TAU          :: 6.28318530717958647692528676655900576;
PI           :: 3.14159265358979323846264338327950288;
ONE_OVER_TAU :: 0.636619772367581343075535053490057448;
ONE_OVER_PI  :: 0.159154943091895335768883763372514362;

E            :: 2.71828182845904523536;
SQRT_TWO     :: 1.41421356237309504880168872420969808;
SQRT_THREE   :: 1.73205080756887729352744634150587236;
SQRT_FIVE    :: 2.23606797749978969640917366873127623;

LOG_TWO      :: 0.693147180559945309417232121458176568;
LOG_TEN      :: 2.30258509299404568401799145468436421;

EPSILON      :: 1.19209290e-7;

τ :: TAU;
π :: PI;

Vec2 :: [vector 2]f32;
Vec3 :: [vector 3]f32;
Vec4 :: [vector 4]f32;

Mat2 :: [2]Vec2;
Mat3 :: [3]Vec3;
Mat4 :: [4]Vec4;

sqrt32 :: proc(x: f32) -> f32 #foreign "llvm.sqrt.f32"
sqrt64 :: proc(x: f64) -> f64 #foreign "llvm.sqrt.f64"

sin32 :: proc(x: f32) -> f32 #foreign "llvm.sin.f32"
sin64 :: proc(x: f64) -> f64 #foreign "llvm.sin.f64"

cos32 :: proc(x: f32) -> f32 #foreign "llvm.cos.f32"
cos64 :: proc(x: f64) -> f64 #foreign "llvm.cos.f64"

tan32 :: proc(x: f32) -> f32 #inline { return sin32(x)/cos32(x); }
tan64 :: proc(x: f64) -> f64 #inline { return sin64(x)/cos64(x); }

lerp32 :: proc(a, b, t: f32) -> f32 { return a*(1-t) + b*t; }
lerp64 :: proc(a, b, t: f64) -> f64 { return a*(1-t) + b*t; }

sign32 :: proc(x: f32) -> f32 { if x >= 0 { return +1; } return -1; }
sign64 :: proc(x: f64) -> f64 { if x >= 0 { return +1; } return -1; }



copy_sign32 :: proc(x, y: f32) -> f32 {
	ix := x transmute u32;
	iy := y transmute u32;
	ix &= 0x7fffffff;
	ix |= iy & 0x80000000;
	return ix transmute f32;
}
round32 :: proc(x: f32) -> f32 {
	if x >= 0 {
		return floor32(x + 0.5);
	}
	return ceil32(x - 0.5);
}
floor32 :: proc(x: f32) -> f32 {
	if x >= 0 {
		return x as int as f32;
	}
	return (x-0.5) as int as f32;
}
ceil32 :: proc(x: f32) -> f32 {
	if x < 0 {
		return x as int as f32;
	}
	return ((x as int)+1) as f32;
}

remainder32 :: proc(x, y: f32) -> f32 {
	return x - round32(x/y) * y;
}

fmod32 :: proc(x, y: f32) -> f32 {
	y = abs(y);
	result := remainder32(abs(x), y);
	if sign32(result) < 0 {
		result += y;
	}
	return copy_sign32(result, x);
}


to_radians :: proc(degrees: f32) -> f32 { return degrees * TAU / 360; }
to_degrees :: proc(radians: f32) -> f32 { return radians * 360 / TAU; }




dot2 :: proc(a, b: Vec2) -> f32 { c := a*b; return c.x + c.y; }
dot3 :: proc(a, b: Vec3) -> f32 { c := a*b; return c.x + c.y + c.z; }
dot4 :: proc(a, b: Vec4) -> f32 { c := a*b; return c.x + c.y + c.z + c.w; }

cross3 :: proc(x, y: Vec3) -> Vec3 {
	a := swizzle(x, 1, 2, 0) * swizzle(y, 2, 0, 1);
	b := swizzle(x, 2, 0, 1) * swizzle(y, 1, 2, 0);
	return a - b;
}


vec2_mag :: proc(v: Vec2) -> f32 { return sqrt32(dot2(v, v)); }
vec3_mag :: proc(v: Vec3) -> f32 { return sqrt32(dot3(v, v)); }
vec4_mag :: proc(v: Vec4) -> f32 { return sqrt32(dot4(v, v)); }

vec2_norm :: proc(v: Vec2) -> Vec2 { return v / Vec2{vec2_mag(v)}; }
vec3_norm :: proc(v: Vec3) -> Vec3 { return v / Vec3{vec3_mag(v)}; }
vec4_norm :: proc(v: Vec4) -> Vec4 { return v / Vec4{vec4_mag(v)}; }

vec2_norm0 :: proc(v: Vec2) -> Vec2 {
	m := vec2_mag(v);
	if m == 0 {
		return Vec2{0};
	}
	return v / Vec2{m};
}

vec3_norm0 :: proc(v: Vec3) -> Vec3 {
	m := vec3_mag(v);
	if m == 0 {
		return Vec3{0};
	}
	return v / Vec3{m};
}

vec4_norm0 :: proc(v: Vec4) -> Vec4 {
	m := vec4_mag(v);
	if m == 0 {
		return Vec4{0};
	}
	return v / Vec4{m};
}



