###############################################################################
## burn-console.ps1
##
## Create a fire effect in PowerShell, using the Console text buffer as the 
## rendering surface.
##
## Great overview of the fire effect algorithm here: 
## http://freespace.virgin.net/hugo.elias/models/m_fire.htm
##
###############################################################################

function main
{
    write-debug "ENTER main"
    ## Rather than a simple red fire, we'll introduce oranges and yellows
    ## by including Yellow as one of the base colours
    $colours = "Yellow","Red","DarkRed","Black"
    
    ## The four characters that we use to dither with, along with the 
    ## percentage of the foreground colour that they show
    $dithering = [System.Text.Encoding]::Unicode.GetString(@(136, 37, 147, 37, 146, 37, 145, 37)).ToCharArray()
    $ditherFactor = 1,0.75,0.5,0.25
    
    ## Hold the palette.  We actually store each entry as a BufferCell,
    ## since we need to retain a foreground colour, background colour,
    ## and dithering character.
    [System.Management.Automation.Host.BufferCell[]] $palette = `
        new-object System.Management.Automation.Host.BufferCell[] 256
    
    ## Resize the console to 70, 61 so we have a consistent buffer
    ## size for performance comparison.
    $bufferSize = new-object System.Management.Automation.Host.Size 70,61
    $host.UI.RawUI.WindowSize = $bufferSize

    ## Retrieve some commonly used dimensions
    $windowWidth = $host.UI.RawUI.WindowSize.Width
    $windowHeight = $host.UI.RawUI.WindowSize.Height
    $origin = `
        new-object System.Management.Automation.Host.Coordinates 0,0
    $dimensions = `
        new-object System.Management.Automation.Host.Rectangle `
            0,0,$windowWidth,$windowHeight
    
    ## Create our random number generator
    $random = new-object Random
    $workingBuffer = new-object System.Int32[] ($windowHeight * $windowWidth)
    $screenBuffer = new-object System.Int32[] ($windowHeight * $windowWidth)

    clear-host
    
    ## Generate the palette
    generatePalette
    # displayPalette
    # return;

    ## Update the buffer, then update the screen until the user presses a key.  
    ## Keep track of the total time and frames generated to let us display
    ## performance statistics.
    $frameCount = 0
    while($true)
    {
        $totalTime = measure-command {            
            updateBuffer
            updateScreen
            $frameCount++
        }

        ## Restrict to 100FPS
        if($totalTime.TotalMilliseconds -lt 10)
        {
            Start-Sleep -Milliseconds (10 - $totalTime.TotalMilliseconds)
        }
    }
    
    ## Clean up and exit
    $host.UI.RawUI.ForegroundColor = "Gray"
    $host.UI.RawUI.BackgroundColor = "Black"
    
    write-host
    write-host "$($frameCount / $totalTime.TotalSeconds) frames per second."
    write-debug "EXIT"
}

## Update a back-buffer to hold all of the information we want to display on
## the screen.  To do this, we first re-generate the fire pixels on the bottom 
## row.  With that done, we visit every pixel in the screen buffer, and figure
## out the average heat of its neighbors.  Once we have that average, we move
## that average heat one pixel up.
function updateBuffer
{
    ## This function takes the most of our time, so we'll do it inline.
    ## Inputs:
    ##  Window Height
    ##  Window Width
    ##  Screen Buffer
    ##  Random Number Generator
    ## Output:
    ##  Working Buffer
    
    [System.Collections.ArrayList] $inputs = `
        new-object System.Collections.ArrayList
    [void] $inputs.Add([int] $windowHeight)
    [void] $inputs.Add([int] $windowWidth)
    [void] $inputs.Add([int[]] $screenBuffer)
    [void] $inputs.Add([System.Random] $random)
    
    $code = @"
    public static Object UpdateBuffer(System.Collections.ArrayList arg)
    {
        // Unpack the inputs from our input object
        int windowHeight = (int) ((System.Collections.ArrayList) arg)[0];
        int windowWidth = (int) ((System.Collections.ArrayList) arg)[1];
        int[] screenBuffer = (int[]) ((System.Collections.ArrayList) arg)[2];
        Random random = (Random) ((System.Collections.ArrayList) arg)[3];
        
