// SPDX-License-Identifier: CC0-1.0
//
// SPDX-FileContributor: Antonio Niño Díaz, 2022

#include <stdint.h>
#include <stdlib.h>

#define GBA_SCREEN_W            240
#define GBA_SCREEN_H            160

#define REG_DISPCNT             *((volatile uint16_t *)0x04000000)

#define REG_KEYINPUT		*((volatile uint16_t *)0x04000130)
#define DEFAULT_REG_KEYINPUT	*((volatile uint16_t *)0x04000130)
#define KEY_DOWN_NOW(key)  (~(REG_KEYINPUT) & key)

#define KEY_A			1
#define KEY_B			2
#define KEY_SELECT		3
#define KEY_START		4
#define KEY_DPAD_RIGHT		5
#define KEY_DPAD_LEFT		6
#define KEY_DPAD_UP		7
#define KEY_DPAD_DOWN		8
#define KEY_TRIGGER_LEFT	9
#define KEY_TRIGGER_RIGHT	10

#define DISPCNT_BG_MODE_MASK    (0x7)
#define DISPCNT_BG_MODE(n)      ((n) & DISPCNT_BG_MODE_MASK) // 0 to 5

#define DISPCNT_BG2_ENABLE      (1 << 10)

#define MEM_VRAM_MODE4       ((uint8_t *)buffer)

#define SHOW_BACK 0x10;
#define FRONT_BUFFER (0x6000000)
#define BACK_BUFFER  (0x600A000)

#define PALETTE ((uint16_t *)0x5000000)
static volatile uint8_t lastPaletteIndex = 0;

#define FIXED_POINT int32_t
#define FP 12
#define SHIFT_THRESHOLD 0.05
#define SHIFT_THRESHOLD_FP ((1 << FP) * SHIFT_THRESHOLD)

#define FLOAT2FIXED(value)     (int)((value) * (1 << FP))
#define FIXED2FLOAT(value)     ((value) / (float)(1 << FP))

static uint8_t *buffer = (uint8_t *)FRONT_BUFFER;

static inline uint16_t
RGB15(uint16_t r, uint16_t g, uint16_t b)
{
	return (r & 0x1F) | ((g & 0x1F) << 5) | ((b & 0x1F) << 10);
}

void
flipBuffers()
{
    if(buffer == (uint8_t *)FRONT_BUFFER) {
        REG_DISPCNT &= ~SHOW_BACK;
        buffer = (uint8_t *)BACK_BUFFER;
    } else {
        REG_DISPCNT |= SHOW_BACK;
        buffer = (uint8_t *)FRONT_BUFFER;
    }
}

void
putPx(uint8_t x, uint8_t y, uint16_t c)
{
    uint16_t pos = (GBA_SCREEN_W * y + x) >> 1;
    uint8_t px = buffer[pos];
    if (y & 1) {
    buffer[pos] = c << 8;
        buffer[pos] = (c << 8) | (px & 0x00ff);
    } else {
        buffer[pos] = (px & 0xff00) | c;
    }
}
///////////////////////////////////////////////////////////

#include <math.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <float.h>

#define VWIDTH 25
#define VHEIGHT 25
#define CUBE_WIDTH 10
#define CUBE_WIDTH_FP ((1 << FP) * CUBE_WIDTH)

enum faces {
	FACE_FRONT = 0,
	FACE_LEFT,
	FACE_RIGHT,
	FACE_BOTTOM,
	FACE_TOP,
	FACE_BACK,
	NUM_FACES,
};

#define STEP 20
#define STEP_FP ((1 << FP) * STEP)

#define ACTION_STEP 0.1
#define ACTION_STEP_FP ((1 << FP) * ACTION_STEP)

#define SCALE 10 // how much is our initial render scaled

volatile FIXED_POINT  K1 = 20;
volatile FIXED_POINT K2 = (2 * CUBE_WIDTH) + 10;

#define MULT_FP(a,b) ((a * b) >> FP)

#define SQ(n) (n * n)
#define SQ_FP(n) (MULT_FP(n, n))

#define COORD2INDEX(x, y) (y * VWIDTH + x)
#define COUPLE2INDEX(x) (COORD2INDEX(x[0], x[1]))
#define PLOT_COORD(x, y, c) \
    for (uint8_t i = 0 ; i < SCALE ; ++i) \
        for (uint8_t j = 0 ; j < SCALE ; ++j) \
            putPx(x * SCALE + i, j + (SCALE * y), chooseColor(c));

