#pragma once
#include <cmath>   // for sqrtf, etc.
#include "../mConstants.h"

namespace math_backend::mat44
{
   //------------------------------------------------------------------
   // Matrix Transpose
   inline void mat44_transpose_impl(float* m)
   {
      f32x4x4 ma = m_load(m);
      f32x4x4 mr = m_transpose(ma);
      m_store(m, mr);
   }

   inline float mat44_get_determinant(const float* m)
   {
      f32x4x4 ma = m_load(m);
      return v_extract0(m_determinant_affine(ma));
   }

   // Matrix Scale: Float3 (assume w = 1.0f)
   inline void mat44_scale_impl(float* m, const float* s)
   {
      f32x4x4 ma = m_load(m);
      f32x4 va = v_load3_pos(s);

      ma.r0 = v_mul(ma.r0, va);
      ma.r1 = v_mul(ma.r1, va);
      ma.r2 = v_mul(ma.r2, va);
      ma.r3 = v_mul(ma.r3, va);
      m_store(m, ma);
   }

   inline void mat44_transform_plane_impl(const float* m, const float* scale, const float* plane, float* plane_result)
   {
      f32x4x4 M = m_load(m);

      f32x4 plane_v = v_load(plane);
      f32x4 scale_v = v_load3_vec(scale);
      f32x4 invScale = v_rcp_nr(scale_v);

      // normal = plane.xyz
      f32x4 normal = plane_v;

      // apply Inv(s)
      normal = v_mul(normal, invScale);

      // multiply by Inv(Tr(m)) (only the rotation part matters)
      f32x4 nx = v_mul(v_swizzle_singular_mask(normal, 0), M.r0);
      f32x4 ny = v_mul(v_swizzle_singular_mask(normal, 1), M.r1);
      f32x4 nz = v_mul(v_swizzle_singular_mask(normal, 2), M.r2);

      normal = v_add(v_add(nx, ny), nz);

      normal = v_normalize3(normal);

      // compute point on plane
      float d = v_extract0(v_swizzle_singular_mask(plane_v, 3));

      f32x4 point = v_mul(plane_v, v_set1(-d));
      point = v_preserve_w(point, v_set1(1.0f));

      // apply scale
      point = v_mul(point, scale_v);

      // transform point by matrix
      point = m_mul_vec4(M, point);

      // compute new plane distance
      float newD = -v_extract0(v_dot3(point, normal));

      alignas(16) float n[4];
      v_store(n, normal);

      plane_result[0] = n[0];
      plane_result[1] = n[1];
      plane_result[2] = n[2];
      plane_result[3] = newD;
   }

   inline void mat44_get_scale_impl(const float* m, float* s)
   {
      f32x4x4 ma = m_load(m);

      // squared lengths
      f32x4 len2_x = v_dot3(ma.r0, ma.r0);
      f32x4 len2_y = v_dot3(ma.r1, ma.r1);
      f32x4 len2_z = v_dot3(ma.r2, ma.r2);

      // extract and sqrt
      s[0] = 1.0f / v_extract0(v_rsqrt_nr(len2_x));
      s[1] = 1.0f / v_extract0(v_rsqrt_nr(len2_y));
      s[2] = 1.0f / v_extract0(v_rsqrt_nr(len2_z));
   }

   // Matrix Scale Uniform: Float value (assume w = 1.0f)
   inline void mat44_scale_uniform(float* m, float s)
   {
      f32x4x4 ma = m_load(m);

      // (s, s, s, 1)
      f32x4 scale = v_set(s, s, s, 1.0f);

      // Scale only rotation rows (xyz part)
      ma.r0 = v_mul(ma.r0, scale);
      ma.r1 = v_mul(ma.r1, scale);
      ma.r2 = v_mul(ma.r2, scale);
      m_store(m, ma);
   }

   // Matrix Inverse
   inline void mat44_inverse_impl(float* m)
   {
      f32x4x4 ma = m_load(m);

