API: Add csv format to device-data action

README.md

@@ -153,6 +153,8 @@ Parameter			| Type		| Meaning
 `start`				| datetime  | The starting datetime.
 `end`				| datetime  | The ending datetime.
 `average-seconds`	| int		| Optional. If specified, readings will be grouped into lumps of this many seconds and averaged. For example a value of 3600 (1 hour) will return 1 data point per hour, with the value of each point an average of all the readings for that hour.
+`format`            | string    | Optional. Specifies the format that the response will be returned in. Valid values: `json`, `csv`. Default: `json`
+
 
 ### changelog
 > Gets the changelog as a fragment of HTML.

logic/Actions/DeviceData.php

@@ -49,8 +49,14 @@ class DeviceData implements IAction {
 		$this->validator->is_max_length("reading-type", 256);
 		$this->validator->is_datetime("start");
 		$this->validator->is_datetime("end");
+		if(!empty($_GET["format"]))
+			$this->validator->is_preset_value("format", ["json", "csv"], 406);
+		
 		$this->validator->run();
 		
+		$format = $_GET["format"] ?? "json";
+		
+		
 		if(new \DateTime($_GET["start"]) > new \DateTime($_GET["end"])) {
 			$this->sender->send_error_plain(
 				400, "Error: The start date must be earlier than the end date.", [
@@ -101,12 +107,35 @@ class DeviceData implements IAction {
 		
 		// 3: Serialise data
 		$start_encode = microtime(true);
-		$response = json_encode($data);
+		$response_type = "application/octet-stream";
+		$response_suggested_filename = "data-" . date(\DateTime::ATOM) . "";
+		$response = null;
+		switch($format) {
+			case "json":
+				$response_type = "application/json";
+				$response_suggested_filename .= ".json";
+				$response = json_encode($data);
+				break;
+			case "csv":
+				$result = fopen('php://temp/maxmemory:'. (5*1024*1024), 'r+');
+				fputcsv($result, array_keys($data[0]));
+				foreach($data as $row)
+					fputcsv($result, array_values($row));
+				rewind($result);
+				
+				$response_type = "text/csv";
+				$response_suggested_filename .= ".json";
+				$response = \stream_get_contents($result);
+				
+				fclose($result);
+				break;
+		}
 		
 		
 		// 4: Send response
 		header("content-length: " . strlen($response));
-		header("content-type: application/json");
+		header("content-type: $response_type");
+		header("content-disposition: inline; filename=data.csv");
 		header("x-time-taken: " . PerfFormatter::format_perf_data($start_time, $start_handle, $start_encode));
 		echo($response);
 		return true;

logic/Validator.php

@@ -42,6 +42,16 @@ class Validator {
 			"Error: The field $key is too long - it must be a maximum of $max_length characters."
 		);
 	}
+	public function is_preset_value(string $key, array $values, int $error_code) {
+		$this->add_test(
+			$key,
+			function($data) use ($values) {
+				return in_array($data, $values);
+			},
+			$error_code,
+			"Error: The value for the field $key is not valid. Valid values: " . implode(", ", $values) . "."
+		);
+	}
 	
 	public function are_equal($key_a, $key_b, $message) {
 		$key_b_data = $this->target_data[$key_b];