// Luanti
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>

#include "mesh.h"
#include "IMeshBuffer.h"
#include "SSkinMeshBuffer.h"
#include "constants.h"
#include "debug.h"
#include <cmath>
#include <IAnimatedMesh.h>
#include "S3DVertex.h"
#include <SMesh.h>
#include "CMeshBuffer.h"

inline static void applyShadeFactor(video::SColor &color, f32 factor)
{
	color.setRed(core::clamp(core::round32(color.getRed()*factor), 0, 255));
	color.setGreen(core::clamp(core::round32(color.getGreen()*factor), 0, 255));
	color.setBlue(core::clamp(core::round32(color.getBlue()*factor), 0, 255));
}

void applyFacesShading(video::SColor &color, v3f normal)
{
	/*
		Some drawtypes have normals set to (0, 0, 0), this must result in
		maximum brightness: shade factor 1.0.
		Shade factors for aligned cube faces are:
		+Y 1.000000 sqrt(1.0)
		-Y 0.447213 sqrt(0.2)
		+-X 0.670820 sqrt(0.45)
		+-Z 0.836660 sqrt(0.7)
	*/
	float x2 = normal.X * normal.X;
	float y2 = normal.Y * normal.Y;
	float z2 = normal.Z * normal.Z;
	if (normal.Y < 0)
		applyShadeFactor(color, 0.670820f * x2 + 0.447213f * y2 + 0.836660f * z2);
	else if ((x2 > 1e-3) || (z2 > 1e-3))
		applyShadeFactor(color, 0.670820f * x2 + 1.000000f * y2 + 0.836660f * z2);
}

scene::IAnimatedMesh* createCubeMesh(v3f scale)
{
	video::SColor c(255,255,255,255);
	video::S3DVertex vertices[24] =
	{
		// Up
		video::S3DVertex(-0.5,+0.5,-0.5, 0,1,0, c, 0,1),
		video::S3DVertex(-0.5,+0.5,+0.5, 0,1,0, c, 0,0),
		video::S3DVertex(+0.5,+0.5,+0.5, 0,1,0, c, 1,0),
		video::S3DVertex(+0.5,+0.5,-0.5, 0,1,0, c, 1,1),
		// Down
		video::S3DVertex(-0.5,-0.5,-0.5, 0,-1,0, c, 0,0),
		video::S3DVertex(+0.5,-0.5,-0.5, 0,-1,0, c, 1,0),
		video::S3DVertex(+0.5,-0.5,+0.5, 0,-1,0, c, 1,1),
		video::S3DVertex(-0.5,-0.5,+0.5, 0,-1,0, c, 0,1),
		// Right
		video::S3DVertex(+0.5,-0.5,-0.5, 1,0,0, c, 0,1),
		video::S3DVertex(+0.5,+0.5,-0.5, 1,0,0, c, 0,0),
		video::S3DVertex(+0.5,+0.5,+0.5, 1,0,0, c, 1,0),
		video::S3DVertex(+0.5,-0.5,+0.5, 1,0,0, c, 1,1),
		// Left
		video::S3DVertex(-0.5,-0.5,-0.5, -1,0,0, c, 1,1),
		video::S3DVertex(-0.5,-0.5,+0.5, -1,0,0, c, 0,1),
		video::S3DVertex(-0.5,+0.5,+0.5, -1,0,0, c, 0,0),
		video::S3DVertex(-0.5,+0.5,-0.5, -1,0,0, c, 1,0),
		// Back
		video::S3DVertex(-0.5,-0.5,+0.5, 0,0,1, c, 1,1),
		video::S3DVertex(+0.5,-0.5,+0.5, 0,0,1, c, 0,1),
		video::S3DVertex(+0.5,+0.5,+0.5, 0,0,1, c, 0,0),
		video::S3DVertex(-0.5,+0.5,+0.5, 0,0,1, c, 1,0),
		// Front
		video::S3DVertex(-0.5,-0.5,-0.5, 0,0,-1, c, 0,1),
		video::S3DVertex(-0.5,+0.5,-0.5, 0,0,-1, c, 0,0),
		video::S3DVertex(+0.5,+0.5,-0.5, 0,0,-1, c, 1,0),
		video::S3DVertex(+0.5,-0.5,-0.5, 0,0,-1, c, 1,1),
	};

