#! /usr/bin/env Rscript

library(testthat)
library(rly)

context("A grammar with an unused rule")

Parser1 <- R6::R6Class("Parser1",
  public = list(
    tokens = c('NAME','NUMBER', 'PLUS','MINUS','TIMES','DIVIDE','EQUALS', 'LPAREN','RPAREN'),
    # Parsing rules
    precedence = list(c('left','PLUS','MINUS'),
                      c('left','TIMES','DIVIDE'),
                      c('right','UMINUS')),
    # dictionary of names
    names = new.env(hash=TRUE),
    p_statement_assign = function(doc='statement : NAME EQUALS expression', p) {
      self$names[[as.character(p$get(2))]] <- p$get(4)
    },
    p_statement_expr = function(doc='statement : expression', p) {
      cat(p$get(2))
      cat('\n')
    },
    p_expression_binop = function(doc='expression : expression PLUS expression
                                                  | expression MINUS expression
                                                  | expression TIMES expression
                                                  | expression DIVIDE expression', p) {
      if(p$get(3) == 'PLUS') p$set(1, p$get(2) + p$get(4))
      else if(p$get(3) == 'MINUS') p$set(1, p$get(2) - p$get(4))
      else if(p$get(3) == 'TIMES') p$set(1, p$get(2) * p$get(4))
      else if(p$get(3) == 'DIVIDE') p$set(1, p$get(2) / p$get(4))
    },
    p_expression_uminus = function(doc='expression : MINUS expression %prec UMINUS', p) {
      p$set(1, -p$get(3))
    },
    p_expression_group = function(doc='expression : LPAREN expression RPAREN', p) {
      p$set(1, p$get(3))
    },
    p_expression_number = function(doc='expression : NUMBER', p) {
      p$set(1, p$get(2))
    },
    p_expression_name = function(doc='expression : NAME', p) {
      p$set(1, self$names[[as.character(p$get(2))]])
    },
    p_expression_list = function(doc='exprlist : exprlist COMMA expression', p) {
    },
    p_error = function(p) {
      cat(sprintf("Syntax error at '%s'", p$value))
    }
  )
)

Parser2 <- R6::R6Class("Parser2",
    public = list(
        tokens = c('NAME','NUMBER', 'PLUS','MINUS','TIMES','DIVIDE','EQUALS', 'LPAREN','RPAREN'),
        # Parsing rules
        precedence = list(c('left','PLUS','MINUS'),
            c('left','TIMES','DIVIDE'),
            c('right','UMINUS')),
        # dictionary of names
        names = new.env(hash=TRUE),
        p_statement_assign = function(doc='statement : NAME EQUALS expression', p) {
          self$names[[as.character(p$get(2))]] <- p$get(4)
        },
        p_statement_expr = function(doc='statement : expression', p) {
          cat(p$get(2))
          cat('\n')
        },
        p_expression_binop = function(doc='expression : expression PLUS expression
                                                      | expression MINUS expression
                                                      | expression TIMES expression
                                                      | expression DIVIDE expression', p) {
          if(p$get(3) == 'PLUS') p$set(1, p$get(2) + p$get(4))
          else if(p$get(3) == 'MINUS') p$set(1, p$get(2) - p$get(4))
          else if(p$get(3) == 'TIMES') p$set(1, p$get(2) * p$get(4))
          else if(p$get(3) == 'DIVIDE') p$set(1, p$get(2) / p$get(4))
        },
        p_expression_uminus = function(doc='expression : MINUS expression %prec UMINUS', p) {
          p$set(1, -p$get(3))
        },
        p_expression_group = function(doc='expression : LPAREN expression RPAREN', p) {
          p$set(1, p$get(3))
        },
        p_expression_number = function(doc='expression : NUMBER', p) {
          p$set(1, p$get(2))
        },
        p_expression_name = function(doc='expression : NAME', p) {
          p$set(1, self$names[[as.character(p$get(2))]])
        },
        p_expression_list_2 = function(doc='exprlist : expression', p) {
        },
        p_error = function(p) {
          cat(sprintf("Syntax error at '%s'", p$value))
        }
    )
)

test_that("grammar", {
  expect_output(expect_error(rly::yacc(Parser1), "Unable to build parser"),
"ERROR .* Symbol COMMA used, but not defined as a token or a rule
WARN .* Symbol COMMA is unreachable
WARN .* Symbol exprlist is unreachable
ERROR .* Infinite recursion detected for symbol exprlist")
  expect_output(rly::yacc(Parser2), 
"WARN .* Rule exprlist defined, but not used
WARN .* There is 1 unused rule
WARN .* Symbol exprlist is unreachable")
})