--- get stat information on a path
-- @param path to stat
-- @param the ftype to return
-- @return false if ftype or path does not exist
function file_info(path, ftype)
    local attr = lighty.stat(path)
    if attr and attr[ftype] then
        return attr[ftype]
    end
    return false
end

--- Wrapper for reading a full file into a string
-- @param filename Full path to the file
-- @return a string with the content of the file
function read_file(filename) 
    local content = ""
    if file_info(filename, "is_file") then
        local file = io.open(filename, "r")
        content = file:read("*a")
        io.close(file)
    end
    return content
end

--- Wrapper for writeing content to a file
-- @param filename Full path to the destionation file
-- @param content The string to write
function write_cache(filename, content) 
    local file = io.open(filename, "w")
    file:write(content)
    io.close(file)
end

--- Concat multiple files into one file 
-- @param lighty lighty global variable passed to the method
-- @param match The files that will be concat into a file
-- @param fileExtension Do !NOT! include the dot ( . )
function combine_files(lighty, files, fileExtension)
    require "md5" 
    
    local charset       = "; charset=utf-8"
    local prefix        = "cache-"
    local rootPath      = lighty.env["physical.doc-root"] .. fileExtension .. "/"
    local concatRoot     = "/tmp/cache/"
    local lastModified  = 0
    
    for file in string.gmatch(files, "(.-\." .. fileExtension .. "),?") do
        local fullPath = rootPath .. file
        modTime = file_info(fullPath, "st_mtime")
        if type(modTime) == "number" then
            lastModified = math.max(lastModified, modTime)
        end            
     end
     
     local hash = lastModified .. "-" .. md5.sumhexa(files)
     lighty.header["Etag"] = '"' .. hash ..'"'
     
    local cacheFile = prefix .. hash .. '.' .. fileExtension
    if not file_info(concatRoot .. cacheFile, "is_file") then
        local content = ""
        for file in string.gmatch(match, "(.-\." .. fileExtension .. "),?") do
            content = content .. "\n"
            content = content .. "/**\n"
            content = content .. " *\n"
            content = content .. " *  " .. file .. "\n"
            content = content .. " *\n"
            content = content .. " */\n"
            content = content .. "\n"
            content = content .. read_file(rootPath .. file)
        end
        write_cache(concatRoot .. cacheFile, content )
    end
    lighty.env["physical.path"] = concatRoot .. cacheFile
end

if (not file_info(lighty.env["physical.path"], "is_file")) then
    css = string.match(lighty.env["physical.path"], "css/(.*\.css)")
	if css then
        return combine_files(lighty, css, "css")
    end
    
    js = string.match(lighty.env["physical.path"], "js/(.*\.js)")	    
	if js then
        return combine_files(lighty, js, "js")
	end 
end