/*
 * Color.c -- Color management module.
 *
 * Authors		: Patrick Lecoanet.
 * Creation date	: Thu Dec 16 15:41:53 1999
 *
 * $Id$
 */

/*
 *  Copyright (c) 1999 CENA, Patrick Lecoanet --
 *
 * This code is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this code; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

/*
 * Most of this file is derived from Tk color code and thus
 * also copyrighted:
 *
 * Copyright (c) 1991-1994 The Regents of the University of California.
 * Copyright (c) 1994-1995 Sun Microsystems, Inc.
 *
 */


#include <string.h>
#include <stdlib.h>

#include "Types.h"
#include "Image.h"
#include "Color.h"
#include "Geo.h"


/*
 * Maximum size of a color name including the \0.
 */
#define COLOR_NAME_SIZE 32

/*
 * Maximum intensity for a color.
 */
#define MAX_INTENSITY 65535

/*
 * Hash table to map from a gradient's values (color, etc.) to a
 * gradient structure for those values.
 */
static Tcl_HashTable gradient_table;

static int initialized = 0;	/* 0 means static structures haven't been
				 * initialized yet. */


/*
 *----------------------------------------------------------------------
 *
 * ColorInit --
 *
 *	Initialize the structure used for color management.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Read the code.
 *
 *----------------------------------------------------------------------
 */
static void
ColorInit()
{
  initialized = 1;
  Tcl_InitHashTable(&gradient_table, TCL_STRING_KEYS);
}


/*
 *----------------------------------------------------------------------
 *
 * ZnGetGradientColor --
 *
 *----------------------------------------------------------------------
 */
XColor *
ZnGetGradientColor(ZnGradient	*grad,
		   ZnReal	position,
		   unsigned short *alpha)
{
  int			index, min, max;
  XColor		*shade=NULL;
  
  if ((grad->num_colors == 1) || (position <= 0.0)) {
    if (alpha) {
      *alpha = grad->colors[0].alpha;
    }
    return grad->colors[0].rgb;
  }
  if (position >= 100.0) {
    if (alpha) {
      *alpha = grad->colors[grad->num_colors-1].alpha;
    }
    shade = grad->colors[grad->num_colors-1].rgb;
  }
  else {
    min = 0;
    max = grad->num_colors-1;
    index = (max + min) / 2;
    while (max - min != 1) {
      /*printf("color index %d, min: %d, max: %d\n", index, min, max);*/
      if (grad->colors[index].position < position) {
	min = index;
      }
      else {
	max = index;
      }
      index = (max + min) / 2;
    }
    shade = grad->colors[index].rgb;
    if (alpha) {
      *alpha = grad->colors[index].alpha;
    }
  }

  return shade;
}


/*
 *--------------------------------------------------------------
 *
 * ZnGradientFlat --
 *
 *	Returns true if the gradient is defined by a single
 *	color.
 *
 *--------------------------------------------------------------
 */
ZnBool
ZnGradientFlat(ZnGradient	*grad)
{
  return (grad->num_colors == 1);
}


/*
 *--------------------------------------------------------------
 *
 * ZnGetReliefGradient --
 *
 *	Create a data structure containing a range of colors
 *	used to display a 3D border. Name contains the base
 *	color for the border. This is a slight variation on
 *	the syntax of a gradient that make life easier in this
 *	simple case.
 *
 * Results:
 *	The return value is a token for a data structure
 *	describing a gradient.  This token may be passed
 *	to the drawing routines.
 *	If an error prevented the gradient from being created
 *	then NULL is returned and an error message will be
 *	left in interp.
 *
 * Side effects:
 *	Data structures, etc. are allocated.
 *	It is the caller's responsibility to eventually call
 *	ZnFreeGradient to release the resources.
 *
 *--------------------------------------------------------------
 */
ZnGradient *
ZnGetReliefGradient(Tcl_Interp	*interp,
		    Tk_Window	tkwin,
		    Tk_Uid	name,
		    unsigned short alpha)
{
  XColor *base, light_color, dark_color, color;
  char	 color_name[COLOR_NAME_SIZE];
  char	 buffer[COLOR_NAME_SIZE*(3+2*ZN_RELIEF_STEPS)];
  int	 j, tmp1, tmp2;
  int	 red_range, green_range, blue_range;
  
