// mouse.cpp
// Glenn G. Chappell
// 13 Sep 2012
//
// For CS 381 Fall 2012
// Mouse Demo

// OpenGL/GLUT includes - DO THESE FIRST
#include <cstdlib>       // Do this before GL/GLUT includes
using std::exit;
#ifndef __APPLE__
# include <GL/glut.h>    // GLUT stuff, includes OpenGL headers as well
#else
# include <GLUT/glut.h>  // Apple puts glut.h in a different place
#endif

// Other includes
#include "lib381/bitmapprinter.h"
                         // For class BitmapPrinter
#include <iostream>
using std::cout;
using std::cerr;
using std::endl;


// Global variables
// Keyboard
const int ESCKEY = 27;         // ASCII value of Escape

// Window/viewport
const int startwinsize = 600;  // Start window width & height (pixels)
int winw = 1, winh = 1;        // Window width, height (pixels)
                               //  (Initialize to avoid spurious errors)
double cam_xmin, cam_xmax, cam_ymin, cam_ymax;
                               // Viewport bdaries in world (camunits)

// Objects

// Square #1
const double s1halfside = 0.1; // Square 1 half side len (camunits)

// Mouse
double cam_mousex, cam_mousey; // Mouse x, y pos (camunits)
                               //  Above initialized to 0., 0.
                               //  then set at first mouse event
bool leftmousedown;            // True if left mouse button down


// drawSquare
// Draws a filled square, using current GL states,
//  in the x,y plane, centered at the origin, aligned w/ x & y axes,
//  with side 2.
void drawSquare()
{
    glBegin(GL_QUADS);
        glVertex2d(-1., -1.);
        glVertex2d( 1., -1.);
        glVertex2d( 1.,  1.);
        glVertex2d(-1.,  1.);
    glEnd();
}


// myDisplay
// The GLUT display function
void myDisplay()
{
    glClearColor(0.7f, 0.7f, 0.7f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    // Draw objects

    // Square @ mouse position
    glLoadIdentity();
    glTranslated(cam_mousex, cam_mousey, 0.);  // Put square @ mouse pos
    glScaled(s1halfside, s1halfside, s1halfside);
    glColor3d(leftmousedown ? 1.0 : 0.0, 0.3, 0.3);
    drawSquare();

    // Draw documentation
    glLoadIdentity();
    glMatrixMode(GL_PROJECTION);  // Set up simple ortho projection
    glPushMatrix();
    glLoadIdentity();
    gluOrtho2D(0., double(winw), 0., double(winh));
    glColor3d(0., 0., 0.);        // Black text
    BitmapPrinter p(20., winh-20., 20.);
    p.print("Move mouse and/or press left button");
    p.print("Also try resizing the window");
    p.print("Esc      Quit");
    glPopMatrix();                // Restore prev projection
    glMatrixMode(GL_MODELVIEW);

    glutSwapBuffers();
}


// myIdle
// The GLUT idle function
void myIdle()
{
    // Print OpenGL errors, if there are any (for debugging)
    static int error_count = 0;
    if (GLenum err = glGetError())
    {
        ++error_count;
        cerr << "OpenGL ERROR " << error_count << ": "
             << gluErrorString(err) << endl;
    }
}


// myKeyboard
// The GLUT keyboard function
void myKeyboard(unsigned char key, int x, int y)
{
    switch (key)
    {
    case ESCKEY:  // Esc: quit
        exit(0);
        break;
    }
}


// myReshape
// The GLUT reshape function
void myReshape(int w, int h)
{
    // Set viewport & save window dimensions in globals
    glViewport(0, 0, w, h);
    winw = w;
    winh = h;

    // Set up projection
    // Save max/min x/y coords in globals
    // Projection is orthographic. Aspect ratio is correct,
    // and region -1..1 in x & y always just fits in viewport.
    if (w > h)
    {
        cam_xmin = -double(w)/h;
        cam_xmax = double(w)/h;
        cam_ymin = -1.;
        cam_ymax = 1.;
    }
    else
    {
        cam_xmin = -1.;
        cam_xmax = 1.;
        cam_ymin = -double(h)/w;
        cam_ymax = double(h)/w;
    }

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(cam_xmin, cam_xmax, cam_ymin, cam_ymax);

    glMatrixMode(GL_MODELVIEW);  // Always go back to model/view mode
}


// saveMousePos
// Given mouse position in GLUT format, compute corresponding camera
// coords and save in globals cam_mousex, cam_mousey.
// Uses globals winw, winh, cam_xmin, cam_xmax, cam_ymin, cam_ymax.
void saveMousePos(int x, int y)
{
    double t;  // Lirping parameter

    t = double(x)/winw;
    cam_mousex = cam_xmin + t*(cam_xmax-cam_xmin);

    t = double(y)/winh;
    cam_mousey = cam_ymax + t*(cam_ymin-cam_ymax);

    glutPostRedisplay();
}


// myMouse
// The GLUT mouse function
void myMouse(int button, int state, int x, int y)
{
    // Save left mouse button state in global
    if (button == GLUT_LEFT_BUTTON)
    {
        leftmousedown = !leftmousedown;
        // Alternate form of above:
        //  leftmousedown = (state == GLUT_DOWN);

        glutPostRedisplay();
    }

    // Compute mouse pos in camera coords & save in globals
    saveMousePos(x, y);
}


// myMotion
// The GLUT motion function
void myMotion(int x, int y)
{
    // Compute mouse pos in camera coords & save in globals
    saveMousePos(x, y);
}


// myPassiveMotion
// The GLUT passiveMotion function
void myPassiveMotion(int x, int y)
{
    // Compute mouse pos in camera coords & save in globals
    saveMousePos(x, y);
}


// init
// Initialize GL states & global data
// Called by main after window creation
void init()
{
    // Objects
    cam_mousex = 0.;
    cam_mousey = 0.;

    // Mouse
    leftmousedown = false;

    // OpenGL Stuff
    // (Nothing here)
}


int main(int argc, char ** argv)
{
    // Initialize OpenGL/GLUT
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);

    // Make a window
    glutInitWindowSize(startwinsize, startwinsize);
    glutInitWindowPosition(50, 50);
    glutCreateWindow("CS 381 - Mouse Demo");

    // Initialize GL states & register GLUT callbacks
    init();
    glutDisplayFunc(myDisplay);
    glutIdleFunc(myIdle);
    glutKeyboardFunc(myKeyboard);
    glutReshapeFunc(myReshape);
    glutMouseFunc(myMouse);
    glutMotionFunc(myMotion);
    glutPassiveMotionFunc(myPassiveMotion);

    // Do something
    glutMainLoop();

    return 0;
}