#include <Arduino.h>
#include <FastLED.h>
#include <Encoder.h>
#include <WiFi.h>
#include <WebServer.h>
#include <Preferences.h>

#ifndef SHOW_BORDER
#define SHOW_BORDER 1
#endif

#define NUM_LEDS 64
const int COLS = 7;
const int ROWS = 6;

CRGB leds[NUM_LEDS];
Encoder myEnc(ENC_A, ENC_B);
WebServer server(80);
Preferences prefs;

int8_t board[COLS][ROWS];
bool winMask[NUM_LEDS];
enum State
{
    MENU,
    PLAYING,
    FINISHED_WIN,
    FINISHED_DRAW,
    DEMO
};
State gameState = MENU;

int8_t menuMode = 0;
int8_t currentPlayer = 1;
int8_t winnerPlayer = 0;
int8_t activeCol = 3;
long oldEncPos = -999;
uint32_t lastActivityTime = 0;
uint32_t demoResetTimer = 0;
bool isDemoOver = false;
uint8_t demoPly = 4;
bool abortAi = false;

uint8_t current_look_ahead;
uint8_t current_brightness;
uint32_t current_idle_timeout_ms;
bool blunder_enabled = false;
bool progressive_difficulty = false;

uint8_t aiBrightness = 0;
bool aiFadeUp = true;

// --- Function Prototypes ---
int getIdx(int x, int y);
void drawStaticUI();
void renderBoard();
int getFirstEmptyRow(int col);
bool isBoardFull();
int8_t scanBoard();
void updateThinkingVisuals(int8_t playerColor, int8_t column);
void animateDrop(int col, int player);
void moveDiscToCol(int startCol, int targetCol, int player, int speed);
int minimax(int depth, int alpha, int beta, bool isMax, int8_t aiPlayer, int8_t humanPlayer, int8_t rootCol);
void performAiMove(int8_t aiPlayer);
void showMenu();
int getDynamicPly();

int getIdx(int x, int y) { return (y * 8) + x; }

void drawStaticUI()
{
    FastLED.clear();
#if SHOW_BORDER == 1
    CRGB borderColor = CRGB::Blue;
    if (gameState == DEMO || gameState >= 2)
    {
        uint8_t glow = beat8(15);
        borderColor = blend(CRGB::Blue, CRGB::White, glow / 4);
    }
    for (int x = 0; x < 7; x++)
        leds[getIdx(x, 1)] = borderColor;
    for (int y = 1; y < 8; y++)
        leds[getIdx(7, y)] = borderColor;
#endif
}

void renderBoard()
{
    drawStaticUI();
    for (int column = 0; column < COLS; column++)
    {
        for (int row = 0; row < ROWS; row++)
        {
            if (board[column][row] == 1)
                leds[getIdx(column, 7 - row)] = CRGB::Yellow;
            if (board[column][row] == 2)
                leds[getIdx(column, 7 - row)] = CRGB::Red;
        }
    }
}

int getFirstEmptyRow(int col)
{
    for (int row = 0; row < ROWS; row++)
    {
        if (board[col][row] == 0)
            return row;
    }
    return -1;
}

bool isBoardFull()
{
    for (int column = 0; column < COLS; column++)
    {
        if (board[column][ROWS - 1] == 0)
            return false;
    }
    return true;
}

int getDynamicPly()
{
    if (!progressive_difficulty && gameState != DEMO)
        return current_look_ahead;
    int occupiedCount = 0;
    for (int column = 0; column < COLS; column++)
        for (int row = 0; row < ROWS; row++)
            if (board[column][row] != 0)
                occupiedCount++;
    return constrain(current_look_ahead + (occupiedCount / 7), 1, 10);
}

