package main

import (
	"fmt"
	"math/rand"
	"strings"
	"time"

	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
)

const (
	gridWidth  = 40
	gridHeight = 20
)

type point struct {
	x, y int
}

type snakeDirection int

const (
	dirUp snakeDirection = iota
	dirDown
	dirLeft
	dirRight
)

type snakeTickMsg time.Time

type SnakeModel struct {
	snake    []point
	dir      snakeDirection
	nextDir  snakeDirection
	food     point
	score    int
	gameOver bool
	rng      *rand.Rand
}

func newSnakeModel() SnakeModel {
	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
	snake := []point{
		{gridWidth/2 + 1, gridHeight / 2},
		{gridWidth / 2, gridHeight / 2},
		{gridWidth/2 - 1, gridHeight / 2},
	}
	m := SnakeModel{
		snake:   snake,
		dir:     dirRight,
		nextDir: dirRight,
		rng:     rng,
	}
	m.food = m.spawnFood()
	return m
}

func (m SnakeModel) spawnFood() point {
	occupied := make(map[point]bool, len(m.snake))
	for _, s := range m.snake {
		occupied[s] = true
	}
	for {
		f := point{m.rng.Intn(gridWidth), m.rng.Intn(gridHeight)}
		if !occupied[f] {
			return f
		}
	}
}

func snakeTickCmd() tea.Cmd {
	return tea.Tick(130*time.Millisecond, func(t time.Time) tea.Msg {
		return snakeTickMsg(t)
	})
}

func (m SnakeModel) Init() tea.Cmd {
	return snakeTickCmd()
}

func (m SnakeModel) Update(msg tea.Msg) (SnakeModel, tea.Cmd) {
	switch msg := msg.(type) {

	case tea.KeyMsg:
		switch msg.String() {
		case "up", "k":
			if m.dir != dirDown {
				m.nextDir = dirUp
			}
		case "down", "j":
			if m.dir != dirUp {
				m.nextDir = dirDown
			}
		case "left", "h":
			if m.dir != dirRight {
				m.nextDir = dirLeft
			}
		case "right", "l":
			if m.dir != dirLeft {
				m.nextDir = dirRight
			}
		case "r":
			if m.gameOver {
				fresh := newSnakeModel()
				return fresh, fresh.Init()
			}
		}

	case snakeTickMsg:
		if m.gameOver {
			return m, nil
		}

		m.dir = m.nextDir
		head := m.snake[0]

		var next point
		switch m.dir {
		case dirUp:
			next = point{head.x, head.y - 1}
		case dirDown:
			next = point{head.x, head.y + 1}
		case dirLeft:
			next = point{head.x - 1, head.y}
		case dirRight:
			next = point{head.x + 1, head.y}
		}

		if next.x < 0 || next.x >= gridWidth || next.y < 0 || next.y >= gridHeight {
			m.gameOver = true
			return m, nil
		}

		for _, s := range m.snake {
			if s == next {
				m.gameOver = true
				return m, nil
			}
		}

		if next == m.food {
			m.snake = append([]point{next}, m.snake...)
			m.score++
			m.food = m.spawnFood()
		} else {
			m.snake = append([]point{next}, m.snake[:len(m.snake)-1]...)
		}

		return m, snakeTickCmd()
	}

	return m, nil
}



//TODO test if the characters are rendered on different terminals
func (m SnakeModel) View() string {

	snakeIndex := make(map[point]int, len(m.snake))
	for i, s := range m.snake {
		snakeIndex[s] = i
	}

	//TODO move to top
	borderStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#8A1D7D"))
	headStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#4ADE80")).Bold(true)
	bodyStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#16A34A"))
	foodStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#FB923C"))
	titleStyle := lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#E2E8F0"))
	scoreStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#94A3B8"))
	footerStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#64748B"))
	gameOverStyle := lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#EF4444"))

	var sb strings.Builder

	sb.WriteString(
		titleStyle.Render("  SNAKE") +
			"   " +
			scoreStyle.Render(fmt.Sprintf("Score: %d", m.score)) +
			"\n",
	)

	sb.WriteString(borderStyle.Render("┌"+strings.Repeat("─", gridWidth)+"┐") + "\n")

	for y := 0; y < gridHeight; y++ {
		sb.WriteString(borderStyle.Render("│"))
		for x := 0; x < gridWidth; x++ {
			p := point{x, y}
			if idx, isSnake := snakeIndex[p]; isSnake {
				if idx == 0 {
					sb.WriteString(headStyle.Render("■"))
				} else {
					sb.WriteString(bodyStyle.Render("□"))
				}
			} else if p == m.food {
				sb.WriteString(foodStyle.Render("●"))
			} else {
				sb.WriteString(" ")
			}
		}
		sb.WriteString(borderStyle.Render("│") + "\n")
	}

	sb.WriteString(borderStyle.Render("└"+strings.Repeat("─", gridWidth)+"┘") + "\n")

	if m.gameOver {
		sb.WriteString(
			gameOverStyle.Render("  GAME OVER") +
				"  " +
				scoreStyle.Render(fmt.Sprintf("Final score: %d", m.score)) +
				"\n",
		)
		sb.WriteString(footerStyle.Render("  r to restart · b to go back · q to quit") + "\n")
	} else {
		sb.WriteString(footerStyle.Render("  ↑↓←→ / hjkl to move · b to go back · q to quit") + "\n")
	}

	return sb.String()
}