package main

import (
    "fmt"
    "os"
    "strings"
    tea "github.com/charmbracelet/bubbletea"
)

const BOARD_SIZE = 4

type GameState int8
const (
    StartTurn GameState = iota
    IsMoving
    HasMoved
    HasPlaced
    GameOver
)

type Player int8
const (
    PNone Player = iota
    POne
    PTwo
)

type Position struct {
    x int
    y int
}

type GameModel struct {
    board [][]Player
    playerTurn Player

    cursor Position
    moveCursor Position
    state GameState
    message string
}

func (m GameModel) PrintBoard() string {
    rowSeparator := "+" + strings.Repeat("---+", len(m.board)) + "\n"
    playerSymbols := map[Player]byte{
        PNone: '_',
        POne: 'X',
        PTwo: 'O',
    }

    lines := make([][]byte, 0)
    for _, row := range m.board {
        // Create the grid row
        line := []byte("|" + strings.Repeat("   |", len(row)))
        // Populate the player symbols
        for i, p := range row {
            line[(i*4)+2] = playerSymbols[p]
        }
        lines = append(lines, line)
    }

    lines[m.cursor.y][(m.cursor.x*4)+1] = '>'
    lines[m.cursor.y][(m.cursor.x*4)+3] = '<'

    if m.state == IsMoving {
        lines[m.moveCursor.y][(m.moveCursor.x*4)+1] = '['
        lines[m.moveCursor.y][(m.moveCursor.x*4)+3] = ']'
    }

    s := rowSeparator
    for _, line := range lines {
        s += string(line) + "\n"
        s += rowSeparator
    }

    return s
}

func RotateBoard(board [][]Player) [][]Player {
    // Clone the board
    nBoard := make([][]Player, len(board))
    for i := range board {
        nBoard[i] = make([]Player, len(board[i]))
        copy(nBoard[i], board[i])
    }

    // Rotate each ring of the board counter-clockwise
    for ringStart := range len(board)/2 {
        ringEnd := len(board)-ringStart-1

        // Top
        for x := ringStart; x < ringEnd; x++ {
            nBoard[ringStart][x] = board[ringStart][x+1]
        }
        // Bottom
        for x := ringStart+1; x <= ringEnd; x++ {
            nBoard[ringEnd][x] = board[ringEnd][x-1]
        }
        // Left
        for y := ringStart+1; y <= ringEnd; y++ {
            nBoard[y][ringStart] = board[y-1][ringStart]
        }
        // Right
        for y := ringStart; y < ringEnd; y++ {
            nBoard[y][ringEnd] = board[y+1][ringEnd]
        }
    }

    return nBoard
}

func (m GameModel) Move() GameModel {
    m.message = ""

    switch m.state {
    case IsMoving:
        if m.board[m.cursor.y][m.cursor.x] != PNone {
            m.message = "You cannot move to an occupied space"
            break
        }
        // TODO: Valid that cursor is out of bounds?
        xDiff := m.cursor.x - m.moveCursor.x
        yDiff := m.cursor.y - m.moveCursor.y

        if !(
            (xDiff ==  0 && yDiff == -1) || // Up
            (xDiff ==  0 && yDiff ==  1) || // Down
            (xDiff == -1 && yDiff ==  0) || // Left
            (xDiff ==  1 && yDiff ==  0)) { // Right
            m.message = "You cannot move here. You can only move one square laterally."
            break
        }

        m.board[m.cursor.y][m.cursor.x] = m.board[m.moveCursor.x][m.moveCursor.y]
        m.board[m.moveCursor.x][m.moveCursor.y] = PNone
        m.state = HasMoved

    case HasPlaced:
        m.board = RotateBoard(m.board)
        m.message = "The board has been rotated."
        if m.playerTurn == POne {
            m.playerTurn = PTwo
        } else {
            m.playerTurn = POne
        }
        m.state = StartTurn

    default:
        switch m.board[m.cursor.y][m.cursor.x] {
        case PNone:
            // Place piece
            m.board[m.cursor.y][m.cursor.x] = m.playerTurn
            m.state = HasPlaced
        case m.playerTurn:
            m.message = "You cannot move your own piece."
        default:
            m.state = IsMoving
            m.moveCursor = m.cursor
        }
    }

    return m
}

func initialModel() GameModel {
    initialBoard := make([][]Player, BOARD_SIZE)
    for i := range BOARD_SIZE {
        initialBoard[i] = make([]Player, BOARD_SIZE)
        for j := range initialBoard[i] {
            initialBoard[i][j] = PNone
        }
    }

    return GameModel{
        board: initialBoard,
        playerTurn: POne,
    }
}

func (m GameModel) Init() tea.Cmd {
    return nil
}

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

    case tea.KeyMsg:

        switch msg.String() {

        case "ctrl+c", "q":
            return m, tea.Quit

        case "up", "k":
            switch m.state {
                case GameOver:
                    break
                case HasPlaced:
                    break
                case IsMoving:
                    if m.moveCursor.y > 0 {
                        m.cursor.x = m.moveCursor.x
                        m.cursor.y = m.moveCursor.y-1
                    }
                default:
                    m.cursor.y = (m.cursor.y + len(m.board) - 1) % len(m.board)
            }

        case "down", "j":
            switch m.state {
                case GameOver:
                    break
                case HasPlaced:
                    break
                case IsMoving:
                    if m.moveCursor.y < len(m.board)-1 {
                        m.cursor.x = m.moveCursor.x
                        m.cursor.y = m.moveCursor.y+1
                    }
                default:
                    m.cursor.y = (m.cursor.y + 1) % len(m.board)
            }

        case "left", "h":
            switch m.state {
                case GameOver:
                    break
                case HasPlaced:
                    break
                case IsMoving:
                    if m.moveCursor.x > 0 {
                        m.cursor.x = m.moveCursor.x-1
                        m.cursor.y = m.moveCursor.y
                    }
                default:
                    m.cursor.x = (m.cursor.x + len(m.board) - 1) % len(m.board)
            }

        case "right", "l":
            switch m.state {
                case GameOver:
                    break
                case HasPlaced:
                    break
                case IsMoving:
                    if m.moveCursor.x < len(m.board)-1 {
                        m.cursor.x = m.moveCursor.x+1
                        m.cursor.y = m.moveCursor.y
                    }
                default:
                    m.cursor.x = (m.cursor.x + 1) % len(m.board)
            }

        case "enter", " ":
            m = m.Move()
        }
    }

    return m, nil
}

func (m GameModel) View() string {
    s := m.PrintBoard()
    msg := ""

    switch m.playerTurn {
    case POne:
        msg += "Player 1 (X) plays\n"
    case PTwo:
        msg += "Player 2 (O) plays\n"
    default:
        // Something is wrong!
        msg += "DEBUG: \n"
        msg += fmt.Sprintf("Current player: %v\nCurrent MoveState: %v\nCurrent Board: %v\nCurrent Cursor: %#v\n", m.playerTurn, m.state, m.board, m.cursor)
    }

    switch m.state {
    case StartTurn:
        msg += "Place a new piece or move an opponent piece >_< \n"
    case IsMoving:
        msg += "Move opponent piece from [_] to >_<. \n"
    case HasMoved:
        msg += "Place your piece at >_< \n"
    case HasPlaced:
        msg += "Finish your turn, rotating the board \n"
    }

    s += "\n" + msg
    s += "\n" + m.message
    return s
}

func main() {
    fmt.Println("==== Gorbito ====")

    p := tea.NewProgram(initialModel())
    if _, err := p.Run(); err != nil {
        fmt.Printf("Alas, there's been an error: %v", err)
        os.Exit(1)
    }
}