void updateThinkingVisuals(int8_t playerColor, int8_t column)
{
    static uint32_t lastCycle = 0;
    if (millis() - lastCycle < 25)
        return;
    lastCycle = millis();
    if (aiFadeUp)
    {
        aiBrightness += 15;
        if (aiBrightness >= 240)
            aiFadeUp = false;
    }
    else
    {
        aiBrightness -= 15;
        if (aiBrightness <= 15)
            aiFadeUp = true;
    }
    for (int x = 0; x < COLS; x++)
        leds[getIdx(x, 0)] = CRGB::Black;
    CRGB aiColor = (playerColor == 1) ? CRGB::Yellow : CRGB::Red;
    leds[getIdx(column, 0)] = aiColor.nscale8(aiBrightness);
    FastLED.show();
}

void animateDrop(int col, int player)
{
    int targetRow = getFirstEmptyRow(col);
    if (targetRow == -1)
        return;
    for (int row = 5; row >= targetRow; row--)
    {
        renderBoard();
        leds[getIdx(col, 7 - row)] = (player == 1) ? CRGB::Yellow : CRGB::Red;
        FastLED.show();
        delay(max(20, 80 - (5 - row) * 15));
    }
    board[col][targetRow] = player;
    renderBoard();
    FastLED.show();
}

void moveDiscToCol(int startCol, int targetCol, int player, int speed)
{
    int current = startCol;
    CRGB pColor = (player == 1) ? CRGB::Yellow : CRGB::Red;
    while (current != targetCol && !abortAi)
    {
        leds[getIdx(current, 0)] = CRGB::Black;
        current += (targetCol > current) ? 1 : -1;
        renderBoard();
        leds[getIdx(current, 0)] = pColor;
        FastLED.show();
        delay(speed);
        if (digitalRead(ENC_SW) == LOW)
            abortAi = true;
    }
    activeCol = targetCol;
}

int8_t scanBoard()
{
    memset(winMask, 0, sizeof(winMask));
    auto checkMatch = [&](int col, int row, int dCol, int dRow)
    {
        int8_t pAtPos = board[col][row];
        if (pAtPos != 0 && board[col + dCol][row + dRow] == pAtPos &&
            board[col + 2 * dCol][row + 2 * dRow] == pAtPos && board[col + 3 * dCol][row + 3 * dRow] == pAtPos)
        {
            for (int i = 0; i < 4; i++)
                winMask[getIdx(col + i * dCol, 7 - (row + i * dRow))] = true;
            return pAtPos;
        }
        return (int8_t)0;
    };
    for (int r = 0; r < 6; r++)
        for (int c = 0; c < 4; c++)
        {
            int8_t res = checkMatch(c, r, 1, 0);
            if (res)
                return res;
        }
    for (int r = 0; r < 3; r++)
        for (int c = 0; c < 7; c++)
        {
            int8_t res = checkMatch(c, r, 0, 1);
            if (res)
                return res;
        }
    for (int r = 0; r < 3; r++)
        for (int c = 0; c < 4; c++)
        {
            int8_t res = checkMatch(c, r, 1, 1);
            if (res)
                return res;
        }
    for (int r = 3; r < 6; r++)
        for (int c = 0; c < 4; c++)
        {
            int8_t res = checkMatch(c, r, 1, -1);
            if (res)
                return res;
        }
    return 0;
}

int minimax(int depth, int alpha, int beta, bool isMax, int8_t aiPlayer, int8_t humanPlayer, int8_t rootCol)
{
    if (depth % 2 == 0)
    {
        if (digitalRead(ENC_SW) == LOW)
        {
            abortAi = true;
            return 0;
        }
    }
    if (depth >= current_look_ahead - 1)
        updateThinkingVisuals(aiPlayer, rootCol);
    else
        yield();
    if (abortAi)
        return 0;

    int8_t winner = scanBoard();
    if (winner == aiPlayer)
        return 1000 + depth; // Win sooner is better
    if (winner == humanPlayer)
        return -1000 - depth; // Lose later is better
    if (depth == 0 || isBoardFull())
        return 0;

    int colOrder[] = {3, 2, 4, 1, 5, 0, 6};
    int bestScore = isMax ? -10000 : 10000;