  base = Tk_GetColor(interp, tkwin, name);
  /*
   * Compute the border gradient.
   *
   * Always consider that we are dealing with a color display with
   * enough colors available. If the colormap is full (stressed)
   * then just pray, the susbstitution algorithm may return something
   * adequate ;-).
   *
   * The extremum colors get computed using whichever formula results
   * in the greatest change in color:
   * 1. Lighter color is half-way to white, darker color is half
   *    way to dark.
   * 2. Lighter color is 40% brighter than base, darker color
   *    is 40% darker than base.
   * The first approach works better for unsaturated colors, the
   * second for saturated ones.
   *
   * NOTE: Colors are computed with integers not color shorts which
   * may lead to overflow errors.
   */
  tmp1 = (30 * (int) base->red)/100;
  tmp2 = ((int) base->red)/2;
  dark_color.red = MIN(tmp1, tmp2);
  tmp1 = (30 * (int) base->green)/100;
  tmp2 = ((int) base->green)/2;
  dark_color.green = MIN(tmp1, tmp2);
  tmp1 = (30 * (int) base->blue)/100;
  tmp2 = ((int) base->blue)/2;
  dark_color.blue = MIN(tmp1, tmp2);
  
  tmp1 = MAX_INTENSITY;/*(170 * (int) base->red)/10;*/
  if (tmp1 > MAX_INTENSITY) {
    tmp1 = MAX_INTENSITY;
  }
  tmp2 = (MAX_INTENSITY + (int) base->red)/2;
  light_color.red = MAX(tmp1, tmp2);
  tmp1 = MAX_INTENSITY;/*(170 * (int) base->green)/10;*/
  if (tmp1 > MAX_INTENSITY) {
    tmp1 = MAX_INTENSITY;
  }
  tmp2 = (MAX_INTENSITY + (int) base->green)/2;
  light_color.green = MAX(tmp1, tmp2);
  tmp1 = MAX_INTENSITY;/*(170 * (int) base->blue)/10;*/
  if (tmp1 > MAX_INTENSITY) {
    tmp1 = MAX_INTENSITY;
  }
  tmp2 = (MAX_INTENSITY + (int) base->blue)/2;
  light_color.blue = MAX(tmp1, tmp2);

  buffer[0] = 0;
  sprintf(color_name, "#%02x%02x%02x;%d|",
 	  dark_color.red/256, dark_color.green/256, dark_color.blue/256, alpha);
  red_range = (int) base->red - (int) dark_color.red;
  green_range = (int) base->green - (int) dark_color.green;
  blue_range = (int) base->blue - (int) dark_color.blue;
  strcat(buffer, color_name);
  for (j = 1; j < ZN_RELIEF_STEPS; j++) {
    color.red =(int) dark_color.red +  red_range * j/ZN_RELIEF_STEPS;
    color.green = (int) dark_color.green + green_range * j/ZN_RELIEF_STEPS;
    color.blue = (int) dark_color.blue + blue_range * j/ZN_RELIEF_STEPS;
    sprintf(color_name, "#%02x%02x%02x;%d %d|",
	    color.red/256, color.green/256, color.blue/256, alpha, 50/ZN_RELIEF_STEPS*j);
    strcat(buffer, color_name);
  }
  sprintf(color_name, "#%02x%02x%02x;%d 50|",
	  base->red/256, base->green/256, base->blue/256, alpha);
  strcat(buffer, color_name);
  red_range = (int) light_color.red - (int) base->red;
  green_range = (int) light_color.green - (int) base->green;
  blue_range = (int) light_color.blue - (int) base->blue;
  for (j = 1; j < ZN_RELIEF_STEPS; j++) {
    color.red = (int) base->red +  red_range * j/ZN_RELIEF_STEPS;
    color.green = (int) base->green + green_range * j/ZN_RELIEF_STEPS;
    color.blue = (int) base->blue + blue_range * j/ZN_RELIEF_STEPS;
    sprintf(color_name, "#%02x%02x%02x;%d %d|",
	    color.red/256, color.green/256, color.blue/256, alpha, 50+50/ZN_RELIEF_STEPS*j);
    strcat(buffer, color_name);
  }
  sprintf(color_name, "#%02x%02x%02x;%d",
	  light_color.red/256, light_color.green/256, light_color.blue/256, alpha);
  strcat(buffer, color_name);

  /*printf("gradient relief: %s \n", buffer);*/
  return ZnGetGradient(interp, tkwin, buffer);
}


