#ifndef _BASIC_GEOMETRY_TANGENT_H_
#define _BASIC_GEOMETRY_TANGENT_H_

#include <math.h>

#include "basis.h"
#include "angle.h"
#include "vector2.h"
#include "matrix2x2.h"

// =================== Types ==================== //

typedef struct
{
    const float cos, sin;
} tangent_fp32_t;

typedef struct
{
    const double cos, sin;
} tangent_fp64_t;

// ================= Dark Twins ================= //

typedef struct {
    float cos, sin;
} __BgFP32DarkTwinTangent;

typedef struct {
    double cos, sin;
} __BgFP64DarkTwinTangent;

// ================= Constants ================== //

extern const tangent_fp32_t FP32_IDLE_TANGENT;
extern const tangent_fp64_t FP64_IDLE_TANGENT;

// =================== Reset ==================== //

inline void tangent_reset_fp32(tangent_fp32_t* tangent)
{
    __BgFP32DarkTwinTangent* twin = (__BgFP32DarkTwinTangent*)tangent;

    twin->cos = 1.0f;
    twin->sin = 0.0f;
}

inline void tangent_reset_fp64(tangent_fp64_t* tangent)
{
    __BgFP64DarkTwinTangent* twin = (__BgFP64DarkTwinTangent*)tangent;

    twin->cos = 1.0;
    twin->sin = 0.0;
}

// ==================== Set ===================== //

inline void tangent_fp32_set_values(const float x1, const float x2, tangent_fp32_t* tangent)
{
    const float square_module = x1 * x1 + x2 * x2;

    __BgFP32DarkTwinTangent* twin = (__BgFP32DarkTwinTangent*)tangent;

    twin->cos = x1;
    twin->sin = x2;

    if (1.0f - FP32_TWO_EPSYLON <= square_module && square_module <= 1.0f + FP32_TWO_EPSYLON) {
        return;
    }

    if (square_module <= FP32_SQUARE_EPSYLON) {
        twin->cos = 1.0f;
        twin->sin = 0.0f;
        return;
    }

    const float multiplier = sqrtf(1.0f / square_module);

    twin->cos = x1 * multiplier;
    twin->sin = x2 * multiplier;
}

inline void tangent_fp64_set_values(const double x1, const double x2, tangent_fp64_t* tangent)
{
    const double square_module = x1 * x1 + x2 * x2;

    __BgFP64DarkTwinTangent* twin = (__BgFP64DarkTwinTangent*)tangent;

    twin->cos = x1;
    twin->sin = x2;

    if (1.0 - FP64_TWO_EPSYLON <= square_module && square_module <= 1.0 + FP64_TWO_EPSYLON) {
        return;
    }

    if (square_module <= FP64_SQUARE_EPSYLON) {
        twin->cos = 1.0;
        twin->sin = 0.0;
        return;
    }

    const double multiplier = sqrt(1.0 / square_module);

    twin->cos = x1 * multiplier;
    twin->sin = x2 * multiplier;
}

// ==================== Copy ==================== //

inline void tangent_copy_fp32(const tangent_fp32_t* from, tangent_fp32_t* to)
{
    __BgFP32DarkTwinTangent* twin = (__BgFP32DarkTwinTangent*)to;

    twin->cos = from->cos;
    twin->sin = from->sin;
}

inline void tangent_copy_fp64(const tangent_fp64_t* from, tangent_fp64_t* to)
{
    __BgFP64DarkTwinTangent* twin = (__BgFP64DarkTwinTangent*)to;

    twin->cos = from->cos;
    twin->sin = from->sin;
}

// ==================== Swap ==================== //

inline void tangent_swap_fp32(tangent_fp32_t* tangent1, tangent_fp32_t* tangent2)
{
    const float cos = tangent1->cos;
    const float sin = tangent1->sin;

    __BgFP32DarkTwinTangent* twin1 = (__BgFP32DarkTwinTangent*)tangent1;

    twin1->cos = tangent2->cos;
    twin1->sin = tangent2->sin;

