#include "terrain.h"
#include "vector.h"

#include "gl.h"

#include <noise/noise.h>
#include "noiseutils/noiseutils.h"

#include <iostream>
#include <cmath>
#include <queue>
#include <set>

using namespace noise;

using std::min;
using std::max;

Terrain::Node::Node(Chunk *chunk, float x, float y, float width, float height) {
	this->chunk = chunk;
	this->x = x;
	this->y = y;
	this->width = width;
	this->height = height;

	fill();
}

Terrain::Node::~Node() {
}

float Terrain::Node::distance(float px, float pz) {
	bool in_width = px > x && px < x+width;
	bool in_height = pz > y && pz < y+height;

	if(in_width && in_height)
		return 0;

	Vector2 p(px, pz);

	float a = (p - Vector2(x, y)).length();
	float b = (p - Vector2(x+width, y)).length();
	float c = (p - Vector2(x, y+height)).length();
	float d = (p - Vector2(x+width, y+height)).length();

	float dist = min(min(min(a, b), c), d);

	if(in_width)
		dist = min(dist, (float)min(abs(y - pz), abs(y+height - pz)));
	if(in_height)
		dist = min(dist, (float)min(abs(x - px), abs(x+width - px)));

	return dist;
}

void Terrain::Node::fill() {
	vertex_array[0] = x + width / 2;
	vertex_array[1] = chunk->heights[(int)floorf((int)(x + width/2)*(chunk->height+1) + (int)(y + height/2))];
	vertex_array[2] = y + height / 2;

	vertex_array[3] = x;
	vertex_array[4] = chunk->heights[(int)floorf((x)*(chunk->height+1)+y)];
	vertex_array[5] = y;

	vertex_array[6] = x;
	vertex_array[7] = chunk->heights[(int)floorf((x)*(chunk->height+1) + (y + height))];
	vertex_array[8] = y + height;

	vertex_array[9] = x + width;
	vertex_array[10] = chunk->heights[(int)floorf((x + width)*(chunk->height+1) + (y + height))];
	vertex_array[11] = y + height;

	vertex_array[12] = x + width;
	vertex_array[13] = chunk->heights[(int)floorf((x + width)*(chunk->height+1) + y)];
	vertex_array[14] = y;

	/* midpoint is average of corner heights when width == 1 */
	if(width == 1) {
		vertex_array[1] = (vertex_array[4] + vertex_array[7] + vertex_array[10] + vertex_array[13])/4;
	}
}

void Terrain::Node::draw() {
	float tex_coords[4][3][2] = {
		{{.5, .5}, {0, 0}, {0, 1}},
		{{.5, .5}, {0, 1}, {1, 1}},
		{{.5, .5}, {1, 1}, {1, 0}},
		{{.5, .5}, {1, 0}, {0, 0}}
	};

	glBegin(GL_TRIANGLES);
	for(int i = 0; i < 4; i++) {
		Vector3 a(vertex_array[0], vertex_array[1], vertex_array[2]);
		Vector3 b(vertex_array[i*3+3], vertex_array[i*3+4], vertex_array[i*3+5]);
		Vector3 c(vertex_array[i == 3 ? 3 : (i*3+6)], vertex_array[i == 3 ? 4 : (i*3+7)], vertex_array[i == 3 ? 5 : (i*3+8)]);

		Vector3 U(c.x-a.x, c.y-a.y, c.z-a.z);
		Vector3 V(b.x-a.x, b.y-a.y, b.z-a.z);
		Vector3 N(V.cross(U));
		glNormal3f(N.x, N.y, N.z);

		glTexCoord2f(tex_coords[i][0][0], tex_coords[i][0][1]);
		glVertex3f(a.x, a.y, a.z);

		glTexCoord2f(tex_coords[i][1][0], tex_coords[i][1][1]);
		glVertex3f(b.x, b.y, b.z);

		glTexCoord2f(tex_coords[i][2][0], tex_coords[i][2][1]);
		glVertex3f(c.x, c.y, c.z);
	}
	glEnd();
}

void Terrain::Node::draw_grid() {
	glNormal3f(0, 1, 0);
	glBegin(GL_LINES);
	for(int i = 0; i < 4; i++) {
		Vector3 a(vertex_array[0], vertex_array[1], vertex_array[2]);
		Vector3 b(vertex_array[i*3+3], vertex_array[i*3+4], vertex_array[i*3+5]);

