#!/usr/bin/perl -w

use Math::Trig;
use POSIX qw/ceil/;
##
# PEEVE 2(To) Turtle
# Converts a PEEVE script to a Turtle Script.
##

#FILENAME Variables
$FILE=$ARGV[0];
$FILEEXT=$FILEEXT= ($ARGV[0] =~ /([^.]+)$/)[0];
$FILEOUT=0; #If 0, print to stdOut, if 1, print to file specified by ARGV[1]

#Initalisation checks
#Check to see if there is at least 1 argument
if($FILEEXT ne "peeve")
{
    #Print error message and close if there is no arguments
    print("Invalid filetype in file argument.");
    exit;
}

if($#ARGV == 1)
{
    $FILEOUT=1;
}

#Turtle Variables
$xPos=200; #The current x position of the turtle
$yPos=200; #The current y position of the turtle
$dir=0; #The direction in degrees, that the turtle is facing.


#File Variables
$lineCount=0; #Keeps track of what line in the file we're at. Used for error checking.

#---Main---#
#Open the file, or close if not found.
if($#ARGV < 0)
{
    $FILE=*STDIN;
}
else
{
    open(FILE) or die("File not found.");
}
#@output is the array which holds the text to be written to the svg file.
#Add the header information onto the output

#Iterate through the file line by line
foreach $line (<FILE>)
{
    $lineCount=$lineCount + 1;
    preProc($line);
    @line = split(' ', $line);
    if($line ne "\n")
    {
        #Check syntax
        checkSyntax(@line);

    }
    if(@line[0] eq "LINE")
    {
        drawLine(@line[1], @line[2], @line[3], @line[4]);
    }
    elsif(@line[0] eq "POLYGON")
    {
        drawPolygon(@line[1], @line[2], @line[3], @line[4],@line[5]);
    }
    elsif(@line[0] eq "CIRCLE")
    {
        drawCircle(@line[1], @line[2], @line[3]);
    }
    #Else we have style commands.
    else
    {
        push(@output, $line);
    }
}

#Output to file
if($FILEOUT == 1)
{
    open(MYFILE, ">${ARGV[1]}.turtle");
    print MYFILE @output;
    close(MYFILE);
}
else
{
    print @output;
}
#Draws line
#Accepts 4 arguments:
#Starting Coordinates x1,y1
#Ending Coordinates x2, y2
sub drawLine
{
    #Move to start coordinates
    moveTurtle($xPos, $yPos, @_[0], @_[1]);
    #PENDOWN
    push(@output, "PENDOWN\n");
    moveTurtle(@_[0], @_[1], @_[2], @_[3]);
    #PENUP
    push(@output, "PENUP\n");
}

#Draws polygon
sub drawPolygon
{
    $init_angle=@_[2];
    $n_sides=@_[3];
    $side_length=@_[4];

    #Calculate turning angle
    $turningAngle=180-((180*($n_sides-2))/($n_sides));
    #Move to start coordinates
    moveTurtle($xPos, $yPos, $_[0], $_[1]);
    #Rotate to init_angle
    rotate($init_angle);
    #PENDOWN
    push(@output, "PENDOWN\n");
    #Give our turtle a little workout
    for($count = 0; $count < $n_sides; $count++)
    {
        push(@output, "FORWARD ${side_length}\n");
        rotate($dir+$turningAngle);
    }
    #PENUP
    push(@output, "PENUP\n");
}

#Draws circle
sub drawCircle
{
    $radius=@_[2];
    $circumference=2*$radius*pi;
    #Polygon variables
    $init_angle=0;

    #Calculate number of sides. If the radius is less than 4, the side length must also be calculated.
    if($radius < 4)
    {
        $side_length=2*$radius*sin(deg2rad(22.5));
        $n_sides = 8; #Minimum of 8 sides.
    }
    else
    {
        $side_length=3; #This is the maximum side length allowed.
        $n_sides = ((360) / (2 * rad2deg(asin(1.5/$radius))));
        #$n_sides = ceil($circumference / 3)
    }

    #Move turtle to the start + the radius to the left and half side length down
    moveTurtle($xPos, $yPos, ($_[0]-$radius), ($_[1]+($side_length/2)));
    #Start position is our current position, since we moved here above.
    #Call drawPolygon to draw the circle.
    drawPolygon($xPos, $yPos, 0, $n_sides, $side_length);
}

#Moves the turtle from point A to point B
sub moveTurtle
{
    $x1=@_[0];
    $y1=@_[1];
    $x2=@_[2];
    $y2=@_[3];