    __BgFP32DarkTwinTangent* twin2 = (__BgFP32DarkTwinTangent*)tangent2;

    twin2->cos = cos;
    twin2->sin = sin;
}

inline void tangent_swap_fp64(tangent_fp64_t* tangent1, tangent_fp64_t* tangent2)
{
    const double cos = tangent1->cos;
    const double sin = tangent1->sin;

    __BgFP64DarkTwinTangent* twin1 = (__BgFP64DarkTwinTangent*)tangent1;

    twin1->cos = tangent2->cos;
    twin1->sin = tangent2->sin;

    __BgFP64DarkTwinTangent* twin2 = (__BgFP64DarkTwinTangent*)tangent2;

    twin2->cos = cos;
    twin2->sin = sin;
}

// ================== Set Turn ================== //

inline void tangent_fp32_set_turn(const float angle, const angle_unit_t unit, tangent_fp32_t* tangent)
{
    const float radians = fp32_angle_to_radians(angle, unit);

    __BgFP32DarkTwinTangent* twin = (__BgFP32DarkTwinTangent*)tangent;

    twin->cos = cosf(radians);
    twin->sin = sinf(radians);
}

inline void tangent_fp64_set_turn(const double angle, const angle_unit_t unit, tangent_fp64_t* tangent)
{
    const double radians = fp64_angle_to_radians(angle, unit);

    __BgFP64DarkTwinTangent* twin = (__BgFP64DarkTwinTangent*)tangent;

    twin->cos = cos(radians);
    twin->sin = sin(radians);
}

// ============= Copy to twin type ============== //

inline void tangent_fp32_set_from_fp64(const tangent_fp64_t* from, tangent_fp32_t* to)
{
    tangent_fp32_set_values((float)from->cos, (float)from->sin, to);
}

inline void tangent_fp64_set_from_fp32(const tangent_fp32_t* from, tangent_fp64_t* to)
{
    tangent_fp64_set_values((double)from->cos, (double)from->sin, to);
}

// ================= Inversion ================== //

inline void tangent_invert_fp32(tangent_fp32_t* tangent)
{
    ((__BgFP32DarkTwinTangent*)tangent)->sin = -tangent->sin;
}

inline void tangent_invert_fp64(tangent_fp64_t* tangent)
{
    ((__BgFP64DarkTwinTangent*)tangent)->sin = -tangent->sin;
}

// ================ Set Inverted ================ //

inline void tangent_fp32_set_inverted(const tangent_fp32_t* tangent, tangent_fp32_t* result)
{
    __BgFP32DarkTwinTangent* twin = (__BgFP32DarkTwinTangent*)result;

    twin->cos = tangent->cos;
    twin->sin = -tangent->sin;
}

inline void tangent_fp64_set_inverted(const tangent_fp64_t* tangent, tangent_fp64_t* result)
{
    __BgFP64DarkTwinTangent* twin = (__BgFP64DarkTwinTangent*)result;

    twin->cos = tangent->cos;
    twin->sin = -tangent->sin;
}

// ============== Rotation Matrix =============== //

inline void tangent_fp32_make_rotation_matrix(const tangent_fp32_t* tangent, matrix2x2_fp32_t* matrix)
{
    matrix->r1c1 = tangent->cos;
    matrix->r1c2 = -tangent->sin;
    matrix->r2c1 = tangent->sin;
    matrix->r2c2 = tangent->cos;
}

inline void tangent_fp64_make_rotation_matrix(const tangent_fp64_t* tangent, matrix2x2_fp64_t* matrix)
{
    matrix->r1c1 = tangent->cos;
    matrix->r1c2 = -tangent->sin;
    matrix->r2c1 = tangent->sin;
    matrix->r2c2 = tangent->cos;
}

// ============== Reverse Matrix ================ //

inline void tangent_fp32_make_reverse_matrix(const tangent_fp32_t* tangent, matrix2x2_fp32_t* matrix)
{
    matrix->r1c1 = tangent->cos;
    matrix->r1c2 = tangent->sin;
    matrix->r2c1 = -tangent->sin;
    matrix->r2c2 = tangent->cos;
}

inline void tangent_fp64_make_reverse_matrix(const tangent_fp64_t* tangent, matrix2x2_fp64_t* matrix)
{
    matrix->r1c1 = tangent->cos;
    matrix->r1c2 = tangent->sin;
    matrix->r2c1 = -tangent->sin;
    matrix->r2c2 = tangent->cos;
}

