/*
 * Copyright (C) 2008 Google, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#include "config.h"
#include "Gradient.h"

#include "CSSParser.h"
#include "GraphicsContext.h"
#include "NotImplemented.h"

#include "SkGradientShader.h"
#include "SkiaUtils.h"

namespace WebCore {

void Gradient::platformDestroy()
{
    if (m_gradient)
        m_gradient->safeUnref();
    m_gradient = 0;
}

static inline U8CPU F2B(float x)
{
    return static_cast<int>(x * 255);
}

static SkColor makeSkColor(float a, float r, float g, float b)
{
    return SkColorSetARGB(F2B(a), F2B(r), F2B(g), F2B(b));
}

// Determine the total number of stops needed, including pseudo-stops at the
// ends as necessary.
static size_t total_stops_needed(const Gradient::ColorStop* stopData, size_t count)
{
    const Gradient::ColorStop* stop = stopData;
    size_t count_used = count;
    if (count < 1 || stop->stop > 0.0)
      count_used++;
    stop += count - 1;
    if (count < 2 || stop->stop < 1.0)
      count_used++;
    return count_used;
}

// Collect sorted stop position and color information into the pos and colors 
// buffers, ensuring stops at both 0.0 and 1.0.  The buffers must be large
// enough to hold information for all stops, including the new endpoints if
// stops at 0.0 and 1.0 aren't already included.
static void fill_stops(const Gradient::ColorStop* stopData,
                       size_t count, SkScalar* pos, SkColor* colors)
{ 
    const Gradient::ColorStop* stop = stopData;
    size_t start = 0;
    if (count < 1) {
        // A gradient with no stops must be transparent black.
        pos[0] = WebCoreFloatToSkScalar(0.0);
        colors[0] = makeSkColor(0.0, 0.0, 0.0, 0.0);
        start = 1;
    } else if (stop->stop > 0.0) {
        // Copy the first stop to 0.0. The first stop position may have a slight
        // rounding error, but we don't care in this float comparison, since
        // 0.0 comes through cleanly and people aren't likely to want a gradient
        // with a stop at (0 + epsilon).
        pos[0] = WebCoreFloatToSkScalar(0.0);
        colors[0] = makeSkColor(stop->alpha, stop->red, stop->green, stop->blue);
        start = 1;
    }

    for (size_t i = start; i < start + count; i++) {
        pos[i] = WebCoreFloatToSkScalar(stop->stop);
        colors[i] = makeSkColor(stop->alpha, stop->red, stop->green, stop->blue);
        ++stop;
    }

    // Copy the last stop to 1.0 if needed.  See comment above about this float
    // comparison.
    if (count < 1 || (--stop)->stop < 1.0) {
        pos[start + count] = WebCoreFloatToSkScalar(1.0);
        colors[start + count] = colors[start + count - 1];
    }
}

SkShader* Gradient::platformGradient()
{
    if (m_gradient)
        return m_gradient;

    size_t count_used = total_stops_needed(m_stops.data(), m_stops.size());
    ASSERT(count_used >= 2);
    ASSERT(count_used >= m_stops.size());

    // FIXME: Why is all this manual pointer math needed?!
    SkAutoMalloc storage(count_used * (sizeof(SkColor) + sizeof(SkScalar)));
    SkColor* colors = (SkColor*)storage.get();
    SkScalar* pos = (SkScalar*)(colors + count_used);
    
    fill_stops(m_stops.data(), m_stops.size(), pos, colors);

    if (m_radial) {
        m_gradient = SkGradientShader::CreateRadial(m_p1,
            WebCoreFloatToSkScalar(m_r1), colors, pos,
            static_cast<int>(count_used), SkShader::kClamp_TileMode);
    } else {
        SkPoint pts[2] = { m_p0, m_p1 };
        m_gradient = SkGradientShader::CreateLinear(pts, colors, pos,
            static_cast<int>(count_used), SkShader::kClamp_TileMode);
    }

    return m_gradient;
}

void Gradient::fill(GraphicsContext* context, const FloatRect& rect)
{
    // Until this is filled, we don't support CSSGradients
    notImplemented();
}

} // namespace WebCore