# Generating HTML report Dynamically from a template

library(XML)
search()
objects(2)

# We can use the xmlOutputDOM function to create HTML dynamically
# We use a super simple example that creates a little snippet of HTML

testDom = xmlOutputDOM()
class(testDom)
names(testDom)

# The value function returns the value of the document
testDom$value()

# Note that it starts with a begin and end <doc> tag
# We insert tags into this tree

args(testDom$addTag)
args(testDom$closeTag)

# Add a list tag
testDom$addTag("ol", attrs= c("example" ="AK", "extra" = "Hi"), close=FALSE)
testDom$value()
testDom$addTag("li", "This is my first idea", close=TRUE)
testDom$addTag("li", "This is my first second", close=TRUE)
testDom$closeTag("ol")
testDom$value()

testDom$addTag("ul", close=FALSE)
testDom$addTag("li", "This is my another idea", close=TRUE)
testDom$addTag("li", "And yet another", close=TRUE)
testDom$closeTag("ul")

subTree = testDom$value()
class(subTree)
subTree[[1]]
subTree[[2]] 

# We can write it out using the save XML function
saveXML(test, file="myTest.xml")

# We can read the template into R with the htmlTreeParse function
myTree = htmlTreeParse("template.html", asTree = TRUE)
myTree
class(myTree)
myRoot = xmlRoot(myTree)

xmlSApply(myRoot[[2]], xmlName)
# Here is one of the include tags
# One way to find these tags is with recursions
# move through the tree looking for xmlName of include
# and replace with the appropirate xmlNode

myRoot[[2]][[5]] 
myRoot[[2]][[5]] = subTree[[1]]
myRoot[[2]][[5]]
class(myRoot)
saveXML(myRoot, file="xyz.xml")

# An alternative is to let the tree parser find these tags for you.
# To do this we would write a handler.
# The following shows how we can use global variables as inputs to
# the insertTag handler function

whichState = 2

insertHandlers =
function()
{
  includeTag = function(x) {
    subTree[[ whichState ]] 
  }
  list(include = includeTag)
}

myNewTree = htmlTreeParse("template.html", asTree = TRUE, 
                     handlers=insertHandlers())


myNewRoot = xmlRoot(myNewTree)

# Notice that where the include tag appeared in the original tree
# we now have a node from another tree.
# we could have called another funtion to dynamically generate
# this replacement node and we could take input from the attributes
# in the include node as well as arguments from the user.

myNewRoot[[2]][[5]]
myNewRoot[[2]][[7]]

saveXML(myNewRoot, file = "myHandlerReport.html")