/*
 * Copyright (c) 2005, 2025, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.java2d.pipe;

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Composite;
import java.awt.Paint;
import java.awt.geom.AffineTransform;
import java.lang.annotation.Native;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;

import sun.java2d.InvalidPipeException;
import sun.java2d.SunGraphics2D;
import sun.java2d.loops.XORComposite;
import sun.java2d.pipe.hw.AccelSurface;

import static sun.java2d.pipe.BufferedOpCodes.BEGIN_SHAPE_CLIP;
import static sun.java2d.pipe.BufferedOpCodes.END_SHAPE_CLIP;
import static sun.java2d.pipe.BufferedOpCodes.RESET_CLIP;
import static sun.java2d.pipe.BufferedOpCodes.RESET_COMPOSITE;
import static sun.java2d.pipe.BufferedOpCodes.RESET_TRANSFORM;
import static sun.java2d.pipe.BufferedOpCodes.SET_ALPHA_COMPOSITE;
import static sun.java2d.pipe.BufferedOpCodes.SET_RECT_CLIP;
import static sun.java2d.pipe.BufferedOpCodes.SET_SHAPE_CLIP_SPANS;
import static sun.java2d.pipe.BufferedOpCodes.SET_SURFACES;
import static sun.java2d.pipe.BufferedOpCodes.SET_TRANSFORM;
import static sun.java2d.pipe.BufferedOpCodes.SET_XOR_COMPOSITE;
import static sun.java2d.pipe.BufferedRenderPipe.BYTES_PER_SPAN;

/**
 * Base context class for managing state in a single-threaded rendering
 * environment.  Each state-setting operation (e.g. SET_COLOR) is added to
 * the provided RenderQueue, which will be processed at a later time by a
 * single thread.  Note that the RenderQueue lock must be acquired before
 * calling the validate() method (or any other method in this class).  See
 * the RenderQueue class comments for a sample usage scenario.
 *
 * @see RenderQueue
 */
public abstract class BufferedContext {

    /*
     * The following flags help the internals of validate() determine
     * the appropriate (meaning correct, or optimal) code path when
     * setting up the current context.  The flags can be bitwise OR'd
     * together as needed.
     */

    /**
     * Indicates that no flags are needed; take all default code paths.
     */
    @Native public static final int NO_CONTEXT_FLAGS = (0 << 0);
    /**
     * Indicates that the source surface (or color value, if it is a simple
     * rendering operation) is opaque (has an alpha value of 1.0).  If this
     * flag is present, it allows us to disable blending in certain
     * situations in order to improve performance.
     */
    @Native public static final int SRC_IS_OPAQUE    = (1 << 0);
    /**
     * Indicates that the operation uses an alpha mask, which may determine
     * the code path that is used when setting up the current paint state.
     */
    @Native public static final int USE_MASK         = (1 << 1);

    private final RenderQueue rq;
    private final RenderBuffer buf;

    /**
     * This is a reference to the most recently validated BufferedContext.  If
     * this value is null, it means that there is no current context.  It is
     * provided here so that validate() only needs to do a quick reference
     * check to see if the BufferedContext passed to that method is the same
     * as the one we've cached here.
     */
    protected static BufferedContext currentContext;

    private Reference<AccelSurface> validSrcDataRef = null;
    private Reference<AccelSurface> validDstDataRef = null;
    private Reference<Region> validClipRef = null;
    private Reference<Composite> validCompRef = null;
    private Reference<Paint> validPaintRef = null;
    // renamed from isValidatedPaintAColor as part of a work around for 6764257
    private boolean         isValidatedPaintJustAColor;
    private int             validatedRGB;
    private int             validatedFlags;
    private boolean         xformInUse;
    private AffineTransform transform;

    protected BufferedContext(RenderQueue rq) {
        this.rq = rq;
        this.buf = rq.getBuffer();
    }

    /**
     * Fetches the BufferedContextContext associated with the dst. surface
     * and validates the context using the given parameters.  Most rendering
     * operations will call this method first in order to set the necessary
     * state before issuing rendering commands.
     *
     * Note: must be called while the RenderQueue lock is held.
     *
     * It's assumed that the type of surfaces has been checked by the Renderer
     *
     * @throws InvalidPipeException if either src or dest surface is not valid
     * or lost
     * @see RenderQueue#lock
     * @see RenderQueue#unlock
     */
    public static void validateContext(AccelSurface srcData,
                                       AccelSurface dstData,
                                       Region clip, Composite comp,
                                       AffineTransform xform,
                                       Paint paint, SunGraphics2D sg2d,
                                       int flags)
    {
        // assert rq.lock.isHeldByCurrentThread();
        BufferedContext context = dstData.getContext();
        context.validate(srcData, dstData,
                         clip, comp, xform, paint, sg2d, flags);
    }