        // Start fire on the last row of the screen buffer
        for(int column = 0; column < windowWidth; column++)
        {
            // There is an 80% chance that a pixel on the bottom row will
            // start new fire.
            if(random.NextDouble() >= 0.20)
            {
                // The chosen pixel gets a random amount of heat.  This gives
                // us a lot of nice colour variation.
                screenBuffer[(windowHeight - 2) * (windowWidth) + column] = 
                    (int) (random.NextDouble() * 255);
            }
        }
        
        int[] tempWorkingBuffer = (int[]) screenBuffer.Clone();
        
        // Propigate the fire
        int baseOffset = windowWidth + 1;
        for(int row = 1; row < (windowHeight - 1); row++)
        {
            for(int column = 1; column < (windowWidth - 1); column++)
            {
                // Get the average colour from the four pixels surrounding
                // the current pixel
                double colour = 
                    (
                        screenBuffer[baseOffset] + 
                        screenBuffer[baseOffset - 1] + 
                        screenBuffer[baseOffset + 1] + 
                        screenBuffer[baseOffset + windowWidth]
                     ) / 4.0;

                // Cool it off a little.  We apply uneven cooling, otherwise
                // the cool dark red tends to stretch up for too long.
                if(colour > 0)
                {
                    if(colour > 70)
                    { 
                        colour -= 1; 
                    }
                    else
                    {
                        colour -= 3;
                        
                        if(colour < 1)
                        {
                            colour = 0;
                        }
                        else if(colour < 20)
                        {
                            colour -= 1;
                        }
                    }
                }

                // Store the result into the previous row -- that is, one buffer 
                // cell up.
                tempWorkingBuffer[baseOffset - windowWidth] = (int) colour;
                baseOffset ++;
            }
            
            baseOffset += 2;
        }

        return tempWorkingBuffer;
    }
"@
    $returnClass = Add-Type -MemberDefinition $code -Name BurnConsoleUtils1 -PassThru 
    $returned = $returnClass::UpdateBuffer($inputs)
    $SCRIPT:workingBuffer = $returned
}

## Take the contents of our working buffer and blit it to the screen
## We do this in one highly-efficent step (the SetBufferContents) so that
## users don't see each individial pixel get updated.
function updateScreen
{
    write-debug "ENTER updateScreen"
    
    ## This function takes up a lot of time, so we'll do it inline.
    ## Inputs:
    ##  host.UI.RawUI
    ##  palette
    ##  workingBuffer
    ##  origin
    ##  dimensions
    ##  windowHeight
    ##  windowWidth
    ## Output:
    ##  None
    
    [System.Collections.ArrayList] $inputs = `
        new-object System.Collections.ArrayList
    [void] $inputs.Add([System.Management.Automation.Host.PSHostRawUserInterface] $host.UI.RawUI)
    [void] $inputs.Add([System.Management.Automation.Host.BufferCell[]] $palette)
    [void] $inputs.Add([int[]] $workingBuffer)
    [void] $inputs.Add([System.Management.Automation.Host.Coordinates] $origin)
    [void] $inputs.Add([System.Management.Automation.Host.Rectangle] $dimensions)
    [void] $inputs.Add([int] $windowHeight)
    [void] $inputs.Add([int] $windowWidth)
    
    $code = @"
    public static void UpdateScreen(System.Collections.ArrayList arg)
    {
        System.Management.Automation.Host.PSHostRawUserInterface rawUI = 
            (System.Management.Automation.Host.PSHostRawUserInterface)
                ((System.Collections.ArrayList) arg)[0];
        System.Management.Automation.Host.BufferCell[] palette =
            (System.Management.Automation.Host.BufferCell[]) 
                ((System.Collections.ArrayList) arg)[1];
        int[] workingBuffer = 
            (int[]) ((System.Collections.ArrayList) arg)[2];
        System.Management.Automation.Host.Coordinates origin = 
            (System.Management.Automation.Host.Coordinates)
                ((System.Collections.ArrayList) arg)[3];
        System.Management.Automation.Host.Rectangle dimensions = 
            (System.Management.Automation.Host.Rectangle)
                ((System.Collections.ArrayList) arg)[4];
        int windowHeight = (int) ((System.Collections.ArrayList) arg)[5];
        int windowWidth = (int) ((System.Collections.ArrayList) arg)[6];

        // Create a working buffer to hold the next screen that we want to
        // create.
        System.Management.Automation.Host.BufferCell[,] nextScreen = 
            rawUI.GetBufferContents(dimensions);
        
