/*
 * Copyright © 2022 Collabora Ltc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "nir.h"
#include "nir_builder.h"

static unsigned int
gs_in_prim_for_topology(enum shader_prim prim)
{
   switch (prim) {
   case SHADER_PRIM_QUADS:
      return SHADER_PRIM_LINES_ADJACENCY;
   default:
      return prim;
   }
}

static enum shader_prim
gs_out_prim_for_topology(enum shader_prim prim)
{
   switch (prim) {
   case SHADER_PRIM_POINTS:
      return SHADER_PRIM_POINTS;
   case SHADER_PRIM_LINES:
   case SHADER_PRIM_LINE_LOOP:
   case SHADER_PRIM_LINES_ADJACENCY:
   case SHADER_PRIM_LINE_STRIP_ADJACENCY:
   case SHADER_PRIM_LINE_STRIP:
      return SHADER_PRIM_LINE_STRIP;
   case SHADER_PRIM_TRIANGLES:
   case SHADER_PRIM_TRIANGLE_STRIP:
   case SHADER_PRIM_TRIANGLE_FAN:
   case SHADER_PRIM_TRIANGLES_ADJACENCY:
   case SHADER_PRIM_TRIANGLE_STRIP_ADJACENCY:
   case SHADER_PRIM_POLYGON:
      return SHADER_PRIM_TRIANGLE_STRIP;
   case SHADER_PRIM_QUADS:
   case SHADER_PRIM_QUAD_STRIP:
   case SHADER_PRIM_PATCHES:
   default:
      return SHADER_PRIM_QUADS;
   }
}

static unsigned int
vertices_for_prim(enum shader_prim prim)
{
   switch (prim) {
   case SHADER_PRIM_POINTS:
      return 1;
   case SHADER_PRIM_LINES:
   case SHADER_PRIM_LINE_LOOP:
   case SHADER_PRIM_LINES_ADJACENCY:
   case SHADER_PRIM_LINE_STRIP_ADJACENCY:
   case SHADER_PRIM_LINE_STRIP:
      return 2;
   case SHADER_PRIM_TRIANGLES:
   case SHADER_PRIM_TRIANGLE_STRIP:
   case SHADER_PRIM_TRIANGLE_FAN:
   case SHADER_PRIM_TRIANGLES_ADJACENCY:
   case SHADER_PRIM_TRIANGLE_STRIP_ADJACENCY:
   case SHADER_PRIM_POLYGON:
      return 3;
   case SHADER_PRIM_QUADS:
   case SHADER_PRIM_QUAD_STRIP:
      return 4;
   case SHADER_PRIM_PATCHES:
   default:
      unreachable("unsupported primitive for gs input");
   }
}

static unsigned int
array_size_for_prim(enum shader_prim prim)
{
   switch (prim) {
   case SHADER_PRIM_POINTS:
      return 1;
   case SHADER_PRIM_LINES:
   case SHADER_PRIM_LINE_LOOP:
   case SHADER_PRIM_LINE_STRIP:
      return 2;
   case SHADER_PRIM_LINES_ADJACENCY:
   case SHADER_PRIM_LINE_STRIP_ADJACENCY:
      return 4;
   case SHADER_PRIM_TRIANGLES:
   case SHADER_PRIM_TRIANGLE_STRIP:
   case SHADER_PRIM_TRIANGLE_FAN:
   case SHADER_PRIM_POLYGON:
      return 3;
   case SHADER_PRIM_TRIANGLES_ADJACENCY:
   case SHADER_PRIM_TRIANGLE_STRIP_ADJACENCY:
      return 6;
   case SHADER_PRIM_QUADS:
   case SHADER_PRIM_QUAD_STRIP:
      return 4;
   case SHADER_PRIM_PATCHES:
   default:
      unreachable("unsupported primitive for gs input");
   }
}

