Add --last-days arg, and fix user agent windowing.

source/report/gen.d

@@ -6,6 +6,7 @@ import std.datetime;
 import std.algorithm;
 import std.array;
 import std.file;
+import std.conv : to;
 import d2sqlite3;
 import data;
 import std.json;
@@ -54,6 +55,10 @@ are accepted:
     date and time. Timestamps are always interpretted as UTC timezone. Defaults
     to the current time.
 
+--last-days <days>
+    A convenience to show stats from the last N days. If provided, overrides
+    any --start or --end timestamps given.
+
 -f <format> | --format <format>
     Specify the desired output format for the report(s) generated by this
     command. The following formats are available: text, json, csv.
@@ -104,6 +109,10 @@ ReportPeriod parseReportPeriod(string[] args) {
             } else if (args[i] == "--end" && !endParsed) {
                 end = tryParseTime(args[i + 1]);
                 endParsed = true;
+            } else if (args[i] == "--last-days") {
+                end = Clock.currTime(UTC());
+                start = end - days(args[i + 1].to!uint);
+                return ReportPeriod(start, end);
             }
         }
     }
@@ -198,9 +207,12 @@ SQL",
     ResultRange userAgentsResult = db.execute(q"SQL
         SELECT user_agent, COUNT(user_agent) AS c
         FROM session
+        WHERE start_timestamp >= ? AND end_timestamp <= ?
         GROUP BY user_agent
         ORDER BY c DESC
-SQL");
+SQL",
+        TS_START, TS_END
+    );
     foreach (Row row; userAgentsResult) {
         string userAgent = row["user_agent"].as!string;
         ulong count = row["c"].as!ulong;