class SFML::SpriteSheet

# File lib/sfml/graphics/sprite_sheet.rb, line 23
def self.load(path, frame_size:, padding: 0, margin: 0, smooth: true)
  new(texture: Texture.load(path, smooth: smooth),
      frame_size: frame_size, padding: padding, margin: margin)
end

# File lib/sfml/graphics/sprite_sheet.rb, line 28
def initialize(texture:, frame_size:, padding: 0, margin: 0)
  @texture = texture
  fw, fh = _pair(frame_size)
  pw, ph = _pair(padding)
  mw, mh = _pair(margin)

  tex_w, tex_h = texture.size.x, texture.size.y
  @cols = (tex_w - 2 * mw + pw) / (fw + pw)
  @rows = (tex_h - 2 * mh + ph) / (fh + ph)
  @frame_w, @frame_h = fw, fh

  # Pre-compute every rect once. Cheap (a few hundred at most),
  # and #region becomes a flat array lookup.
  @regions = Array.new(@cols * @rows) do |i|
    col = i % @cols
    row = i / @cols
    x = mw + col * (fw + pw)
    y = mh + row * (fh + ph)
    Rect.new([x, y], [fw, fh])
  end.freeze
end

# File lib/sfml/graphics/sprite_sheet.rb, line 95
def _pair(value)
  case value
  when Numeric then [Integer(value), Integer(value)]
  when Vector2 then [Integer(value.x), Integer(value.y)]
  when Array   then value.map { |n| Integer(n) }
  else raise ArgumentError, "expected Integer, [w, h], or Vector2; got #{value.class}"
  end
end

# File lib/sfml/graphics/sprite_sheet.rb, line 78
def animation(frame_indexes: nil, fps: 12, loop: true)
  indexes = frame_indexes || (0...frame_count).to_a
  Animation.new(
    self,
    frames: indexes.map { |i| region(i) },
    fps:    fps,
    loop:   loop,
  )
end

# File lib/sfml/graphics/sprite_sheet.rb, line 54
    def frame_count = @regions.size

    # The pixel Rect for cell `index` (0 = top-left, increases
    # row-major). Negative indexes wrap (e.g. -1 = last).
    def region(index)
      i = Integer(index) % frame_count
      @regions[i]
    end

    # `[col, row]` accessor for callers who prefer 2D coords.
    def region_at(col, row)
      raise IndexError, "col #{col} out of range (cols: #{@cols})" if col < 0 || col >= @cols
      raise IndexError, "row #{row} out of range (rows: #{@rows})" if row < 0 || row >= @rows
      @regions[row * @cols + col]
    end

    # Fresh Sprite pointing at cell `index`. Combine with `#sprite=`
    # patterns or feed into `SFML::Animation`.
    def sprite(index, **opts)
      Sprite.new(@texture, **opts).tap { |s| s.texture_rect = region(index) }
    end

    # An Animation looping through `frame_indexes` (defaults to all
    # frames in row-major order).
    def animation(frame_indexes: nil, fps: 12, loop: true)
      indexes = frame_indexes || (0...frame_count).to_a
      Animation.new(
        self,
        frames: indexes.map { |i| region(i) },
        fps:    fps,
        loop:   loop,
      )
    end

    # String representation for debugging.
    def to_s = "#<SpriteSheet #{@cols}×#{@rows} (#{@frame_w}×#{@frame_h}px cells)>"
    alias inspect to_s

    private

    # Accept 32 OR [32, 32] OR Vector2[32, 32].
    def _pair(value)
      case value
      when Numeric then [Integer(value), Integer(value)]
      when Vector2 then [Integer(value.x), Integer(value.y)]
      when Array   then value.map { |n| Integer(n) }
      else raise ArgumentError, "expected Integer, [w, h], or Vector2; got #{value.class}"
      end
    end
  end
end

# File lib/sfml/graphics/sprite_sheet.rb, line 58
def region(index)
  i = Integer(index) % frame_count
  @regions[i]
end

# File lib/sfml/graphics/sprite_sheet.rb, line 64
def region_at(col, row)
  raise IndexError, "col #{col} out of range (cols: #{@cols})" if col < 0 || col >= @cols
  raise IndexError, "row #{row} out of range (rows: #{@rows})" if row < 0 || row >= @rows
  @regions[row * @cols + col]
end

# File lib/sfml/graphics/sprite_sheet.rb, line 72
def sprite(index, **opts)
  Sprite.new(@texture, **opts).tap { |s| s.texture_rect = region(index) }
end

# File lib/sfml/graphics/sprite_sheet.rb, line 89
  def to_s = "#<SpriteSheet #{@cols}×#{@rows} (#{@frame_w}×#{@frame_h}px cells)>"
  alias inspect to_s

  private

  # Accept 32 OR [32, 32] OR Vector2[32, 32].
  def _pair(value)
    case value
    when Numeric then [Integer(value), Integer(value)]
    when Vector2 then [Integer(value.x), Integer(value.y)]
    when Array   then value.map { |n| Integer(n) }
    else raise ArgumentError, "expected Integer, [w, h], or Vector2; got #{value.class}"
    end
  end
end