mat4_identity :: proc() -> Mat4 {
	return Mat4{
		{1, 0, 0, 0},
		{0, 1, 0, 0},
		{0, 0, 1, 0},
		{0, 0, 0, 1},
	};
}

mat4_transpose :: proc(m: Mat4) -> Mat4 {
	for j : 0..<4 {
		for i : 0..<4 {
			m[i][j], m[j][i] = m[j][i], m[i][j];
		}
	}
	return m;
}

mat4_mul :: proc(a, b: Mat4) -> Mat4 {
	c: Mat4;
	for j : 0..<4 {
		for i : 0..<4 {
			c[j][i] = a[0][i]*b[j][0] +
			          a[1][i]*b[j][1] +
			          a[2][i]*b[j][2] +
			          a[3][i]*b[j][3];
		}
	}
	return c;
}

mat4_mul_vec4 :: proc(m: Mat4, v: Vec4) -> Vec4 {
	return Vec4{
		m[0][0]*v.x + m[1][0]*v.y + m[2][0]*v.z + m[3][0]*v.w,
		m[0][1]*v.x + m[1][1]*v.y + m[2][1]*v.z + m[3][1]*v.w,
		m[0][2]*v.x + m[1][2]*v.y + m[2][2]*v.z + m[3][2]*v.w,
		m[0][3]*v.x + m[1][3]*v.y + m[2][3]*v.z + m[3][3]*v.w,
	};
}

mat4_inverse :: proc(m: Mat4) -> Mat4 {
	o: Mat4;

	sf00 := m[2][2] * m[3][3] - m[3][2] * m[2][3];
	sf01 := m[2][1] * m[3][3] - m[3][1] * m[2][3];
	sf02 := m[2][1] * m[3][2] - m[3][1] * m[2][2];
	sf03 := m[2][0] * m[3][3] - m[3][0] * m[2][3];
	sf04 := m[2][0] * m[3][2] - m[3][0] * m[2][2];
	sf05 := m[2][0] * m[3][1] - m[3][0] * m[2][1];
	sf06 := m[1][2] * m[3][3] - m[3][2] * m[1][3];
	sf07 := m[1][1] * m[3][3] - m[3][1] * m[1][3];
	sf08 := m[1][1] * m[3][2] - m[3][1] * m[1][2];
	sf09 := m[1][0] * m[3][3] - m[3][0] * m[1][3];
	sf10 := m[1][0] * m[3][2] - m[3][0] * m[1][2];
	sf11 := m[1][1] * m[3][3] - m[3][1] * m[1][3];
	sf12 := m[1][0] * m[3][1] - m[3][0] * m[1][1];
	sf13 := m[1][2] * m[2][3] - m[2][2] * m[1][3];
	sf14 := m[1][1] * m[2][3] - m[2][1] * m[1][3];
	sf15 := m[1][1] * m[2][2] - m[2][1] * m[1][2];
	sf16 := m[1][0] * m[2][3] - m[2][0] * m[1][3];
	sf17 := m[1][0] * m[2][2] - m[2][0] * m[1][2];
	sf18 := m[1][0] * m[2][1] - m[2][0] * m[1][1];

	o[0][0] = +(m[1][1] * sf00 - m[1][2] * sf01 + m[1][3] * sf02);
	o[0][1] = -(m[1][0] * sf00 - m[1][2] * sf03 + m[1][3] * sf04);
	o[0][2] = +(m[1][0] * sf01 - m[1][1] * sf03 + m[1][3] * sf05);
	o[0][3] = -(m[1][0] * sf02 - m[1][1] * sf04 + m[1][2] * sf05);

	o[1][0] = -(m[0][1] * sf00 - m[0][2] * sf01 + m[0][3] * sf02);
	o[1][1] = +(m[0][0] * sf00 - m[0][2] * sf03 + m[0][3] * sf04);
	o[1][2] = -(m[0][0] * sf01 - m[0][1] * sf03 + m[0][3] * sf05);
	o[1][3] = +(m[0][0] * sf02 - m[0][1] * sf04 + m[0][2] * sf05);

	o[2][0] = +(m[0][1] * sf06 - m[0][2] * sf07 + m[0][3] * sf08);
	o[2][1] = -(m[0][0] * sf06 - m[0][2] * sf09 + m[0][3] * sf10);
	o[2][2] = +(m[0][0] * sf11 - m[0][1] * sf09 + m[0][3] * sf12);
	o[2][3] = -(m[0][0] * sf08 - m[0][1] * sf10 + m[0][2] * sf12);

	o[3][0] = -(m[0][1] * sf13 - m[0][2] * sf14 + m[0][3] * sf15);
	o[3][1] = +(m[0][0] * sf13 - m[0][2] * sf16 + m[0][3] * sf17);
	o[3][2] = -(m[0][0] * sf14 - m[0][1] * sf16 + m[0][3] * sf18);
	o[3][3] = +(m[0][0] * sf15 - m[0][1] * sf17 + m[0][2] * sf18);