	u16 indices[6] = {0,1,2,2,3,0};

	scene::SMesh *mesh = new scene::SMesh();
	for (u32 i=0; i<6; ++i)
	{
		scene::IMeshBuffer *buf = new scene::SMeshBuffer();
		buf->append(vertices + 4 * i, 4, indices, 6);
		// Set default material
		buf->getMaterial().MaterialType = video::EMT_TRANSPARENT_ALPHA_CHANNEL_REF;
		buf->getMaterial().forEachTexture([] (auto &tex) {
			tex.MinFilter = video::ETMINF_NEAREST_MIPMAP_NEAREST;
			tex.MagFilter = video::ETMAGF_NEAREST;
		});
		// Add mesh buffer to mesh
		mesh->addMeshBuffer(buf);
		buf->drop();
	}
	scaleMesh(mesh, scale);  // also recalculates bounding box
	return mesh;
}

// Apply a mutating function to every vertex of a mesh buffer
template<typename F>
inline static void applyToMeshBuffer(scene::IMeshBuffer *buf, const F &fn)
{
	const u32 stride = buf->getVertexBuffer()->getElementSize();
	u32 vertex_count = buf->getVertexCount();
	u8 *vertices = (u8 *)buf->getVertices();
	for (u32 i = 0; i < vertex_count; i++) {
		auto *vertex = (video::S3DVertex *)(vertices + i * stride);
		fn(vertex);
	}
	buf->setDirty(scene::EBT_VERTEX);
}

void scaleMesh(scene::IMesh *mesh, v3f scale)
{
	if (mesh == NULL)
		return;

	aabb3f bbox{{0.0f, 0.0f, 0.0f}};

	u32 mc = mesh->getMeshBufferCount();
	for (u32 j = 0; j < mc; j++) {
		scene::IMeshBuffer *buf = mesh->getMeshBuffer(j);
		applyToMeshBuffer(buf, [scale](video::S3DVertex *vertex) {
			vertex->Pos *= scale;
		});
		buf->recalculateBoundingBox();

		// calculate total bounding box
		if (j == 0)
			bbox = buf->getBoundingBox();
		else
			bbox.addInternalBox(buf->getBoundingBox());
	}
	mesh->setBoundingBox(bbox);
}

void translateMesh(scene::IMesh *mesh, v3f vec)
{
	if (mesh == NULL)
		return;

	aabb3f bbox{{0.0f, 0.0f, 0.0f}};

	u32 mc = mesh->getMeshBufferCount();
	for (u32 j = 0; j < mc; j++) {
		scene::IMeshBuffer *buf = mesh->getMeshBuffer(j);
		applyToMeshBuffer(buf, [vec](video::S3DVertex *vertex) {
			vertex->Pos += vec;
		});
		buf->recalculateBoundingBox();

		// calculate total bounding box
		if (j == 0)
			bbox = buf->getBoundingBox();
		else
			bbox.addInternalBox(buf->getBoundingBox());
	}
	mesh->setBoundingBox(bbox);
}

void setMeshBufferColor(scene::IMeshBuffer *buf, video::SColor color)
{
	applyToMeshBuffer(buf, [color](auto *vertex) {
		vertex->Color = color;
	});
}

void setMeshColor(scene::IMesh *mesh, video::SColor color)
{
	if (mesh == NULL)
		return;

	u32 mc = mesh->getMeshBufferCount();
	for (u32 j = 0; j < mc; j++)
		setMeshBufferColor(mesh->getMeshBuffer(j), color);
}

template <typename F>
static void applyToMesh(scene::IMesh *mesh, const F &fn)
{
	u16 mc = mesh->getMeshBufferCount();
	for (u16 j = 0; j < mc; j++) {
		applyToMeshBuffer(mesh->getMeshBuffer(j), fn);
	}
}

void colorizeMeshBuffer(scene::IMeshBuffer *buf, video::SColor buf_color,
		f32 ambient_light, v3f dir_light)
{
	applyToMeshBuffer(buf, [=](auto *vertex) {
		// Reset color
		vertex->Color = buf_color;
		// Apply shading
		if (vertex->Normal == v3f())
			return; // leave color unchanged ("fully lit")
		const f32 intensity = std::fabs(vertex->Normal.normalize().dotProduct(-dir_light));
		applyShadeFactor(vertex->Color, std::min(1.0f, ambient_light + intensity));
	});
}

