#include <locale.h>
#include <ncurses.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

typedef enum { MOVING, STILL, EMPTY, WALL } FieldState;

static FieldState** fields;
static int width;
static int height;

static int objectX;
static int objectY;
static int movingObject[8];
static void (*rotateFunction)(void);

static uint32_t seed = 0;

static void initRandom(void) {
    while(seed == 0) {
        struct timespec time;
        timespec_get(&time, TIME_UTC);
        seed = (uint32_t)time.tv_nsec;
    }
}

static int nextRandom(int max) {
    seed = seed * 0x915f77f5 + 1;
    int32_t random = ((int32_t)(seed >> 16)) % max;
    return random;
}

static void initGamefield(int w, int h) {
    width = w;
    height = h;

    fields = (FieldState**)malloc(sizeof(FieldState*) * (size_t)height);
    for(int y = 0; y < height; y++) {
        fields[y] = (FieldState*)malloc(sizeof(FieldState) * (size_t)width);
        for(int x = 0; x < width; x++) {
            fields[y][x] = EMPTY;
        }
    }
}

static void printGamefield(void) {
    clear();
    static const char* MAP[] = {"\u2592", "\u2593", " "};
    static const char* wall = "\u2588";

    int maxX = 0;
    int maxY = 0;
    getmaxyx(stdscr, maxY, maxX);
    int factorX = maxX / (width + 2);
    int factorY = maxY / (height + 2);
    while(factorY > 1 && factorY * 2 > factorX) {
        factorY--;
    }
    factorX = factorY * 2;

    for(int x = 0; x < (width + 2) * factorX; x++) {
        for(int y = 0; y < factorY; y++) {
            mvaddstr(y, x, wall);
            mvaddstr(y + (height + 1) * factorY, x, wall);
        }
    }
    for(int y = 0; y < height; y++) {
        for(int wy = y * factorY; wy < (y + 1) * factorY; wy++) {
            mvaddstr(wy + factorY, 0, wall);
            for(int x = 1; x < factorX; x++) {
                addstr(wall);
            }
            for(int x = 0; x < width; x++) {
                for(int w = 0; w < factorX; w++) {
                    addstr(MAP[fields[y][x]]);
                }
            }
            for(int x = 0; x < factorX; x++) {
                addstr(wall);
            }
        }
    }
}

static void deleteGamefield(void) {
    for(int i = 0; i < height; i++) {
        free(fields[i]);
    }
    free(fields);
}

static void setField(int x, int y, FieldState state) {
    if(x >= 0 && y >= 0 && x < width && y < height) {
        fields[y][x] = state;
    }
}

static FieldState getField(int x, int y) {
    if(x >= 0 && y >= 0 && x < width && y < height) {
        return fields[y][x];
    }
    return WALL;
}

static int canMove(int x, int y) {
    FieldState t = getField(x, y);
    return t == EMPTY || t == MOVING;
}

static void rotate33(void) {
    int data[8];
    for(int i = 0; i < 8; i += 2) {
        data[i] = movingObject[i + 1] - objectY + objectX;
        data[i + 1] = 2 - (movingObject[i] - objectX) + objectY;
        if(!canMove(data[i], data[i + 1])) {
            return;
        }
    }

    for(int i = 0; i < 8; i += 2) {
        setField(movingObject[i], movingObject[i + 1], EMPTY);
        movingObject[i] = data[i];
        movingObject[i + 1] = data[i + 1];
    }
    for(int i = 0; i < 8; i += 2) {
        setField(movingObject[i], movingObject[i + 1], MOVING);
    }
}

static void rotate41(void) {
    int data[8];
    for(int i = 0; i < 8; i += 2) {
        data[i] = movingObject[i + 1] - objectY + objectX;
        data[i + 1] = movingObject[i] - objectX + objectY;
        if(!canMove(data[i], data[i + 1])) {
            return;
        }
    }

    for(int i = 0; i < 8; i += 2) {
        setField(movingObject[i], movingObject[i + 1], EMPTY);
        movingObject[i] = data[i];
        movingObject[i + 1] = data[i + 1];
    }
    for(int i = 0; i < 8; i += 2) {
        setField(movingObject[i], movingObject[i + 1], MOVING);
    }
}

