--Load and save the bmp formats used by DEFCON.
local t = {}
local assert = assert
local print = print
local error = error
local table = table
local math = math
local love = assert( love )



local test = {}

function test.load( filename )
  local imgd = love.image.newImageData( filename )
  print( "LOADING BITMAP: ", filename, imgd:getSize(), imgd:getFormat(), imgd:getDimensions() )
  local img = love.graphics.newImage( imgd )
  img:setFilter( "nearest", "nearest" )
  return img, imgd
end

function test.bitmapToWorld( x, y )
  local w, a = 360.0, 600.0 / 800.0
  local h = 360.0 * a
  x = w * ( x - 800 ) / 800 - w / 2 + 360
  y = h * ( y - 600 ) / 600 + 180
  return x, y
end

function test.compareData( a, b )
  if a == b then return true end
  print( "lengths:", a:len(), b:len() )
  local errors = 0
  for i = 1, math.min( a:len(), b:len() ) do
    local a, b = a:sub( i, i ), b:sub( i, i )
    if a ~= b then
      errors = errors + 1
      print( "mismatch:", errors, i, string.byte( a ), string.byte( b ) )
    end
    if errors > 1000 then break end
  end
  error( "test failed. output bitmap does not match!" )
end

function test.worldToBitmap( x, y )
  x = 800 * ( x + 180 ) / 360
  y = 600 + 800 * ( y - 180 ) / 360
  return x, y
end

local function getHeader( filename )
  local offset = 2 + love.data.unpack( "<I4", assert(love.filesystem.read( "data", filename, 14 )), 11 )
  local header, size = assert( love.filesystem.read( filename, offset ) )
  return header
end

--BGR24 format. Takes the input of Love2D's data:getPixel( x, y )
--on paper we would only care about one channel because all of these images are grayscale,
--but a few of the pixels in the game's default territories are not exactly gray,
--so we do it like this to make sure our output is byte-faithful when saving an unmodified vanilla map
local function bgrChar( r, g, b )
  return string.char( math.floor( b * 255 ), math.floor( g * 255 ), math.floor( r * 255 ) )
end


local formats = {
  ["africa"]     = {
    header = getHeader( "data/earth/africa.bmp" ),
    w = 512,
    h = 285,
  },
  ["sailable"]     = {
    header = getHeader( "data/earth/sailable.bmp" ),
    w = 512,
    h = 285,
    --technically this information is in the header already but I don't want to write code to parse it we only use one palette ever
    palette = {
      [0] = 0,
      [8] = 1,
      [20] = 2,
      [33] = 3,
      [49] = 4,
      [90] = 5,
      [139] = 6,
      [169] = 7,
      [189] = 8,
      [206] = 9,
      [214] = 10,
      [222] = 11,
      [231] = 12,
      [239] = 13,
      [247] = 14,
      [255] = 15
    },
  },
  ["travel"]     = {
    header = getHeader( "data/earth/travel_nodes.bmp" ),
    w = 800,
    h = 400,
  },
  ["ai"]     = {
    header = getHeader( "data/earth/ai_markers.bmp" ),
    w = 512,
    h = 285,
  },
}

function formats.ai:test( )
  print "testing ai nodes"
  local filename = "data/earth/ai_markers.bmp" 
  local img, imgd = test.load( filename )
  local idx = 1
  local nodes = {}
  for x = 0, 511 do
    for y = 0, 284 do
      local r, g = imgd:getPixel( x, 284 - y )
      if r > 0.5 or g > 0.5 then
        local long = x * (360 / imgd:getWidth()) - 180
        local lat = y * (200 / img:getHeight()) - 100
        local attacking = (r > 0.5)
        local node = {x = long, y = lat, attacking = attacking, idx = idx}
        print( "ai marker", idx, x, y, long, lat )
        nodes[ idx ] = node
        idx = idx + 1
      end
    end
  end

  local encodedString = self:encode( nodes )
  love.filesystem.write( "ai_markers.bmp", encodedString )

  local eimg, eimgd = test.load( "ai_markers.bmp" ) --the one we just saved
  for x = 0, 511 do
    for y = 0, 284 do
      local r, g = imgd:getPixel( x, 284 - y )
      local er, eg = eimgd:getPixel( x, 284 - y )
      if math.max( r, g, er, eg ) > 0.5 then
        print( "node pixel: ", x, 284 - y, r, g, er, eg )
        assert( ( r > 0.5 and er > 0.5 ) or ( g > 0.5 and eg > 0.5 ), "ai marker mismatch!" )
      end
    end
  end
  print( "ai markers OK" )
end

function formats.ai:encode( data )

  --set up bitmap as an array of pixels
  local w, h = self.w, self.h
  local size = 2 + self.w * self.h
  local bitmap = { self.header:sub( 1, -3 ) }
  for j = 2, size do bitmap[j] = 0 end


  for i, point in ipairs( data ) do
    local wx, wy = point.x, point.y
    --get bitmap coordinates
    local x = math.floor(self.w * (wx + 180) / 360)
    --idk why exactly I need to round the value here instead of truncating it
    local y = math.floor(0.5 + self.h * (wy + 100) / 200)
    --get index into byte array
    local idx = 2 + y * self.w + x
    --in-editor we could have two points in the same place, possibly of the same or different types
    --in case we miss something upstream, don't corrupt these duplicate points,
    --just saturate the attack/defense value
    if bitmap[idx] == 0 then bitmap[idx] = { attack = point.attacking, place = not(point.attacking)}
    else 
      bitmap[idx].attack = bitmap[idx].attack or point.attacking
      bitmap[idx].place  = bitmap[idx].place  or not(point.attacking)
    end
  end

