#ifndef _MOVIT_UTIL_H
#define _MOVIT_UTIL_H 1

// Various utilities.

#include <epoxy/gl.h>
#include <stdio.h>
#include <stdlib.h>
#include <Eigen/Core>
#include <string>

#define BUFFER_OFFSET(i) ((char *)NULL + (i))

namespace movit {

// Converts a HSV color to RGB. Assumes h in [0, 2pi> or [-pi, pi>
void hsv2rgb(float h, float s, float v, float *r, float *g, float *b);

// Converts a HSV color to RGB, but keeps luminance constant
// (ie. color luminance is as if S=0).
void hsv2rgb_normalized(float h, float s, float v, float *r, float *g, float *b);

// Read a file from disk and return its contents.
// Dies if the file does not exist.
std::string read_file(const std::string &filename);

// Reads <base>.<extension>, <base>.130.<extension> or <base>.300es.<extension> and
// returns its contents, depending on <movit_shader_level>.
std::string read_version_dependent_file(const std::string &base, const std::string &extension);

// Compile the given GLSL shader (typically a vertex or fragment shader)
// and return the object number.
GLuint compile_shader(const std::string &shader_src, GLenum type);

// Print a 3x3 matrix to standard output. Useful for debugging.
void print_3x3_matrix(const Eigen::Matrix3d &m);

// Output a GLSL 3x3 matrix declaration.
std::string output_glsl_mat3(const std::string &name, const Eigen::Matrix3d &m);

// Output GLSL scalar, 2-length and 3-length vector declarations.
std::string output_glsl_float(const std::string &name, float x);
std::string output_glsl_vec2(const std::string &name, float x, float y);
std::string output_glsl_vec3(const std::string &name, float x, float y, float z);

// Calculate a / b, rounding up. Does not handle overflow correctly.
unsigned div_round_up(unsigned a, unsigned b);

enum CombineRoundingBehavior {
	COMBINE_DO_NOT_ROUND = 0,
	COMBINE_ROUND_TO_FP16 = 1,
};

// Calculate where to sample, and with what weight, if one wants to use
// the GPU's bilinear hardware to sample w1 * x[pos1] + w2 * x[pos2],
// where pos1 and pos2 must be normalized coordinates describing neighboring
// texels in the mipmap level at which you sample. <num_subtexels> is the
// number of distinct accessible subtexels in the given mipmap level,
// calculated by num_texels / movit_texel_subpixel_precision. It is a float
// for performance reasons, even though it is expected to be a whole number.
// <inv_num_subtexels> is simply its inverse (1/x).
//
// Note that since the GPU might have limited precision in its linear
// interpolation, the effective weights might be different from the ones you
// asked for. sum_sq_error, if not NULL, will contain the sum of the
// (estimated) squared errors of the two weights.
//
// The answer, in "offset", comes as a normalized coordinate,
// so if e.g. w2 = 0, you have simply offset = pos1. If <rounding_behavior>
// is COMBINE_ROUND_TO_FP16, the coordinate is assumed to be stored as a
// rounded fp16 value. This enables more precise calculation of total_weight
// and sum_sq_error.
template<class DestFloat>
void combine_two_samples(float w1, float w2, float pos1, float pos2, float num_subtexels, float inv_num_subtexels,
                         DestFloat *offset, DestFloat *total_weight, float *sum_sq_error);

// Create a VBO with the given data, and bind it to the vertex attribute
// with name <attribute_name>. Returns the VBO number.
GLuint fill_vertex_attribute(GLuint glsl_program_num, const std::string &attribute_name, GLint size, GLenum type, GLsizeiptr data_size, const GLvoid *data);

// Clean up after fill_vertex_attribute().
void cleanup_vertex_attribute(GLuint glsl_program_num, const std::string &attribute_name, GLuint vbo);

// If v is not already a power of two, return the first higher power of two.
unsigned next_power_of_two(unsigned v);

// Get a pointer that represents the current OpenGL context, in a cross-platform way.
// This is not intended for anything but identification (ie., so you can associate
// different FBOs with different contexts); you should probably not try to cast it
// back into anything you intend to pass into OpenGL.
void *get_gl_context_identifier();

}  // namespace movit

#ifdef NDEBUG
#define check_error()
#else
#define check_error() { int err = glGetError(); if (err != GL_NO_ERROR) { printf("GL error 0x%x at %s:%d\n", err, __FILE__, __LINE__); abort(); } }
#endif

// CHECK() is like assert(), but retains any side effects no matter the compilation mode.
#ifdef NDEBUG
#define CHECK(x) (void)(x)
#else
#define CHECK(x) do { bool ok = x; if (!ok) { fprintf(stderr, "%s:%d: %s: Assertion `%s' failed.\n", __FILE__, __LINE__, __PRETTY_FUNCTION__, #x); abort(); } } while (false)
#endif

#endif // !defined(_MOVIT_UTIL_H)