    /**
     * Fetches the BufferedContext associated with the surface
     * and disables all context state settings.
     *
     * Note: must be called while the RenderQueue lock is held.
     *
     * It's assumed that the type of surfaces has been checked by the Renderer
     *
     * @throws InvalidPipeException if the surface is not valid
     * or lost
     * @see RenderQueue#lock
     * @see RenderQueue#unlock
     */
    public static void validateContext(AccelSurface surface) {
        // assert rt.lock.isHeldByCurrentThread();
        validateContext(surface, surface,
                        null, null, null, null, null, NO_CONTEXT_FLAGS);
    }

    /**
     * Validates the given parameters against the current state for this
     * context.  If this context is not current, it will be made current
     * for the given source and destination surfaces, and the viewport will
     * be updated.  Then each part of the context state (clip, composite,
     * etc.) is checked against the previous value.  If the value has changed
     * since the last call to validate(), it will be updated accordingly.
     *
     * Note that the SunGraphics2D parameter is only used for the purposes
     * of validating a (non-null) Paint parameter.  In all other cases it
     * is safe to pass a null SunGraphics2D and it will be ignored.
     *
     * Note: must be called while the RenderQueue lock is held.
     *
     * It's assumed that the type of surfaces has been checked by the Renderer
     *
     * @throws InvalidPipeException if either src or dest surface is not valid
     * or lost
     */
    private void validate(AccelSurface srcData, AccelSurface dstData,
                         Region clip, Composite comp,
                         AffineTransform xform,
                         Paint paint, SunGraphics2D sg2d, int flags)
    {
        // assert rq.lock.isHeldByCurrentThread();

        boolean updateClip = false;
        boolean updatePaint = false;

        if (!dstData.isValid() ||
            dstData.isSurfaceLost() || srcData.isSurfaceLost())
        {
            invalidateContext();
            throw new InvalidPipeException("bounds changed or surface lost");
        }

        if (paint instanceof Color) {
            // REMIND: not 30-bit friendly
            int newRGB = ((Color)paint).getRGB();
            if (isValidatedPaintJustAColor) {
                if (newRGB != validatedRGB) {
                    validatedRGB = newRGB;
                    updatePaint = true;
                }
            } else {
                validatedRGB = newRGB;
                updatePaint = true;
                isValidatedPaintJustAColor = true;
            }
        } else if (stateChanged(validPaintRef, paint)) {
            updatePaint = true;
            // this should be set when we are switching from paint to color
            // in which case this condition will be true
            isValidatedPaintJustAColor = false;
        }

        final boolean srcChanged = stateChanged(validSrcDataRef, srcData);
        final boolean dstChanged = stateChanged(validDstDataRef, dstData);
        if ((currentContext != this) || srcChanged || dstChanged)
        {
            if (dstChanged) {
                // the clip is dependent on the destination surface, so we
                // need to update it if we have a new destination surface
                updateClip = true;
            }

            if (paint == null) {
                // make sure we update the color state (otherwise, it might
                // not be updated if this is the first time the context
                // is being validated)
                updatePaint = true;
            }

            // update the current source and destination surfaces
            setSurfaces(srcData, dstData);

            currentContext = this;
            validSrcDataRef = wrapState(srcData);
            validDstDataRef = wrapState(dstData);
        }

        // validate clip
        final Region validatedClip = validClipRef == null ? null : validClipRef.get();
        if (stateChanged(validClipRef, clip) || updateClip) {
            if (clip != null) {
                if (updateClip ||
                    validatedClip == null ||
                    !(validatedClip.isRectangular() && clip.isRectangular()) ||
                    ((clip.getLoX() != validatedClip.getLoX() ||
                      clip.getLoY() != validatedClip.getLoY() ||
                      clip.getHiX() != validatedClip.getHiX() ||
                      clip.getHiY() != validatedClip.getHiY())))
                {
                    setClip(clip);
                }
            } else {
                resetClip();
            }
            validClipRef = wrapState(clip);
        }

        // validate composite (note that a change in the context flags
        // may require us to update the composite state, even if the
        // composite has not changed)
        if (stateChanged(validCompRef, comp) || (flags != validatedFlags)) {
            if (comp != null) {
                setComposite(comp, flags);
            } else {
                resetComposite();
            }
            // the paint state is dependent on the composite state, so make
            // sure we update the color below
            updatePaint = true;
            validCompRef = wrapState(comp);
            validatedFlags = flags;
        }

        // validate transform
        boolean txChanged = false;
        if (xform == null) {
            if (xformInUse) {
                resetTransform();
                xformInUse = false;
                txChanged = true;
            } else if (sg2d != null && !sg2d.transform.equals(transform)) {
                txChanged = true;
            }
            if (sg2d != null && txChanged) {
                transform = new AffineTransform(sg2d.transform);
            }
        } else {
            setTransform(xform);
            xformInUse = true;
            txChanged = true;
        }
        // non-Color paints may require paint revalidation
        if (!isValidatedPaintJustAColor && txChanged) {
            updatePaint = true;
        }

        // validate paint
        if (updatePaint) {
            if (paint != null) {
                BufferedPaints.setPaint(rq, sg2d, paint, flags);
            } else {
                BufferedPaints.resetPaint(rq);
            }
            validPaintRef = wrapState(paint);
        }