  --now map pixels to 3-byte strings
  for j = 2, size do
    if   bitmap[j] == 0
    then bitmap[j] = "\0\0\0"
    else bitmap[j] = string.char( 0, bitmap[j].place and 0xff or 0, bitmap[j].attack and 0xff or 0 ) --bgr24
    end
  end

  return table.concat( bitmap )
end

function formats.travel:test()
  print "testing travel nodes"
  local filename = "data/earth/travel_nodes.bmp" 
  local img, imgd = test.load( filename )
  local nodes = {}
  local n = 1
  for x = 0, 799 do
    for y = 0, 399 do
      if imgd:getPixel( x, 399 - y ) > 0 then
        local long, lat = test.bitmapToWorld( x, y )
        nodes[n] = {x = long, y = lat, idx = n}
        print( "read:", n, long, lat, x, y )
        n = n + 1
      end
    end
  end

  print( "loaded ", n, "nodes" )
  local encodedString = self:encode( nodes )
  test.compareData( love.filesystem.read( filename ), encodedString )
  love.filesystem.write( "travel_nodes.bmp", encodedString )
  print( "travel nodes OK" )
end

--Sparse bitmap with a few white pixels.
function formats.travel:encode( points )
  --set up bitmap as an array of 8-bit pixels
  local w, h = self.w, self.h
  local size = 2 + w * h
  local bitmap = { self.header }
  for j = 2, size do bitmap[j] = 0 end

  --write white pixels
  for i, point in ipairs( points ) do
    local wx, wy = point.x, point.y
    -- get bitmap coordinates:
    local x = 800 * ( wx + 180 ) / 360
    local y = 600 + 800 * ( wy - 180 ) / 360
    local offset = math.floor( y * self.w + x - 2 )
    --1 := white
    bitmap[offset] = 1
  end

  --fold into 4-bit pixel array
  local nybbles = { bitmap[1] }
  for j = 2, size / 2 do
    local a, b = bitmap[ 2 * j - 2 ], bitmap[ 2 * j - 1 ]
    nybbles[j] = string.char( 16 * a + b )
  end

  return table.concat( nybbles )
end

function formats.sailable:test()
  print "testing sailable"
  local filename = "data/earth/sailable.bmp" 
  local img, imgd = test.load( filename )
  local encoded = self:encode( imgd )
  love.filesystem.write( "sailable_out.bmp", encoded )
  test.compareData( love.filesystem.read( filename ), encoded )
  print "sailable OK"
end


do --sailable
  
  local reversePalette = {}
  for eight, four in pairs( formats.sailable.palette ) do
    reversePalette[ four ] = eight
  end
  
  --take the red channel in float [0, 1] format
  --expand it to a byte, then quantize it to 4 bits
  --according to the sailable palette
  local function sailableQuantize( r )
    if r == 0 then return 0 end
    if r >= 1 then return 15 end
    r = math.floor( r * 255 )
    
    for four = 1, #reversePalette do
      if reversePalette[ four ] > r then return four end
    end
    
    error( "Could not quantize sailable.bmp!" )
  end

  function formats.sailable:encode( data )
    local w, h = self.w, self.h
    local bytes = { self.header:sub( 1, -2 ) }
    local i = 2

    --y coordinates are written top to bottom
    for y = h - 1, 0, -1 do
      for x = 0, w - 1 do
        bytes[i] = sailableQuantize( data:getPixel(x, y) )
        i = i + 1
      end  
    end

    --fold into 4-bit pixel array
    local nybbles = { bytes[1] }
    for j = 2, #bytes / 2 do
      local a, b = bytes[ 2 * j ], bytes[ 2 * j + 1 ]
      nybbles[j] = string.char( 16 * a + b )
    end

    return table.concat( nybbles )
  end

  function formats.africa:test()
    print "testing africa"
    local filename = "data/earth/africa.bmp" 
    local img, imgd = test.load( filename )
    local encoded = self:encode( imgd )
    love.filesystem.write( "africa_out.bmp", encoded )
    test.compareData( love.filesystem.read( filename ), encoded )
    print "africa OK"
  end
end

function formats.africa:encode( data )
  local w, h = self.w, self.h
  local bytes = { self.header:sub( 1, -3 ) }
  local i = 2

  --y coordinates are written top to bottom
  for y = h - 1, 0, -1 do
    for x = 0, w - 1 do
      bytes[i] = bgrChar( data:getPixel(x, y) )
      i = i + 1
    end  
  end
  return table.concat( bytes )
end

function t.load( filename )
  local imgd = love.image.newImageData( filename )
  print( "LOADING BITMAP: ", filename, imgd:getSize(), imgd:getFormat(), imgd:getDimensions() )
  local img = love.graphics.newImage( imgd )
  img:setFilter( "nearest", "nearest" )
  return img, imgd
end

function t.save( data, format )
  return assert(formats[format]):encode( data )
end

--convenience
formats.territory = formats.africa
for fmt, tbl in pairs( formats ) do
  t[fmt] = function( data ) return tbl:encode( data ) end
  --TESTING
  --tbl:test()
end

return t