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 :: type [vector 2]f32
Vec3 :: type [vector 3]f32
Vec4 :: type [vector 4]f32

Mat2 :: type [2]Vec2
Mat3 :: type [3]Vec3
Mat4 :: type [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; j < 4; j++ {
		for i := 0; i < 4; i++ {
			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; j < 4; j++ {
		for i := 0; i < 4; i++ {
			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