		glVertex3f(chunk->x + a.x, a.y, chunk->y + a.z);
		glVertex3f(chunk->x + b.x, b.y, chunk->y + b.z);
	}
	glEnd();
	glBegin(GL_LINE_LOOP);
		glVertex3f(chunk->x + vertex_array[3], vertex_array[4], chunk->y + vertex_array[5]);
		glVertex3f(chunk->x + vertex_array[6], vertex_array[7], chunk->y + vertex_array[8]);
		glVertex3f(chunk->x + vertex_array[9], vertex_array[10], chunk->y + vertex_array[11]);
		glVertex3f(chunk->x + vertex_array[12], vertex_array[13], chunk->y + vertex_array[14]);
	glEnd();
}

void Terrain::Node::draw_normal() {
	glNormal3f(0, 1, 0);
	glColor3f(1, 0, 0);
	int i = (int)(x*(chunk->height+1) + y);
	glBegin(GL_LINES);
		Vector3 N = chunk->normals[i];
		glVertex3f(chunk->x + x, chunk->heights[i], chunk->y + y);
		glVertex3f(chunk->x + x + N.x, chunk->heights[i] + N.y, chunk->y + y + N.z);
	glEnd();
}

float Terrain::Node::get_height(float px, float py) {
	px -= chunk->x;
	py -= chunk->y;
	bool left;
	bool top;
	top = px - x >= height - (py - y);
	left = px - x >= py - y;
	Vector3 a(vertex_array[0], vertex_array[1], vertex_array[2]);
	Vector3 b, c;
	int bi, ci;
	if(left) {
		if(top) {
			bi = 3*3;
			ci = 4*3;
		} else {
			bi = 4*3;
			ci = 1*3;
		}
	} else {
		if(top) {
			bi = 2*3;
			ci = 3*3;
		} else {
			bi = 1*3;
			ci = 2*3;
		}
	}
	b = Vector3(vertex_array[bi], vertex_array[bi+1], vertex_array[bi+2]);
	c = Vector3(vertex_array[ci], vertex_array[ci+1], vertex_array[ci+2]);
	float det1 = (b.z - c.z) * (a.x - c.x) + (c.x - b.x) * (a.z - c.z);
	float det2 = (c.z - a.z) * (b.x - c.x) + (a.x - c.x) * (b.z - c.z);
	float l1 = ((b.z - c.z) * (px - c.x) + (c.x - b.x) * (py - c.z)) / det1;
	float l2 = ((c.z - a.z) * (px - c.x) + (a.x - c.x) * (py - c.z)) / det2;
	float l3 = 1 - l1 - l2;
	return l1 * a.y + l2 * b.y + l3 * c.y;
}

/* Chunk */

Terrain::Chunk::Chunk(Terrain *terrain, float x, float y, float width, float height) {
	this->terrain = terrain;
	this->x = x;
	this->y = y;
	this->width = width;
	this->height = height;
	this->vbo_object = this->node_count = this->vertices = 0;
	this->nodes = NULL;
	heights = terrain->generate_heights(x, y, width+1, height+1);
	normals = new Vector3[(int)((width+1)*(height+1))];

	calc_normals();

	node_count = width*height;
	nodes = new Node*[node_count];
	for(int i = 0; i < height; i++) {
		for(int j = 0; j < width; j++) {
			nodes[j*(int)height + i] = new Node(this, j, i, 1, 1);
		}
	}
	make_vbo();
}

Terrain::Chunk::~Chunk() {
	for(unsigned int i = 0; i < node_count; i++)
		delete nodes[i];
	delete[] nodes;
	delete[] heights;
	delete[] normals;
}

float Terrain::Chunk::distance(float px, float pz) {
	bool in_width = px > x && px < x+width;
	bool in_height = pz > y && pz < y+height;

	if(in_width && in_height)
		return 0;