      // Compute cofactors using cross products
      f32x4x4 mTemp;
      mTemp.r0 = v_cross(ma.r1, ma.r2);
      mTemp.r1 = v_cross(ma.r2, ma.r0);
      mTemp.r2 = v_cross(ma.r0, ma.r1);

      // Determinant = dot(ma.r0, c0)
      f32x4 det = v_dot3(ma.r0, mTemp.r0);
      f32x4 invDet = v_rcp_nr(det);

      // Scale cofactors
      mTemp.r0 = v_mul(mTemp.r0, invDet);
      mTemp.r1 = v_mul(mTemp.r1, invDet);
      mTemp.r2 = v_mul(mTemp.r2, invDet);

      // Store inverse 3x3 (transpose of cofactor matrix)

      mTemp = m_transpose(mTemp);
      mTemp.r3 = ma.r3;

      // ---- Translation ----

      // Load original translation
      f32x4 T = v_set(m[3], m[7], m[11], 0.0f);
      
      // Compute -(Tx*ma.r0 + Ty*ma.r1 + Tz*ma.r2)
      f32x4 result = v_mul(ma.r0, v_swizzle_singular_mask(T, 0));
      result = v_add(result, v_mul(ma.r1, v_swizzle_singular_mask(T, 1)));
      result = v_add(result, v_mul(ma.r2, v_swizzle_singular_mask(T, 2)));
      result = v_mul(result, v_set1(-1.0f));

      m_store(m, mTemp);

      // Store translation
      m[3] = v_extract0(result);
      m[7] = v_extract0(v_swizzle_singular_mask(result, 1));
      m[11] = v_extract0(v_swizzle_singular_mask(result, 2));
   }

   // Matrix Inverse
   inline void mat44_inverse_to_impl(const float* m, float* dst)
   {
      f32x4x4 ma = m_load(m);

      // Compute cofactors using cross products
      f32x4x4 mTemp;
      mTemp.r0 = v_cross(ma.r1, ma.r2);
      mTemp.r1 = v_cross(ma.r2, ma.r0);
      mTemp.r2 = v_cross(ma.r0, ma.r1);

      // Determinant = dot(ma.r0, c0)
      f32x4 det = v_dot3(ma.r0, mTemp.r0);
      f32x4 invDet = v_rcp_nr(det);

      // Scale cofactors
      mTemp.r0 = v_mul(mTemp.r0, invDet);
      mTemp.r1 = v_mul(mTemp.r1, invDet);
      mTemp.r2 = v_mul(mTemp.r2, invDet);

      // Store inverse 3x3 (transpose of cofactor matrix)

      mTemp = m_transpose(mTemp);
      mTemp.r3 = ma.r3;

      // ---- Translation ----

      // Load original translation
      f32x4 T = v_set(m[3], m[7], m[11], 0.0f);

      // Compute -(Tx*ma.r0 + Ty*ma.r1 + Tz*ma.r2)
      f32x4 result = v_mul(ma.r0, v_swizzle_singular_mask(T, 0));
      result = v_add(result, v_mul(ma.r1, v_swizzle_singular_mask(T, 1)));
      result = v_add(result, v_mul(ma.r2, v_swizzle_singular_mask(T, 2)));
      result = v_mul(result, v_set1(-1.0f));

      m_store(dst, mTemp);

      // Store translation
      dst[3] = v_extract0(result);
      dst[7] = v_extract0(v_swizzle_singular_mask(result, 1));
      dst[11] = v_extract0(v_swizzle_singular_mask(result, 2));
   }

   // Matrix Affine Inverse
   inline void mat44_affine_inverse_impl(float* m)
   {
      f32x4x4 ma = m_load(m);

      f32x4x4 mTemp = m_transpose(ma);
      mTemp.r3 = v_set(0, 0, 0, 1);

      // ---- Translation ----
      // Load original translation
      f32x4 T = v_set(m[3], m[7], m[11], 0.0f);