#define GET_ROTATE_X_Q(a) ({ float _a = (a) ; \
		struct Quaternions q = {}; q.w = FLOAT2FIXED(cos(_a * .5)); \
		q.x = FLOAT2FIXED(sin(_a * .5)); q; })
#define GET_ROTATE_Y_Q(a) ({ float _a = (a) ; \
		struct Quaternions q = {}; q.w = FLOAT2FIXED(cos(_a * .5)); \
		q.y = FLOAT2FIXED(sin(_a * .5)); q; })
#define GET_ROTATE_Z_Q(a) ({ float _a = (a) ; \
		struct Quaternions q = {}; q.w = FLOAT2FIXED(cos(_a * .5)); \
		q.z = FLOAT2FIXED(sin(_a * .5)); q; })

//TODO Idle animations
#define IS_IDLE (Idle.x || Idle.y || Idle.z)
#define RESET_IDLE {Idle.x = 0; Idle.y = 0; Idle.z = 0;}

void
init_colors()
{
    const uint16_t color_order[NUM_FACES + 1] = {
        RGB15(0,  0,  0),
        RGB15(31, 0,  0),
        RGB15(0,  31, 0),
        RGB15(0,  0,  31),
        RGB15(0,  31, 31),
        RGB15(31, 31, 0),
        RGB15(31, 0,  31),
    };

    for ( ; lastPaletteIndex <= NUM_FACES ; ++lastPaletteIndex) {
           PALETTE[lastPaletteIndex] = color_order[lastPaletteIndex];
    }
}

struct {
	uint8_t x;
	uint8_t y;
	uint8_t z;
} Idle;


struct Quaternions {
	FIXED_POINT w;
	FIXED_POINT x;
	FIXED_POINT y;
	FIXED_POINT z;
} Target, Current;

static FIXED_POINT		interpolationStep = 0;
static FIXED_POINT		zBuffer[VHEIGHT * VWIDTH];
static FIXED_POINT		maxZbufByColor[NUM_FACES * 2];
static uint8_t			output[VHEIGHT * VWIDTH];

static volatile uint8_t shouldBreak = 1;
static volatile uint8_t currentlyMoving = 0;
static volatile uint8_t currentCountR = 0;
static volatile uint8_t frontFacingFace = FACE_FRONT;

void
normalize(struct Quaternions *q)
{
	float n = sqrt(FIXED2FLOAT(SQ_FP(q->w) + SQ_FP(q->x) +
				SQ_FP(q->y) + SQ_FP(q->z)));
	if (n == 0 || n == 1)
		return;

	q->w = FLOAT2FIXED(FIXED2FLOAT(q->w) / n);
	q->x = FLOAT2FIXED(FIXED2FLOAT(q->x) / n);
	q->y = FLOAT2FIXED(FIXED2FLOAT(q->y) / n);
	q->z = FLOAT2FIXED(FIXED2FLOAT(q->z) / n);
}

struct Quaternions
mult(struct Quaternions *q, FIXED_POINT x, FIXED_POINT y, FIXED_POINT z)
{
	//p = q * p * qbar
	struct Quaternions res;

	res.w = 0;
	res.x = MULT_FP(x, (SQ_FP(q->w) + SQ_FP(q->x) - SQ_FP(q->y) - SQ_FP(q->z)))
		+ (MULT_FP(y, (MULT_FP(q->x, q->y) - MULT_FP(q->w, q->z))) * 2)
		+ (MULT_FP(z, (MULT_FP(q->x, q->z) + MULT_FP(q->w, q->y))) * 2);

	res.y = (MULT_FP(x, (MULT_FP(q->x, q->y) + MULT_FP(q->w,q->z))) * 2)
		+ (MULT_FP(y, (SQ_FP(q->w) - SQ_FP(q->x) + SQ_FP(q->y) - SQ_FP(q->z))))
		+ (MULT_FP(z, (MULT_FP(q->y, q->z) - MULT_FP(q->w, q->x))) << 2);

	res.z = (MULT_FP(x, (MULT_FP(q->x, q->z) - MULT_FP(q->w, q->y)))* 2)
		+ (MULT_FP(y, (MULT_FP(q->y, q->z) + MULT_FP(q->w, q->x))) * 2)
		+ MULT_FP(z, (SQ_FP(q->w) - SQ_FP(q->x) - SQ_FP(q->y) + SQ_FP(q->z)));

