# server.R

library(shiny)

Trim <- function( x ) {

  # http://stackoverflow.com/questions/2261079/how-to-trim-leading-and-trailing-whitespace-in-r

  gsub("(^[[:space:]]+|[[:space:]]+$)", "", x)

}

http://127.0.0.1:37673/rstudio/clear.cache.gif

# load ngram data set

all_ngrams <- read.table('c:/cordova/pubmed_cardiology_ngrams.csv', sep=",", header=TRUE)

all_ngrams <- as.character(all_ngrams$x)

# Define server logic required to summarize and view the selected dataset

shinyServer(function(input, output) {

  # Return the requested dataset

  datasetInput <- reactive({

    find_next_word(tolower(input$current_sentence))

  })

  # You can access the value of the widget with input$text, e.g.

  output$value <- renderPrint({ paste(tolower(input$text), find_next_word(tolower(input$text))) })

  find_next_word <- function(current_sentence) { 

    if (nchar(Trim(current_sentence)) == 0)

      return ('')

    # find the best next word

    # trailing space at end to avoid picking last word

    matches <- c()

    current_sentence <- paste0(Trim(current_sentence)," ")

    for (sentence in all_ngrams) {

      # find exact match with double backslash and escape

      if (grepl(paste0('\\<',current_sentence), sentence)) {

        matches <- c(matches, sentence)

      }

    }

    # didn't find a match so return nothing

    if (is.null(matches))

      return ('')

    # find highest probability word

    precision_match <- c()

    for (a_match in matches) {

      # how many spaces in from of search word

      precision_match <- c(precision_match,nchar(strsplit(x = a_match, split = word)[[1]][[1]]))

    }

    # use highest number and a random of highest for multiples

    best_matched_sentence <- sample(matches[precision_match == max(precision_match)],size = 1)

    # split the best matching sentence by the search word

    best_match <- strsplit(x = best_matched_sentence, split = current_sentence)[[1]]

    # split second part by spaces and pick first word

    best_match <-  strsplit(x = best_match[[2]], split = " ")[[1]]

    # return first word

    return (best_match[[1]]) 

  }

})