      // Compute -(Tx*ma.r0 + Ty*ma.r1 + Tz*ma.r2)
      f32x4 result = v_mul(ma.r0, v_swizzle_singular_mask(T, 0));
      result = v_add(result, v_mul(ma.r1, v_swizzle_singular_mask(T, 1)));
      result = v_add(result, v_mul(ma.r2, v_swizzle_singular_mask(T, 2)));
      result = v_mul(result, v_set1(-1.0f));

      m_store(m, mTemp);

      // Store translation
      m[3] = v_extract0(result);
      m[7] = v_extract0(v_swizzle_singular_mask(result, 1));
      m[11] = v_extract0(v_swizzle_singular_mask(result, 2));
   }

   inline void mat44_normalize_impl(float* m)
   {
      // Load the matrix into SIMD registers
      f32x4x4 mat = m_load(m);

      // Transpose: now rows are columns
      mat = m_transpose(mat);

      // Extract columns (which are now rows)
      f32x4 col0 = mat.r0;
      f32x4 col1 = mat.r1;

      // Rebuild orthonormal basis
      f32x4 col2 = v_cross(col0, col1);
      col1 = v_cross(col2, col0);

      // Normalize columns
      col0 = v_normalize3(col0);
      col1 = v_normalize3(col1);
      col2 = v_normalize3(col2);

      // Write back directly into transposed matrix
      mat.r0 = col0;
      mat.r1 = col1;
      mat.r2 = col2;

      // Transpose back to row-major
      mat = m_transpose(mat);

      // Store back
      m_store(m, mat);
   }

   // Matrix Multiply: a * b
   inline void mat44_mul_mat44_impl(const float* a, const float* b, float* r)
   {
      f32x4x4 ma = m_load(a);
      f32x4x4 mb = m_load(b);

      f32x4x4 mr = m_mul(ma, mb);
      m_store(r, mr);
   }

   // Vector Multiply: m * p (assume w = 1.0f)
   inline void mat44_mul_pos3_impl(const float *m, const float *p, float* r)
   {
      f32x4x4 ma = m_load(m);
      f32x4 va = v_load3_pos(p);
      f32x4 vr = m_mul_vec4(ma, va);
      v_store3(r, vr);
   }

   // Vector Multiply: m * v (assume w = 0.0f)
   inline void mat44_mul_vec3_impl(const float* m, const float* v, float* r)
   {
      f32x4x4 ma = m_load(m);
      f32x4 va = v_load3_vec(v);
      f32x4 vr = m_mul_vec3(ma, va);
      v_store3(r, vr);
   }

   // Vector Multiply: m * p (full [4x4] * [1x4])
   inline void mat44_mul_float4_impl(const float* m, const float* p, float* r)
   {
      f32x4x4 ma = m_load(m);
      f32x4 va = v_load(p);
      f32x4 vr = m_mul_vec4(ma, va);
      v_store(r, vr);
   }

   //--------------------------------------------------
   // MATRIX ROTATION FUNCTIONS
   //--------------------------------------------------

   inline void mat44_rotation_x_impl(float* m, float angle)
   {
      float c = cosf(angle), s = sinf(angle);
      f32x4x4 mr = m_identity();
      mr.r1 = v_set(0, c, s, 0);
      mr.r2 = v_set(0, -s, c, 0);
      m_store(m, mr);
   }

   inline void mat44_rotation_y_impl(float* m, float angle)
   {
      float c = cosf(angle), s = sinf(angle);
      f32x4x4 mr = m_identity();
      mr.r0 = v_set(c, 0, -s, 0);
      mr.r2 = v_set(s, 0, c, 0);
      m_store(m, mr);
   }

   inline void mat44_rotation_z_impl(float* m, float angle)
   {
      float c = cosf(angle), s = sinf(angle);
      f32x4x4 mr = m_identity();
      mr.r0 = v_set(c, s, 0, 0);
      mr.r1 = v_set(-s, c, 0, 0);
      m_store(m, mr);
   }

