package conway

import (
	"errors"
	"fmt"
	"math/rand"
	"strings"
)

type GameOfLife struct {
	State *GameState
}

type gameGridRow struct {
	Cols []int
}

type GameState struct {
	Rows []*gameGridRow
}

type GenerationScoreCard struct {
	GameState
}

func NewGameState(height, width int) *GameState {
	state := &GameState{}
	for i := 0; i < height; i++ {
		row := &gameGridRow{}
		for j := 0; j < width; j++ {
			row.Cols = append(row.Cols, 0)
		}
		state.Rows = append(state.Rows, row)
	}
	return state
}

func (state *GameState) Height() int {
	return len(state.Rows)
}

func (state *GameState) Width() int {
	if len(state.Rows) < 1 {
		return -1
	}
	return len(state.Rows[0].Cols)
}

func (state *GameState) GetRow(y int) (*gameGridRow, error) {
	if y+1 > len(state.Rows) {
		return nil, errors.New("y coordinate is out of bounds!")
	}

	return state.Rows[y], nil
}

func (state *GameState) Set(x, y, value int) error {
	if x < 0 || y < 0 {
		errMsg := fmt.Sprintf("coordinates (%v, %v) are out of bounds!", x, y)
		return errors.New(errMsg)
	}

	row, err := state.GetRow(y)
	if err != nil {
		return err
	}

	if x+1 > len(row.Cols) {
		errMsg := fmt.Sprintf("x coordinate %v is out of bounds!", x)
		return errors.New(errMsg)
	}

	row.Cols[x] = value
	return nil
}

func (state *GameState) Get(x, y int) (int, error) {
	row, err := state.GetRow(y)
	if err != nil {
		return -1, err
	}

	if len(row.Cols) < x+1 {
		return -1, errors.New("x coordinate is out of bounds!")
	}

	return row.Cols[x], nil
}

func (state *GameState) Enliven(x, y int) error {
	return state.Set(x, y, 1)
}

func (state *GameState) Deaden(x, y int) error {
	return state.Set(x, y, 0)
}

func (state *GameState) Import(other *GameState) (err error) {
	for y, row := range other.Rows {
		for x, cell := range row.Cols {
			if err = state.Set(x, y, cell); err != nil {
				return err
			}
		}
	}
	return nil
}

func NewGameOfLife(height, width int) *GameOfLife {
	return &GameOfLife{
		State: NewGameState(height, width),
	}
}

func (game *GameOfLife) EvaluateGeneration() error {
	height, width := game.State.Height(), game.State.Width()

	genScore := NewGenerationScoreCard(height, width)
	genScore.Calculate(game.State)

	for y := 0; y < height; y++ {
		for x := 0; x < width; x++ {
			score, err := genScore.Get(x, y)
			if err != nil {
				return err
			}

			curState, err := game.State.Get(x, y)
			if err != nil {
				return err
			}

			if curState == 1 {

				if score < 2 {
					err = game.State.Deaden(x, y)
					if err != nil {
						return err
					}
					continue
				}

				if score == 2 || score == 3 {
					continue
				}

				if score > 3 {
					err = game.State.Deaden(x, y)
					if err != nil {
						return err
					}
					continue
				}
			} else if curState == 0 {

				if score == 3 {
					err = game.State.Enliven(x, y)
					if err != nil {
						return err
					}
					continue
				} else {
					continue
				}
			}
		}
	}

	return nil
}

func (game *GameOfLife) ImportState(state *GameState) error {
	return game.State.Import(state)
}

func (game *GameOfLife) ImportRandomState() error {
	height := game.State.Height()
	width := game.State.Width()

	if height < 0 || width < 0 {
		errStr := fmt.Sprintf("current game has invalid dimensions! %vx%v",
			height, width)
		return errors.New(errStr)
	}

	randState := NewGameState(height, width)

	for y := 0; y < height; y++ {
		for x := 0; x < width; x++ {
			err := randState.Set(x, y, rand.Intn(2))
			if err != nil {
				return err
			}
		}
	}

	return game.ImportState(randState)
}

func (game *GameOfLife) String() string {
	return fmt.Sprintf("%s\n", game.State)
}

func (state *GameState) String() string {
	var rows []string

	height := state.Height()
	width := state.Width()

	for y := 0; y < height; y++ {
		var cells []string
		for x := 0; x < width; x++ {
			stringVal := "Φ"

			value, err := state.Get(x, y)
			if err != nil {
				return ""
			}

			if value == 0 {
				stringVal = "·"
			}
			cells = append(cells, stringVal)
		}
		rows = append(rows, strings.Join(cells, ""))
	}
	return strings.Join(rows, "\n")
}

func NewGenerationScoreCard(height, width int) *GenerationScoreCard {
	genScore := &GenerationScoreCard{}
	for i := 0; i < height; i++ {
		row := &gameGridRow{}
		for j := 0; j < width; j++ {
			row.Cols = append(row.Cols, 0)
		}
		genScore.Rows = append(genScore.Rows, row)
	}
	return genScore
}

func (genScore *GenerationScoreCard) Calculate(state *GameState) error {
	stateHeight, stateWidth := state.Height(), state.Width()
	for y := 0; y < stateHeight; y++ {
		for x := 0; x < stateWidth; x++ {
			value, err := state.Get(x, y)
			if err != nil {
				return err
			}

			if value == 1 {
				for yOffset := -1; yOffset < 2; yOffset++ {
					for xOffset := -1; xOffset < 2; xOffset++ {
						xTarget := x + xOffset
						yTarget := y + yOffset

						if xTarget < 0 || yTarget < 0 {
							continue
						}

						if xTarget+1 > stateWidth || yTarget+1 > stateWidth {
							continue
						}

						if xTarget == x && yTarget == y {
							continue
						}

						curScore, err := genScore.Get(xTarget, yTarget)
						if err != nil {
							continue // assume out of bounds, which is stinky
						}
						err = genScore.Set(xTarget, yTarget, curScore+1)
						if err != nil {
							return err
						}
					}
				}
			}
		}
	}

	return nil
}