%VOR instrument simulator
%Draws a VOR indicator and a heading indicator on the screen that correspond to a virtual aircraft and VOR station to allow pilots to practice VOR intercepts.
%Controls: a/d: Rotate VOR face. Holding Shift + a/d rotates the VOR faster. Left/right turns the aircraft by 1 degree per second. Shift+left/right turns the aircraft by 3 degrees per second, a rate 1 turn.

View.Set("graphics:400,400, offscreenonly")%The compass and VOR scales are slaved to the length of the screen, so the UI is scaled automatically

/*Type definitions*/

%Holds values required for drawing a compass face
type Compass : record
    x : int %(x,y) is the bottom left corner of the compass
    y : int
    scale : int %the square dimensions of the compass are (scale, scale)
    centreX : int%The centre of the compass face
    centreY : int
    radius : int %the radius of the compass face
    heading : real %the heading to display at the top of the compass
end record

%Holds values for drawing the VOR face, as well as coordinates for the VOR tower
type VOR : record
    compass:Compass %A VOR is nearly identical to a compass and uses all the same values.
    x : real%(x,y) is the location of the vor tower
    y : real
end record

%Represents an aircraft.
type Plane : record
    x, y : real%(x,y) is the location of the plane
    heading : real%the heading of the aircraft
    velocity : real%the speed of the aircraft.
end record

%Fills up a plane record with values
fcn newPlane (x:real, y:real, heading:real, velocity:real):Plane
    var out : Plane
    out.x := x
    out.y := y
    out.heading := heading
    out.velocity := velocity
    result out
end newPlane

%fills up a compass record. Size
fcn newCompass (x:int, y:int, scale:int): Compass %generates a Compass. scale = width = height, (x,y) = lower left corner
var out : Compass
out.x := x
out.y := y
out.scale := scale
out.radius := round(scale/2)
out.centreX := x+out.radius
out.centreY := y+out.radius
out.heading := 0
result out
end newCompass

%fills up a VOR record
fcn newVOR (display_x:int, display_y:int, scale:int, tower_x:real, tower_y:real):VOR
    var out : VOR
    out.compass := newCompass (display_x, display_y, scale)
    out.x := tower_x
    out.y := tower_y
    result out
end newVOR
   
%This function returns the angle between the positive horizontal axis and ((0,0)(x,y)).
fcn atan2 (x:real, y:real) : real
    if x > 0 then result 90-arctand(y/x)
    elsif x < 0 then result 270-arctand(y/x)
    elsif x = 0 then
        if y > 0 then result 0
        elsif y < 0 then result 180
        elsif y = 0 then result -1
        end if
    end if
    result -1
end atan2

%draws the face of the compass with the current heading at the top
proc drawCompass (compass : Compass)
    var text_font := Font.New ("Times New Roman:" + intstr (round (compass.scale/30)))%the font for drawing headings is scaled to fit the compass face
    %draw the outline of the compass
    %Just drawing the outline of the compass
    Draw.FillBox (compass.x, compass.y, compass.x+compass.scale, compass.y + compass.scale, black)
    Draw.FillOval (compass.centreX, compass.centreY, compass.radius, compass.radius, white)
    Draw.Oval (compass.centreX, compass.centreY, compass.radius, compass.radius, grey)

    %draw the 5 degree ticks, scaled to fit the compass and offset by the current heading of the compass.
    %First I draw lines radiating from the centre of the compass, then draw a white circle over part to create ticks.
    var tick_length : int := round (compass.radius / 20)
    for x: 5..355 by 10
        Draw.Line (compass.centreX, compass.centreY, compass.centreX + round (compass.radius * cosd(x+compass.heading)), compass.centreY + round (compass.centreY * sind(x+compass.heading)), black)
    end for
    Draw.FillOval (compass.centreX, compass.centreY, compass.radius - tick_length, compass.radius - tick_length, white)