    for (int column : colOrder)
    {
        if (abortAi)
            return 0;
        int row = getFirstEmptyRow(column);
        if (row != -1)
        {
            board[column][row] = isMax ? aiPlayer : humanPlayer;
            int score = minimax(depth - 1, alpha, beta, !isMax, aiPlayer, humanPlayer, (depth == current_look_ahead ? column : rootCol));
            board[column][row] = 0;
            if (isMax)
            {
                bestScore = max(bestScore, score);
                alpha = max(alpha, bestScore);
            }
            else
            {
                bestScore = min(bestScore, score);
                beta = min(beta, bestScore);
            }
            if (beta <= alpha)
                break;
        }
    }
    return bestScore;
}

void performAiMove(int8_t aiPlayer)
{
    abortAi = false;
    int humanPlayer = (aiPlayer == 1) ? 2 : 1;
    int bestScore = -30000;
    int bestCol = 3;
    int originalPly = current_look_ahead;
    current_look_ahead = (gameState == DEMO) ? demoPly : getDynamicPly();

    // PHASE 1: Immediate Win Check (OFFENSE)
    for (int column = 0; column < COLS; column++)
    {
        int row = getFirstEmptyRow(column);
        if (row != -1)
        {
            board[column][row] = aiPlayer;
            if (scanBoard() == aiPlayer)
            {
                board[column][row] = 0;
                bestCol = column;
                goto finalizeMove; // TAKE THE WIN IMMEDIATELY
            }
            board[column][row] = 0;
        }
    }

    // PHASE 2: Immediate Block Check (DEFENSE)
    for (int column = 0; column < COLS; column++)
    {
        int row = getFirstEmptyRow(column);
        if (row != -1)
        {
            board[column][row] = humanPlayer;
            if (scanBoard() == humanPlayer)
            {
                board[column][row] = 0;
                bestCol = column;
                goto finalizeMove; // MUST BLOCK
            }
            board[column][row] = 0;
        }
    }

    // PHASE 3: Minimax Look-ahead
    for (int column : {3, 2, 4, 1, 5, 0, 6})
    {
        if (abortAi)
            goto finalizeMove;
        int row = getFirstEmptyRow(column);
        if (row != -1)
        {
            board[column][row] = aiPlayer;
            int score = minimax(current_look_ahead, -30000, 30000, false, aiPlayer, humanPlayer, column);
            board[column][row] = 0;
            if (score > bestScore)
            {
                bestScore = score;
                bestCol = column;
            }
        }
    }

    if ((gameState == DEMO || blunder_enabled) && random(100) < 20 && !abortAi)
    {
        int randomColumn = random(0, 7);
        if (getFirstEmptyRow(randomColumn) != -1)
            bestCol = randomColumn;
    }

finalizeMove:
    current_look_ahead = originalPly;
    if (!abortAi)
    {
        moveDiscToCol(activeCol, bestCol, aiPlayer, 100);
        delay(450);
        animateDrop(bestCol, aiPlayer);
    }
}

void handleRoot()
{
    String html = "<html><head><meta name='viewport' content='width=device-width, initial-scale=1'><style>body{font-family:sans-serif;background:#121212;color:white;text-align:center;} .card{background:#222;padding:25px;border-radius:15px;display:inline-block;margin-top:20px;} input{width:100%;padding:10px;margin:10px 0;border-radius:5px;border:none;}</style></head><body><h1>Connect 4 Admin</h1><div class='card'><form action='/save' method='POST'>";
    html += "Base AI Ply:<input type='number' name='ply' value='" + String(current_look_ahead) + "'>Brightness:<input type='number' name='br' value='" + String(current_brightness) + "'>Idle Timeout (s):<input type='number' name='idle' value='" + String(current_idle_timeout_ms / 1000) + "'>";
    html += "Blunders: <input type='checkbox' name='blunder' " + String(blunder_enabled ? "checked" : "") + "><br>Evolution: <input type='checkbox' name='evolve' " + String(progressive_difficulty ? "checked" : "") + "><br><br><input type='submit' value='Save' style='background:#28a745;color:white;'></form></div></body></html>";
    server.send(200, "text/html", html);
}

