X-Git-Url: https://git.xandkar.net/?a=blobdiff_plain;f=tt.rkt;h=e93c26f4a20e67426ec608c863204e638dead67f;hb=HEAD;hp=be88095464a2edae575c79e1a68b4230744d87e1;hpb=26d172a9fb38101f3cc64eed8f2366309d55b9d2;p=tt.git

diff --git a/tt.rkt b/tt.rkt
index be88095..e93c26f 100644
--- a/tt.rkt
+++ b/tt.rkt
@@ -1,64 +1,213 @@
-; TODO optional text wrap
-; TODO write
-; TODO caching (use cache by default, unless explicitly asked for update)
-; - [x] value --> cache
-; - [ ] value <-- cache
-;   requires: commands
-; TODO timeline limits
-; TODO feed set operations (perhaps better done externally?)
-; TODO timeline as a result of a query (feed set op + filter expressions)
-; TODO named timelines
-; TODO CLI params
-; TODO config files
-; TODO parse "following" from feed
-; - following = <nick> <uri>
-; TODO parse mentions:
-; - @<source.nick source.url> | @<source.url>
-; TODO highlight mentions
-; TODO filter on mentions
-; TODO highlight hashtags
-; TODO filter on hashtags
-; TODO hashtags as channels? initial hashtag special?
-; TODO query language
-; TODO console logger colors by level ('error)
-; TODO file logger ('debug)
-; TODO commands:
-; - r | read
-;   - see timeline ops above
-; - w | write
-;   - arg or stdin
-;   - nick expand to URI
-; - q | query
-;   - see timeline ops above
-;   - see hashtag and channels above
-; - d | download
-; - u | upload
-;   - calls user-configured command to upload user's own feed file to their server
-;
-; Looks like a better CLI parser than "racket/cmdline":
-; https://docs.racket-lang.org/natural-cli/
-
-#lang racket
+#lang typed/racket/no-check
 
 (require openssl/sha1)
 (require racket/date)
+(require
+  net/head
+  net/uri-codec
+  net/url)
 
-(require http-client)
-(require rfc3339-old)
+(require (prefix-in info: "info.rkt"))
 
 (module+ test
   (require rackunit))
 
-(struct msg  (ts_epoch ts_rfc3339 nick uri text))
-(struct feed (nick uri))
+(define-type Url
+  net/url-structs:url)
+
+(define-type Out-Format
+  (U 'single-line
+     'multi-line))
+
+(define-type Timeline-Order
+  (U 'old->new
+     'new->old))
+
+(define-type Result
+  (∀ (α β) (U (cons 'ok α)
+              (cons 'error β))))
+
+(define-type Download-Result
+  (Result (U 'skipped-cached 'downloaded-new)
+          (U 'timeout
+             (Pair 'unsupported-url-scheme String)
+             (Pair 'http-not-ok Positive-Integer)
+             (Pair 'net-error Any)
+             (Pair 'other Any))))
+
+(struct Hist
+        ([freq : Nonnegative-Integer]
+         [last : Nonnegative-Integer])
+        #:transparent)
+
+(define-type Url-Nick-Hist
+  (Immutable-HashTable Url (Immutable-HashTable (Option String) Hist)))
+
+(struct User
+        ([url  : Url]
+         [nick : (Option String)]))
+
+(struct User-Agent
+        ([user : User]
+         [prog : Prog]))
+
+(struct Prog
+        ([name    : String]
+         [version : String]))
+
+(struct Msg
+        ([ts-epoch   : Integer]
+         [ts-orig    : String]
+         [from       : Peer]
+         [text       : String]
+         [mentions   : (Listof Peer)]))
+
+(struct Peer
+        ([nick    : (Option String)]
+         [url     : Url]
+         [url-str : String]
+         [comment : (Option String)])
+        #:transparent)
 
-(define (concurrent-filter-map num_workers f xs)