void setMeshColorByNormalXYZ(scene::IMesh *mesh,
		video::SColor colorX, video::SColor colorY, video::SColor colorZ)
{
	if (!mesh)
		return;
	auto colorizator = [=] (video::S3DVertex *vertex) {
		f32 x = fabs(vertex->Normal.X);
		f32 y = fabs(vertex->Normal.Y);
		f32 z = fabs(vertex->Normal.Z);
		if (x >= y && x >= z)
			vertex->Color = colorX;
		else if (y >= z)
			vertex->Color = colorY;
		else
			vertex->Color = colorZ;
	};
	applyToMesh(mesh, colorizator);
}

void setMeshColorByNormal(scene::IMesh *mesh, v3f normal, video::SColor color)
{
	if (!mesh)
		return;
	auto colorizator = [normal, color] (video::S3DVertex *vertex) {
		if (vertex->Normal == normal)
			vertex->Color = color;
	};
	applyToMesh(mesh, colorizator);
}

template <float v3f::*U, float v3f::*V>
static void rotateMesh(scene::IMesh *mesh, float degrees)
{
	degrees *= M_PI / 180.0f;
	float c = std::cos(degrees);
	float s = std::sin(degrees);
	auto rotator = [c, s] (video::S3DVertex *vertex) {
		auto rotate_vec = [c, s] (v3f &vec) {
			float u = vec.*U;
			float v = vec.*V;
			vec.*U = c * u - s * v;
			vec.*V = s * u + c * v;
		};
		rotate_vec(vertex->Pos);
		rotate_vec(vertex->Normal);
	};
	applyToMesh(mesh, rotator);
}

void rotateMeshXYby(scene::IMesh *mesh, f64 degrees)
{
	rotateMesh<&v3f::X, &v3f::Y>(mesh, degrees);
}

void rotateMeshXZby(scene::IMesh *mesh, f64 degrees)
{
	rotateMesh<&v3f::X, &v3f::Z>(mesh, degrees);
}

void rotateMeshYZby(scene::IMesh *mesh, f64 degrees)
{
	rotateMesh<&v3f::Y, &v3f::Z>(mesh, degrees);
}

void rotateMeshBy6dFacedir(scene::IMesh *mesh, u8 facedir)
{
	u8 axisdir = facedir >> 2;
	facedir &= 0x03;
	switch (facedir) {
		case 1: rotateMeshXZby(mesh, -90); break;
		case 2: rotateMeshXZby(mesh, 180); break;
		case 3: rotateMeshXZby(mesh, 90); break;
	}
	switch (axisdir) {
		case 1: rotateMeshYZby(mesh, 90); break; // z+
		case 2: rotateMeshYZby(mesh, -90); break; // z-
		case 3: rotateMeshXYby(mesh, -90); break; // x+
		case 4: rotateMeshXYby(mesh, 90); break; // x-
		case 5: rotateMeshXYby(mesh, -180); break;
	}
}

void recalculateBoundingBox(scene::IMesh *src_mesh)
{
	aabb3f bbox{{0.0f, 0.0f, 0.0f}};
	for (u16 j = 0; j < src_mesh->getMeshBufferCount(); j++) {
		scene::IMeshBuffer *buf = src_mesh->getMeshBuffer(j);
		buf->recalculateBoundingBox();
		if (j == 0)
			bbox = buf->getBoundingBox();
		else
			bbox.addInternalBox(buf->getBoundingBox());
	}
	src_mesh->setBoundingBox(bbox);
}

bool checkMeshNormals(scene::IMesh *mesh)
{
	u32 buffer_count = mesh->getMeshBufferCount();

	for (u32 i = 0; i < buffer_count; i++) {
		scene::IMeshBuffer *buffer = mesh->getMeshBuffer(i);
		if (!buffer->getVertexCount())
			continue;

