// It's often convenient to express recipes in a textual fashion.
:(scenarios add_recipe)
:(scenario first_recipe)
recipe main [
  1:integer <- copy 23:literal
]
+parse: instruction: 1
+parse:   ingredient: {name: "23", type: 0}
+parse:   product: {name: "1", type: 1}

:(code)
int add_recipe(string form) {
  istringstream in(form);
  in >> std::noskipws;

  string _recipe = next_word(in);
  if (_recipe != "recipe")
    raise << "top-level forms must be of the form 'recipe _name_ [ _instruction_ ... ]'\n";

  string recipe_name = next_word(in);
  if (recipe_name.empty())
    raise << "empty recipe name in " << form << '\n';
  int r = Recipe_number[recipe_name] = Next_recipe_number++;

  if (next_word(in) != "[")
    raise << "recipe body must begin with '['\n";

  skip_newlines(in);

  instruction curr;
  while (next_instruction(in, &curr)) {
    Recipe[r].steps.push_back(curr);
  }
  return r;
}

bool next_instruction(istream& in, instruction* curr) {
  curr->clear();
  if (in.eof()) return false;
  skip_whitespace(in);  if (in.eof()) return false;
  skip_newlines(in);  if (in.eof()) return false;

  vector<string> words;
  while (in.peek() != '\n') {
    skip_whitespace(in);  if (in.eof()) return false;
    string word = next_word(in);  if (in.eof()) return false;
    words.push_back(word);
    skip_whitespace(in);  if (in.eof()) return false;
  }
  skip_newlines(in);  if (in.eof()) return false;

  if (words.size() == 1 && *(words[0].end()-1) == ':') {
    curr->is_label = true;
    words[0].erase(words[0].end()-1);
    curr->label = words[0];
    trace("parse") << "label: " << curr->label;
    return !in.eof();
  }

  vector<string>::iterator p = words.begin();
  if (find(words.begin(), words.end(), "<-") != words.end()) {
    for (; *p != "<-"; ++p) {
      if (*p == ",") continue;
      curr->products.push_back(reagent(*p));
    }
    ++p;  // skip <-
  }

  curr->operation = Recipe_number[*p];  ++p;

  for (; p != words.end(); ++p) {
    if (*p == ",") continue;
    curr->ingredients.push_back(reagent(*p));
  }

  trace("parse") << "instruction: " << curr->operation;
  for (vector<reagent>::iterator p = curr->ingredients.begin(); p != curr->ingredients.end(); ++p) {
    trace("parse") << "  ingredient: " << p->to_string();
  }
  for (vector<reagent>::iterator p = curr->products.begin(); p != curr->products.end(); ++p) {
    trace("parse") << "  product: " << p->to_string();
  }
  return !in.eof();
}

string next_word(istream& in) {
  ostringstream out;
  skip_whitespace(in);
  slurp_word(in, out);
  return out.str();
}

void slurp_word(istream& in, ostream& out) {
  char c;
  if (in.peek() == ',') {
    in >> c;
    out << c;
    return;
  }
  while (in >> c) {
    if (isspace(c) || c == ',') {
      in.putback(c);
      break;
    }
    out << c;
  }
}

void skip_whitespace(istream& in) {
  while (isspace(in.peek()) && in.peek() != '\n') {
    in.get();
  }
}

void skip_newlines(istream& in) {
  while (in.peek() == '\n')
    in.get();
}

void skip_comma(istream& in) {
  skip_whitespace(in);
  if (in.peek() == ',') in.get();
  skip_whitespace(in);
}

:(scenario parse_label)
recipe main [
  foo:
]
+parse: label: foo
-parse: instruction: 1

:(scenario parse_multiple_products)
recipe main [
  1:integer, 2:integer <- copy 23:literal
]
+parse: instruction: 1
+parse:   ingredient: {name: "23", type: 0}
+parse:   product: {name: "1", type: 1}
+parse:   product: {name: "2", type: 1}

:(scenario parse_multiple_ingredients)
recipe main [
  1:integer, 2:integer <- copy 23:literal, 4:integer
]
+parse: instruction: 1
+parse:   ingredient: {name: "23", type: 0}
+parse:   ingredient: {name: "4", type: 1}
+parse:   product: {name: "1", type: 1}
+parse:   product: {name: "2", type: 1}