/*
 *--------------------------------------------------------------
 *
 * ZnNameGradient
 * ZnDeleteGradientName --
 *
 *	Save a gradient under a name or suppress the gradient
 *	name binding. The save function returns false if the
 *	name is already in use.
 *
 *--------------------------------------------------------------
 */
ZnBool
ZnNameGradient(Tcl_Interp	*interp,
	       Tk_Window	tkwin,
	       char		*grad_descr,
	       char		*name)
{
  Tcl_HashEntry	*hash;
  int		new;
  ZnGradient	*grad;
  XColor	color;

  grad = ZnGetGradient(interp, tkwin, grad_descr);
  if (!grad) {
    Tcl_AppendResult(interp, "gradient specification \"", grad_descr,
		     "\", is invalid", NULL);
    return False;
  }
  /*
   * First try to find if the name interfere with a color name,
   * this must be avoided. Gradients may be described by a single
   * color name and gradient descriptions / names share the same
   * name space.
   */
  if (XParseColor(Tk_Display(tkwin), Tk_Colormap(tkwin), name, &color)) {
    Tcl_AppendResult(interp, "gradient name \"", name,
		     "\", is a color name", NULL);
    return False;
  }
  hash = Tcl_CreateHashEntry(&gradient_table, Tk_GetUid(name), &new);
  if (!new) {
    Tcl_AppendResult(interp, "gradient name \"", name,
		     "\", is already in use", NULL);
    return False;
  }
  else {
    Tcl_SetHashValue(hash, grad);
  }
  
  return True;
}

ZnBool
ZnGradientNameExists(char	*name)
{
  if (!initialized) {
    return False;
  }
  return Tcl_FindHashEntry(&gradient_table, Tk_GetUid(name)) != NULL;
}

void
ZnDeleteGradientName(char	*name)
{
  Tcl_HashEntry	*hash;

  if (!initialized) {
    return;
  }
  
  hash = Tcl_FindHashEntry(&gradient_table, Tk_GetUid(name));
  if (hash) {
    Tcl_DeleteHashEntry(hash);
    ZnFreeGradient((ZnGradient *) Tcl_GetHashValue(hash));
  }
}

/*
 *--------------------------------------------------------------
 *
 * ZnGetGradient --
 *
 *	Create a data structure containing a range of colors
 *	used to display a gradient. 
 *
 *	The gradient should have the following syntax:
 *
 *	gradient := [graddesc|]color[|....|color]
 *	  where the | are real characters not meta-syntax.
 *
 *	graddesc := =type args
 *	  where type := axial | radial | path
 *		args := angle if type = axial; angle in (0..360)
 *		args := x y if type = (radial| path); x and
 *		y being real valued.
 *	  
 *	color := colorvalue | colorvalue position |
 *		 colorvalue control position
 *	  where position and control are in (0..100)
 *
 *	colorvalue := (colorname | #rgb | cievalue)[;alpha]
 *	  where alpha is in (0..100)
 *
 * Results:
 *	The return value is a token for a data structure
 *	describing a gradient.  This token may be passed
 *	to the drawing routines.
 *	If an error prevented the gradient from being created
 *	then NULL is returned and an error message will be
 *	left in interp.
 *
 * Side effects:
 *	Data structures, etc. are allocated.
 *	It is the caller's responsibility to eventually call
 *	ZnFreeGradient to release the resources.
 *
 *--------------------------------------------------------------
 */
ZnGradient *
ZnGetGradientByValue(ZnGradient	*grad)
{
  grad->ref_count++;
  return grad;
}


ZnGradient *
ZnGetGradient(Tcl_Interp	*interp,
	      Tk_Window		tkwin,
	      Tk_Uid		desc)
{
  #define SEGMENT_SIZE 64
  Tcl_HashEntry	*hash;
  ZnGradient	*grad;
  unsigned int	i, j, nspace, num_colors;
  unsigned int	size;
  char		type;
  char const	*scan_ptr, *next_ptr, *str_ptr;
  int		angle, position, control;
  double	x=0, y=0;
  char		*color_ptr, *end, segment[SEGMENT_SIZE];
  ZnGradientColor *first, *last;
  XColor	color;
  int		new, red_range, green_range, blue_range;

  /*  printf("ZnGetGradient : %s\n", desc);*/
  if (!desc || !*desc) {
    return NULL;
  }
  if (!initialized) {
    ColorInit();
  }
  