		// Here we intentionally check only first normal, assuming that if buffer
		// has it valid, then most likely all other ones are fine too. We can
		// check all of the normals to have length, but it seems like an overkill
		// hurting the performance and covering only really weird broken models.
		f32 length = buffer->getNormal(0).getLength();

		if (!std::isfinite(length) || length < 1e-10f)
			return false;
	}

	return true;
}

template<class VertexType, class SMeshBufferType>
static scene::IMeshBuffer *cloneMeshBuffer(scene::IMeshBuffer *mesh_buffer)
{
	auto *v = static_cast<VertexType *>(mesh_buffer->getVertices());
	u16 *indices = mesh_buffer->getIndices();
	auto *cloned_buffer = new SMeshBufferType();
	cloned_buffer->append(v, mesh_buffer->getVertexCount(), indices,
			mesh_buffer->getIndexCount());
	// Rigidly animated meshes may have transformation matrices that need to be applied
	if (auto *sbuf = dynamic_cast<scene::SSkinMeshBuffer *>(mesh_buffer)) {
		applyToMeshBuffer(cloned_buffer, [sbuf](video::S3DVertex *vertex) {
			sbuf->Transformation.transformVect(vertex->Pos);
			vertex->Normal = sbuf->Transformation.rotateAndScaleVect(vertex->Normal);
			vertex->Normal.normalize();
		});
		sbuf->recalculateBoundingBox();
	}
	return cloned_buffer;
}

scene::IMeshBuffer* cloneMeshBuffer(scene::IMeshBuffer *mesh_buffer)
{
	switch (mesh_buffer->getVertexType()) {
	case video::EVT_STANDARD:
		return cloneMeshBuffer<video::S3DVertex, scene::SMeshBuffer>(mesh_buffer);
	case video::EVT_2TCOORDS:
		return cloneMeshBuffer<video::S3DVertex2TCoords, scene::SMeshBufferLightMap>(mesh_buffer);
	case video::EVT_TANGENTS:
		return cloneMeshBuffer<video::S3DVertexTangents, scene::SMeshBufferTangents>(mesh_buffer);
	}
	sanity_check(false);
	return NULL;
}

scene::SMesh* cloneStaticMesh(scene::IMesh *src_mesh)
{
	scene::SMesh* dst_mesh = new scene::SMesh();
	for (u16 j = 0; j < src_mesh->getMeshBufferCount(); j++) {
		scene::IMeshBuffer *temp_buf = cloneMeshBuffer(
			src_mesh->getMeshBuffer(j));
		dst_mesh->addMeshBuffer(temp_buf);
		dst_mesh->setTextureSlot(j, src_mesh->getTextureSlot(j));
		temp_buf->drop();
	}
	return dst_mesh;
}

scene::IMesh* convertNodeboxesToMesh(const std::vector<aabb3f> &boxes,
		const f32 *uv_coords, f32 expand)
{
	scene::SMesh* dst_mesh = new scene::SMesh();

	for (u16 j = 0; j < 6; j++)
	{
		scene::IMeshBuffer *buf = new scene::SMeshBuffer();
		buf->getMaterial().forEachTexture([] (auto &tex) {
			tex.MinFilter = video::ETMINF_NEAREST_MIPMAP_NEAREST;
			tex.MagFilter = video::ETMAGF_NEAREST;
		});
		dst_mesh->addMeshBuffer(buf);
		buf->drop();
	}

	video::SColor c(255,255,255,255);

	for (aabb3f box : boxes) {
		box.repair();

		box.MinEdge.X -= expand;
		box.MinEdge.Y -= expand;
		box.MinEdge.Z -= expand;
		box.MaxEdge.X += expand;
		box.MaxEdge.Y += expand;
		box.MaxEdge.Z += expand;

		// Compute texture UV coords
		f32 tx1 = (box.MinEdge.X / BS) + 0.5;
		f32 ty1 = (box.MinEdge.Y / BS) + 0.5;
		f32 tz1 = (box.MinEdge.Z / BS) + 0.5;
		f32 tx2 = (box.MaxEdge.X / BS) + 0.5;
		f32 ty2 = (box.MaxEdge.Y / BS) + 0.5;
		f32 tz2 = (box.MaxEdge.Z / BS) + 0.5;

		f32 txc_default[24] = {
			// up
			tx1, 1 - tz2, tx2, 1 - tz1,
			// down
			tx1, tz1, tx2, tz2,
			// right
			tz1, 1 - ty2, tz2, 1 - ty1,
			// left
			1 - tz2, 1 - ty2, 1 - tz1, 1 - ty1,
			// back
			1 - tx2, 1 - ty2, 1 - tx1, 1 - ty1,
			// front
			tx1, 1 - ty2, tx2, 1 - ty1,
		};