    $angle=0;
    $forwardLength=0;
    #If we're moving to the right
    if($x2 > $x1)
    {
        print "In first/second quad";
        #If we're moving up (First Quadrant)
        if($y2 > $y1)
        {
            print "First Quad\n";
            $angle=rad2deg(atan(($y2-$y1)/($x2-$y1)));
            #Rotate the turtle
            rotate(($angle + 90));
            #Pythagoras to get length of forward
            $forwardLength=sqrt((($x2-$x1)** 2) + (($y2-$y1)**2));
            push(@output, "FORWARD ${forwardLength}\n");
        }
        #If we're moving up (Second Quadrant)
        elsif($y1 > $y2)
        {
            print "Second Quad\n";
            $angle=rad2deg(atan(($x2-$x1)/($y1-$y2)));
            rotate($angle);
            #Pythagoras to get length of forward
            $forwardLength=sqrt((($x2-$x1)** 2) + (($y1-$y2)**2));
            push(@output, "FORWARD ${forwardLength}\n");
        }
        #We're moving to the right directly on the x axis.
        elsif($y1 == $y2)
        {
            print "Direct Right\n";
            #Rotate to 90 degrees (EAST)
            rotate(90);
            push(@output, "FORWARD @{[$x2-$x1]}\n");
        }
    }
    #If we're moving to the left
    elsif($x1 > $x2)
    {
        #If we're moving up (Third)
        if($y2 > $y1)
        {
            print "Fourth Quad\n";
            $angle=rad2deg(atan(($x1-$x2)/($y2-$y1)));
            rotate(($angle + 180)); #Add 180 as offset to Fourth Quadrant
            #Pythagoras to get length of forward
            $forwardLength=sqrt((($x1-$x2)** 2) + (($y2-$y1)** 2));
            push(@output, "FORWARD ${forwardLength}\n");
        }
        #If we're moving up (Third Quadrant)
        elsif($y1 > $y2)
        {
            print "Third Quad\n";
            $angle=rad2deg(atan(($y1-$y2)/($x1-$x2)));
            rotate(($angle + 270)); #Add 270 as offset to Third Quadrant
            #Pythagoras to get length of forward
            $forwardLength=sqrt((($x1-$x2)** 2) + (($y1-$y2)** 2));
            push(@output, "FORWARD ${forwardLength}\n");
        }
        #We're moving to the left directly on the x axis.
        else
        {
            print "Direct Left\n";
            #Rotate to 270 degrees (WEST)
            rotate(270);
            push(@output, "FORWARD @{[$x1-$x2]}\n");
        }
    }
    #We're moving directly up or down the y axis.
    else
    {
        #Move down
        if($y2 > $y1)
        {
            print "Direct Up\n";
            rotate(180); #Rotate to 0 degrees
            push(@output, "FORWARD @{[$y2-$y1]}\n");
        }
        #Move up
        elsif($y1 > $y2)
        {
            rotate(0); #Rotate to 180 degrees
            push(@output, "FORWARD @{[$y1-$y2]}\n");
        }
        #May as well account for all possibilities.
        else
        {
            #No change in position, really?
        }
    }
    $xPos = $x2;
    $yPos = $y2;
}

#Preprocesses the lines read from the peeve script.
#Chops new lines and comments.
sub preProc
{
    #Remove comments
    $_[0] =~ s/#.*$//;
}

#Used for smart rotations of the turtle.
#Accepts the new direction the turtle will face as parameter.
sub rotate
{
    $newDir=@_[0];
    if($dir != $newDir)
    {
        #Make smart turns :D
        if($dir > $newDir)
        {
            if(($dir - $newDir) > 180)
            {
                push(@output, "RIGHT @{[360 - $dir + $newDir]}\n");
            }
            else
            {
                push(@output, "LEFT @{[$dir - $newDir]}\n");
            }
        }
        else
        {
            if(($newDir - $dir) > 180)
            {
                push(@output, "LEFT @{[$dir + 360-$newDir]}\n");
            }
            else
            {
                push(@output, "RIGHT @{[$newDir - $dir]}\n");
            }
        }
        $dir = $newDir;
    }
}

sub checkSyntax
{
    #TODO: Check each invidual argument...
    @lineRead=@_;
    $lineLength = @lineRead;
    #Check command
    if(@lineRead[0] ne "LINE" and @lineRead[0] ne "POLYGON" and @lineRead[0] ne "CIRCLE" and @lineRead[0] ne "SETSTYLE" and @lineRead[0] ne "DEFINESTYLE")
    {
        print "Syntax error (Invalid Command: ${lineRead[0]}) at line ${lineCount} of ${FILE}. Terminating execution.\n";
        exit;
    }

    if(@lineRead[0] eq "LINE" and $lineLength != 5)
    {
        print "Syntax error at line (Invalid Arguments) ${lineCount} of ${FILE}.\n Terminating execution.\n";
        exit;
    }
    elsif(@lineRead[0] eq "POLYGON" and $lineLength != 6)
    {
        print "Syntax error at line (Invalid Arguments) ${lineCount} of ${FILE}.\n Terminating execution.\n";
        exit;
    }
    elsif(@lineRead[0] eq "CIRCLE" and $lineLength != 4)
    {
        print "Syntax error at line (Invalid Arguments) ${lineCount} of ${FILE}.\n Terminating execution.\n";
        exit;
    }
}