	Vector2 p(px, pz);

	float a = (p - Vector2(x, y)).length();
	float b = (p - Vector2(x+width, y)).length();
	float c = (p - Vector2(x, y+height)).length();
	float d = (p - Vector2(x+width, y+height)).length();

	float dist = min(min(min(a, b), c), d);

	if(in_width)
		dist = min(dist, (float)min(abs(y - pz), abs(y+height - pz)));
	if(in_height)
		dist = min(dist, (float)min(abs(x - px), abs(x+width - px)));

	return dist;
}

void Terrain::Chunk::make_vbo() {
	node_count = width*height;
	vertices = node_count*12;
	if(vbo_object)
		glDeleteBuffers(1, &vbo_object);
	glGenBuffers(1, &vbo_object);
	glBindBuffer(GL_ARRAY_BUFFER, vbo_object);

	const size_t vertex_chunk_size = /*sizeof(float)*/3*12;
	const size_t vertices_size = vertex_chunk_size*node_count;
	const size_t normal_chunk_size = vertex_chunk_size;
	const size_t normals_size = normal_chunk_size*node_count;
	const size_t tex_coord_chunk_size = /*sizeof(float)*/2*12;
	const size_t tex_coords_size = tex_coord_chunk_size*node_count;

	buf_size = sizeof(float)*(vertices_size + normals_size + tex_coords_size);

	glBufferData(GL_ARRAY_BUFFER, buf_size, NULL, GL_STATIC_DRAW);

	float *buffer = (float*)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);

	for(unsigned int index = 0; index < node_count; index++) {
		Terrain::Node *node = nodes[index];
		float tex_coords[4][4][3][2] = {
			{{{.25, .25}, {0, 0}, {0, .5}},
			{{.25, .25}, {0, .5}, {.5, .5}},
			{{.25, .25}, {.5, .5}, {.5, 0}},
			{{.25, .25}, {.5, 0}, {0, 0}}},

			{{{.75, .25}, {.5, 0}, {.5, .5}},
			{{.75, .25}, {.5, .5}, {1, .5}},
			{{.75, .25}, {1, .5}, {1, 0}},
			{{.75, .25}, {1, 0}, {.5, 0}}},

			{{{.25, .75}, {0, .5}, {0, 1}},
			{{.25, .75}, {0, 1}, {.5, 1}},
			{{.25, .75}, {.5, 1}, {.5, .5}},
			{{.25, .75}, {.5, .5}, {0, .5}}},

			{{{.75, .75}, {.5, .5}, {.5, 1}},
			{{.75, .75}, {.5, 1}, {1, 1}},
			{{.75, .75}, {1, 1}, {1, .5}},
			{{.75, .75}, {1, .5}, {.5, .5}}}
		};
		for(int i = 0; i < 4; i++) {
			float *v = buffer + vertex_chunk_size*index + 3*3*i;
			for(int j = 0; j < 3; j++) {
				float *tc = buffer + vertices_size + normals_size + tex_coord_chunk_size*index + 6*i + 2*j;
				int k = (fmodf(node->x, 2) == 0 ? 1 : 0) + (fmodf(node->y, 2) == 0 ? 2 : 0);
				tc[0] = tex_coords[k][i][j][0]*node->width;
				tc[1] = tex_coords[k][i][j][1]*node->height;
			}

			v[0] = node->vertex_array[0];
			v[1] = node->vertex_array[1];
			v[2] = node->vertex_array[2];

			v[3] = node->vertex_array[i*3+3];
			v[4] = node->vertex_array[i*3+4];
			v[5] = node->vertex_array[i*3+5];

			v[6] = node->vertex_array[i == 3 ? 3 : (i*3+6)];
			v[7] = node->vertex_array[i == 3 ? 4 : (i*3+7)];
			v[8] = node->vertex_array[i == 3 ? 5 : (i*3+8)];
		}

		float *n = buffer + vertices_size + normal_chunk_size*index;

		Vector3 bl = normals[(int)((node->x+1)*(height+1) + node->y)];
		Vector3 br = normals[(int)((node->x)*(height+1) + node->y)];
		Vector3 tr = normals[(int)((node->x)*(height+1) + node->y+1)];
		Vector3 tl = normals[(int)((node->x+1)*(height+1) + node->y+1)];

		n[24] = n[30] = bl.x;
		n[25] = n[31] = bl.y;
		n[26] = n[32] = bl.z;

		n[3] = n[33] = br.x;
		n[4] = n[34] = br.y;
		n[5] = n[35] = br.z;

		n[6] = n[12] = tr.x;
		n[7] = n[13] = tr.y;
		n[8] = n[14] = tr.z;