		// use default texture UV mapping if not provided
		const f32 *txc = uv_coords ? uv_coords : txc_default;

		v3f min = box.MinEdge;
		v3f max = box.MaxEdge;

		video::S3DVertex vertices[24] =
		{
			// up
			video::S3DVertex(min.X,max.Y,max.Z, 0,1,0, c, txc[0],txc[1]),
			video::S3DVertex(max.X,max.Y,max.Z, 0,1,0, c, txc[2],txc[1]),
			video::S3DVertex(max.X,max.Y,min.Z, 0,1,0, c, txc[2],txc[3]),
			video::S3DVertex(min.X,max.Y,min.Z, 0,1,0, c, txc[0],txc[3]),
			// down
			video::S3DVertex(min.X,min.Y,min.Z, 0,-1,0, c, txc[4],txc[5]),
			video::S3DVertex(max.X,min.Y,min.Z, 0,-1,0, c, txc[6],txc[5]),
			video::S3DVertex(max.X,min.Y,max.Z, 0,-1,0, c, txc[6],txc[7]),
			video::S3DVertex(min.X,min.Y,max.Z, 0,-1,0, c, txc[4],txc[7]),
			// right
			video::S3DVertex(max.X,max.Y,min.Z, 1,0,0, c, txc[ 8],txc[9]),
			video::S3DVertex(max.X,max.Y,max.Z, 1,0,0, c, txc[10],txc[9]),
			video::S3DVertex(max.X,min.Y,max.Z, 1,0,0, c, txc[10],txc[11]),
			video::S3DVertex(max.X,min.Y,min.Z, 1,0,0, c, txc[ 8],txc[11]),
			// left
			video::S3DVertex(min.X,max.Y,max.Z, -1,0,0, c, txc[12],txc[13]),
			video::S3DVertex(min.X,max.Y,min.Z, -1,0,0, c, txc[14],txc[13]),
			video::S3DVertex(min.X,min.Y,min.Z, -1,0,0, c, txc[14],txc[15]),
			video::S3DVertex(min.X,min.Y,max.Z, -1,0,0, c, txc[12],txc[15]),
			// back
			video::S3DVertex(max.X,max.Y,max.Z, 0,0,1, c, txc[16],txc[17]),
			video::S3DVertex(min.X,max.Y,max.Z, 0,0,1, c, txc[18],txc[17]),
			video::S3DVertex(min.X,min.Y,max.Z, 0,0,1, c, txc[18],txc[19]),
			video::S3DVertex(max.X,min.Y,max.Z, 0,0,1, c, txc[16],txc[19]),
			// front
			video::S3DVertex(min.X,max.Y,min.Z, 0,0,-1, c, txc[20],txc[21]),
			video::S3DVertex(max.X,max.Y,min.Z, 0,0,-1, c, txc[22],txc[21]),
			video::S3DVertex(max.X,min.Y,min.Z, 0,0,-1, c, txc[22],txc[23]),
			video::S3DVertex(min.X,min.Y,min.Z, 0,0,-1, c, txc[20],txc[23]),
		};

		u16 indices[] = {0,1,2,2,3,0};

		for(u16 j = 0; j < 24; j += 4)
		{
			scene::IMeshBuffer *buf = dst_mesh->getMeshBuffer(j / 4);
			buf->append(vertices + j, 4, indices, 6);
		}
	}
	return dst_mesh;
}

void setMaterialFilters(video::SMaterialLayer &tex, bool bilinear, bool trilinear, bool anisotropic)
{
	if (trilinear)
		tex.MinFilter = video::ETMINF_LINEAR_MIPMAP_LINEAR;
	else if (bilinear)
		tex.MinFilter = video::ETMINF_LINEAR_MIPMAP_NEAREST;
	else
		tex.MinFilter = video::ETMINF_NEAREST_MIPMAP_NEAREST;

	tex.MagFilter = (trilinear || bilinear) ? video::ETMAGF_LINEAR : video::ETMAGF_NEAREST;

	tex.AnisotropicFilter = anisotropic ? 0xFF : 0;
}