BackgroundRunner (#3008)

* Use getCapacityHW() to ensure latest battery capacity can be retrieved

* BackgroundRunner

* Start background_runner_spec.lua

* AutofrontLight plugin now uses BackgroundRunner plugin

plugins/backgroundrunner.koplugin/commandrunner.lua

@@ -0,0 +1,90 @@
+local logger = require("logger")
+
+local CommandRunner = {
+    pio = nil,
+    job = nil,
+}
+
+function CommandRunner:createEnvironmentFromTable(t)
+    if t == nil then return "" end
+
+    local r = ""
+    for k, v in pairs(t) do
+        r = r .. k .. "=" .. v .. " "
+    end
+
+    if string.len(r) > 0 then r = "export " .. r .. ";" end
+    return r
+end
+
+function CommandRunner:createEnvironment()
+    if type(self.job.environment) == "table" then
+        return self:createEnvironmentFromTable(self.job.environment)
+    end
+    if type(self.job.environment) == "function" then
+        local status, result = pcall(self.job.environment)
+        if status then
+            return self:createEnvironmentFromTable(result)
+        end
+    end
+    return ""
+end
+
+function CommandRunner:start(job)
+    assert(self ~= nil)
+    assert(self.pio == nil)
+    assert(self.job == nil)
+    self.job = job
+    self.job.start_sec = os.time()
+    assert(type(self.job.executable) == "string")
+    local command = self:createEnvironment() .. " " ..
+                    "sh plugins/backgroundrunner.koplugin/luawrapper.sh " ..
+                    "\"" .. self.job.executable .. "\""
+    logger.dbg("CommandRunner: Will execute command " .. command)
+    self.pio = io.popen(command)
+end
+
+--- Polls the status of self.pio.
+-- @return a table contains the result from luawrapper.sh. Returns nil if the
+--         command has not been finished.
+function CommandRunner:poll()
+    assert(self ~= nil)
+    assert(self.pio ~= nil)
+    assert(self.job ~= nil)
+    local line = self.pio:read()
+    if line == "" then
+        return nil
+    else
+        if line == nil then
+            -- The binary crashes without output. This should not happen.
+            self.job.result = 223
+        else
+            line = line .. self.pio:read("*a")
+            logger.dbg("CommandRunner: Receive output " .. line)
+            local status, result = pcall(loadstring(line))
+            if status and result ~= nil then
+                for k, v in pairs(result) do
+                    self.job[k] = v
+                end
+            else
+                -- The output from binary is invalid.
+                self.job.result = 222
+            end
+        end
+        self.pio:close()
+        self.pio = nil
+        self.job.end_sec = os.time()
+        local job = self.job
+        self.job = nil
+        return job
+    end
+end
+
+--- Whether this is a running job.
+-- @treturn boolean
+function CommandRunner:pending()
+    assert(self ~= nil)
+    return self.pio ~= nil
+end
+
+return CommandRunner