/**************************************************************************
 * 
 * Copyright 2007 VMware, Inc.
 * All Rights Reserved.
 *
 * 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, sub license, 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 NON-INFRINGEMENT.
 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS 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.
 * 
 **************************************************************************/

/* Authors:  Keith Whitwell <keithw@vmware.com>
 */

#include "util/u_math.h"
#include "util/u_memory.h"

#include "pipe/p_shader_tokens.h"
#include "draw_vs.h"
#include "draw_fs.h"
#include "draw_pipe.h"


/** subclass of draw_stage */
struct flat_stage
{
   struct draw_stage stage;

   uint num_flat_attribs;
   uint flat_attribs[PIPE_MAX_SHADER_OUTPUTS];  /* flatshaded attribs */
};


static inline struct flat_stage *
flat_stage(struct draw_stage *stage)
{
   return (struct flat_stage *) stage;
}


/** Copy all the constant attributes from 'src' vertex to 'dst' vertex */
static inline void copy_flats( struct draw_stage *stage,
                               struct vertex_header *dst,
                               const struct vertex_header *src )
{
   const struct flat_stage *flat = flat_stage(stage);
   uint i;

   for (i = 0; i < flat->num_flat_attribs; i++) {
      const uint attr = flat->flat_attribs[i];
      COPY_4FV(dst->data[attr], src->data[attr]);
   }
}


/** Copy all the color attributes from src vertex to dst0 & dst1 vertices */
static inline void copy_flats2( struct draw_stage *stage,
                                struct vertex_header *dst0,
                                struct vertex_header *dst1,
                                const struct vertex_header *src )
{
   const struct flat_stage *flat = flat_stage(stage);
   uint i;
   for (i = 0; i < flat->num_flat_attribs; i++) {
      const uint attr = flat->flat_attribs[i];
      COPY_4FV(dst0->data[attr], src->data[attr]);
      COPY_4FV(dst1->data[attr], src->data[attr]);
   }
}


/**
 * Flatshade tri. Not required for clipping which handles this on its own,
 * but required for unfilled tris and other primitive-changing stages
 * (like widelines). If no such stages are active, handled by hardware.
 */
static void flatshade_tri_0( struct draw_stage *stage,
                             struct prim_header *header )
{
   struct prim_header tmp;

   tmp.det = header->det;
   tmp.flags = header->flags;
   tmp.pad = header->pad;
   tmp.v[0] = header->v[0];
   tmp.v[1] = dup_vert(stage, header->v[1], 0);
   tmp.v[2] = dup_vert(stage, header->v[2], 1);

   copy_flats2(stage, tmp.v[1], tmp.v[2], tmp.v[0]);

   stage->next->tri( stage->next, &tmp );
}


static void flatshade_tri_2( struct draw_stage *stage,
                             struct prim_header *header )
{
   struct prim_header tmp;

   tmp.det = header->det;
   tmp.flags = header->flags;
   tmp.pad = header->pad;
   tmp.v[0] = dup_vert(stage, header->v[0], 0);
   tmp.v[1] = dup_vert(stage, header->v[1], 1);
   tmp.v[2] = header->v[2];

   copy_flats2(stage, tmp.v[0], tmp.v[1], tmp.v[2]);

   stage->next->tri( stage->next, &tmp );
}


/**
 * Flatshade line.
 */
static void flatshade_line_0( struct draw_stage *stage,
                              struct prim_header *header )
{
   struct prim_header tmp;

   tmp.det = header->det;
   tmp.flags = header->flags;
   tmp.pad = header->pad;
   tmp.v[0] = header->v[0];
   tmp.v[1] = dup_vert(stage, header->v[1], 0);

   copy_flats(stage, tmp.v[1], tmp.v[0]);

   stage->next->line( stage->next, &tmp );
}


static void flatshade_line_1( struct draw_stage *stage,
                              struct prim_header *header )
{
   struct prim_header tmp;

   tmp.det = header->det;
   tmp.flags = header->flags;
   tmp.pad = header->pad;
   tmp.v[0] = dup_vert(stage, header->v[0], 0);
   tmp.v[1] = header->v[1];

   copy_flats(stage, tmp.v[0], tmp.v[1]);

   stage->next->line( stage->next, &tmp );
}


static int
find_interp(const struct draw_fragment_shader *fs, int *indexed_interp,
            uint semantic_name, uint semantic_index)
{
   int interp;
   /* If it's gl_{Front,Back}{,Secondary}Color, pick up the mode
    * from the array we've filled before. */
   if (semantic_name == TGSI_SEMANTIC_COLOR ||
       semantic_name == TGSI_SEMANTIC_BCOLOR) {
      interp = indexed_interp[semantic_index];
   } else {
      /* Otherwise, search in the FS inputs, with a decent default
       * if we don't find it.
       */
      uint j;
      interp = TGSI_INTERPOLATE_PERSPECTIVE;
      if (fs) {
         for (j = 0; j < fs->info.num_inputs; j++) {
            if (semantic_name == fs->info.input_semantic_name[j] &&
                semantic_index == fs->info.input_semantic_index[j]) {
               interp = fs->info.input_interpolate[j];
               break;
            }
         }
      }
   }
   return interp;
}


static void flatshade_init_state( struct draw_stage *stage )
{
   struct flat_stage *flat = flat_stage(stage);
   const struct draw_context *draw = stage->draw;
   const struct draw_fragment_shader *fs = draw->fs.fragment_shader;
   const struct tgsi_shader_info *info = draw_get_shader_info(draw);
   uint i, j;

