minix/share/beaglebone/weather/weatherstation.lua

   1 #!/usr/bin/lua
   2 --
   3 -- weatherstation.lua - a simple web server intended to be run from tcpd to
   4 -- expose sensors from the BeagleBone Weather cape and serve the web app.
   5 --
   6
   7 -- List of files shared by this service.
   8 distfiles={}
   9 distfiles["/index.html"] = true
  10 distfiles["/style.css"] = true
  11 distfiles["/jquery.js"] = true
  12 distfiles["/processing.js"] = true
  13 distfiles["/spin.js"] = true
  14 distfiles["/weatherstation.js"] = true
  15
  16 -- Base path for distfiles
  17 prefix="/usr/share/beaglebone/weather"
  18
  19 -- Check that the filename is part of this demo.
  20 function filename_is_valid(filename)
  21         return distfiles[filename] ~= nil
  22 end
  23
  24 -- Check if the string 's' starts with 'starting'
  25 function starts_with(s, starting)
  26         return string.sub(s, 1, string.len(starting)) == starting
  27 end
  28
  29 -- Check if the string 's' ends with 'ending'
  30 function ends_with(s, ending)
  31         return string.sub(s, -string.len(ending)) == ending
  32 end
  33
  34 -- Return the content type of the file based only on the file extension.
  35 function get_content_type(filename)
  36
  37         if ends_with(filename, ".js") then
  38                 return "application/javascript"
  39         elseif ends_with(filename, ".css") then
  40                 return "text/css"
  41         elseif ends_with(filename, ".html") then
  42                 return "text/html"
  43         elseif ends_with(filename, ".json") then
  44                 return "application/json"
  45         else
  46                 return "text/plain"
  47         end
  48 end
  49
  50 -- Reads from STDIN until an empty or nil line is received.
  51 -- Returns the first line of the request.
  52 function read_request()
  53
  54         local i = 0
  55         local lines = {}
  56
  57         repeat
  58                 local line = io.read("*line")
  59                 if line == nil or line == "\r" then
  60                         break
  61                 end
  62                 lines[i] = line
  63                 i = i + 1
  64         until false
  65
  66         return lines[0]
  67 end
  68
  69 -- Return the entire contents of a file
  70 function read_file(filename)
  71         local f = io.open(filename, "rb")
  72
  73         if f == nil then
  74                 return nil
  75         end
  76         local content = f:read("*all")
  77         f:close()
  78
  79         return content
  80 end
  81
  82 -- Extract the value of the LABEL:VALUE pairs read from the device files.
  83 function extract_value(data, pat)
  84
  85         local x = string.match(data, pat)
  86
  87         if x == nil then
  88                 return "0"
  89         end
  90         return x
  91 end
  92
  93 -- Read the sensor values and generate json output
  94 function generate_json()
  95         local json = ""
  96
  97         local tsl2550 = read_file("/dev/tsl2550b3s39")
  98         if tsl2550 == nil then
  99                 return nil
 100         end
 101         local illuminance = extract_value(tsl2550, "ILLUMINANCE: (%d+)")
 102
 103         local sht21 = read_file("/dev/sht21b3s40")
 104         if sht21 == nil then
 105                 return nil
 106         end
 107         local temperature = extract_value(sht21, "TEMPERATURE: (%d+.%d+)")
 108         local humidity = extract_value(sht21, "HUMIDITY: (%d+.%d+)")
 109
 110         local bmp085 = read_file("/dev/bmp085b3s77")
 111         if bmp085 == nil then
 112                 return nil
 113         end
 114         local pressure = extract_value(bmp085, "PRESSURE: (%d+)")
 115
 116         json = json .. "{\n"
 117         json = json .. "\"temperature\": " .. temperature .. ",\n"
 118         json = json .. "\"humidity\": " .. humidity .. ",\n"
 119         json = json .. "\"illuminance\": " .. illuminance .. ",\n"
 120         json = json .. "\"pressure\": " .. pressure .. "\n"
 121         json = json .. "}\n"
 122
 123         return json
 124 end
 125
 126 function handle_request(req)
 127
 128         if req == nil then
 129                 response("404 Not Found", "text/plain", "Unknown Request")
 130                 return
 131         end
 132
 133         -- Parse filename out of HTTP request
 134         local filename = (string.match(req, " %S+ "):gsub("^%s+", ""):gsub("%s+$", ""))
 135         if filename == "" or filename == "/" then
 136                 filename = "/index.html"
 137         end
 138
 139         -- Check if the filename is known (i.e. it's a file in the web app)
 140         if filename_is_valid(filename) then
 141                 local contents = read_file(prefix .. filename)
 142
 143                 if contents ~= nil then
 144                         response("200 OK", get_content_type(filename), contents)
 145                 else
 146                         response("404 Not Found", "text/plain", "Failed to load known file")
 147                 end
 148         -- Else maybe the user is requesting the dynamic json data
 149         elseif starts_with(filename, "/weather.json") then
 150                 local json = generate_json()
 151                 if json == nil then
 152                         response("500 Internal Server Error", "text/plain", "Could not get sensor values")
 153                 else
 154                         response("200 OK", get_content_type("/weather.json"), json)
 155                 end
 156         -- Else, the user is requesting something not part of the app
 157         else
 158                 response("403 Forbidden", "text/plain", "File not allowed.")
 159         end
 160
 161         return
 162 end
 163
 164 -- Send the response to the HTTP request.
 165 function response(err_code, content_type, content)
 166         io.write("HTTP/1.1 " .. err_code .. "\r\n")
 167         io.write("Content-Type: " .. content_type .. "\r\n")
 168         io.write("\r\n")
 169         io.write(content)
 170         io.write("\r\n")
 171 end
 172
 173 -- Read the request and then handle it.
 174 handle_request(read_request())
 175