#define _XOPEN_SOURCE_EXTENDED

#include <curses.h>
#include <locale.h>
#include <ncursesw/curses.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
#include <wchar.h>

static const wchar_t moving = L'\u2592';
static const wchar_t still = L'\u2593';
static const wchar_t wall = L'\u2588';
static const wchar_t empty = L' ';

static wchar_t** 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) {
    struct timeval time;
    struct timezone zone = {.tz_dsttime = 0, .tz_minuteswest = 0};
    gettimeofday(&time, &zone);
    seed = (uint32_t)time.tv_usec;
}

static int nextRandom(int max) {
    seed = seed * 27697u + 13711u;
    int32_t random = ((int32_t)(seed >> 1)) % max;
    return random;
}

static void initGamefield(int w, int h) {
    width = w + 3;
    height = h + 2;

    fields = (wchar_t**)malloc(sizeof(wchar_t*) * (size_t)height);
    for(int y = 0; y < height; y++) {
        fields[y] = (wchar_t*)malloc(sizeof(wchar_t) * (size_t)width);
        for(int x = 0; x < width; x++) {
            fields[y][x] = empty;
        }
        fields[y][width - 1] = '\0';
    }

    for(int y = 0; y < height; y++) {
        fields[y][0] = wall;
        fields[y][width - 2] = wall;
    }

    for(int x = 0; x < width - 1; x++) {
        fields[0][x] = wall;
        fields[height - 1][x] = wall;
    }
}

static void printGamefield(void) {
    wchar_t* line = malloc(sizeof(wchar_t) * (size_t)width * 2);
    for(int y = 0; y < height; y++) {
        for(int x = 0; x < width; x++) {
            line[x * 2] = fields[y][x];
            line[x * 2 + 1] = fields[y][x];
        }
        mvaddwstr(y, 0, line);
    }
    free(line);
}

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

static void setField(int x, int y, wchar_t c) {
    if(x >= 0 && y >= 0 && x < width - 3 && y < height - 2) {
        fields[y + 1][x + 1] = c;
    }
}

static wchar_t getField(int x, int y) {
    if(x >= 0 && y >= 0 && x < width - 3 && y < height - 2) {
        return fields[y + 1][x + 1];
    }
    return 0;
}

static int canMove(int x, int y) {
    wchar_t 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;
    switch(nextRandom(7)) {
        // .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..
        // .X..
        // .X..
        // .X..
        case 3:
            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;
        // X..
        // XX.
        // .X.
        case 4:
            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 5:
            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 6:
            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;
    }

    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 - 2; y++) {
        int remove = 1;
        for(int x = 0; x < width - 3; x++) {
            remove = remove && getField(x, y) == still;
        }
        if(remove) {
            for(int ry = y; ry > 0; ry--) {
                for(int rx = 0; rx < width - 3; 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;
}