+(: prog Prog)
+(define prog
+  (Prog "tt" (info:#%info-lookup 'version)))
+
+(: user-default User)
+(define user-default
+  (User (string->url "https://github.com/xandkar/tt") #f))
+
+(: user->str (-> User String))
+(define (user->str user)
+  (match-define (User u0 n) user)
+  (define u (url->string u0))
+  (if n
+      (format "+~a; @~a" u n)
+      (format "+~a"      u  )))
+
+(: user-agent->str (-> User-Agent String))
+(define (user-agent->str ua)
+  (match-define (User-Agent u p) ua)
+  (format "~a/~a (~a)" (Prog-name p) (Prog-version p) (user->str u)))
+
+(: user->user-agent User)
+(define (user->user-agent user)
+  (User-Agent user prog))
+
+(: user-agent-str String)
+(define user-agent-str
+  (user-agent->str (user->user-agent user-default)))
+
+(: set-user-agent-str (-> Path-String Void))
+(define (set-user-agent-str filename)
+  (set! user-agent-str (user-agent->str (user->user-agent (file->user filename))))
+  (log-info "User-Agent string is now set to: ~v" user-agent-str))
+
+(: file->user (-> Path-String User))
+(define (file->user filename)
+  (if (file-exists? filename)
+      (match (file->peers filename)
+        [(list p)
+         (log-info
+           "User-Agent. Found one peer in file: ~v. Using the found peer: ~a"
+           filename
+           (peer->str p))
+         (peer->user p)]
+        [(list* p _)
+         (log-warning
+           "User-Agent. Multiple peers in file: ~v. Picking arbitrary: ~a"
+           filename
+           (peer->str p))
+         (peer->user p)]
+        ['()
+         (log-warning
+           "User-Agent. No peers found in file: ~v. Using the default user: ~a"
+           filename
+           user-default)
+         user-default])
+      (begin
+        (log-warning
+          "User-Agent. File doesn't exist: ~v. Using the default user: ~a"
+          filename
+          user-default)
+        user-default)))
+
+(: peer->user (-> Peer User))
+(define (peer->user p)
+  (match-define (Peer n u _ _) p)
+  (User u n))
+
+(: peers-equal? (-> Peer Peer Boolean))
+(define (peers-equal? p1 p2)
+  (equal? (Peer-url-str p1)
+          (Peer-url-str p2)))
+
+(: peer-hash (-> Peer Fixnum))
+(define (peer-hash p)
+  (equal-hash-code (Peer-url-str p)))
+
+(define-custom-set-types peers
+  #:elem? Peer?
+  peers-equal?
+  peer-hash)
+; XXX Without supplying above explicit hash procedure, we INTERMITTENTLY get
+;     the following contract violations:
+;
+;         custom-elem-contents: contract violation
+;           expected: custom-elem?
+;           given: #f
+;           context...:
+;            /usr/share/racket/collects/racket/private/set-types.rkt:104:0: custom-set->list
+;            /home/siraaj/proj/pub/tt/tt.rkt:716:0: crawl
+;            /usr/share/racket/collects/racket/cmdline.rkt:191:51
+;            body of (submod "/home/siraaj/proj/pub/tt/tt.rkt" main)
+;
+; TODO Investigate why and make a minimal reproducible test case.
+
+(: peers-merge (-> (Listof Peer) * (Listof Peer)))
+(define (peers-merge . peer-sets)
+  (define (merge-2 p1 p2)
+    (match* (p1 p2)
+      [((Peer n1 _ _ _) (Peer n2 _ _ _)) #:when (and n1 n2) p1] ; TODO compare which is more-common?
+      [((Peer #f _ _ _) (Peer #f _ _ _))                    p1] ; TODO update with most-common nick?