	return res;
}

// res in quat p
void
multQ(struct Quaternions *p, struct Quaternions *q)
{
	if (p->x <= SHIFT_THRESHOLD_FP && p->x >= -SHIFT_THRESHOLD_FP
            && p->y <= SHIFT_THRESHOLD_FP && p->y >= -SHIFT_THRESHOLD_FP
            && p->z <= SHIFT_THRESHOLD_FP && p->z >= -SHIFT_THRESHOLD_FP) {
        p = q;
        return;
    }

	if (q->x <= SHIFT_THRESHOLD_FP && q->x >= -SHIFT_THRESHOLD_FP
            && q->y <= SHIFT_THRESHOLD_FP && q->y >= -SHIFT_THRESHOLD_FP
            && q->z <= SHIFT_THRESHOLD_FP && q->z >= -SHIFT_THRESHOLD_FP)
		return;

    FIXED_POINT w = MULT_FP(p->w, q->w) - MULT_FP(p->x, q->x) -
                    MULT_FP(p->y, q->y) - MULT_FP(p->z, q->z);
    FIXED_POINT x = MULT_FP(p->w, q->x) + MULT_FP(p->x, q->w) +
                    MULT_FP(p->y, q->z) - MULT_FP(p->z, q->y);
    FIXED_POINT y = MULT_FP(p->w, q->y) - MULT_FP(p->x, q->z) +
                    MULT_FP(p->y, q->w) + MULT_FP(p->z, q->x);
    FIXED_POINT z = MULT_FP(p->w, q->z) + MULT_FP(p->x, q->y) -
                    MULT_FP(p->y, q->x) + MULT_FP(p->z, q->w);
    p->w = w;
    p->x = x;
    p->y = y;
    p->z = z;
}


uint16_t
chooseColor(uint8_t c)
{
    if (c >= 1 && c <= NUM_FACES)
        return c;
    else
        return 0;
}

uint8_t
chooseMainFace()
{
	int total = 0;
	int faces[NUM_FACES] = {0};

	for (int k = 0; k < VWIDTH * VHEIGHT; ++k)
		if (output[k] >= 0 && output[k] < NUM_FACES) {
			faces[output[k]]++;
			++total;
		}

	int max = 0, idx = 0;
	for (int k = 0; k < NUM_FACES; ++k)
		if (faces[k] > max) {
			max = faces[k];
			idx = k;
		}

	frontFacingFace = max > total * 0.9 ? idx : -1;
	return frontFacingFace;
}

uint8_t
isInQuad(uint8_t curr[2], uint8_t points[8])
{
	uint8_t pos = 0, neg = 0;
	uint8_t x = curr[0];
	uint8_t y = curr[1];;
	int d;

	for (uint8_t i = 0; i < 4; ++i) {
		if (points[2 * i] == curr[0] && points[2 * i + 1] == curr[1])
		    return 1;

		//Form a segment between the i'th point
		uint8_t x1 = points[2 * i];
		uint8_t y1 = points[2 * i + 1];

		//And the i+1'th, or if i is the last, with the first point
		uint8_t i2 = (i + 1) % 4;

		uint8_t x2 = points[2 * i2];
		uint8_t y2 = points[2 * i2 + 1];


		//Compute the cross product
		d = (x - x1) * (y2 - y1) - (y - y1) * (x2 - x1);

		if (d > 0) ++pos;
		if (d < 0) ++neg;

		//If the sign changes, then point is outside
		if (pos > 0 && neg > 0)
		    return 0;
	}

	return 1;
}

void
fill_quads(uint8_t *points, uint8_t current_face)
{
    uint8_t top = 0, bot = 0, left = 0, right = 0;
    for (uint8_t x = 0 ; x < 8 ; ++x) {
        if (x % 2 == 0) {
            if (points[x] > right)
                right = points[x];
            if (points[x] < left)
                left = points[x];
        } else {
            if (points[x] > bot)
                bot = points[x];
            if (points[x] < top)
                top = points[x];
        }
    }
	for (int y = top ; y < bot ; ++y) {
		for (int x = left ; x < right ; ++x) {
			uint8_t curr[2] = {x, y};
			if (isInQuad(curr, points))
				PLOT_COORD(x, y, current_face + 1);
		}
	}
}

uint8_t
detect(uint8_t *points, uint8_t current_face) {
    uint8_t i = 0;
    for (uint8_t y = 0; y < VHEIGHT; ++y) {
        for (uint8_t x = 0; x < VWIDTH; ++x) {
            if (output[COORD2INDEX(x, y)] != current_face)
                continue;
            // only 4 points are ploted
            points[i] = x;
            points[i + 1] = y;
            i += 2;
        }
    }