        // mark dstData dirty
        // REMIND: is this really needed now? we do it in SunGraphics2D..
        dstData.markDirty();
    }

    private static <T> boolean stateChanged(Reference<T> ref, T obj) {
        // null ref means "true" null object
        if (ref == null) return obj != null;
        T old = ref.get();
        // null ref value means the object was GC'ed, return true in that case
        return old == null || old != obj;
    }

    private static <T> Reference<T> wrapState(T obj) {
        return obj == null ? null : new WeakReference<>(obj);
    }

    private void setSurfaces(AccelSurface srcData,
                             AccelSurface dstData)
    {
        // assert rq.lock.isHeldByCurrentThread();
        rq.ensureCapacityAndAlignment(20, 4);
        buf.putInt(SET_SURFACES);
        buf.putLong(srcData.getNativeOps());
        buf.putLong(dstData.getNativeOps());
    }

    private void resetClip() {
        // assert rq.lock.isHeldByCurrentThread();
        rq.ensureCapacity(4);
        buf.putInt(RESET_CLIP);
    }

    private void setClip(Region clip) {
        // assert rq.lock.isHeldByCurrentThread();
        if (clip.isRectangular()) {
            rq.ensureCapacity(20);
            buf.putInt(SET_RECT_CLIP);
            buf.putInt(clip.getLoX()).putInt(clip.getLoY());
            buf.putInt(clip.getHiX()).putInt(clip.getHiY());
        } else {
            rq.ensureCapacity(28); // so that we have room for at least a span
            buf.putInt(BEGIN_SHAPE_CLIP);
            buf.putInt(SET_SHAPE_CLIP_SPANS);
            // include a placeholder for the span count
            int countIndex = buf.position();
            buf.putInt(0);
            int spanCount = 0;
            int remainingSpans = buf.remaining() / BYTES_PER_SPAN;
            int[] span = new int[4];
            SpanIterator si = clip.getSpanIterator();
            while (si.nextSpan(span)) {
                if (remainingSpans == 0) {
                    buf.putInt(countIndex, spanCount);
                    rq.flushNow();
                    buf.putInt(SET_SHAPE_CLIP_SPANS);
                    countIndex = buf.position();
                    buf.putInt(0);
                    spanCount = 0;
                    remainingSpans = buf.remaining() / BYTES_PER_SPAN;
                }
                buf.putInt(span[0]); // x1
                buf.putInt(span[1]); // y1
                buf.putInt(span[2]); // x2
                buf.putInt(span[3]); // y2
                spanCount++;
                remainingSpans--;
            }
            buf.putInt(countIndex, spanCount);
            rq.ensureCapacity(4);
            buf.putInt(END_SHAPE_CLIP);
        }
    }

    private void resetComposite() {
        // assert rq.lock.isHeldByCurrentThread();
        rq.ensureCapacity(4);
        buf.putInt(RESET_COMPOSITE);
    }

    private void setComposite(Composite comp, int flags) {
        // assert rq.lock.isHeldByCurrentThread();
        if (comp instanceof AlphaComposite) {
            AlphaComposite ac = (AlphaComposite)comp;
            rq.ensureCapacity(16);
            buf.putInt(SET_ALPHA_COMPOSITE);
            buf.putInt(ac.getRule());
            buf.putFloat(ac.getAlpha());
            buf.putInt(flags);
        } else if (comp instanceof XORComposite) {
            int xorPixel = ((XORComposite)comp).getXorPixel();
            rq.ensureCapacity(8);
            buf.putInt(SET_XOR_COMPOSITE);
            buf.putInt(xorPixel);
        } else {
            throw new InternalError("not yet implemented");
        }
    }

    private void resetTransform() {
        // assert rq.lock.isHeldByCurrentThread();
        rq.ensureCapacity(4);
        buf.putInt(RESET_TRANSFORM);
    }

    private void setTransform(AffineTransform xform) {
        // assert rq.lock.isHeldByCurrentThread();
        rq.ensureCapacityAndAlignment(52, 4);
        buf.putInt(SET_TRANSFORM);
        buf.putDouble(xform.getScaleX());
        buf.putDouble(xform.getShearY());
        buf.putDouble(xform.getShearX());
        buf.putDouble(xform.getScaleY());
        buf.putDouble(xform.getTranslateX());
        buf.putDouble(xform.getTranslateY());
    }

    /**
     * Resets this context's surfaces and all attributes.
     *
     * Note: must be called while the RenderQueue lock is held.
     *
     * @see RenderQueue#lock
     * @see RenderQueue#unlock
     */
    public final void invalidateContext() {
        resetTransform();
        resetComposite();
        resetClip();
        BufferedPaints.resetPaint(rq);
        validSrcDataRef = null;
        validDstDataRef = null;
        validCompRef = null;
        validClipRef = null;
        validPaintRef = null;
        isValidatedPaintJustAColor = false;
        xformInUse = false;
    }

    /**
     * Returns a singleton {@code RenderQueue} object used by the rendering
     * pipeline.
     *
     * @return a render queue
     * @see RenderQueue
     */
    public final RenderQueue getRenderQueue() {
        return rq;
    }
}