+      [((Peer n1 _ _ _) (Peer #f _ _ _))                    p1]
+      [((Peer #f _ _ _) (Peer n2 _ _ _))                    p2]))
+  (: merge-n (-> (Listof Peer) Peer))
+  (define (merge-n peers)
+    (match peers
+      ['() (raise 'impossible)]
+      [(list p) p]
+      [(list* p1 p2 ps) (merge-n (cons (merge-2 p1 p2) ps))]))
+  (sort (map merge-n (group-by Peer-url-str (append* peer-sets)))
+        (match-lambda**
+          [((Peer _ _ u1 _) (Peer _ _ u2 _)) (string<? u1 u2)])))
+
+(module+ test
+  (let* ([u1 "http://foo/bar"]
+         [u2 "http://baz/quux"]
+         [p1 (Peer #f (string->url u1) u1 #f)]
+         [p2 (Peer "a" (string->url u1) u1 #f)]
+         [p3 (Peer "b" (string->url u2) u2 #f)]
+         [s1 (list p1)]
+         [s2 (list p2 p3)])
+    (check-equal? (list p3 p2) (peers-merge s1 s2))
+    (check-equal? (list p3 p2) (peers-merge s2 s1))))
+
+(: tt-home-dir Path-String)
+(define tt-home-dir (build-path (expand-user-path "~") ".tt"))
+
+(: pub-peers-dir Path-String)
+(define pub-peers-dir (build-path tt-home-dir "peers"))
+
+(: concurrent-filter-map (∀ (α β) (-> Natural (-> α β) (Listof α) (Listof β))))
+(define (concurrent-filter-map num-workers f xs)
   ; TODO preserve order of elements OR communicate that reorder is expected
   ; TODO switch from mailboxes to channels
   (define (make-worker id f)
     (define parent (current-thread))
     (λ ()
-       (define self (current-thread))
+       (define self : Thread (current-thread))
+       (: work (∀ (α) (-> α)))
        (define (work)
          (thread-send parent (cons 'next self))
          (match (thread-receive)
@@ -68,194 +217,920 @@
                              (when y (thread-send parent (cons 'result y)))
                              (work))]))
        (work)))
+  (: dispatch (∀ (α β) (-> (Listof Nonnegative-Integer) (Listof α) (Listof β))))
   (define (dispatch ws xs ys)
     (if (empty? ws)
-      ys
-      (match (thread-receive)
-        [(cons 'exit w)   (dispatch (remove w ws =) xs ys)]
-        [(cons 'result y) (dispatch ws xs (cons y ys))]
-        [(cons 'next thd) (match xs
-                            ['()         (begin
-                                           (thread-send thd 'done)
-                                           (dispatch ws xs ys))]
-                            [(cons x xs) (begin
-                                           (thread-send thd (cons 'unit x))
-                                           (dispatch ws xs ys))])])))
-  (define workers (range num_workers))
+        ys
+        (match (thread-receive)
+          [(cons 'exit w)   (dispatch (remove w ws =) xs ys)]
+          [(cons 'result y) (dispatch ws xs (cons y ys))]
+          [(cons 'next thd) (match xs
+                              ['()         (begin
+                                             (thread-send thd 'done)
+                                             (dispatch ws xs ys))]
+                              [(cons x xs) (begin
+                                             (thread-send thd (cons 'unit x))
+                                             (dispatch ws xs ys))])])))
+  (define workers (range num-workers))
   (define threads (map (λ (id) (thread (make-worker id f))) workers))
   (define results (dispatch workers xs '()))
   (for-each thread-wait threads)
   results)
 
 (module+ test
-  (define n-workers 10)
-  (define given (list
-                  (λ (x) (if (even? x) x #f))
-                  (range 11)))
-  (check-equal?