		n[15] = n[21] = tl.x;
		n[16] = n[22] = tl.y;
		n[17] = n[23] = tl.z;

		if(node->width == 1) {
			Vector3 v(bl + br + tr + tl);
			v /= v.length();
			n[0] = n[9] = n[18] = n[27] = v.x;
			n[1] = n[10] = n[19] = n[28] = v.y;
			n[2] = n[11] = n[20] = n[29] = v.z;
		} else {
			Vector3 v(normals[(int)((node->x+node->width/2)*(height+1) + node->y+node->height/2)]);
			n[0] = n[9] = n[18] = n[27] = v.x;
			n[1] = n[10] = n[19] = n[28] = v.y;
			n[2] = n[11] = n[20] = n[29] = v.z;
		}
	}

	glUnmapBuffer(GL_ARRAY_BUFFER);
}

Terrain::Node* Terrain::Chunk::find(float x, float y) {
	if(!(x >= this->x && x < this->x+width && y >= this->y && y < this->y+height)) {
		return NULL;
	}
	return nodes[(int)(x-this->x)*(int)height + (int)(y - this->y)];
}

void Terrain::Chunk::calc_normals() {
	float *right, *left, *up, *down;
	right = left = up = down = NULL;
	if(terrain->has_chunk(this->x - chunk_size, this->y))
		right = terrain->get_chunk(this->x - chunk_size, this->y, width, height);
	if(terrain->has_chunk(this->x + chunk_size, this->y))
		left = terrain->get_chunk(this->x + chunk_size, this->y, width, height);
	if(terrain->has_chunk(this->x, this->y + chunk_size))
		up = terrain->get_chunk(this->x, this->y + chunk_size, width, height);
	if(terrain->has_chunk(this->x, this->y - chunk_size))
		down = terrain->get_chunk(this->x, this->y - chunk_size, width, height);

	for(int x = 0; x < width; x++) {
		for(int y = 0; y < height; y++) {
			Vector3 p(x, heights[x*(int)(height+1) + y], y);
			Vector3 N;
			Vector3 temp;

			// TODO: fix border bugginess
			float h;
			if(x > 0 || right) {
				if(x == 0)
					h = right[(chunk_size-1)*(int)(height) + y];
				else
					h = heights[(x-1)*(int)(height+1) + y];
				Vector3 U = Vector3(x-1, h, y) - p;
				if(y > 0 || down) {
					if(y == 0)
						h = down[x*(int)(height) + chunk_size - 1];
					else
						h = heights[x*(int)(height+1) + y - 1];
					Vector3 V = Vector3(x, h, y-1) - p;
					N += V.cross(U);
				}
				if(y < height-1 || up) {
					if(y == height-1)
						h = up[x*(int)(height)]; // y == 0
					else
						h = heights[x*(int)(height+1) + y + 1];
					Vector3 V = Vector3(x, h, y+1) - p;
					N += U.cross(V);
				}
			}
			if(x < width-1 || left) {
				if(x == width-1)
					h = left[y]; // x == 0
				else
					h = heights[(x+1)*(int)(height+1) + y];
				Vector3 U = Vector3(x+1, h, y) - p;
				if(y > 0 || down) {
					if(y == 0)
						h = down[x*(int)(height) + chunk_size - 1];
					else
						h = heights[x*(int)(height+1) + y - 1];
					Vector3 V = Vector3(x, h, y-1) - p;
					N += U.cross(V);
				}
				if(y < height-1 || up) {
					if(y == height-1)
						h = up[x*(int)(height)]; // y == 0
					else
						h = heights[x*(int)(height+1) + y + 1];
					Vector3 V = Vector3(x, h, y+1) - p;
					N += V.cross(U);
				}
			}
			N /= N.length();
			normals[x*(int)(height+1) + y] = N;
		}
	}

	if(right)
		delete[] right;
	if(left)
		delete[] left;
	if(up)
		delete[] up;
	if(down)
		delete[] down;
}