  /*
   * First, check to see if there's already a gradient that will work
   * for this request.
   */  
  desc = Tk_GetUid(desc);

  hash = Tcl_CreateHashEntry(&gradient_table, desc, &new);
  if (!new) {
    grad = (ZnGradient *) Tcl_GetHashValue(hash);
    grad->ref_count++;
  }
  else {
    /*
     * No satisfactory gradient exists yet.  Initialize a new one.
     */
    type = ZN_AXIAL_GRADIENT;
    angle = 0;
    /*
     * Skip the trailing spaces.
     */
    while (*desc == ' ') {
      desc++;
    }
    /*
     * Count the sections in the description. It should give
     * the number of colors plus may be the gradient description.
     */
    scan_ptr = desc;
    /*
     * If the first section is the gradient description, start color
     * counts up from zero.
     */
    num_colors = (*scan_ptr == '=') ? 0 : 1;
    while ((scan_ptr = strchr(scan_ptr, '|'))) {
      num_colors++;
      scan_ptr++;
    }
    if (num_colors == 0) {
      Tcl_AppendResult(interp, "gradient should have at least one color \"",
		       desc, "\",", NULL);
    grad_err1:
      Tcl_DeleteHashEntry(hash);
      /*printf("ZnGetGradient error : %s\n", desc);*/
      return NULL;
    }
    /*
     * Then look at the gradient type.
     */
    scan_ptr = desc;
    /*
     * next_ptr can't be NULL in the following code,
     * we checked that at least one color was specified
     * after the gradient description.
     */
    next_ptr = strchr(scan_ptr, '|');
    if (*scan_ptr == '=') {
      scan_ptr++;
      if ((*scan_ptr == 'a') && (strncmp(scan_ptr, "axial", 5) == 0)) {
	scan_ptr += 5;
	angle = strtol(scan_ptr, &end, 10);
	nspace = strspn(end, " \t");
	if ((end+nspace) != next_ptr) {
	grad_err3:
	  Tcl_AppendResult(interp, "invalid gradient parameter \"",
			   desc, "\",", NULL);
	  goto grad_err1;
	}
      }
      else if (((*scan_ptr == 'r') && (strncmp(scan_ptr, "radial", 6) == 0)) ||
	       ((*scan_ptr == 'p') && (strncmp(scan_ptr, "path", 4) == 0))) {
	if (*scan_ptr == 'r') {
	  type = ZN_RADIAL_GRADIENT;
	  scan_ptr += 6;
	}
	else {
	  type = ZN_PATH_GRADIENT;
	  scan_ptr += 4;
	}
	x = strtod(scan_ptr, &end);
	if (end == scan_ptr) {
	  goto grad_err3;
	}
	scan_ptr = end;
	y = strtod(scan_ptr, &end);
	nspace = strspn(end, " \t");	
	if ((end+nspace) != next_ptr) {
	  goto grad_err3;
	}
      }
      else {
	Tcl_AppendResult(interp, "invalid gradient type \"",
			 desc, "\",", NULL);
	goto grad_err1;
      }
      scan_ptr = next_ptr + 1;
      next_ptr = strchr(scan_ptr, '|');
    }
    /*
     * Create the gradient structure.
     */
    grad = (ZnGradient *) ZnMalloc(sizeof(ZnGradient) +
				   sizeof(ZnGradientColor)*(num_colors-1));
    grad->ref_count = 1;
    grad->num_colors = num_colors;
    grad->type = type;
    if (type == ZN_AXIAL_GRADIENT) {
      grad->g.angle = angle;
    }
    else {
      grad->g.p.x = x;
      grad->g.p.y = y;
    }
    grad->hash = hash;
    Tcl_SetHashValue(hash, grad);

    for (i = 0; i < num_colors; i++) {
      grad->colors[i].alpha = 100;
      /*
       * Try to parse the color name.
       */
      nspace = strspn(scan_ptr, " \t");	
      scan_ptr += nspace;
      str_ptr = strpbrk(scan_ptr, " \t|");
      if (str_ptr) {
	size = str_ptr - scan_ptr;
      }
      else {
	size = strlen(scan_ptr);
      }
      if (size > (SEGMENT_SIZE-1)) {
	Tcl_AppendResult(interp, "color name too long in gradient \"",
			 desc, "\",", NULL);
      grad_err2:
	for (j = 0; j < i; j++) {
	  Tk_FreeColor(grad->colors[j].rgb);
	}
	ZnFree(grad);
	goto grad_err1;
      }
      strncpy(segment, scan_ptr, size);
      segment[size] = 0;
      scan_ptr += size;
      /*
       * Try to parse the color position.
       */
      grad->colors[i].position = 0;
      grad->colors[i].control = 50;
      position = strtol(scan_ptr, &end, 10);
      if (end != scan_ptr) {
	grad->colors[i].position = position;
	scan_ptr = end;
	/*
	 * Try to parse the control point
	 */
	control = strtol(scan_ptr, &end, 10);
	if (end != scan_ptr) {
	  grad->colors[i].control = control;
	  scan_ptr = end;
	}
      }
      nspace = strspn(scan_ptr, " \t");
      if ((scan_ptr[nspace] != 0) && (scan_ptr+nspace != next_ptr)) {
	Tcl_AppendResult(interp, "incorrect color description in gradient \"",
			 desc, "\",", NULL);
	goto grad_err2;
      }

