# Holds globals, and (for now at least), global constants.
# Note that Ruby-like "constants" aren't really - they are "assign-once"
# variables. As such, some of them can be treated as true constants
# (because their value is known at compile time), but some of them are
# not. For now, we'll treat all of them as global variables.
class GlobalScope
  attr_accessor :globals

  def initialize
    @globals = Set.new
  end

  def get_arg a
    return [:global,a] if @globals.member?(a)
    return [:addr,a]
  end
end

class FuncScope
  def initialize func, next_scope = nil
    @func = func
    @next = next_scope
  end

  def rest?
    @func ? @func.rest? : false
  end

  def get_arg a
    a = a.to_sym
    if @func
      arg = @func.get_arg(a)
      return arg if arg
    end
    return @next.get_arg(a) if @next
    return [:addr,a]
  end
end


class LocalVarScope
  def initialize locals, next_scope
    @next = next_scope
    @locals = locals
  end

  def rest?
    @next ? @next.rest? : false
  end

  def get_arg a
    a = a.to_sym
    return [:lvar,@locals[a] + (rest? ? 1 : 0)] if @locals.include?(a)
    return @next.get_arg(a) if @next
    return [:addr,a] # Shouldn't get here normally
  end
end


VTableEntry = Struct.new(:name,:realname,:offset,:function)

# Need a global list of vtable offsets since
# we can't usually statically determine what class
# an object belongs to.
class VTableOffsets
  def initialize
    @vtable = {}
    @vtable_max = 1 # Start at 1 since offset 0 is reserved for the vtable pointer for the Class object
    # Then we insert the "new" method.
    get_offset(:new)
  end

  def get_offset(name)
    name = name.to_sym
    if !@vtable[name]
      @vtable[name] = @vtable_max
      @vtable_max += 1
    end
    return @vtable[name]
  end

  def max
    @vtable_max
  end
end

class ClassScope
  attr_reader :name,:vtable

  def initialize next_scope,name,offsets
    @next = next_scope
    @name = name
    @vtable = {}
    @vtableoffsets = offsets
  end

  def rest?
    false
  end

  def get_arg a
    return @next.get_arg(a) if @next
    return [:addr,a]
  end

  def klass_size
    @vtableoffsets.max * Emitter::PTR_SIZE
  end

  def add_vtable_entry(name)
    @vtable[name] ||= VTableEntry.new
    v = @vtable[name]
    v.name = name.to_s
    v.offset = @vtableoffsets.get_offset(name) if !v.offset
    return v
  end

  def set_vtable_entry(name,realname,f)
    v = add_vtable_entry(name)
    v.realname = realname
    v.function = f
  end
end