-    (sort (apply concurrent-filter-map (cons n-workers given)) <)
-    (sort (apply            filter-map                 given ) <)))
-
-(define (msg-print out-format odd msg)
-  (printf
-    (match out-format
-      ['single-line "~a  \033[1;37m<~a ~a>\033[0m  \033[0;~am~a\033[0m~n"]
-      ['multi-line  "~a~n\033[1;37m<~a ~a>\033[0m~n\033[0;~am~a\033[0m~n~n"]
-      [_           (raise (format "Invalid output format: ~a" out-format))])
-    (date->string (seconds->date [msg-ts_epoch msg]) #t)
-    (msg-nick msg)
-    (msg-uri  msg)
-    (if odd 36 33)
-    (msg-text msg)))
-
-(define re-msg-begin
-  ; TODO Zulu offset. Maybe in several formats. Which ones?
-  (pregexp "^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}"))
-
-(define (str->msg nick uri str)
-  (if (not (regexp-match? re-msg-begin str))
-    (begin
-      (log-debug "Non-msg line from nick:~a, line:~a" nick str)
-      #f)
-    (let ([toks (string-split str (regexp "\t+"))])
-      (if (not (= 2 (length toks)))
-        (begin
-          (log-warning "Invalid msg line from nick:~a, msg:~a" nick str)
-          #f)
-        (let*
-          ([ts_rfc3339 (first  toks)]
-           [text       (second toks)]
-           [t          (string->rfc3339-record ts_rfc3339)]
-           ; TODO handle tz offset
-           [ts_epoch (find-seconds [rfc3339-record:second t]
-                                   [rfc3339-record:minute t]
-                                   [rfc3339-record:hour   t]
-                                   [rfc3339-record:mday   t]
-                                   [rfc3339-record:month  t]
-                                   [rfc3339-record:year   t])])
-          (msg ts_epoch ts_rfc3339 nick uri text))))))
+  (let* ([f        (λ (x) (if (even? x) x #f))]
+         [xs       (range 11)]
+         [actual   (sort (concurrent-filter-map 10 f xs) <)]
+         [expected (sort (           filter-map    f xs) <)])
+    (check-equal? actual expected "concurrent-filter-map")))
+
+(: msg-print (-> Out-Format Integer Msg Void))
+(define msg-print
+  (let* ([colors (vector 36 33)]
+         [n      (vector-length colors)])
+    (λ (out-format color-i msg)
+       (let ([color (vector-ref colors (modulo color-i n))]
+             [nick  (Peer-nick (Msg-from msg))]
+             [url   (Peer-url-str (Msg-from msg))]
+             [text  (Msg-text msg)])
+         (match out-format
+           ['single-line
+            (let ([nick (if nick nick url)])
+              (printf "~a  \033[1;37m<~a>\033[0m  \033[0;~am~a\033[0m~n"
+                      (parameterize
+                        ([date-display-format 'iso-8601])
+                        (date->string (seconds->date (Msg-ts-epoch msg)) #t))
+                      nick color text))]
+           ['multi-line
+            (let ([nick (if nick (string-append nick " ") "")])
+              (printf "~a (~a)~n\033[1;37m<~a~a>\033[0m~n\033[0;~am~a\033[0m~n~n"
+                      (parameterize
+                        ([date-display-format 'rfc2822])
+                        (date->string (seconds->date (Msg-ts-epoch msg)) #t))
+                      (Msg-ts-orig msg)
+                      nick url color text))])))))
+
+(: rfc3339->epoch (-> String (Option Nonnegative-Integer)))
+(define rfc3339->epoch
+  (let ([re (pregexp "^([0-9]{4})-([0-9]{2})-([0-9]{2})T([0-9]{2}):([0-9]{2})(:([0-9]{2}))?(\\.[0-9]+)?(Z|([+-])([0-9]{1,2}):?([0-9]{2}))?$")])
+    (λ (ts)
+       (match (regexp-match re ts)
+         [(list _wholething yyyy mm dd HH MM _:SS SS _fractional tz-whole tz-sign tz-HH tz-MM)
+          (let*
+            ([tz-offset
+               (match* (tz-whole tz-sign tz-HH tz-MM)
+                 [("Z" #f #f #f)
+                  0]
+                 [(_  (or "-" "+") (? identity h)  (? identity m))
+                  (let ([h (string->number h)]
+                        [m (string->number m)]
+                        ; Reverse to get back to UTC:
+                        [op (match tz-sign ["+" -] ["-" +])])
+                    (op 0 (+ (* 60 m) (* 60 (* 60 h)))))]
+                 [(a b c d)
+                  (log-warning "Impossible TZ string: ~v, components: ~v ~v ~v ~v" tz-whole a b c d)
+                  0])]
+             [ts-orig ts]
+             [local-time? #f]
+             [ts-epoch (find-seconds (if SS (string->number SS) 0)
+                                     (string->number MM)
+                                     (string->number HH)
+                                     (string->number dd)
+                                     (string->number mm)
+                                     (string->number yyyy)
+                                     local-time?)])
