewCellType, int, int) {
	newX := x
	newY := y
	switch facingDir {
	case botFacingUp:
		newY--
	case botFacingLeft:
		newX--
	case botFacingDown:
		newY++
	case botFacingRight:
		newX++
	}

	if newY < 0 || newY >= len(d.grid) || newX < 0 || newX >= len(d.grid[0]) {
		return cellTypeInvalid, newY, newX
	}

	return d.grid[newY][newX], newY, newX
}

func (d *Day17) Part1() string {
	y := 0
	d.program.RunIn(func(inputStep int) int64 {
		return 0
	}, func(val int64, state u.IntcodeProgramState) {
		rVal := rune(val)
		switch rVal {
		case '\n':
			y++
			d.grid = append(d.grid, make([]camViewCellType, 0))
		case '#':
			d.grid[y] = append(d.grid[y], cellTypeScaffold)
		case '.':
			d.grid[y] = append(d.grid[y], cellTypeOpen)
		case '^', '<', 'v', '>':
			d.botLocation = u.Vec2i{X: len(d.grid[y]), Y: y}
			d.grid[y] = append(d.grid[y], cellTypeScaffold)
			switch rVal {
			case '^':
				d.botFacingDir = botFacingUp
			case '<':
				d.botFacingDir = botFacingLeft
			case 'v':
				d.botFacingDir = botFacingDown
			case '>':
				d.botFacingDir = botFacingRight
			}
		}
	})

	for y := len(d.grid) - 1; y >= 0; y-- {
		if len(d.grid[y]) == 0 {
			d.grid = d.grid[0 : len(d.grid)-1]
		}
	}

	alignmentParameterTotal := 0
	d.forEachCellOfType(cellTypeScaffold, func(y, x int) {
		if numSurrounding := d.getNumSurroundingScaffolds(y, x); numSurrounding == 4 {
			alignmentParameterTotal += y * x
		} else if numSurrounding == 1 {
			if d.botLocation.X != x || d.botLocation.Y != y {
				d.endLocation = u.Vec2i{X: x, Y: y}
			}
		}
	})

	// d.Draw()

	return fmt.Sprintf("Alignment parameter sum: %s%d%s", u.TextBold, alignmentParameterTotal, u.TextReset)
}

func (d *Day17) Part2() string {
	instructions := make([]string, 0)

	pos := d.botLocation
	botFacingDir := d.botFacingDir
	for {
		if pos == d.endLocation {
			fmt.Println()
			break
		}

		adj := d.getAdjacentScaffolds(pos.Y, pos.X)
		turnDirection := dirType(0)
		if botFacingDir == botFacingUp || botFacingDir == botFacingDown {
			if u.ArrayContains(adj, u.Vec2i{X: pos.X - 1, Y: pos.Y}) {
				if botFacingDir == botFacingUp {
					turnDirection = dirLeft
				} else if botFacingDir == botFacingDown {
					turnDirection = dirRight
				}
			} else if u.ArrayContains(adj, u.Vec2i{X: pos.X + 1, Y: pos.Y}) {
				if botFacingDir == botFacingUp {
					turnDirection = dirRight
				} else if botFacingDir == botFacingDown {
					turnDirection = dirLeft
				}
			}
		} else {
			if u.ArrayContains(adj, u.Vec2i{X: pos.X, Y: pos.Y - 1}) {
				if botFacingDir == botFacingLeft {
					turnDirection = dirRight
				} else if botFacingDir == botFacingRight {
					turnDirection = dirLeft
				}
			} else if u.ArrayContains(adj, u.Vec2i{X: pos.X, Y: pos.Y + 1}) {
				if botFacingDir == botFacingLeft {
					turnDirection = dirLeft
				} else if botFacingDir == botFacingRight {
					turnDirection = dirRight
				}
			}
		}

		if turnDirection == 0 {
			panic("at an invalid location somehow")
		}

		dirAscii := "L"
		if turnDirection == dirRight {
			dirAscii = "R"
		}
		instructions = append(instructions, dirAscii)

		botFacingDir = d.getNewFacingDir(botFacingDir, turnDirection)
		numMoved := 0
		for {
			cell, newY, newX := d.getCellTypeInDirection(pos.Y, pos.X, botFacingDir)
			if cell != cellTypeScaffold {
				break
			}
			pos.X = newX
			pos.Y = newY
			numMoved++
		}
		instructions = append(instructions, fmt.Sprintf("%d", numMoved))
	}

	return fmt.Sprintf("%s%s%s", u.TextBold, strings.Join(instructions, ","), u.TextReset)
}