    %draw the 10 degree ticks. Works the same as the 5 degree ticks, but these are a bit bigger.
    tick_length := round (compass.radius / 10)
    for x:0..350 by 10
        Draw.Line (compass.centreX, compass.centreY, compass.centreX + round (compass.radius * cosd(x+compass.heading)), compass.centreY + round (compass.centreY * sind(x+compass.heading)), black)
    end for
    Draw.FillOval (compass.centreX, compass.centreY, compass.radius - tick_length, compass.radius - tick_length, white)
   
    %draw the 30-degree headings on the compass face.
    /*This is actually a little complicated. The function calculates where to draw the headings using the
     *formula (x+x_radius * cosd(degree), y + y_radius * sind(degree)), however the radii are adjusted depending
     *on the scale of the compass face and an offset is applied to the X and Y coordinates to centre the text. The size
     *of the text font is also dependant on the compass scale.
    */
    var font_height : int
    var font_ascent, font_descent, font_internal_leading : int %see Font.Sizes docs for information on this
    var dummy : int %I don't need this value, but I need it.
    Font.Sizes (text_font, dummy, font_ascent, font_descent, font_internal_leading)%I use this to find the centre of the font, for centering the text.
    font_height := font_ascent - font_descent
    var text_y_radius := compass.radius - tick_length - font_height
    var text_x_radius : real
    var heading_text : string
    var text_x_offset : real
    var text_y_offset : real := font_height/2
    for x:0..330 by 30
        heading_text := intstr ((-1*x+90) mod 360)
        text_x_offset := Font.Width (heading_text, text_font)/2
        text_x_radius := compass.radius - tick_length - Font.Width (heading_text, text_font)
        Font.Draw (heading_text, compass.centreX + round (text_x_radius * cosd(x+compass.heading) - text_x_offset), compass.centreY + round (text_y_radius * sind(x+compass.heading) - text_y_offset), text_font, black)
    end for
    if round (compass.heading)= 0 then
        heading_text := "360"
    else
        heading_text := intstr (round (compass.heading), 3)
    end if
    Font.Draw (heading_text, round (compass.centreX-(Font.Width(heading_text, text_font)/2)), round (compass.centreY + compass.radius*0.7), text_font, black)
end drawCompass
   

%Draws the VOR CDI, what else?
proc drawCDI(vor:VOR, plane:Plane)
    var bearing := atan2(vor.x - plane.x, vor.y - plane.y)
    var deviation := 60*sind(bearing - vor.compass.heading + 360)
    if deviation > 10 then
        Draw.Line (round (vor.compass.centreX + 10 * vor.compass.radius/20), round (vor.compass.centreY + vor.compass.radius/5), round(vor.compass.centreX + 10 * vor.compass.radius/20), round (vor.compass.centreY - vor.compass.radius/5), red)
    elsif deviation < -10 then
        Draw.Line (round (vor.compass.centreX - 10 * vor.compass.radius/20), round (vor.compass.centreY + vor.compass.radius/5), round(vor.compass.centreX - 10 * vor.compass.radius/20), round (vor.compass.centreY - vor.compass.radius/5), red)
    else
         Draw.Line (round (vor.compass.centreX + (deviation/10) * vor.compass.radius/2), round (vor.compass.centreY + vor.compass.radius/5), round(vor.compass.centreX + deviation * vor.compass.radius/20), round (vor.compass.centreY - vor.compass.radius/5), red)
    end if
end drawCDI



%Draws the TO/FROM flag, of course!
%Basically takes the cosine of the angle between the vor and then plane
%if the angle is positive, it draws TO, negative FROM, and 0 (or near 0) OFF.
proc drawToFromFlag(vor:VOR, plane:Plane)
    var text_font := Font.New ("Times New Roman:" + intstr (round (vor.compass.scale/30)))
    var bearing := atan2(vor.x - plane.x, vor.y - plane.y)
    var deviation := cosd (bearing - vor.compass.heading + 360)
    if (deviation > 0.1) then
        Font.Draw ("TO", round (vor.compass.centreX + vor.compass.radius *0.2), round (vor.compass.centreY - vor.compass.radius / 2), text_font, black)
    elsif (deviation < -0.1) then
        Font.Draw ("FROM", round (vor.compass.centreX+vor.compass.radius *0.2), round (vor.compass.centreY - vor.compass.radius / 2), text_font, black)
    else
        Font.Draw ("OFF", round (vor.compass.centreX+vor.compass.radius *0.2), round (vor.compass.centreY - vor.compass.radius / 2), text_font, red)
    end if
end drawToFromFlag