+            (+ ts-epoch tz-offset))]
+         [_
+           (log-debug "Invalid timestamp: ~v" ts)
+           #f]))))
+
+(: str->msg (-> Peer String (Option Msg)))
+(define str->msg
+  (let ([re (pregexp "^([^\\s\t]+)[\\s\t]+(.*)$")])
+    (λ (from str)
+       (define from-str (peer->str from))
+       (define str-head (substring str 0 (min 100 (string-length str))))
+       (with-handlers*
+         ([exn:fail?
+            (λ (e)
+               (log-debug
+                 "Failed to parse msg: ~v, from: ~v, at: ~v, because: ~v"
+                 str-head from-str e)
+               #f)])
+         (match (regexp-match re str)
+           [(list _wholething ts-orig text)
+            (let ([ts-epoch (rfc3339->epoch ts-orig)])
+              (if ts-epoch
+                  (let ([mentions
+                          (filter-map
+                            (λ (m) (match (regexp-match #px"@<([^>]+)>" m)
+                                     [(list _wholething nick-url)
+                                      (str->peer nick-url)]))
+                            (regexp-match* #px"@<[^\\s]+([\\s]+)?[^>]+>" text))])
+                    (Msg ts-epoch ts-orig from text mentions))
+                  (begin
+                    (log-debug
+                      "Msg rejected due to invalid timestamp. From:~v. Line:~v"
+                      from-str str-head)
+                    #f)))]
+           [_
+             (log-debug "Non-msg line. From:~v. Line:~v" from-str str-head)
+             #f])))))
+
+(module+ test
+  ; TODO Test for when missing-nick case
+  (let* ([tzs (for*/list ([d '("-" "+")]
+                          [h '("5" "05")]
+                          [m '("00" ":00" "57" ":57")])
+                         (string-append d h m))]
+         [tzs (list* "" "Z" tzs)])
+    (for* ([n   '("fake-nick")]
+           [u   '("http://fake-url")]
+           [p   (list (Peer n (string->url u) u #f))]
+           [s   '("" ":10")]
+           [f   '("" ".1337")]
+           [z   tzs]
+           [sep (list "\t" " ")]
+           [txt '("foo bar baz" "'jaz poop bear giraffe / tea" "@*\"``")])
+          (let* ([ts (string-append "2020-11-18T22:22"
+                                    (if (non-empty-string? s) s ":00")
+                                    z)]
+                 [m  (str->msg p (string-append ts sep txt))])
+            (check-not-false m)
+            (check-equal? (Msg-from m) p)
+            (check-equal? (Msg-text m) txt)
+            (check-equal? (Msg-ts-orig m) ts (format "Given: ~v" ts))
+            )))
+
+  (let* ([ts       "2020-11-18T22:22:09-0500"]
+         [tab      "	"]
+         [text     "Lorem ipsum"]
+         [nick     "foo"]
+         [url      "http://bar/"]
+         [peer     (Peer nick (string->url url) url #f)]
+         [actual   (str->msg peer (string-append ts tab text))]
+         [expected (Msg 1605756129 ts peer text '())])
+    (check-equal?