    for (uint8_t x = 0 ; x < 8 ; ++x)
        if (points[x] == 0)
            return 0;
    return 1;
}

int
comp(const void *p1, const void *p2) {
     FIXED_POINT left  = *(const FIXED_POINT *)p1;
     FIXED_POINT right = *(const FIXED_POINT *)p2;

     return ((left > right) - (left < right));
}

void
detect_and_fill_quads()
{
    qsort(maxZbufByColor, NUM_FACES, 2 * sizeof(FIXED_POINT), comp);
	for (uint8_t idx = 0 ; idx < NUM_FACES ; ++idx) {
        uint8_t current_face = maxZbufByColor[2 * idx + 1];
        uint8_t points[8] = { 0 };
        if (detect(points, current_face))
            fill_quads(points, current_face);
	}
}

void
printAscii()
{
	detect_and_fill_quads();
    flipBuffers();

    // DISPLAY POINTS
	//for (int i = 0; i < VHEIGHT; ++i) {
	//	for (int j = 0; j < VWIDTH; ++j) {
	//		uint8_t prevc = 0;
	//		uint8_t c = output[i * VWIDTH + j];
    //        MEM_VRAM_MODE4[i * GBA_SCREEN_W + j] = chooseColor(c);
	//	}
	//}
}

void
rotateCube(FIXED_POINT cubeX, FIXED_POINT cubeY, FIXED_POINT cubeZ, uint8_t ch)
{
	struct Quaternions q = mult(&Current, cubeX, cubeY, cubeZ);

	int x = q.x >> FP;
	int y = q.y >> FP;

	// not fixed point yet!!
	float invZ = (1 << FP) / (float)(q.z + K2 * (1 << FP));

	int screenX = (int)(VWIDTH * 0.5) + (int)((x) * K1) * invZ;
	int screenY = (int)(VHEIGHT * 0.5) + (int)((y) * K1) * invZ;
	//TODO luminescence

	if (screenX > VWIDTH || screenX < 0) return;

	int idx = screenY * VWIDTH + screenX;
	if (idx >= 0 && idx < VWIDTH * VHEIGHT) {
		invZ = FLOAT2FIXED(invZ);
		if (zBuffer[idx] < invZ) {
			zBuffer[idx] = invZ;
			output[idx] = ch;
            if (invZ > maxZbufByColor[ch]) {
                maxZbufByColor[2 * ch] = invZ;
                maxZbufByColor[2 * ch + 1] = ch; //palette[0] is bg
            }
		}
	}
}

void
interpolate(struct Quaternions *qa, struct Quaternions *qb)
{
	frontFacingFace = -1;
	float cosHalfTheta =
		FIXED2FLOAT(MULT_FP(qa->w, qb->w) +
		MULT_FP(qa->x, qb->x) +
		MULT_FP(qa->y, qb->y) +
		MULT_FP(qa->z, qb->z));
	//if qa = qb or qa = -qb then theta = 0 and we can return qa
	if (cosHalfTheta >= 1.0 || cosHalfTheta <= -1.0) {
		goto exit;
	}
	if (cosHalfTheta < 0) {
		qb->w = -qb->w;
		qb->x = -qb->x;
		qb->y = -qb->y;
		qb->z = qb->z;
		cosHalfTheta = -cosHalfTheta;
	}

	float		halfTheta = acos(cosHalfTheta);
	float		sinHalfTheta = sqrt(1.0 - cosHalfTheta * cosHalfTheta);
	//if theta = 180 degrees then result is not fully defined
	// we could rotate around any axis normal to qa or qb
	if (sinHalfTheta < 0.01 && sinHalfTheta > -0.01) {
		qa->w = ((qa->w >> 1) + (qb->w >> 1));
		qa->x = ((qa->x >> 1) + (qb->x >> 1));
		qa->y = ((qa->y >> 1) + (qb->y >> 1));
		qa->z = ((qa->z >> 1) + (qb->z >> 1));
		goto exit;
	}