void handleSave()
{
    if (server.hasArg("ply"))
    {
        current_look_ahead = server.arg("ply").toInt();
        prefs.putUChar("ply", current_look_ahead);
    }
    if (server.hasArg("br"))
    {
        current_brightness = server.arg("br").toInt();
        FastLED.setBrightness(current_brightness);
        prefs.putUChar("br", current_brightness);
    }
    if (server.hasArg("idle"))
    {
        current_idle_timeout_ms = server.arg("idle").toInt() * 1000;
        prefs.putUInt("idle", current_idle_timeout_ms / 1000);
    }
    blunder_enabled = server.hasArg("blunder");
    prefs.putBool("blunder", blunder_enabled);
    progressive_difficulty = server.hasArg("evolve");
    prefs.putBool("evolve", progressive_difficulty);
    server.sendHeader("Location", "/");
    server.send(303);
}

void showMenu()
{
    isDemoOver = false;
    FastLED.clear();
#if SHOW_BORDER == 1
    for (int x = 0; x < 7; x++)
        leds[getIdx(x, 1)] = CRGB::Blue;
    for (int y = 1; y < 8; y++)
        leds[getIdx(7, y)] = CRGB::Blue;
#endif
    if (menuMode < 2)
    {
        CRGB pCol = (menuMode == 1) ? CRGB::Red : CRGB::Yellow;
        for (int y = 3; y <= 6; y++)
            leds[getIdx(3, y)] = pCol;
        leds[getIdx(2, 3)] = pCol;
        leds[getIdx(4, 3)] = pCol;
        leds[getIdx(2, 6)] = pCol;
        leds[getIdx(4, 6)] = pCol;
    }
    else
    {
        for (int y = 3; y <= 6; y++)
        {
            leds[getIdx(2, y)] = CRGB::Yellow;
            leds[getIdx(4, y)] = CRGB::Red;
        }
        leds[getIdx(1, 3)] = CRGB::Yellow;
        leds[getIdx(3, 3)] = CRGB::Yellow;
        leds[getIdx(1, 6)] = CRGB::Yellow;
        leds[getIdx(3, 6)] = CRGB::Yellow;
        leds[getIdx(3, 3)] = CRGB::Red;
        leds[getIdx(5, 3)] = CRGB::Red;
        leds[getIdx(3, 6)] = CRGB::Red;
        leds[getIdx(5, 6)] = CRGB::Red;
    }
    FastLED.show();
}

void setup()
{
    Serial.begin(115200);
    prefs.begin("c4-game", false);
    current_look_ahead = prefs.getUChar("ply", 8);
    current_brightness = prefs.getUChar("br", 25);
    current_idle_timeout_ms = prefs.getUInt("idle", 60) * 1000;
    blunder_enabled = prefs.getBool("blunder", false);
    progressive_difficulty = prefs.getBool("evolve", false);
    FastLED.addLeds<WS2812B, LED_PIN, GRB>(leds, NUM_LEDS);
    FastLED.setBrightness(current_brightness);
    pinMode(ENC_SW, INPUT_PULLUP);
    WiFi.softAP("Connect4-Config", WIFI_PASSWORD);
    server.on("/", handleRoot);
    server.on("/save", HTTP_POST, handleSave);
    server.begin();
    lastActivityTime = millis();
    showMenu();
}

void loop()
{
    server.handleClient();
    long newPos = myEnc.read() / SENSITIVITY;
    bool pressed = (digitalRead(ENC_SW) == LOW);

    if (newPos != oldEncPos || (pressed && (millis() - lastActivityTime > 500)))
    {
        if (gameState >= 2 || gameState == DEMO)
        {
            abortAi = true;
            memset(board, 0, sizeof(board));
            winnerPlayer = 0;
            demoResetTimer = 0;
            for (int i = 0; i < 10; i++)
            {
                fadeToBlackBy(leds, NUM_LEDS, 40);
                FastLED.show();
                delay(20);
            }
            gameState = MENU;
            showMenu();
            oldEncPos = newPos;
            lastActivityTime = millis();
            delay(300);
            return;
        }
        lastActivityTime = millis();
    }

