first commit

.gitignore

@@ -0,0 +1,3 @@
+crystal.dwarf
+crystal
+.DS_Store

crystal.cr

@@ -0,0 +1,186 @@
+require "option_parser"
+
+BASE_SHAPE = [
+  "      #      ",
+  "     ###     ",
+  "    #####    ",
+  "   #######   ",
+  "  #########  ",
+  "   #######   ",
+  "    #####    ",
+  "     ###     ",
+  "      #      ",
+]
+
+struct TermSize
+  getter cols : Int32
+  getter rows : Int32
+  def initialize(@cols : Int32, @rows : Int32); end
+end
+
+def terminal_size : TermSize
+  if STDOUT.tty?
+    if (cols_env = ENV["COLUMNS"]?) && (rows_env = ENV["LINES"]?)
+      cols = cols_env.to_i
+      rows = rows_env.to_i
+      return TermSize.new(cols: cols, rows: rows) if cols > 0 && rows > 0
+    end
+    buf = IO::Memory.new
+    status = Process.run("stty", ["size"], output: buf, input: Process::Redirect::Close, error: Process::Redirect::Close)
+    if status.success?
+      parts = buf.to_s.strip.split(/\s+/)
+      if parts.size == 2
+        rows = parts[0].to_i
+        cols = parts[1].to_i
+        return TermSize.new(cols: cols, rows: rows) if cols > 0 && rows > 0
+      end
+    end
+  end
+  TermSize.new(cols: 80, rows: 24)
+end
+
+def enter_alt(io : IO)
+  io << "\e[?1049h\e[?25l"
+end
+
+def leave_alt(io : IO)
+  io << "\e[0m\e[?25h\e[?1049l"
+end
+
+def move_cursor(io : IO, row : Int32, col : Int32)
+  io << "\e[#{row};#{col}H"
+end
+
+def scale_shape(shape : Array(String), factor : Int32) : Array(String)
+  return shape if factor <= 1
+  scaled = [] of String
+  shape.each do |row|
+    expanded = String.build do |io|
+      row.each_char do |ch|
+        fill = ch == ' ' ? ' ' : '#'
+        factor.times { io << fill }
+      end
+    end
+    factor.times { scaled << expanded }
+  end
+  scaled
+end
+
+fps = 24
+scale = 1
+band = 2
+frames : Int32? = nil
+no_color = false
+use_alt = true
+show_last = false
+
+OptionParser.parse do |p|
+  p.banner = "Animated crystal"
+  p.on("--fps=FPS", "Frames per second") { |s| fps = s.to_i }
+  p.on("--scale=N", "Integer scale >=1") { |s| scale = s.to_i; scale = 1 if scale < 1; scale = 8 if scale > 8 }
+  p.on("--band=W", "Highlight band width") { |s| band = s.to_i; band = 1 if band < 1; band = 10 if band > 10 }
+  p.on("--frames=N", "Stop after N frames") { |s| frames = s.to_i }
+  p.on("--no-color", "Disable ANSI colors") { no_color = true }
+  p.on("--no-alt", "Do not use alternate screen") { use_alt = false }
+  p.on("--show-last", "Print last frame after exit") { show_last = true }
+  p.on("-h", "--help", "Show help") { puts p; exit 0 }
+end
+
+shape = scale_shape(BASE_SHAPE, scale)
+height = shape.size
+width = shape.max_of(&.size)
+
+base_color = no_color ? nil : "\e[38;5;45m"
+highlight_color = no_color ? nil : "\e[38;5;123m"
+reset = no_color ? nil : "\e[0m"
+
+running = true
+Signal::INT.trap { running = false }
+
+phase = 0
+period = (width + height)
+band_units = band * scale
+
+if use_alt
+  STDOUT << String.build { |io| enter_alt(io) }
+else
+  STDOUT << "\e[?25l"
+end
+STDOUT.flush
+
+begin
+  frame_target_ns = (1_000_000_000_i64 // fps)
+  frames_left = frames
+  last_frame : String? = nil
+  while running
+    sz = terminal_size
+    top = ((sz.rows - height) // 2) + 1
+    left = ((sz.cols - width) // 2) + 1
+    top = 1 if top < 1
+    left = 1 if left < 1
+
+    start = Time.monotonic
+
+    frame_str = String.build do |io|
+      io << "\e[2J"
+      y = 0
+      while y < height
+        move_cursor(io, top + y, left)
+        row = shape[y]
+        x = 0
+        while x < row.size
+          ch = row.byte_at(x).unsafe_chr
+          if ch != ' '
+            sum = x + y
+            d = sum - phase
+            d %= period
+            d += period if d < 0
+            d = period - d if d > period // 2
+            if d <= band_units
+              io << highlight_color if highlight_color
+            else
+              io << base_color if base_color
+            end
+            io << '#'
+          else
+            io << ' '
+          end
+          x += 1
+        end
+        io << reset if reset
+        y += 1
+      end
+      io << reset if reset
+    end
+    last_frame = frame_str
+    STDOUT << frame_str
+    STDOUT.flush
+
+    phase += 1
+    phase = 0 if phase >= period
+
+    if frames_left
+      frames_left -= 1
+      break if frames_left <= 0
+    end
+
+    elapsed = Time.monotonic - start
+    sleep_ns = frame_target_ns - elapsed.nanoseconds
+    if sleep_ns > 0
+      sleep sleep_ns.nanoseconds
+    end
+  end
+ensure
+  if use_alt
+    STDOUT << String.build { |io| leave_alt(io) }
+  else
+    STDOUT << "\e[0m\e[?25h"
+  end
+  STDOUT.flush
+  if show_last && last_frame
+    STDOUT << last_frame
+    STDOUT.flush
+  end
+end
+
+