// =================== Angle =================== //

inline float tangent_fp32_get_angle(const tangent_fp32_t* tangent, const angle_unit_t unit)
{
    if (tangent->cos >= 1.0f - FP32_TWO_EPSYLON) {
        return 0.0f;
    }

    if (tangent->cos <= -1.0f + FP32_TWO_EPSYLON) {
        return fp32_angle_get_half_circle(unit);
    }

    if (tangent->sin >= 1.0f - FP32_TWO_EPSYLON) {
        return fp32_angle_get_quater_circle(unit);
    }

    if (tangent->sin <= -1.0f + FP32_TWO_EPSYLON) {
        return 0.75f * fp32_angle_get_full_circle(unit);
    }

    return fp32_radians_to_units(atan2f(tangent->cos, tangent->sin), unit);
}

inline double tangent_fp64_get_angle(const tangent_fp64_t* tangent, const angle_unit_t unit)
{
    if (tangent->cos >= 1.0 - FP64_TWO_EPSYLON) {
        return 0.0;
    }

    if (tangent->cos <= -1.0 + FP64_TWO_EPSYLON) {
        return fp64_angle_get_half_circle(unit);
    }

    if (tangent->sin >= 1.0 - FP64_TWO_EPSYLON) {
        return fp64_angle_get_quater_circle(unit);
    }

    if (tangent->sin <= -1.0 + FP64_TWO_EPSYLON) {
        return 0.75 * fp64_angle_get_full_circle(unit);
    }

    return fp64_radians_to_units(atan2(tangent->cos, tangent->sin), unit);
}

// ================ Combination ================= //

inline void tangent_fp32_combine(const tangent_fp32_t* tangent1, const tangent_fp32_t* tangent2, tangent_fp32_t* result)
{
    tangent_fp32_set_values(
        tangent1->cos * tangent2->cos - tangent1->sin * tangent2->sin,
        tangent1->cos * tangent2->sin + tangent1->sin * tangent2->cos,
        result
    );
}

inline void tangent_fp64_combine(const tangent_fp64_t* tangent1, const tangent_fp64_t* tangent2, tangent_fp64_t* result)
{
    tangent_fp64_set_values(
        tangent1->cos * tangent2->cos - tangent1->sin * tangent2->sin,
        tangent1->cos * tangent2->sin + tangent1->sin * tangent2->cos,
        result
    );
}

// ================ Turn Vector ================= //

inline void tangent_fp32_turn(const tangent_fp32_t* tangent, const vector2_fp32_t* vector, vector2_fp32_t* result)
{
    const float x1 = tangent->cos * vector->x1 - tangent->sin * vector->x2;
    const float x2 = tangent->sin * vector->x1 + tangent->cos * vector->x2;

    result->x1 = x1;
    result->x2 = x2;
}

inline void tangent_fp64_turn(const tangent_fp64_t* tangent, const vector2_fp64_t* vector, vector2_fp64_t* result)
{
    const double x1 = tangent->cos * vector->x1 - tangent->sin * vector->x2;
    const double x2 = tangent->sin * vector->x1 + tangent->cos * vector->x2;

    result->x1 = x1;
    result->x2 = x2;
}

// ============ Turn Vector Backward ============ //

inline void tangent_fp32_turn_back(const tangent_fp32_t* tangent, const vector2_fp32_t* vector, vector2_fp32_t* result)
{
    const float x1 = tangent->sin * vector->x2 + tangent->cos * vector->x1;
    const float x2 = tangent->cos * vector->x2 - tangent->sin * vector->x1;

    result->x1 = x1;
    result->x2 = x2;
}

inline void tangent_fp64_turn_back(const tangent_fp64_t* tangent, const vector2_fp64_t* vector, vector2_fp64_t* result)
{
    const double x1 = tangent->sin * vector->x2 + tangent->cos * vector->x1;
    const double x2 = tangent->cos * vector->x2 - tangent->sin * vector->x1;

    result->x1 = x1;
    result->x2 = x2;
}

#endif