        // Go through our working buffer (that holds our next animation frame)
        // and place its contents into the buffer that we will soon blast into
        // the real RawUI
        for(int row = 0; row < windowHeight; row++)
        {
            for(int column = 0; column < windowWidth; column++)
            {
                nextScreen[row, column] = palette[workingBuffer[(row * windowWidth) + column]];
            }
        }
        
        // Bulk update the RawUI's buffer with the contents of our next screen
        rawUI.SetBufferContents(origin, nextScreen);
    }
"@

    $returnClass = Add-Type -MemberDefinition $code -Name BurnConsoleUtils2 -PassThru 
    $returnClass::UpdateScreen($inputs)

    ## And finally update our representation of the screen buffer to hold
    ## what actually is on the screen
    $SCRIPT:screenBuffer = $workingBuffer.Clone()

    write-debug "EXIT"
}

## Generates a palette of 256 colours.  We create every combination of 
## foreground colour, background colour, and dithering character, and then
## order them by their visual intensity.
##
## The visual intensity of a colour can be expressed by the NTSC luminance 
## formula.  That formula depicts the apparent brightness of a colour based on 
## our eyes' sensitivity to different wavelengths that compose that colour.
## http://en.wikipedia.org/wiki/Luminance_%28video%29
function generatePalette
{
    ## The apparent intensities of our four primary colours.
    ## However, the formula under-represents the intensity of our straight
    ## red colour, so we artificially inflate it.
    $luminances = 225.93,106.245,38.272,0
    $apparentBrightnesses = @{}

    ## Cycle through each foreground, background, and dither character
    ## combination.  For each combination, find the apparent intensity of the 
    ## foreground, and the apparent intensity of the background.  Finally,
    ## weight the contribution of each based on how much of each colour the
    ## dithering character shows.
    ## This provides an intensity range between zero and some maximum.
    ## For each apparent intensity, we store the colours and characters
    ## that create that intensity.
    $maxBrightness = 0
    for($fgColour = 0; $fgColour -lt $colours.Count; $fgColour++)
    {
        for($bgColour = 0; $bgColour -lt $colours.Count; $bgColour++)
        {
            for($ditherCharacter = 0; 
                $ditherCharacter -lt $dithering.Count; 
                $ditherCharacter++)
            {
                $apparentBrightness = `
                    $luminances[$fgColour] * $ditherFactor[$ditherCharacter] +
                    $luminances[$bgColour] *
                        (1 - $ditherFactor[$ditherCharacter])
                    
                if($apparentBrightness -gt $maxBrightness) 
                { 
                    $maxBrightness = $apparentBrightness 
                }
                    
                $apparentBrightnesses[$apparentBrightness] = `
                    "$fgColour$bgColour$ditherCharacter"
            }
       }
    }

    ## Finally, we normalize our computed intesities into a pallete of
    ## 0 to 255.  If a given intensity is 30% towards our maximum intensity,
    ## then it should be in the palette at 30% of index 255.
    $paletteIndex = 0
    foreach($key in ($apparentBrightnesses.Keys | sort))
    {
        $keyValue = $apparentBrightnesses[$key]
        do
        {
            $character = $dithering[[Int32]::Parse($keyValue[2])]
            $fgColour = $colours[[Int32]::Parse($keyValue[0])]
            $bgColour = $colours[[Int32]::Parse($keyValue[1])]
            
            $bufferCell = `
                new-object System.Management.Automation.Host.BufferCell `
                    $character,
                    $fgColour,
                    $bgColour,
                    "Complete"
                    
            $palette[$paletteIndex] = $bufferCell
            $paletteIndex++
        } while(($paletteIndex / 256) -lt ($key / $maxBrightness))
    }
}

## Dump the palette to the screen.
function displayPalette
{
    for($paletteIndex = 254; $paletteIndex -ge 0; $paletteIndex--)
    {
        $bufferCell = $palette[$paletteIndex]
        $fgColor = $bufferCell.ForegroundColor
        $bgColor = $bufferCell.BackgroundColor
        $character = $bufferCell.Character

        $host.UI.RawUI.ForegroundColor = $fgColor
        $host.UI.RawUI.BackgroundColor = $bgColor
        write-host -noNewLine $character
    }
    
    write-host
}

. main