      color_ptr = strchr(segment, ';');
      if (color_ptr) {
	*color_ptr = 0;
      }
      grad->colors[i].rgb = Tk_GetColor(interp, tkwin, Tk_GetUid(segment));
      if (grad->colors[i].rgb == NULL) {
	Tcl_AppendResult(interp, "incorrect color value in gradient \"",
			 desc, "\",", NULL);
	goto grad_err2;
      }
      if (color_ptr) {
	color_ptr++;
	grad->colors[i].alpha = atoi(color_ptr);
      }
      if (i == 0) {
	grad->colors[i].position = 0;
      }
      else if (i == num_colors - 1) {
	grad->colors[i].position = 100;
      }
      if ((i > 0) &&
	  ((grad->colors[i].position > 100) ||
	   (grad->colors[i].position < grad->colors[i-1].position))) {
	Tcl_AppendResult(interp, "incorrect color position in gradient \"",
			 desc, "\",", NULL);
	goto grad_err2;
      }
      if (grad->colors[i].control > 100) {
	grad->colors[i].control = 100;
      }
      if (grad->colors[i].alpha > 100) {
	grad->colors[i].alpha = 100;
      }
      if (next_ptr) {
	scan_ptr = next_ptr + 1;
	next_ptr = strchr(scan_ptr, '|');
      }
    }
  }

  /*
   * Compute the mid alpha and mid color values. These will be
   * used by the gradient rendering primitives when a control
   * is not at mid range. The last color has no mid_* values.
   */
  for (i = 0; i < grad->num_colors-1; i++) {
    first = &grad->colors[i];
    last = &grad->colors[i+1];
    red_range = (int) last->rgb->red - (int) first->rgb->red;
    green_range = (int) last->rgb->green - (int) first->rgb->green;
    blue_range = (int) last->rgb->blue - (int) first->rgb->blue;
    color.red =(int) first->rgb->red +  red_range/2;
    color.green = (int) first->rgb->green + green_range/2;
    color.blue = (int) first->rgb->blue + blue_range/2;
    first->mid_rgb = Tk_GetColorByValue(tkwin, &color);
    first->mid_alpha = first->alpha + (last->alpha-first->alpha)/2;
  }
  grad->colors[grad->num_colors-1].mid_rgb = NULL;

  /* printf("ZnGetGradient end : %s\n", desc);*/
  return grad;
}


/*
 *--------------------------------------------------------------
 *
 * ZnNameOfGradient --
 *
 *	Given a gradient, return a textual string identifying
 *	the gradient.
 *
 * Results:
 *	The return value is the string that was used to create
 *	the gradient.
 *
 * Side effects:
 *	None.
 *
 *--------------------------------------------------------------
 */
char *
ZnNameOfGradient(ZnGradient	*grad)
{
  return (char *) grad->hash->key.words;
}


/*
 *--------------------------------------------------------------
 *
 * ZnFreeGradient --
 *
 *	This procedure is called when a gradient is no longer
 *	needed.  It frees the resources associated with the
 *	gradient.  After this call, the caller should never
 *	again use the gradient.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Resources are freed.
 *
 *--------------------------------------------------------------
 */
void
ZnFreeGradient(ZnGradient	*grad)
{
  unsigned int	i;
  
  grad->ref_count--;
  if (grad->ref_count == 0) {
    Tcl_DeleteHashEntry(grad->hash);
    for (i = 0; i < grad->num_colors; i++) {
      Tk_FreeColor(grad->colors[i].rgb);
      if (grad->colors[i].mid_rgb) {
	Tk_FreeColor(grad->colors[i].mid_rgb);
      }
    }
    ZnFree(grad);
  }
}


/*
 *--------------------------------------------------------------
 *
 * ZnComposeAlpha --
 *
 *	This procedure takes two alpha values in percent and
 *	returns the composite value between 0 and 65535.
 *
 *--------------------------------------------------------------
 */
int
ZnComposeAlpha(unsigned short	alpha1,
	       unsigned short	alpha2)
{
  return (alpha1*alpha2/100)*65535/100;
}