   /* Find which vertex shader outputs need constant interpolation, make a list */

   /* XXX: this code is a near exact copy of the one in clip_init_state.
    * The latter also cares about perspective though.
    */

   /* First pick up the interpolation mode for
    * gl_Color/gl_SecondaryColor, with the correct default.
    */
   int indexed_interp[2];
   indexed_interp[0] = indexed_interp[1] = draw->rasterizer->flatshade ?
      TGSI_INTERPOLATE_CONSTANT : TGSI_INTERPOLATE_PERSPECTIVE;

   if (fs) {
      for (i = 0; i < fs->info.num_inputs; i++) {
         if (fs->info.input_semantic_name[i] == TGSI_SEMANTIC_COLOR) {
            if (fs->info.input_interpolate[i] != TGSI_INTERPOLATE_COLOR)
               indexed_interp[fs->info.input_semantic_index[i]] = fs->info.input_interpolate[i];
         }
      }
   }

   /* Then resolve the interpolation mode for every output attribute.
    *
    * Given how the rest of the code, the most efficient way is to
    * have a vector of flat-mode attributes.
    */
   flat->num_flat_attribs = 0;
   for (i = 0; i < info->num_outputs; i++) {
      /* Find the interpolation mode for a specific attribute */
      int interp = find_interp(fs, indexed_interp,
                               info->output_semantic_name[i],
                               info->output_semantic_index[i]);
      /* If it's flat, add it to the flat vector. */

      if (interp == TGSI_INTERPOLATE_CONSTANT) {
         flat->flat_attribs[flat->num_flat_attribs] = i;
         flat->num_flat_attribs++;
      }
   }
   /* Search the extra vertex attributes */
   for (j = 0; j < draw->extra_shader_outputs.num; j++) {
      /* Find the interpolation mode for a specific attribute */
      int interp = find_interp(fs, indexed_interp,
                               draw->extra_shader_outputs.semantic_name[j],
                               draw->extra_shader_outputs.semantic_index[j]);
      /* If it's flat, add it to the flat vector. */
      if (interp == TGSI_INTERPOLATE_CONSTANT) {
         flat->flat_attribs[flat->num_flat_attribs] = i + j;
         flat->num_flat_attribs++;
      }
   }

   /* Choose flatshade routine according to provoking vertex:
    */
   if (draw->rasterizer->flatshade_first) {
      stage->line = flatshade_line_0;
      stage->tri = flatshade_tri_0;
   }
   else {
      stage->line = flatshade_line_1;
      stage->tri = flatshade_tri_2;
   }
}

static void flatshade_first_tri( struct draw_stage *stage,
                                 struct prim_header *header )
{
   flatshade_init_state( stage );
   stage->tri( stage, header );
}

static void flatshade_first_line( struct draw_stage *stage,
                                  struct prim_header *header )
{
   flatshade_init_state( stage );
   stage->line( stage, header );
}


static void flatshade_flush( struct draw_stage *stage, 
                             unsigned flags )
{
   stage->tri = flatshade_first_tri;
   stage->line = flatshade_first_line;
   stage->next->flush( stage->next, flags );
}


static void flatshade_reset_stipple_counter( struct draw_stage *stage )
{
   stage->next->reset_stipple_counter( stage->next );
}


static void flatshade_destroy( struct draw_stage *stage )
{
   draw_free_temp_verts( stage );
   FREE( stage );
}


/**
 * Create flatshading drawing stage.
 */
struct draw_stage *draw_flatshade_stage( struct draw_context *draw )
{
   struct flat_stage *flatshade = CALLOC_STRUCT(flat_stage);
   if (flatshade == NULL)
      goto fail;

   flatshade->stage.draw = draw;
   flatshade->stage.name = "flatshade";
   flatshade->stage.next = NULL;
   flatshade->stage.point = draw_pipe_passthrough_point;
   flatshade->stage.line = flatshade_first_line;
   flatshade->stage.tri = flatshade_first_tri;
   flatshade->stage.flush = flatshade_flush;
   flatshade->stage.reset_stipple_counter = flatshade_reset_stipple_counter;
   flatshade->stage.destroy = flatshade_destroy;

   if (!draw_alloc_temp_verts( &flatshade->stage, 2 ))
      goto fail;

   return &flatshade->stage;

 fail:
   if (flatshade)
      flatshade->stage.destroy( &flatshade->stage );

   return NULL;
}