   // Compose rotation from Euler angles (pitch=X, yaw=Y, roll=Z)
   inline void mat44_rotation_euler_impl(float* m, float pitch, float yaw, float roll)
   {
      f32x4x4 rx, ry, rz;
      mat44_rotation_x_impl((float*)&rx, pitch);
      mat44_rotation_y_impl((float*)&ry, yaw);
      mat44_rotation_z_impl((float*)&rz, roll);

      f32x4x4 r = m_mul(rz, m_mul(ry, rx));
      m_store(m, r);
   }

   inline void mat44_lookat_impl(float* m, const float* eye, const float* target, const float* up)
   {
      f32x4 vEye = v_load3_pos(eye);
      f32x4 vTarget = v_load3_pos(target);
      f32x4 vUp = v_load3_vec(up);

      // Forward (z+)
      f32x4 zaxis = v_normalize3(v_sub(vTarget, vEye));

      // Right (x+)
      f32x4 xaxis = v_normalize3(v_cross(vUp, zaxis));

      // Up (y+)
      f32x4 yaxis = v_cross(zaxis, xaxis);

      // Compute translation components: -dot(axis, eye)
      f32x4 t_x = v_mul(v_dot3(xaxis, vEye), v_set1(-1.0f));
      f32x4 t_y = v_mul(v_dot3(yaxis, vEye), v_set1(-1.0f));
      f32x4 t_z = v_mul(v_dot3(zaxis, vEye), v_set1(-1.0f));

      f32x4x4 view;
      view.r0 = v_insert_w(xaxis, t_x);
      view.r1 = v_insert_w(yaxis, t_y);
      view.r2 = v_insert_w(zaxis, t_z);
      view.r3 = v_set(0, 0, 0, 1.0f);

      m_store(m, view);
   }

   inline void mat44_perspective_impl(float* m, float fovY, float aspect, float znear, float zfar)
   {
      float f = 1.0f / tanf(fovY * 0.5f);
      float nf = 1.0f / (znear - zfar);

      f32x4x4 mp = m_zero();
      mp.r0 = v_set(f / aspect, 0, 0, 0);
      mp.r1 = v_set(0, f, 0, 0);
      mp.r2 = v_set(0, 0, (zfar + znear) * nf, 2 * zfar * znear * nf);
      mp.r3 = v_set(0, 0, -1, 0); // row-major projection
      m_store(m, mp);
   }

   inline void mat44_orthographic_impl(float* m, float left, float right, float bottom, float top, float znear, float zfar)
   {
      f32x4x4 mo = m_zero();
      mo.r0 = v_set(2.0f / (right - left), 0, 0, -(right + left) / (right - left));
      mo.r1 = v_set(0, 2.0f / (top - bottom), 0, -(top + bottom) / (top - bottom));
      mo.r2 = v_set(0, 0, -2.0f / (zfar - znear), -(zfar + znear) / (zfar - znear));
      mo.r3 = v_set(0, 0, 0, 1.0f);
      m_store(m, mo);
   }

   //--------------------------------------------------
   // MATRIX BATCH FUNCTIONS
   //--------------------------------------------------

   inline void mat44_batch_mul_pos3(const float* m, const float* points, int count, float* result)
   {
      int i = 0;
      f32x4x4 ma = m_load(m);

      // AVX has 8 lanes to play with
#if defined(MATH_SIMD_AVX2) || defined(MATH_SIMD_AVX)
      // 8-wide AVX only
      for (; i + 8 <= count; i += 8)
      {
         vec4_batch8 va = load_vec3_batch8(&points[i*3], 1.0f, false);
         vec4_batch8 vr = m_mul_pos3_batch8(ma, va);
         store_vec3_batch8(&result[i*3], vr);
      }
#endif // MATH_SIMD_AVX2 || MATH_SIMD_AVX

      // 4-wide
      for (; i + 4 <= count; i += 4)
      {
         vec4_batch4 va = load_vec3_batch4(&points[i * 3], 1.0f, false);
         vec4_batch4 vr = m_mul_pos3_batch4(ma, va);
         store_vec3_batch4(&result[i * 3], vr);
      }

      for (; i < count; ++i)
      {
         size_t idx = i * 3;
         mat44_mul_pos3_impl(m, &points[idx], &result[idx]);
      }
   }

} // namespace math_backend::mat44