%This just draws a compass, then overlays the VOR specific stuff onto it.
proc drawVOR (vor:VOR, plane:Plane)
    drawCompass(vor.compass)
    for x: -5 .. 5
   
    %These ovals should technically correspond to 2-degree deviations, but since sine isn't linear, it doesn't actually do that.
    Draw.Oval (round (vor.compass.centreX +2*x * vor.compass.radius/20), round (vor.compass.centreY), round (vor.compass.scale/50), round (vor.compass.scale/50), black)
    end for
    drawToFromFlag (vor, plane)
    drawCDI (vor, plane)
end drawVOR

%Draws a compass with heading indicator stuff overlayed
proc drawHeadingIndicator (compass:Compass)
    drawCompass (compass)
    Draw.ThickLine (compass.centreX, round (compass.centreY + compass.radius*0.6), compass.centreX, round (compass.centreY - compass.radius * 0.6), 3, black)
    Draw.ThickLine (round (compass.centreX + compass.radius * 0.6), compass.centreY, round (compass.centreX - compass.radius * 0.6), compass.centreY, 3, black)
end drawHeadingIndicator


var compass : Compass := newCompass (0, 0, round (maxx / 2))
var vor : VOR := newVOR (compass.scale, compass.y, compass.scale, 300, 300)
var plane : Plane := newPlane (300, 300, 90, 0.1)
compass.heading := (90-plane.heading) mod 360
vor.compass.heading := compass.heading

%this just applies velocity to the aircraft to move it around.
proc movePlane
    plane.x := plane.x+plane.velocity * cosd (plane.heading)
    plane.y := plane.y+plane.velocity * sind (plane.heading)
end movePlane

var keys : array char of boolean

loop
    Input.KeyDown (keys)
    movePlane
    compass.heading := (90-plane.heading) mod 360
    %a/d rotate the vor by 0.01 degrees. Shift+a/d rotate the vor by 0.3 degrees.
    if keys ('a') and keys (KEY_SHIFT) then
        vor.compass.heading := (vor.compass.heading + 0.3)
    elsif keys ('d') and keys (KEY_SHIFT) then
        vor.compass.heading := (vor.compass.heading - 0.3)
    elsif keys ('a') then
        vor.compass.heading := (vor.compass.heading + 0.01)
    elsif keys ('d') then
        vor.compass.heading := (vor.compass.heading - 0.01)
    end if
    if vor.compass.heading <= 0 then vor.compass.heading += 360
    elsif vor.compass.heading >360 then vor.compass.heading -= 360
    end if
   
    %left/right arrows rotate the aircraft by 0.01 degrees. Shift+left/right rotate the aircraft by 0.03 degrees (rate 1)
    if keys (KEY_LEFT_ARROW) and keys (KEY_SHIFT) then
        plane.heading := (plane.heading + 0.03)
    elsif keys (KEY_RIGHT_ARROW) and keys (KEY_SHIFT) then
        plane.heading := (plane.heading - 0.03)
    elsif keys (KEY_LEFT_ARROW) then
        plane.heading := (plane.heading + 0.01)
    elsif keys (KEY_RIGHT_ARROW) then
        plane.heading := (plane.heading - 0.01)
    end if
    if plane.heading <= 0 then plane.heading += 360
    elsif plane.heading >360 then plane.heading -= 360
    end if
   
    %draw stuff
    drawVOR (vor, plane)
    drawHeadingIndicator (compass)
    Draw.FillArc (maxx div 2, round (maxy * 0.75), 5, 10, round (plane.heading - 5 mod 360), round (plane.heading + 5 mod 360), blue)
    Draw.FillOval (round (vor.x - plane.x + maxx div 2), round (vor.y - plane.y + maxy * 0.75), 5, 5, red)
    View.Update
    Time.DelaySinceLast (10)
    cls
end loop