class ActionDispatch::Journey::GTG::TransitionTable

def []=: (Integer from, Integer to, String sym) -> untyped

def []=(from, to, sym)
  to_mappings = states_hash_for(sym)[from] ||= {}
  case sym
  when Regexp
    # we must match the whole string to a token boundary
    if sym == DEFAULT_EXP
      sym = DEFAULT_EXP_ANCHORED
    else
      sym = /\A#{sym}\Z/
    end
  when Symbol
    # account for symbols in the constraints the same as strings
    sym = sym.to_s
  end
  to_mappings[sym] = to
end

def accepting?(state)
  @accepting[state]
end

def accepting_states
  @accepting.keys
end

def add_accepting(state)
  @accepting[state] = true
end

def add_memo(idx, memo)
  @memos[idx] << memo
end

def as_json(options = nil)
  simple_regexp = Hash.new { |h, k| h[k] = {} }
  @regexp_states.each do |from, hash|
    hash.each do |re, to|
      simple_regexp[from][re.source] = to
    end
  end
  {
    regexp_states:   simple_regexp,
    string_states:   @string_states,
    stdparam_states: @stdparam_states,
    accepting:       @accepting
  }
end

def eclosure(t)
  Array(t)
end

def initialize
  @stdparam_states = {}
  @regexp_states   = {}
  @string_states   = {}
  @accepting       = {}
  @memos           = Hash.new { |h, k| h[k] = [] }
end

def memo(idx)
  @memos[idx]
end

def move(t, full_string, start_index, end_index)
  return [] if t.empty?
  next_states = []
  tok = full_string.slice(start_index, end_index - start_index)
  token_matches_default_component = DEFAULT_EXP_ANCHORED.match?(tok)
  t.each { |s, previous_start|
    if previous_start.nil?
      # In the simple case of a "default" param regex do this fast-path
      # and add all next states.
      if token_matches_default_component && states = @stdparam_states[s]
        states.each { |re, v| next_states << [v, nil].freeze if !v.nil? }
      end
      # When we have a literal string, we can just pull the next state
      if states = @string_states[s]
        next_states << [states[tok], nil].freeze unless states[tok].nil?
      end
    end
    # For regexes that aren't the "default" style, they may potentially
    # not be terminated by the first "token" [./?], so we need to continue
    # to attempt to match this regexp as well as any successful paths that
    # continue out of it. both paths could be valid.
    if states = @regexp_states[s]
      slice_start = if previous_start.nil?
        start_index
      else
        previous_start
      end
      slice_length = end_index - slice_start
      curr_slice = full_string.slice(slice_start, slice_length)
      states.each { |re, v|
        # if we match, we can try moving past this
        next_states << [v, nil].freeze if !v.nil? && re.match?(curr_slice)
      }
      # and regardless, we must continue accepting tokens and retrying this regexp.
      # we need to remember where we started as well so we can take bigger slices.
      next_states << [s, slice_start].freeze
    end
  }
  next_states
end

def states
  ss = @string_states.keys + @string_states.values.flat_map(&:values)
  ps = @stdparam_states.keys + @stdparam_states.values.flat_map(&:values)
  rs = @regexp_states.keys + @regexp_states.values.flat_map(&:values)
  (ss + ps + rs).uniq
end

def states_hash_for(sym)
  case sym
  when String, Symbol
    @string_states
  when Regexp
    if sym == DEFAULT_EXP
      @stdparam_states
    else
      @regexp_states
    end
  else
    raise ArgumentError, "unknown symbol: %s" % sym.class
  end
end

def to_svg
  svg = IO.popen("dot -Tsvg", "w+") { |f|
    f.write(to_dot)
    f.close_write
    f.readlines
  }
  3.times { svg.shift }
  svg.join.sub(/width="[^"]*"/, "").sub(/height="[^"]*"/, "")
end

def transitions
  @string_states.flat_map { |from, hash|
    hash.map { |s, to| [from, s, to] }
  } + @stdparam_states.flat_map { |from, hash|
    hash.map { |s, to| [from, s, to] }
  } + @regexp_states.flat_map { |from, hash|
    hash.map { |s, to| [from, s, to] }
  }
end

def visualizer(paths, title = "FSM")
  viz_dir   = File.join __dir__, "..", "visualizer"
  fsm_js    = File.read File.join(viz_dir, "fsm.js")
  fsm_css   = File.read File.join(viz_dir, "fsm.css")
  erb       = File.read File.join(viz_dir, "index.html.erb")
  states    = "function tt() { return #{to_json}; }"
  fun_routes = paths.sample(3).map do |ast|
    ast.filter_map { |n|
      case n
      when Nodes::Symbol
        case n.left
        when ":id" then rand(100).to_s
        when ":format" then %w{ xml json }.sample
        else
          "omg"
        end
      when Nodes::Terminal then n.symbol
      else
        nil
      end
    }.join
  end
  stylesheets = [fsm_css]
  svg         = to_svg
  javascripts = [states, fsm_js]
  fun_routes  = fun_routes
  stylesheets = stylesheets
  svg         = svg
  javascripts = javascripts
  require "erb"
  template = ERB.new erb
  template.result(binding)
end