send files to contacts (#94)

* schema for sending files

* send file "invitation"

* receive file "invitation"

* send/receive file flow (with stubs)

* update simplexmq

* send and receive the file (WIP - only the first chunk)

* sending and receiving file works (but it is slow)

* use correct terminal output for file sending/receiving

* improve file transfer, support cancellation

* command to show file transfer status and progress

* file transfer tests

* resume file transfer on restart (WIP)

* stabilize test of recipient cancelling file transfer

* trying to improve file transfer on restart

* update SMP block size and file chunk size

* acquire agent lock before chat lock to test whether it avoids deadlock

* fix resuming sending file on client restart

* manual message ACK (prevents losing messages between agent and chat client and stabilizes resuming file reception after restart)

* do NOT send file chunk after receiving it before it is appended to the file

* update file chunk size for SMP block size 8192 (set in smpDefaultConfig)

* save received files to ~/Downloads folder by default; create empty file when file is accepted

* keep file handle used to create empty file

* check message integrity

* fix trying to resume sending file when it was not yet accepted

* fix subscribing to pending connections on start

* update simplexmq (fixes smp-server syntax parser)

migrations/20210612_initial.sql

@@ -130,17 +130,68 @@ CREATE TABLE group_member_intros (
   UNIQUE (re_group_member_id, to_group_member_id)
 );
 
+CREATE TABLE files (
+  file_id INTEGER PRIMARY KEY,
+  contact_id INTEGER REFERENCES contacts ON DELETE RESTRICT,
+  group_id INTEGER REFERENCES groups ON DELETE RESTRICT,
+  file_name TEXT NOT NULL,
+  file_path TEXT,
+  file_size INTEGER NOT NULL,
+  chunk_size INTEGER NOT NULL,
+  created_at TEXT NOT NULL DEFAULT (datetime('now')),
+  user_id INTEGER NOT NULL REFERENCES users
+);
+
+CREATE TABLE snd_files (
+  file_id INTEGER NOT NULL REFERENCES files ON DELETE RESTRICT,
+  connection_id INTEGER NOT NULL REFERENCES connections ON DELETE RESTRICT,
+  file_status TEXT NOT NULL, -- new, accepted, connected, completed
+  group_member_id INTEGER REFERENCES group_members ON DELETE RESTRICT,
+  PRIMARY KEY (file_id, connection_id)
+) WITHOUT ROWID;
+
+CREATE TABLE rcv_files (
+  file_id INTEGER PRIMARY KEY REFERENCES files ON DELETE RESTRICT,
+  file_status TEXT NOT NULL, -- new, accepted, connected, completed
+  group_member_id INTEGER REFERENCES group_members ON DELETE RESTRICT,
+  file_queue_info BLOB
+);
+
+CREATE TABLE snd_file_chunks (
+  file_id INTEGER NOT NULL,
+  connection_id INTEGER NOT NULL,
+  chunk_number INTEGER NOT NULL,
+  chunk_agent_msg_id INTEGER,
+  chunk_sent INTEGER NOT NULL DEFAULT 0, -- 0 (sent to agent), 1 (sent to server)
+  FOREIGN KEY (file_id, connection_id) REFERENCES snd_files ON DELETE CASCADE,
+  PRIMARY KEY (file_id, connection_id, chunk_number)
+) WITHOUT ROWID;
+
+CREATE TABLE rcv_file_chunks (
+  file_id INTEGER NOT NULL REFERENCES rcv_files,
+  chunk_number INTEGER NOT NULL,
+  chunk_agent_msg_id INTEGER NOT NULL,
+  chunk_stored INTEGER NOT NULL DEFAULT 0, -- 0 (received), 1 (appended to file)
+  PRIMARY KEY (file_id, chunk_number)
+) WITHOUT ROWID;
+
 CREATE TABLE connections ( -- all SMP agent connections
   connection_id INTEGER PRIMARY KEY,
   agent_conn_id BLOB NOT NULL UNIQUE,
   conn_level INTEGER NOT NULL DEFAULT 0,
   via_contact INTEGER REFERENCES contacts (contact_id),
   conn_status TEXT NOT NULL,
-  conn_type TEXT NOT NULL, -- contact, member, member_direct
+  conn_type TEXT NOT NULL, -- contact, member, rcv_file, snd_file
   contact_id INTEGER REFERENCES contacts ON DELETE RESTRICT,
   group_member_id INTEGER REFERENCES group_members ON DELETE RESTRICT,
+  snd_file_id INTEGER,
+  rcv_file_id INTEGER REFERENCES rcv_files (file_id) ON DELETE RESTRICT,
   created_at TEXT NOT NULL DEFAULT (datetime('now')),
-  user_id INTEGER NOT NULL REFERENCES users
+  user_id INTEGER NOT NULL REFERENCES users,
+  FOREIGN KEY (snd_file_id, connection_id)
+    REFERENCES snd_files (file_id, connection_id)
+    ON DELETE RESTRICT
+    DEFERRABLE INITIALLY DEFERRED
 );
 
 CREATE TABLE events ( -- messages received by the agent, append only