	ood := 1.0 / (m[0][0] * o[0][0] +
	              m[0][1] * o[0][1] +
	              m[0][2] * o[0][2] +
	              m[0][3] * o[0][3]);

	o[0][0] *= ood;
	o[0][1] *= ood;
	o[0][2] *= ood;
	o[0][3] *= ood;
	o[1][0] *= ood;
	o[1][1] *= ood;
	o[1][2] *= ood;
	o[1][3] *= ood;
	o[2][0] *= ood;
	o[2][1] *= ood;
	o[2][2] *= ood;
	o[2][3] *= ood;
	o[3][0] *= ood;
	o[3][1] *= ood;
	o[3][2] *= ood;
	o[3][3] *= ood;

	return o;
}


mat4_translate :: proc(v: Vec3) -> Mat4 {
	m := mat4_identity();
	m[3][0] = v.x;
	m[3][1] = v.y;
	m[3][2] = v.z;
	m[3][3] = 1;
	return m;
}

mat4_rotate :: proc(v: Vec3, angle_radians: f32) -> Mat4 {
	c := cos32(angle_radians);
	s := sin32(angle_radians);

	a := vec3_norm(v);
	t := a * Vec3{1-c};

	rot := mat4_identity();

	rot[0][0] = c + t.x*a.x;
	rot[0][1] = 0 + t.x*a.y + s*a.z;
	rot[0][2] = 0 + t.x*a.z - s*a.y;
	rot[0][3] = 0;

	rot[1][0] = 0 + t.y*a.x - s*a.z;
	rot[1][1] = c + t.y*a.y;
	rot[1][2] = 0 + t.y*a.z + s*a.x;
	rot[1][3] = 0;

	rot[2][0] = 0 + t.z*a.x + s*a.y;
	rot[2][1] = 0 + t.z*a.y - s*a.x;
	rot[2][2] = c + t.z*a.z;
	rot[2][3] = 0;

	return rot;
}

mat4_scale :: proc(m: Mat4, v: Vec3) -> Mat4 {
	m[0][0] *= v.x;
	m[1][1] *= v.y;
	m[2][2] *= v.z;
	return m;
}

mat4_scalef :: proc(m: Mat4, s: f32) -> Mat4 {
	m[0][0] *= s;
	m[1][1] *= s;
	m[2][2] *= s;
	return m;
}


mat4_look_at :: proc(eye, centre, up: Vec3) -> Mat4 {
	f := vec3_norm(centre - eye);
	s := vec3_norm(cross3(f, up));
	u := cross3(s, f);

	m: Mat4;

	m[0] = Vec4{+s.x, +s.y, +s.z, 0};
	m[1] = Vec4{+u.x, +u.y, +u.z, 0};
	m[2] = Vec4{-f.x, -f.y, -f.z, 0};
	m[3] = Vec4{dot3(s, eye), dot3(u, eye), dot3(f, eye), 1};

	return m;
}
mat4_perspective :: proc(fovy, aspect, near, far: f32) -> Mat4 {
	m: Mat4;
	tan_half_fovy := tan32(0.5 * fovy);
	m[0][0] = 1.0 / (aspect*tan_half_fovy);
	m[1][1] = 1.0 / (tan_half_fovy);
	m[2][2] = -(far + near) / (far - near);
	m[2][3] = -1.0;
	m[3][2] = -2.0*far*near / (far - near);
	return m;
}


mat4_ortho3d :: proc(left, right, bottom, top, near, far: f32) -> Mat4 {
	m := mat4_identity();
	m[0][0] = +2.0 / (right - left);
	m[1][1] = +2.0 / (top - bottom);
	m[2][2] = -2.0 / (far - near);
	m[3][0] = -(right + left)   / (right - left);
	m[3][1] = -(top   + bottom) / (top   - bottom);
	m[3][2] = -(far + near) / (far - near);
	return m;
}





F32_DIG        :: 6;
F32_EPSILON    :: 1.192092896e-07;
F32_GUARD      :: 0;
F32_MANT_DIG   :: 24;
F32_MAX        :: 3.402823466e+38;
F32_MAX_10_EXP :: 38;
F32_MAX_EXP    :: 128;
F32_MIN        :: 1.175494351e-38;
F32_MIN_10_EXP :: -37;
F32_MIN_EXP    :: -125;
F32_NORMALIZE  :: 0;
F32_RADIX      :: 2;
F32_ROUNDS     :: 1;

F64_DIG        :: 15;                       // # of decimal digits of precision
F64_EPSILON    :: 2.2204460492503131e-016;  // smallest such that 1.0+F64_EPSILON != 1.0
F64_MANT_DIG   :: 53;                       // # of bits in mantissa
F64_MAX        :: 1.7976931348623158e+308;  // max value
F64_MAX_10_EXP :: 308;                      // max decimal exponent
F64_MAX_EXP    :: 1024;                     // max binary exponent
F64_MIN        :: 2.2250738585072014e-308;  // min positive value
F64_MIN_10_EXP :: -307;                     // min decimal exponent
F64_MIN_EXP    :: -1021;                    // min binary exponent
F64_RADIX      :: 2;                        // exponent radix
F64_ROUNDS     :: 1;                        // addition rounding: near