+      (Msg-ts-epoch actual)
+      (Msg-ts-epoch expected)
+      "str->msg ts-epoch")
+    (check-equal?
+      (Msg-ts-orig actual)
+      (Msg-ts-orig expected)
+      "str->msg ts-orig")
+    (check-equal?
+      (Peer-nick (Msg-from actual))
+      (Peer-nick (Msg-from expected))
+      "str->msg nick")
+    (check-equal?
+      (Peer-url (Msg-from actual))
+      (Peer-url (Msg-from expected))
+      "str->msg url")
+    (check-equal?
+      (Peer-url-str (Msg-from actual))
+      (Peer-url-str (Msg-from expected))
+      "str->msg url-str")
+    (check-equal?
+      (Msg-text actual)
+      (Msg-text expected)
+      "str->msg text")))
 
+(: str->lines (-> String (Listof String)))
 (define (str->lines str)
   (string-split str (regexp "[\r\n]+")))
 
-(define (str->msgs nick uri str)
-  (filter-map (λ (line) (str->msg nick uri line)) (str->lines str)))
-
-(define (hash-sha1 str)
-  (define in (open-input-string str))
-  (define digest (sha1 in))
-  (close-input-port in)
-  digest)
-
-(define (uri-fetch uri)
-  (log-info "GET ~a" uri)
-  (define resp (http-get uri))
-  (define status (http-response-code resp))
-  (define body (http-response-body resp))
-  (log-debug "finished GET ~a status:~a  body length:~a"
-             uri status (string-length body))
-  ; TODO Handle redirects
-  (if (= status 200)
-    (let*
-      ([url-digest
-         (hash-sha1 uri)]
-       [cache-file-path
-         (expand-user-path (string-append "~/.tt/cache/" url-digest))])
-      (display-to-file
-        body cache-file-path
-        #:exists 'replace)
-      body)
-    ; TODO A more-informative exception
-    (raise status)))
+(module+ test
+  (check-equal? (str->lines "abc\ndef\n\nghi") '("abc" "def" "ghi")))
+
+; TODO Should return 2 things: 1) msgs; 2) metadata parsed from comments
+; TODO Update peer nick based on metadata?
+(: str->msgs (-> Peer String (Listof Msg)))
+(define (str->msgs peer str)
+  (filter-map (λ (line) (str->msg peer line))
+              (filter-comments (str->lines str))))
+
+(: cache-dir Path-String)
+(define cache-dir (build-path tt-home-dir "cache"))
+
+(define cache-object-dir (build-path cache-dir "objects"))
+
+(: url->cache-file-path-v1 (-> Url Path-String))
+(define (url->cache-file-path-v1 url)
+  (define (hash-sha1 str) : (-> String String)
+    (define in (open-input-string str))
+    (define digest (sha1 in))
+    (close-input-port in)
+    digest)
+  (build-path cache-object-dir (hash-sha1 (url->string url))))
+
+(: url->cache-file-path-v2 (-> Url Path-String))
+(define (url->cache-file-path-v2 url)
+  (build-path cache-object-dir (uri-encode (url->string url))))
+
+(define url->cache-object-path
+  url->cache-file-path-v2)
+
+(define (url->cache-etag-path url)
+  (build-path cache-dir "etags" (uri-encode (url->string url))))
+
+(define (url->cache-lmod-path url)
+  (build-path cache-dir "lmods" (uri-encode (url->string url))))
+
+(: url-read-cached (-> Url (Option String)))
+(define (url-read-cached url)
+  (define path-v1 (url->cache-file-path-v1 url))
+  (define path-v2 (url->cache-file-path-v2 url))
+  (when (file-exists? path-v1)
+    (rename-file-or-directory path-v1 path-v2 #t))
+  (if (file-exists? path-v2)
+      (file->string path-v2)
+      (begin
+        (log-debug "Cache file not found for URL: ~a" (url->string url))
+        #f)))
+
+(: str->url (-> String (Option String)))
+(define (str->url s)
+  (with-handlers*
+    ([exn:fail? (λ (e) #f)])
+    (string->url s)))
+
+(: peer->str (-> Peer String))
+(define (peer->str peer)
+  (match-define (Peer n _ u c) peer)
+  (format "~a~a~a"
+          (if n (format "~a " n) "")
+          u
+          (if c (format " # ~a" c) "")))
 
+(: str->peer (-> String (Option Peer)))
+(define (str->peer str)
+  (log-debug "Parsing peer string: ~v" str)
+  (match
+    (regexp-match
+      #px"(([^\\s\t]+)[\\s\t]+)?([a-zA-Z]+://[^\\s\t]*)[\\s\t]*(#\\s*(.*))?"
