New API for loading and saving sketches (or arbitrary data really). Status call not implemented yet.

src/rest/api/api_sketch.lua

@@ -0,0 +1,158 @@
+--[[
+	This module uses the Lua filesystem library to iterate over all sketches.
+	A more flexible approach would be to use an index file (like the update module does).
+	That way, we could also store arbitrary meta-data together with the sketches.
+]]--
+
+local lfs = require('lfs')
+local log = require('util.logger')
+local utils = require('util.utils')
+
+local M = {
+	isApi = true,
+	SKETCH_DIR = '/root/sketches',
+	MIN_FREE_SPACE = 1024 * 80
+}
+
+local NUMBER_PAD_WIDTH = 5
+local SKETCH_FILE_EXTENSION = 'sketch'
+
+
+-- creates sketch directory, and sets response to error state on failure
+local function createSketchDirectory()
+	if os.execute('mkdir -p ' .. M.SKETCH_DIR) ~= 0 then
+		log:error("Error: could not create sketch directory '" .. M.SKETCH_DIR .. "'")
+		response:setError("could not create sketch directory")
+		return false
+	end
+	return true
+end
+
+local function constructSketchFilename(idx)
+	return string.format('%0' .. NUMBER_PAD_WIDTH .. '.0f.%s', idx, SKETCH_FILE_EXTENSION)
+end
+
+--should this return 1k-blocks or bytes?
+local function getFreeDiskSpace()
+	local kb = utils.captureCommandOutput('df / -k | awk \'$3 ~ /[0-9]+/ { print $4 }\'')
+	return kb * 1024
+end
+
+local function createSketchList()
+	local result = {}
+
+	for item in lfs.dir(M.SKETCH_DIR) do
+		if item ~= '.' and item ~= '..' then
+			local idx = item:match('^(%d+)\.sketch$')
+			if idx and idx:len() == NUMBER_PAD_WIDTH then
+				table.insert(result, tonumber(idx))
+			end
+		end
+	end
+
+	table.sort(result)
+	return result
+end
+
+
+-- retrieve sketches, requires id(int)
+function M._global_GET(request, response)
+	local argId = request:getBlankArgument() -- try this one first
+	if not argId then argId = request:get("id") end -- and fall back to this one
+
+	if not argId then
+		response:setError("missing id argument")
+		return
+	end
+	argId = tonumber(argId)
+
+	if not createSketchDirectory(request, response) then return end
+	local sketches = createSketchList()
+
+	local exists = false
+	for _,sketchId in ipairs(sketches) do
+		if sketchId == argId then
+			exists = true
+			break
+		end
+	end
+
+	response:addData('id', argId)
+	if exists then
+		local loadFile,msg = io.open(M.SKETCH_DIR .. '/' .. constructSketchFilename(argId))
+
+		if not loadFile then
+			response:setError("could not open sketch file for reading (" .. msg .. ")")
+			return
+		end
+
+		local data = loadFile:read('*a')
+		if not data then data = '' end
+		response:addData('data', data)
+
+		loadFile:close()
+		response:setSuccess()
+	else
+		response:setFail("sketch not found")
+	end
+end
+
+-- TODO: do we need locking?
+-- save sketches, requires data(string)
+function M._global_POST(request, response)
+	local argData = request:get("data")
+
+	if not argData then
+		response:setFail("missing data argument")
+		return
+	elseif argData:len() == 0 then
+		response:setFail("data argument must be non-empty")
+		return
+	end
+
+	if getFreeDiskSpace() - M.MIN_FREE_SPACE < argData:len() then
+		response:setFail("not enough free space")
+		response:addData('available', getFreeDiskSpace())
+		response:addData('reserved', M.MIN_FREE_SPACE)
+		response:addData('sketch_size', argData:len())
+		return
+	end
+
+	if not createSketchDirectory(request, response) then return end
+	local sketches = createSketchList()
+
+	local listSize = table.getn(sketches)
+	local sketchIdx = listSize > 0 and sketches[listSize] + 1 or 1
+	local sketchFile = M.SKETCH_DIR .. '/' .. constructSketchFilename(sketchIdx)
+
+	log:debug("saving sketch #" .. sketchIdx .. " (" .. argData:len() .. " bytes)")
+	local saveFile,msg = io.open(sketchFile, 'w')
+
+	if not saveFile then
+		response:setError("error opening sketch file for writing (".. msg .. ")")
+		return
+	end
+
+	saveFile:write(argData)
+	saveFile:close()
+
+	response:addData('id', sketchIdx)
+	response:setSuccess()
+end
+
+-- get info on number of sketches, used space, free space (and reserved space for printserver?)
+function M.status(request, response)
+	if not createSketchDirectory(request, response) then return end
+	--return amount of sketches, free space (and space used by sketches?)
+	response:setSuccess()
+end
+
+-- remove all sketches
+function M.clear_POST(request, response)
+	local rv = os.execute("rm -f " .. M.SKETCH_DIR .. '/*')
+	if rv == 0 then response:setSuccess()
+	else response:setFail("could not remove contents of sketch directory")
+	end
+end
+
+return M