#
# = ImageVoodoo
# == Description
#
# ImageVoodoo is an ImageScience-API-compatible image manipulation library for 
# JRuby.  
#
# == Examples
#
# === Simple block-based examples
#
#    ImageVoodoo.with_image(ARGV[0]) do |img|
#      img.cropped_thumbnail(100) { |img2| img2.save "CTH.jpg" }
#      img.with_crop(100, 200, 400, 600) { |img2| img2.save "CR.jpg" }
#      img.thumbnail(50) { |img2| img2.save "TH.jpg" }
#      img.resize(100, 150) do |img2|
#        img2.save "HEH.jpg"
#        img2.save "HEH.png"
#      end
#    end
#
# === Non-block return (not image_science compatible)
#
# img = ImageVoodoo.with_image(ARGV[0])
# negative_img = img.negative
#
class ImageVoodoo
  include Java

  JFile = java.io.File

  # FIXME: This has an issue when used in test/unit where the classcastexception
  #   is throwing the stack trace to output.  This does not happen when used
  #   directly.  Not sure....
  # gae and awt define the technology-specific methods and more importantly
  # all the *_impl methods which you will see referenced in this file.
  begin
     require 'image_voodoo/gae'
  rescue
     require 'image_voodoo/awt'
  end

  def initialize(src)
    @src = src
  end

  #
  # Adjusts the brightness of each pixel in image by the following formula:
  # new_pixel = pixel * scale + offset
  #
  def adjust_brightness(scale, offset)
    image = guard { adjust_brightness_impl(scale, offset) }
    block_given? ? yield(image) : image
  end

  #
  # Converts rgb hex color value to an alpha value an yields/returns the new 
  # image.
  #
  def alpha(rgb)
    target = guard { alpha_impl(rgb) }
    block_given? ? yield(target) : target
  end

  # 
  # Get current image bytes as a String using provided format. Format parameter
  # is the informal name of an image type - for instance,
  # "bmp" or "jpg". If the backend is AWT the types available are listed in
  # javax.imageio.ImageIO.getWriterFormatNames()
  # 
  def bytes(format)
    java_bytes = guard { bytes_impl(format) }
    String.from_java_bytes java_bytes
  end

  #
  # Creates a square thumbnail of the image cropping the longest edge to 
  # match the shortest edge, resizes to size, and yields/returns the new image. 
  #
  def cropped_thumbnail(size)
    l, t, r, b, half = 0, 0, width, height, (width - height).abs / 2
    l, r = half, half + height if width > height
    t, b = half, half + width if height > width

    target = with_crop(l, t, r, b).thumbnail(size)
    block_given? ? yield(target) : target
  end

  #
  # Flips the image horizontally and yields/returns the new image.
  #
  def flip_horizontally
    target = guard { flip_horizontally_impl }
    block_given? ? yield(target) : target
  end

  #
  # Flips the image vertically and yields/returns the new image.
  #
  def flip_vertically
    target = guard { flip_vertically_impl }
    block_given? ? yield(target) : target
  end

  # 
  # Creates a grayscale version of image and yields/returns the new image.
  #
  def greyscale
    target = guard { greyscale_impl }
    block_given? ? yield(target) : target
  end
  alias_method :grayscale, :greyscale

  # 
  # Creates a negative and yields/returns the new image.
  #
  def negative
    target = guard { negative_impl }
    block_given? ? yield(target) : target
  end

  #
  # Resizes the image to width and height and yields/returns the new image. 
  #
  def resize(width, height)
    target = guard { resize_impl(width, height) }
    block_given? ? yield(target) : target
  rescue NativeException => ne
    raise ArgumentError, ne.message
  end

  # 
  # Saves the image out to path. Changing the file extension will convert 
  # the file type to the appropriate format. 
  #
  def save(file)
    format = File.extname(file)
    return false if format == ""
    format = format[1..-1].downcase
    guard { save_impl(format, JFile.new(file)) }
    true
  end

  #
  # Resize (scale) the current image by the provided ratio and yield/return
  # the new image.
  #
  def scale(ratio)
    new_width, new_height = (width * ratio).to_i, (height * ratio).to_i
    target = resize(new_width, new_height)
    block_given? ? yield(target) : target
  end

  #
  # Creates a proportional thumbnail of the image scaled so its longest 
  # edge is resized to size and yields/returns the new image. 
  #
  def thumbnail(size)
    target = scale(size.to_f / (width > height ? width : height))
    block_given? ? yield(target) : target
  end

  #
  # Crops an image to left, top, right, and bottom and then yields/returns the 
  # new image. 
  #
  def with_crop(left, top, right, bottom)
    image = guard { with_crop_impl(left, top, right, bottom) }
    block_given? ? yield(image) : image
  end

  # 
  # A top-level image loader opens path and then yields/returns the image.
  #
  def self.with_image(file)
    raise ArgumentError, "file does not exist" unless File.file?(file)
    image = guard { with_image_impl(JFile.new(file)) }
    image && block_given? ? yield(image) : image
  end

  # 
  # A top-level image loader reads bytes and then yields/returns the image.
  #
  def self.with_bytes(bytes)
    bytes = bytes.to_java_bytes if String === bytes
    image = guard { with_bytes_impl(bytes) }
    block_given? ? yield(image) : image
  end

  class << self
    alias_method :with_image_from_memory, :with_bytes
  end

  #
  # *_impl providers only need provide the implementation if it can
  # support it.  Otherwise, this method will detect that the method is 
  # missing.
  #
  def self.guard(&block)
    begin
      return block.call
    rescue NoMethodError => e
      "Unimplemented Feature: #{e}"
    end
  end
  def guard(&block)
    ImageVoodoo.guard(&block)
  end

  #
  # Returns the height of the image, in pixels. 
  #
  def height
    @src.height
  end

  #
  # Returns the width of the image, in pixels. 
  #
  def width
    @src.width
  end

  #
  # Returns the underlying Java class associated with this object. Note:
  # Depending on whether you are using AWT or GAE/J you will get a totally
  # different Java class.  So caveat emptor!
  #
  def to_java
    @src
  end
end