give downloaded .mp4s a useful filename

This is effective both for Chrome's "Save As" dialog and for curl -OJ.
It makes the filename like 20190717135519-driveway-main.mp4 rather than
view.mp4 (Chrome) or view.mp4?s=33-36&ts=true (Curl).

src/mp4.rs

@@ -95,6 +95,7 @@ use reffers::ARefss;
 use crate::slices::{self, Slices};
 use smallvec::SmallVec;
 use std::cell::UnsafeCell;
+use std::convert::TryFrom;
 use std::cmp;
 use std::fmt;
 use std::io;
@@ -104,7 +105,7 @@ use std::sync::Arc;
 use std::time::SystemTime;
 
 /// This value should be incremented any time a change is made to this file that causes different
-/// bytes to be output for a particular set of `Mp4Builder` options. Incrementing this value will
+/// bytes to be output for a particular set of `FileBuilder` options. Incrementing this value will
 /// cause the etag to change as well.
 const FORMAT_VERSION: [u8; 1] = [0x06];
 
@@ -551,6 +552,7 @@ pub struct FileBuilder {
     body: BodyState,
     type_: Type,
     include_timestamp_subtitle_track: bool,
+    content_disposition: Option<HeaderValue>,
 }
 
 /// The portion of `FileBuilder` which is mutated while building the body of the file.
@@ -711,7 +713,7 @@ macro_rules! write_length {
     }}
 }
 
-#[derive(PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Type {
     Normal,
     InitSegment,
@@ -734,6 +736,7 @@ impl FileBuilder {
             },
             type_: type_,
             include_timestamp_subtitle_track: false,
+            content_disposition: None,
         }
     }
 
@@ -773,6 +776,13 @@ impl FileBuilder {
         Ok(())
     }
 
+    pub fn set_filename(&mut self, filename: &str) -> Result<(), Error> {
+        self.content_disposition =
+            Some(HeaderValue::try_from(format!("attachment; filename=\"{}\"", filename))
+                 .err_kind(ErrorKind::InvalidArgument)?);
+        Ok(())
+    }
+
     /// Builds the `File`, consuming the builder.
     pub fn build(mut self, db: Arc<db::Database>,
                  dirs_by_stream_id: Arc<::fnv::FnvHashMap<i32, Arc<dir::SampleFileDir>>>)
@@ -784,6 +794,10 @@ impl FileBuilder {
         if self.include_timestamp_subtitle_track {
             etag.update(b":ts:").err_kind(ErrorKind::Internal)?;
         }
+        if let Some(cd) = self.content_disposition.as_ref() {
+            etag.update(b":cd:").err_kind(ErrorKind::Internal)?;
+            etag.update(cd.as_bytes()).err_kind(ErrorKind::Internal)?;
+        }
         match self.type_ {
             Type::Normal => {},
             Type::InitSegment => etag.update(b":init:").err_kind(ErrorKind::Internal)?,
@@ -884,8 +898,9 @@ impl FileBuilder {
             video_sample_entries: self.video_sample_entries,
             initial_sample_byte_pos,
             last_modified,
-            etag: HeaderValue::from_str(&format!("\"{}\"", &strutil::hex(&etag)))
+            etag: HeaderValue::try_from(format!("\"{}\"", &strutil::hex(&etag)))
                   .expect("hex string should be valid UTF-8"),
+            content_disposition: self.content_disposition,
         })))
     }
 
@@ -1433,6 +1448,7 @@ struct FileInner {
     initial_sample_byte_pos: u64,
     last_modified: SystemTime,
     etag: HeaderValue,
+    content_disposition: Option<HeaderValue>,
 }
 
 impl FileInner {
@@ -1513,6 +1529,10 @@ impl http_serve::Entity for File {
         mime.extend_from_slice(b"\"");
         hdrs.insert(http::header::CONTENT_TYPE,
                     http::header::HeaderValue::from_maybe_shared(mime.freeze()).unwrap());
+
+        if let Some(cd) = self.0.content_disposition.as_ref() {
+            hdrs.insert(http::header::CONTENT_DISPOSITION, cd.clone());
+        }
     }
     fn last_modified(&self) -> Option<SystemTime> { Some(self.0.last_modified) }
     fn etag(&self) -> Option<HeaderValue> { Some(self.0.etag.clone()) }

src/web.rs

@@ -399,16 +399,20 @@ impl ServiceInner {
         if !caller.permissions.view_video {
             return Err(plain_response(StatusCode::UNAUTHORIZED, "view_video required"));
         }
-        let stream_id = {
+        let (stream_id, camera_name);
+        {
             let db = self.db.lock();
             let camera = db.get_camera(uuid)
                            .ok_or_else(|| plain_response(StatusCode::NOT_FOUND,
                                                          format!("no such camera {}", uuid)))?;
-            camera.streams[stream_type.index()]
+            camera_name = camera.short_name.clone();
+            stream_id = camera.streams[stream_type.index()]
                 .ok_or_else(|| plain_response(StatusCode::NOT_FOUND,
                                               format!("no such stream {}/{}", uuid,
-                                                      stream_type)))?
+                                                      stream_type)))?;
+
         };
+        let mut start_time_for_filename = None;
         let mut builder = mp4::FileBuilder::new(mp4_type);
         if let Some(q) = req.uri().query() {
             for (key, value) in form_urlencoded::parse(q.as_bytes()) {
@@ -465,6 +469,10 @@ impl ServiceInner {
                                 let times = start as i32 .. end as i32;
                                 debug!("...appending recording {} with times {:?} \
                                        (out of dur {})", r.id, times, d);
+                                if start_time_for_filename.is_none() {
+                                    start_time_for_filename =
+                                        Some(r.start + recording::Duration(start));
+                                }
                                 builder.append(&db, r, start as i32 .. end as i32)?;
                             } else {
                                 debug!("...skipping recording {} dur {}", r.id, d);
@@ -499,6 +507,14 @@ impl ServiceInner {
                 }
             };
         }
+        if let Some(start) = start_time_for_filename {
+            let tm = time::at(time::Timespec{sec: start.unix_seconds(), nsec: 0});
+            let stream_abbrev = if stream_type == db::StreamType::MAIN { "main" } else { "sub" };
+            let suffix = if mp4_type == mp4::Type::Normal { "mp4" } else { "m4s" };
+            builder.set_filename(&format!("{}-{}-{}.{}", tm.strftime("%Y%m%d%H%M%S").unwrap(),
+                                          camera_name, stream_abbrev, suffix))
+                .map_err(from_base_error)?;
+        }
         let mp4 = builder.build(self.db.clone(), self.dirs_by_stream_id.clone())
                          .map_err(from_base_error)?;
         if debug {
@@ -572,7 +588,7 @@ impl ServiceInner {
         let flags = (auth::SessionFlags::HttpOnly as i32) |
                     (auth::SessionFlags::SameSite as i32) |
                     (auth::SessionFlags::SameSiteStrict as i32) |
-                    if is_secure { (auth::SessionFlags::Secure as i32) } else { 0 };
+                    if is_secure { auth::SessionFlags::Secure as i32 } else { 0 };
         let (sid, _) = l.login_by_password(authreq, &r.username, r.password, Some(domain),
             flags)
             .map_err(|e| plain_response(StatusCode::UNAUTHORIZED, e.to_string()))?;