/* Terrain */

Terrain::Terrain() {
}

Terrain::~Terrain() {
	for(std::list<Chunk*>::iterator it = chunks.begin(); it != chunks.end(); it++) {
		delete *it;
	}
}

float *Terrain::generate_heights(int x, int y, int width, int height) {
	module::Perlin mod;
	mod.SetSeed(0);

	utils::NoiseMap heightmap;
	utils::NoiseMapBuilderPlane heightmap_builder;

	heightmap_builder.SetSourceModule(mod);
	heightmap_builder.SetDestNoiseMap(heightmap);

	heightmap_builder.SetDestSize(width, height);
	heightmap_builder.SetBounds((double)x / 100, (double)(x+width) / 100, (double)y / 100, (double)(y+height) / 100);
	heightmap_builder.Build();

	float *heights = new float[width*height];
	for(int i = 0; i < width; i++) {
		for(int j = 0; j < height; j++) {
			heights[i*height + j] = 10*(1+heightmap.GetValue(i, j));
		}
	}

	chunk_indices.insert(std::pair<int, int>(x, y));

	return heights;
}

float *Terrain::get_chunk(int x, int y, int width, int height) {
	return generate_heights(x, y, width, height);
}

bool Terrain::has_chunk(int x, int y) {
	return chunk_indices.find(std::pair<int, int>(x, y)) != chunk_indices.end();
}

void Terrain::raise(float x, float z, float radius, float focus, float strength, bool up) {
	// TODO: fix this
/*	if(x < 0 || x >= width-1 || z < 0 || z >= height-1)
		return;

	/* adjust heights */
	/*for(int i = x-radius; i < x+radius; i++) {
		if(i < 0 || i >= width-1)
			continue;
		for(int j = z-radius; j < z+radius; j++) {
			if(j < 0 || j >= height-1)
				continue;
			float v = powf((radius - min((Vector2(x, z) - Vector2(i, j)).length(), radius)) * strength, 1+focus);

			if(focus > 0)
				/* Scale v with radius based on focus.
				 * Not 100% accurate, but close enough.
				 */
				/*v /= radius * (focus/2);

			if(up)
				heights[i*height + j] += v;
			else
				heights[i*height + j] -= v;
		}
	}

	/* recalculate normals */
	/*for(int i = x-radius-1; i < x+radius; i++) {
		if(i < 0 || i >= width-1)
			continue;
		for(int j = z-radius-1; j < z+radius; j++) {
			if(j < 0 || j >= height-1)
				continue;
			calc_normal(i, j);
		}
	}

	/* refill nodes and remake VBOs */
	/*for(int nx = x-radius-1; nx < x+radius+chunk_size; nx+=chunk_size) {
		if(nx < 0 || nx >= width-1)
			continue;
		for(int nz = z-radius-1; nz < z+radius+chunk_size; nz+=chunk_size) {
			if(nz < 0 || nz >= height-1)
				continue;
			Node *node = find(nx, nz);
			for(unsigned int i = 0; i < node->chunk->node_count; i++) {
				node->chunk->nodes[i]->fill();
			}
			node->chunk->make_vbo();
		}
	}*/
}

void Terrain::update(float x, float z) {
	std::set<std::pair<int, int> > chunk_indices;
	int i = x - 100;
	i -= i % chunk_size;
	for(; i < x + 100; i += chunk_size) {
		int j = z - 100;
		j -= j % chunk_size;
		for(; j < z + 100; j += chunk_size) {
			float a = i - x;
			float b = j - z;
			if(sqrtf(a*a + b*b) < 100)
				chunk_indices.insert(std::pair<int, int>(i, j));
		}
	}
	for(std::list<Chunk*>::iterator it = chunks.begin(); it != chunks.end(); it++) {
		std::set<std::pair<int, int> >::iterator ind_it = chunk_indices.find(std::pair<int, int>((*it)->x, (*it)->y));
		if(ind_it != chunk_indices.end()) {
			chunk_indices.erase(ind_it);
		}
		if((*it)->distance(x, z) > 100) {
			it = chunks.erase(it);
		}
	}
	for(std::set<std::pair<int, int> >::iterator it = chunk_indices.begin(); it != chunk_indices.end(); it++) {
		Chunk *chunk = new Chunk(this, it->first, it->second, chunk_size, chunk_size);
		chunks.push_back(chunk);
	}
}

Terrain::Node *Terrain::find(float x, float y) {
	for(std::list<Chunk*>::iterator it = chunks.begin(); it != chunks.end(); it++) {
		Node *node = (*it)->find(x, y);
		if(node)
			return node;
	}
	return NULL;
}