+      str)
+    [(list _wholething
+           _nick-with-space
+           nick
+           url
+           _comment-with-hash
+           comment)
+     (match (str->url url)
+       [#f
+         (log-error "Invalid URL in peer string: ~v" str)
+         #f]
+       [url
+         (Peer nick url (url->string url) comment)])]
+    [_
+      (log-debug "Invalid peer string: ~v" str)
+      #f]))
+
+(module+ test
+  (check-equal?
+    (str->peer "foo http://bar/file.txt # some rando")
+    (Peer "foo" (str->url "http://bar/file.txt") "http://bar/file.txt" "some rando"))
+  (check-equal?
+    (str->peer "http://bar/file.txt # some rando")
+    (Peer #f (str->url "http://bar/file.txt") "http://bar/file.txt" "some rando"))
+  (check-equal?
+    (str->peer "http://bar/file.txt #")
+    (Peer #f (str->url "http://bar/file.txt") "http://bar/file.txt" ""))
+  (check-equal?
+    (str->peer "http://bar/file.txt#") ; XXX URLs can have #s
+    (Peer #f (str->url "http://bar/file.txt#") "http://bar/file.txt#" #f))
+  (check-equal?
+    (str->peer "http://bar/file.txt")
+    (Peer #f (str->url "http://bar/file.txt") "http://bar/file.txt" #f))
+  (check-equal?
+    (str->peer "foo http://bar/file.txt")
+    (Peer "foo" (str->url "http://bar/file.txt") "http://bar/file.txt" #f))
+  (check-equal?
+    (str->peer "foo bar # baz")
+    #f)
+  (check-equal?
+    (str->peer "foo bar://baz # quux")
+    (Peer "foo" (str->url "bar://baz") "bar://baz" "quux"))
+  (check-equal?
+    (str->peer "foo bar//baz # quux")
+    #f))
+
+(: filter-comments (-> (Listof String) (Listof String)))
+(define (filter-comments lines)
+  (filter-not (λ (line) (string-prefix? line "#")) lines))
+
+(: str->peers (-> String (Listof Peer)))
+(define (str->peers str)
+  (filter-map str->peer (filter-comments (str->lines str))))
+
+(: peers->file (-> (Listof Peers) Path-String Void))
+(define (peers->file peers path)
+  (make-parent-directory* path)
+  (display-lines-to-file
+    (map peer->str
+         (sort peers
+               (match-lambda**
+                 [((Peer n1 _ _ _) (Peer n2 _ _ _))
+                  (string<? (if n1 n1 "")
+                            (if n2 n2 ""))])))
+    path
+    #:exists 'replace))
+
+(: file->peers (-> Path-String (Listof Peer)))
+(define (file->peers file-path)
+  (if (file-exists? file-path)
+      (str->peers (file->string file-path))
+      (begin
+        (log-warning "File does not exist: ~v" (path->string file-path))
+        '())))
+
+(define re-rfc2822
+  #px"^(Mon|Tue|Wed|Thu|Fri|Sat|Sun), ([0-9]{2}) (Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) ([0-9]{4}) ([0-2][0-9]):([0-6][0-9]):([0-6][0-9]) GMT")
+
+(: b->n (-> Bytes (Option Number)))
+(define (b->n b)
+  (string->number (bytes->string/utf-8 b)))
+
+(: mon->num (-> Bytes Natural))
+(define/match (mon->num mon)
+  [(#"Jan")  1]
+  [(#"Feb")  2]
+  [(#"Mar")  3]
+  [(#"Apr")  4]
+  [(#"May")  5]
+  [(#"Jun")  6]
+  [(#"Jul")  7]
+  [(#"Aug")  8]
+  [(#"Sep")  9]
+  [(#"Oct") 10]
+  [(#"Nov") 11]
+  [(#"Dec") 12])
+
