Add bus_data DB table and have thrimshim able to query it for latest odo reading

postgres/setup.sh

@@ -149,6 +149,24 @@ CREATE TABLE playlists (
 	tags TEXT[] NOT NULL,
 	show_in_description BOOLEAN NOT NULL
 );
+
+-- This table records time series data gleaned from the bus cam (right now, just the odometer).
+-- Each record indicates a timestamp and value, as well as the channel/segment file it was sourced from.
+-- Note the values are nullable and NULL indicates the value was indeterminate at that time.
+-- The "error" column records a free-form human readable message about why a value could not
+-- be determined.
+-- The odometer column is in miles. The game shows the odometer to the 1/10th mile precision.
+CREATE TABLE bus_data (
+	timestamp TIMESTAMP NOT NULL,
+	channel TEXT NOT NULL,
+	segment TEXT,
+	error TEXT,
+	odometer DOUBLE PRECISION,
+);
+
+-- Range index on timestamp as we will often want the closest timestamp to a requested point.
+-- Note btree is the default anyway but we use it explicitly here as we want the range behaviour.
+CREATE INDEX bus_data_timestamp ON bus_data USING btree (timestamp);
 EOSQL
 
 if [ -a /mnt/wubloader/nodes.csv ]; then

thrimshim/setup.py

@@ -11,6 +11,7 @@ setup(
 		"google-auth",
 		"psycogreen",
 		"psycopg2",
+		"python-dateutil",
 		"requests",
 		"wubloader-common",
 	],

thrimshim/thrimshim/main.py

@@ -16,7 +16,7 @@ import psycopg2
 from psycopg2 import sql
 
 import common
-from common import database
+from common import database, dateutil
 from common.flask_stats import request_stats, after_request
 
 import google.oauth2.id_token
@@ -520,6 +520,55 @@ def reset_row(ident, editor=None):
 	return ''
 
 
+@app.route('/thrimshim/odometer/<channel>')
+@request_stats
+def get_odometer(channel):
+	"""Not directly thrimbletrimmer related but easiest to put here as we have DB access.
+	Checks DB for the most recent odometer reading as of `time` param (default now).
+	However, won't consider readings older than `range` param (default 1 minute)
+	You can also pass `extrapolate`=`true` to try to extrapolate the reading at your requested time
+	based on the last known time. Note it will still only look within `range` for the last known time.
+	If it can't find a reading, returns 0.
+	"""
+	time = flask.request.args.get("time")
+	if time is None:
+		time = datetime.datetime.utcnow()
+	else:
+		time = dateutil.parse(time)
+
+	range = int(flask.request.args.get("range", "60"))
+	range = datetime.timedelta(seconds=range)
+
+	extrapolate = (flask.request.args.get("extrapolate") == "true")
+
+	start = time - range
+	end = time
+
+	conn = app.db_manager.get_conn()
+	# Get newest non-errored row within time range
+	results = database.query(conn, """
+		SELECT timestamp, odometer
+		FROM bus_data
+		WHERE odometer IS NOT NULL
+			AND channel = %(channel)s
+			AND timestamp > %(start)s
+			AND timestamp <= %(end)s
+		ORDER BY timestamp DESC
+		LIMIT 1
+	""", channel, start, end)
+	result = results.fetchone()
+	if result is None:
+		# By Sokar's request, we want to return an invalid value rather than an error response.
+		return "0"
+	if not extrapolate:
+		return str(result.odometer)
+	# Current extrapolate strategy is very simple: presume we're going at full speed (45mph).
+	SPEED = 45. / 3600 # in miles per second
+	delta_t = time - timestamp
+	delta_odo = delta_t * SPEED
+	return str(result.odometer + delta_odo)
+
+
 @argh.arg('--host', help='Address or socket server will listen to. Default is 0.0.0.0 (everything on the local machine).')
 @argh.arg('--port', help='Port server will listen on. Default is 8004.')
 @argh.arg('connection-string', help='Postgres connection string, which is either a space-separated list of key=value pairs, or a URI like: postgresql://USER:PASSWORD@HOST/DBNAME?KEY=VALUE')