#! /usr/bin/env Rscript

library(testthat)
library(rly)

context("Tests proper handling of lextab and parsetab files in package structures")

TOKENS = c('NAME','NUMBER', 'PLUS','MINUS','TIMES','DIVIDE','EQUALS', 'LPAREN','RPAREN')

Lexer <- R6::R6Class("Lexer",
  public = list(
    tokens = TOKENS,
    t_PLUS   = '\\+',
    t_MINUS  = '-',
    t_TIMES  = '\\*',
    t_DIVIDE = '/',
    t_EQUALS = '=',
    t_LPAREN = '\\(',
    t_RPAREN = '\\)',
    t_NAME = '[a-zA-Z_][a-zA-Z0-9_]*',
    t_NUMBER = function(re='\\d+', t) {
      t$value <- strtoi(t$value)
      return(t)
    },
    t_ignore = " \t",
    t_newline = function(re='\\n+', t) {
      t$lexer$lineno <- t$lexer$lineno + nchar(t$value)
      return(NULL)
    },
    t_error = function(t) {
      cat(sprintf("Illegal character '%s'", t$value[1]))
      t$lexer$skip(1)
      return(t)
    }
  )
)

Parser <- R6::R6Class("Parser",
  public = list(
    tokens = TOKENS,
    # 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', t) {
      names[t[1]] <- t[3]
    },
    p_statement_expr = function(doc='statement : expression', t) {
      t[0] <- t[1]
    },
    p_expression_binop = function(doc='expression : expression PLUS expression
                                     | expression MINUS expression
                                     | expression TIMES expression
                                     | expression DIVIDE expression', t) {
      if(t[2] == '+')      t[0] <- t[1] + t[3]
      else if(t[2] == '-') t[0] <- t[1] - t[3]
      else if(t[2] == '*') t[0] <- t[1] * t[3]
      else if(t[2] == '/') t[0] <- t[1] / t[3]
    },
    p_expression_uminus = function(doc='expression : MINUS expression %prec UMINUS', t) {
      t[0] <- -t[2]
    },
    p_expression_group = function(doc='expression : LPAREN expression RPAREN', t) {
      t[0] <- t[2]
    },
    p_expression_number = function(doc='expression : NUMBER', t) {
      t[0] <- t[1]
    },
    p_expression_name = function(doc='expression : NAME', t) {
      t[0] <- names[t[1]]
    },
    p_error = function(t) {
      cat(sprintf("Syntax error at '%s'", t$value))
    }
  )
)

test_that("pkg_test", {
  lexer  <- rly::lex(Lexer)
  parser <- rly::yacc(Parser)
})