library(shiny)
library(docstring)
source("drive.R")

problemStatement <- 
    "This is a simulation of a car driving in a city and taking random \
turns left, right, or not turn at all, with some probabilities \
which can be adjusted with the sliders. If we do not turn, we continue \
in the same direction we came from."

function(input, output) {

    output$problemStatement <- renderText(problemStatement)

    output$pathPlot <- renderPlot({
        input$goButton
        nturns  <- input$nturns
        nblocks <- input$nblocks
        pLeft   <- input$pLeft
        pRight  <- input$pRight
        pStraight  <- 1-pLeft-pRight
        prob <- c(pLeft, pRight, pStraight)
        print(c('Prob: ',prob))
        tryCatch({
            drive(nturns, nblocks, prob)
        },
        error = function(cond) {
            plot(NULL,xlim=c(-nblocks,nblocks),ylim=c(-nblocks,nblocks))
            text(0, 0,'Probability of no-turn dropped below 0',col=2,cex = 2)
        })
    })

    output$pStraight  <- renderText({
        pLeft   <- input$pLeft
        pRight  <- input$pRight
        pStraight  <- 1-pLeft-pRight
        print(c('Prob. of going straight through the intersection: ', pStraight))
    })
}