	FIXED_POINT ratioA = FLOAT2FIXED(sin((1 - FIXED2FLOAT(interpolationStep)) * halfTheta) / sinHalfTheta);
	FIXED_POINT ratioB = FLOAT2FIXED(sin(FIXED2FLOAT(interpolationStep) * halfTheta) / sinHalfTheta);

	qa->w = (MULT_FP(qa->w, ratioA) + MULT_FP(qb->w, ratioB));
	qa->x = (MULT_FP(qa->x, ratioA) + MULT_FP(qb->x, ratioB));
	qa->y = (MULT_FP(qa->y, ratioA) + MULT_FP(qb->y, ratioB));
	qa->z = (MULT_FP(qa->z, ratioA) + MULT_FP(qb->z, ratioB));

exit:
	interpolationStep += ACTION_STEP_FP;
}

void
handleAngle(uint8_t input)
{
	// TODO
	if (currentlyMoving == 0) {
		currentlyMoving = input;
        struct Quaternions tmp;
		switch (input) {
		case 'w':
		case 'W':
            tmp = GET_ROTATE_X_Q(M_PI_2);
			break;
		case 'a':
		case 'A':
			tmp = GET_ROTATE_Y_Q(-M_PI_2);
			break;
		case 's':
		case 'S':
			tmp = GET_ROTATE_X_Q(-M_PI_2);
			break;
		case 'd':
		case 'D':
			tmp = GET_ROTATE_Y_Q(M_PI_2);
			break;
		case 'q':
		case 'Q':
			tmp = GET_ROTATE_Z_Q(-M_PI_2);
			break;
		case 'e':
		case 'E':
			tmp = GET_ROTATE_Z_Q(M_PI_2);
			break;
		default:
			currentlyMoving = 0;
            return;
			//TODO idle movement
		}
        multQ(&tmp, &Target);
        Target = tmp;
		normalize(&Target);
	} else {
		if (interpolationStep < (1 << FP) ) {
			interpolate(&Current, &Target);
			normalize(&Current);
		}
		else {
			Current = Target;
			interpolationStep = 0;
			currentlyMoving = 0;
		}
	}
}

uint8_t
getInput()
{
	// TODO
	uint8_t c = 'd';
	handleAngle(c);
	return c;
}

int
main()
{
	REG_DISPCNT = DISPCNT_BG_MODE(4) | DISPCNT_BG2_ENABLE;

	Current = GET_ROTATE_Z_Q(0);

    init_colors();

	while (1) {
		memset(MEM_VRAM_MODE4, 0, GBA_SCREEN_H * GBA_SCREEN_W);
		memset(output, NUM_FACES, VWIDTH * VHEIGHT);
		memset(maxZbufByColor, 0, 2 * sizeof(FIXED_POINT) * NUM_FACES);
		memset(zBuffer, 0xffffffff, VWIDTH * VHEIGHT * sizeof(FIXED_POINT));

		for (FIXED_POINT cubeX = -CUBE_WIDTH_FP + 2 * (1 << FP);
				cubeX <= CUBE_WIDTH_FP - 2 * (1 << FP); cubeX += STEP_FP - 4 * (1 << FP)) {
			for (FIXED_POINT cubeY = -CUBE_WIDTH_FP + 2 * (1 << FP);
					cubeY <= CUBE_WIDTH_FP - 2 * (1 << FP); cubeY += STEP_FP - 4 * (1 << FP)) {
				switch (frontFacingFace) {
				case FACE_FRONT:
					rotateCube(cubeX, cubeY, -CUBE_WIDTH_FP, FACE_FRONT);
					break;
				case FACE_LEFT:
					rotateCube(-CUBE_WIDTH_FP, cubeX, cubeY, FACE_LEFT);
					break;
				case FACE_RIGHT:
					rotateCube(CUBE_WIDTH_FP, cubeX, cubeY, FACE_RIGHT);
					break;
				case FACE_BOTTOM:
					rotateCube(cubeX, -CUBE_WIDTH_FP, cubeY, FACE_BOTTOM);
					break;
				case FACE_TOP:
					rotateCube(cubeX, CUBE_WIDTH_FP, cubeY, FACE_TOP);
					break;
				case FACE_BACK:
					rotateCube(cubeX, cubeY, CUBE_WIDTH_FP, FACE_BACK);
					break;
				default: // idk render all
					rotateCube(cubeX, cubeY, -CUBE_WIDTH_FP, FACE_FRONT);
					rotateCube(-CUBE_WIDTH_FP, cubeX, cubeY, FACE_LEFT);
					rotateCube(CUBE_WIDTH_FP, cubeX, cubeY, FACE_RIGHT);
					rotateCube(cubeX, -CUBE_WIDTH_FP, cubeY, FACE_TOP);
					rotateCube(cubeX, CUBE_WIDTH_FP, cubeY, FACE_BOTTOM);
					rotateCube(cubeX, cubeY, CUBE_WIDTH_FP, FACE_BACK);
				}
			}
		}

		printAscii();
		getInput();
	}
}