static void rotate22(void) {
    // nothing to do
}

static void rotate(void) {
    rotateFunction();
}

static void spawnObject(int x, int y) {
    objectX = x;
    objectY = y;
    int u = nextRandom(8);
    objects[u]++;
    switch(u) {
        // .X.
        // XXX
        // ...
        case 0:
            movingObject[0] = x + 1;
            movingObject[1] = y + 0;
            movingObject[2] = x + 0;
            movingObject[3] = y + 1;
            movingObject[4] = x + 1;
            movingObject[5] = y + 1;
            movingObject[6] = x + 2;
            movingObject[7] = y + 1;
            rotateFunction = rotate33;
            break;
        // .X.
        // .X.
        // .XX
        case 1:
            movingObject[0] = x + 1;
            movingObject[1] = y + 0;
            movingObject[2] = x + 1;
            movingObject[3] = y + 1;
            movingObject[4] = x + 1;
            movingObject[5] = y + 2;
            movingObject[6] = x + 2;
            movingObject[7] = y + 2;
            rotateFunction = rotate33;
            break;
        case 2:
            // .X.
            // .X.
            // XX.
            movingObject[0] = x + 1;
            movingObject[1] = y + 0;
            movingObject[2] = x + 1;
            movingObject[3] = y + 1;
            movingObject[4] = x + 1;
            movingObject[5] = y + 2;
            movingObject[6] = x + 0;
            movingObject[7] = y + 2;
            rotateFunction = rotate33;
            break;
        // X..
        // XX.
        // .X.
        case 3:
            movingObject[0] = x + 0;
            movingObject[1] = y + 0;
            movingObject[2] = x + 0;
            movingObject[3] = y + 1;
            movingObject[4] = x + 1;
            movingObject[5] = y + 1;
            movingObject[6] = x + 1;
            movingObject[7] = y + 2;
            rotateFunction = rotate33;
            break;
        // .X.
        // XX.
        // X..
        case 4:
            movingObject[0] = x + 1;
            movingObject[1] = y + 0;
            movingObject[2] = x + 0;
            movingObject[3] = y + 1;
            movingObject[4] = x + 1;
            movingObject[5] = y + 1;
            movingObject[6] = x + 0;
            movingObject[7] = y + 2;
            rotateFunction = rotate33;
            break;
        // XX
        // XX
        case 5:
            movingObject[0] = x + 0;
            movingObject[1] = y + 0;
            movingObject[2] = x + 1;
            movingObject[3] = y + 0;
            movingObject[4] = x + 0;
            movingObject[5] = y + 1;
            movingObject[6] = x + 1;
            movingObject[7] = y + 1;
            rotateFunction = rotate22;
            break;
        // .X..
        // .X..
        // .X..
        // .X..
        case 6:
        case 7:
            movingObject[0] = x + 0;
            movingObject[1] = y + 0;
            movingObject[2] = x + 0;
            movingObject[3] = y + 1;
            movingObject[4] = x + 0;
            movingObject[5] = y + 2;
            movingObject[6] = x + 0;
            movingObject[7] = y + 3;
            rotateFunction = rotate41;
            break;
    }

    for(int i = 0; i < 8; i += 2) {
        setField(movingObject[i], movingObject[i + 1], MOVING);
    }
}

static int moveObject(int x, int y) {
    for(int i = 0; i < 8; i += 2) {
        if(!canMove(movingObject[i] + x, movingObject[i + 1] + y)) {
            return 0;
        }
    }

    objectX += x;
    objectY += y;
    for(int i = 0; i < 8; i += 2) {
        setField(movingObject[i], movingObject[i + 1], EMPTY);
        movingObject[i] += x;
        movingObject[i + 1] += y;
    }
    for(int i = 0; i < 8; i += 2) {
        setField(movingObject[i], movingObject[i + 1], MOVING);
    }
    return 1;
}

static void removeRows(void) {
    for(int y = 0; y < height; y++) {
        int remove = 1;
        for(int x = 0; x < width; x++) {
            remove = remove && getField(x, y) == STILL;
        }
        if(remove) {
            for(int ry = y; ry > 0; ry--) {
                for(int rx = 0; rx < width; rx++) {
                    setField(rx, ry, getField(rx, ry - 1));
                }
            }
        }
    }
}

static void onObjectFall(void) {
    if(!moveObject(0, 1)) {
        for(int i = 0; i < 8; i += 2) {
            setField(movingObject[i], movingObject[i + 1], STILL);
        }
        removeRows();
        spawnObject(0, 0);
    }
}

int main(void) {
    initRandom();
    setlocale(LC_ALL, "en_US.UTF-8");

    initscr();
    cbreak();
    keypad(stdscr, TRUE);
    noecho();
    nodelay(stdscr, TRUE);
    curs_set(0);

    initGamefield(10, 18);
    spawnObject(0, 0);

    long lag = 0;
    clock_t lastTime = clock();
    long ticks = 1000000;

    int running = 1;
    while(running) {
        int key = getch();
        if(key == KEY_LEFT) {
            moveObject(-1, 0);
        } else if(key == KEY_RIGHT) {
            moveObject(1, 0);
        } else if(key == KEY_DOWN) {
            onObjectFall();
        } else if(key == KEY_UP) {
            rotate();
        } else if(key == 'q') {
            running = 0;
        }

        clock_t time = clock();
        lag += (time - lastTime);
        lastTime = time;
        if(lag > ticks) {
            lag -= ticks;
            onObjectFall();
        }

        printGamefield();
        printw("%ld", lag);
        refresh();

        // keep the game from taking a bit too much cpu
        usleep(1000);
        lag += 1000;
    }

    endwin();
    deleteGamefield();
    return 0;
}