/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.ide.eclipse.gltrace.widgets;

import com.android.ide.eclipse.gltrace.GlTracePlugin;

import org.eclipse.core.runtime.Status;
import org.eclipse.jface.dialogs.ErrorDialog;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.graphics.ImageLoader;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.ScrollBar;

import java.io.File;

public class ImageCanvas extends Canvas {
    private static final int SCROLLBAR_INCREMENT = 20;

    private Point mOrigin;

    private ScrollBar mHorizontalScrollBar;
    private ScrollBar mVerticalScrollBar;

    private Image mImage;
    private boolean mFitToCanvas;

    public ImageCanvas(Composite parent) {
        super(parent, SWT.NO_BACKGROUND | SWT.V_SCROLL | SWT.H_SCROLL);
        mOrigin = new Point(0, 0);

        mHorizontalScrollBar = getHorizontalBar();
        mVerticalScrollBar = getVerticalBar();

        mFitToCanvas = true;

        setScrollBarIncrements();
        setScrollBarPageIncrements(getClientArea());

        updateScrollBars();

        SelectionListener scrollBarSelectionListener = new SelectionAdapter() {
            @Override
            public void widgetSelected(SelectionEvent e) {
                if (e.getSource() == mHorizontalScrollBar) {
                    scrollHorizontally();
                } else {
                    scrollVertically();
                }
            }
        };

        mHorizontalScrollBar.addSelectionListener(scrollBarSelectionListener);
        mVerticalScrollBar.addSelectionListener(scrollBarSelectionListener);

        addListener(SWT.Resize,  new Listener() {
            @Override
            public void handleEvent(Event e) {
                setScrollBarPageIncrements(getClientArea());
                updateScrollBars();
            }
        });

        addListener(SWT.Paint, new Listener() {
            @Override
            public void handleEvent(Event e) {
                paintCanvas(e.gc);
            }
        });
    }

    public void setFitToCanvas(boolean en) {
        mFitToCanvas = en;
        updateScrollBars();
        redraw();
    }

    public void setImage(Image image) {
        if (mImage != null) {
            mImage.dispose();
        }

        mImage = image;
        mOrigin = new Point(0, 0);
        updateScrollBars();
        redraw();
    }

    private void updateScrollBars() {
        Rectangle client = getClientArea();

        int imageWidth, imageHeight;
        if (mImage != null & !mFitToCanvas) {
            imageWidth = mImage.getBounds().width;
            imageHeight = mImage.getBounds().height;
        } else {
            imageWidth = client.width;
            imageHeight = client.height;
        }

        mHorizontalScrollBar.setMaximum(imageWidth);
        mVerticalScrollBar.setMaximum(imageHeight);
        mHorizontalScrollBar.setThumb(Math.min(imageWidth, client.width));
        mVerticalScrollBar.setThumb(Math.min(imageHeight, client.height));

        int hPage = imageWidth - client.width;
        int vPage = imageHeight - client.height;
        int hSelection = mHorizontalScrollBar.getSelection();
        int vSelection = mVerticalScrollBar.getSelection();
        if (hSelection >= hPage) {
            if (hPage <= 0) {
                hSelection = 0;
            }
            mOrigin.x = -hSelection;
        }

        if (vSelection >= vPage) {
            if (vPage <= 0) {
                vSelection = 0;
            }
            mOrigin.y = -vSelection;
        }

        redraw();
    }

    private void setScrollBarPageIncrements(Rectangle clientArea) {
        mHorizontalScrollBar.setPageIncrement(clientArea.width);
        mVerticalScrollBar.setPageIncrement(clientArea.height);
    }

    private void setScrollBarIncrements() {
        // The default increment is 1 pixel. Assign a saner default.
        mHorizontalScrollBar.setIncrement(SCROLLBAR_INCREMENT);
        mVerticalScrollBar.setIncrement(SCROLLBAR_INCREMENT);
    }

    private void scrollHorizontally() {
        if (mImage == null) {
            return;
        }

        int selection = mHorizontalScrollBar.getSelection();
        int destX = -selection - mOrigin.x;
        Rectangle imageBounds = mImage.getBounds();
        scroll(destX, 0, 0, 0, imageBounds.width, imageBounds.height, false);
        mOrigin.x = -selection;
    }

    private void scrollVertically() {
        if (mImage == null) {
            return;
        }

        int selection = mVerticalScrollBar.getSelection();
        int destY = -selection - mOrigin.y;
        Rectangle imageBounds = mImage.getBounds();
        scroll(0, destY, 0, 0, imageBounds.width, imageBounds.height, false);
        mOrigin.y = -selection;
    }

    private void paintCanvas(GC gc) {
        gc.fillRectangle(getClientArea()); // clear entire client area
        if (mImage == null) {
            return;
        }

        Rectangle rect = mImage.getBounds();
        Rectangle client = getClientArea();

        if (mFitToCanvas && rect.width > 0 && rect.height > 0) {
            double sx = (double) client.width / (double) rect.width;
            double sy = (double) client.height / (double) rect.height;

            if (sx < sy) {
                // if we need to scale more horizontally, then reduce the client height
                // appropriately so that aspect ratios are maintained
                gc.drawImage(mImage,
                        0, 0, rect.width, rect.height,
                        0, 0, client.width, (int)(rect.height * sx));
                drawBorder(gc, 0, 0, client.width, (int)(rect.height * sx));
            } else {
                // scale client width to maintain aspect ratio
                gc.drawImage(mImage,
                        0, 0, rect.width, rect.height,
                        0, 0, (int)(rect.width * sy), client.height);
                drawBorder(gc, 0, 0, (int)(rect.width * sy), client.height);
            }
        } else {
            gc.drawImage(mImage, mOrigin.x, mOrigin.y);
            drawBorder(gc, mOrigin.x, mOrigin.y, rect.width, rect.height);
        }
    }

    private void drawBorder(GC gc, int x, int y, int width, int height) {
        Color origFg = gc.getForeground();
        gc.setForeground(Display.getDefault().getSystemColor(SWT.COLOR_WIDGET_NORMAL_SHADOW));
        gc.drawRectangle(x, y, width, height);
        gc.setForeground(origFg);
    }

    @Override
    public void dispose() {
        if (mImage != null && !mImage.isDisposed()) {
            mImage.dispose();
        }
    }

    public void exportImageTo(File file) {
        if (mImage == null || file == null) {
            return;
        }

        ImageLoader imageLoader = new ImageLoader();
        imageLoader.data = new ImageData[] { mImage.getImageData() };

        try {
            imageLoader.save(file.getAbsolutePath(), SWT.IMAGE_PNG);
        } catch (Exception e) {
            ErrorDialog.openError(getShell(), "Save Image", "Error saving image",
                    new Status(Status.ERROR, GlTracePlugin.PLUGIN_ID, e.toString()));
        }
    }
}