    uint32_t activeLimit = (gameState == PLAYING) ? (current_idle_timeout_ms * 2) : current_idle_timeout_ms;
    if (gameState != DEMO && (gameState < 2) && (millis() - lastActivityTime > activeLimit))
    {
        gameState = DEMO;
        memset(board, 0, sizeof(board));
        currentPlayer = 1;
        demoPly = random(3, 7);
        return;
    }

    if (gameState == MENU)
    {
        if (newPos != oldEncPos)
        {
            menuMode = (newPos % 3 + 3) % 3;
            oldEncPos = newPos;
            showMenu();
        }
        if (pressed)
        {
            memset(board, 0, sizeof(board));
            gameState = PLAYING;
            if (menuMode == 1)
            {
                performAiMove(1);
                currentPlayer = 2;
            }
            else
            {
                currentPlayer = 1;
            }
            delay(300);
        }
    }
    else if (gameState == PLAYING)
    {
        if (newPos != oldEncPos)
        {
            activeCol = (newPos % 7 + 7) % 7;
            oldEncPos = newPos;
            lastActivityTime = millis();
        }
        renderBoard();
        leds[getIdx(activeCol, 0)] = (currentPlayer == 1) ? CRGB::Yellow : CRGB::Red;
        FastLED.show();
        if (pressed)
        {
            lastActivityTime = millis();
            int row = getFirstEmptyRow(activeCol);
            if (row != -1)
            {
                animateDrop(activeCol, currentPlayer);
                winnerPlayer = scanBoard();
                if (winnerPlayer != 0)
                {
                    gameState = FINISHED_WIN;
                    demoResetTimer = millis();
                }
                else if (isBoardFull())
                {
                    gameState = FINISHED_DRAW;
                    demoResetTimer = millis();
                }
                else
                {
                    if (menuMode < 2)
                    {
                        int8_t aiP = (menuMode == 0) ? 2 : 1;
                        performAiMove(aiP);
                        lastActivityTime = millis();
                        if (!abortAi)
                        {
                            winnerPlayer = scanBoard();
                            if (winnerPlayer != 0)
                            {
                                gameState = FINISHED_WIN;
                                demoResetTimer = millis();
                            }
                            else if (isBoardFull())
                            {
                                gameState = FINISHED_DRAW;
                                demoResetTimer = millis();
                            }
                        }
                    }
                    else
                    {
                        currentPlayer = (currentPlayer == 1) ? 2 : 1;
                    }
                }
                delay(300);
            }
        }
    }
    else if (gameState == DEMO)
    {
        renderBoard();
        FastLED.show();
        delay(600);
        performAiMove(currentPlayer);
        if (!abortAi)
        {
            winnerPlayer = scanBoard();
            if (winnerPlayer != 0)
            {
                gameState = FINISHED_WIN;
                demoResetTimer = millis();
            }
            else if (isBoardFull())
            {
                gameState = FINISHED_DRAW;
                demoResetTimer = millis();
            }
            else
            {
                currentPlayer = (currentPlayer == 1) ? 2 : 1;
            }
        }
    }
    else
    {
        static uint32_t lastFlash = 0;
        static bool toggle = true;
        if (millis() - lastFlash > 300)
        {
            lastFlash = millis();
            toggle = !toggle;
            renderBoard();
            for (int i = 0; i < NUM_LEDS; i++)
            {
#if SHOW_BORDER == 1
                if (leds[i] == CRGB::Blue)
                    continue;
#endif
                if (gameState == FINISHED_WIN)
                {
                    if (winMask[i])
                        leds[i] = toggle ? (winnerPlayer == 1 ? CRGB::Yellow : CRGB::Red) : CRGB::Black;
                    else
                        leds[i].nscale8(60);
                }
                else if (gameState == FINISHED_DRAW)
                {
                    if (!toggle)
                        leds[i] = CRGB::Black;
                }
            }
            FastLED.show();
        }
        if (millis() - demoResetTimer > 15000)
        {
            memset(board, 0, sizeof(board));
            gameState = DEMO;
            demoResetTimer = 0;
            demoPly = random(3, 7);
        }
    }
}