/*
 * A helper to create a passthrough GS shader for drivers that needs to lower
 * some rendering tasks to the GS.
 */

nir_shader *
nir_create_passthrough_gs(const nir_shader_compiler_options *options,
                          const nir_shader *prev_stage,
                          enum shader_prim primitive_type)
{
   unsigned int vertices_out = vertices_for_prim(primitive_type);
   nir_builder b = nir_builder_init_simple_shader(MESA_SHADER_GEOMETRY,
                                                  options,
                                                  "gs passthrough");

   nir_shader *nir = b.shader;
   nir->info.gs.input_primitive = gs_in_prim_for_topology(primitive_type);
   nir->info.gs.output_primitive = gs_out_prim_for_topology(primitive_type);
   nir->info.gs.vertices_in = vertices_out;
   nir->info.gs.vertices_out = vertices_out;
   nir->info.gs.invocations = 1;
   nir->info.gs.active_stream_mask = 1;

   nir_variable *in_vars[VARYING_SLOT_MAX];
   nir_variable *out_vars[VARYING_SLOT_MAX];
   unsigned num_inputs = 0, num_outputs = 0;

   /* Create input/output variables. */
   nir_foreach_shader_out_variable(var, prev_stage) {
      assert(!var->data.patch);

      char name[100];
      if (var->name)
         snprintf(name, sizeof(name), "in_%s", var->name);
      else
         snprintf(name, sizeof(name), "in_%d", var->data.driver_location);

      nir_variable *in = nir_variable_create(nir, nir_var_shader_in,
                                             glsl_array_type(var->type,
                                                             array_size_for_prim(primitive_type),
                                                             false),
                                             name);
      in->data.location = var->data.location;
      in->data.location_frac = var->data.location_frac;
      in->data.driver_location = var->data.driver_location;
      in->data.interpolation = var->data.interpolation;
      in->data.compact = var->data.compact;

      in_vars[num_inputs++] = in;

      nir->num_inputs++;
      if (in->data.location == VARYING_SLOT_EDGE)
         continue;

      if (var->data.location != VARYING_SLOT_POS)
         nir->num_outputs++;

      if (var->name)
         snprintf(name, sizeof(name), "out_%s", var->name);
      else
         snprintf(name, sizeof(name), "out_%d", var->data.driver_location);

      nir_variable *out = nir_variable_create(nir, nir_var_shader_out,
                                              var->type, name);
      out->data.location = var->data.location;
      out->data.location_frac = var->data.location_frac;
      out->data.driver_location = var->data.driver_location;
      out->data.interpolation = var->data.interpolation;
      out->data.compact = var->data.compact;

      out_vars[num_outputs++] = out;
   }

   unsigned int start_vert = 0;
   unsigned int end_vert = vertices_out;
   unsigned int vert_step = 1;
   switch (primitive_type) {
   case PIPE_PRIM_LINES_ADJACENCY:
   case PIPE_PRIM_LINE_STRIP_ADJACENCY:
      start_vert = 1;
      end_vert += 1;
      break;
   case PIPE_PRIM_TRIANGLES_ADJACENCY:
   case PIPE_PRIM_TRIANGLE_STRIP_ADJACENCY:
      end_vert = 5;
      vert_step = 2;
      break;
   default:
      break;
   }

   for (unsigned i = start_vert; i < end_vert; i += vert_step) {
      /* Copy inputs to outputs. */
      for (unsigned j = 0, oj = 0; j < num_inputs; ++j) {
         if (in_vars[j]->data.location == VARYING_SLOT_EDGE) {
            continue;
         }
         /* no need to use copy_var to save a lower pass */
         nir_ssa_def *value = nir_load_array_var_imm(&b, in_vars[j], i);
         nir_store_var(&b, out_vars[oj], value,
                       (1u << value->num_components) - 1);
         ++oj;
      }
      nir_emit_vertex(&b, 0);
   }

   nir_end_primitive(&b, 0);
   nir_shader_gather_info(nir, nir_shader_get_entrypoint(nir));
   nir_validate_shader(nir, "in nir_create_passthrough_gs");

   return nir;
}