+(: rfc2822->epoch (-> Bytes (Option Nonnegative-Integer)))
+(define (rfc2822->epoch timestamp)
+  (match (regexp-match re-rfc2822 timestamp)
+    [(list _ _ dd mo yyyy HH MM SS)
+     #:when (and dd mo yyyy HH MM SS)
+     (find-seconds (b->n SS)
+                   (b->n MM)
+                   (b->n HH)
+                   (b->n dd)
+                   (mon->num mo)
+                   (b->n yyyy)
+                   #f)]
+    [_
+      #f]))
+
+(: header-get (-> (Listof Bytes) Bytes (Option Bytes)))
+(define (header-get headers name)
+  (match (filter-map (curry extract-field name) headers)
+    [(list val) val]
+    [_           #f]))
+
+(: url-download-http-from-port
+   (-> Url (Listof (U Bytes String)) Input-Port
+       (U 'skipped-cached 'downloaded-new))) ; TODO 'ok|'error ?
+(define (url-download-http-from-port u headers body-input)
+   ; TODO Update message db from here? or where?
+   ; - 1st try can just be an in-memory set that gets written-to
+   ;   and read-from disk as a whole.
+  (define u-str (url->string u))
+  (log-debug "url-download-http-from-port ~v into ~v" u-str cached-object-path)
+  (define cached-object-path (url->cache-object-path u))
+  (define cached-etag-path (url->cache-etag-path u))
+  (define cached-lmod-path (url->cache-lmod-path u))
+  (define etag      (header-get headers #"ETag"))
+  (define lmod      (header-get headers #"Last-Modified"))
+  (define lmod-curr (if lmod (rfc2822->epoch lmod) #f))
+  (define lmod-prev (if (file-exists? cached-lmod-path)
+                        (rfc2822->epoch (file->bytes cached-lmod-path))
+                        #f))
+  (log-debug "lmod-curr:~v lmod-prev:~v" lmod-curr lmod-prev)
+  (define cached?
+    (or (and etag
+             (file-exists? cached-etag-path)
+             (bytes=? etag (file->bytes cached-etag-path))
+             (begin
+               (log-debug "ETags match, skipping the rest of ~v" u-str)
+               #t))
+        (and lmod-curr
+             lmod-prev
+             (<= lmod-curr lmod-prev)
+             (begin
+               (log-debug "Last-Modified <= current skipping the rest of ~v" u-str)
+               #t))))
+  (if (not cached?)
+      (begin
+        (log-debug
+          "Downloading the rest of ~v. ETag: ~a, Last-Modified: ~v"
+          u-str etag lmod)
+        (make-parent-directory* cached-object-path)
+        (make-parent-directory* cached-etag-path)
+        (make-parent-directory* cached-lmod-path)
+        (call-with-output-file cached-object-path
+                               (curry copy-port body-input)
+                               #:exists 'replace)
+        (when etag
+          (display-to-file etag cached-etag-path #:exists 'replace))
+        (when lmod
+          (display-to-file lmod cached-lmod-path #:exists 'replace))
+        'downloaded-new)
+      'skipped-cached))
+
+(: url-download-http (-> Positive-Float Url Download-Result))
+(define (url-download-http timeout u)
+  (define u-str (url->string u))
+  (define timeout-chan (make-channel))
+  (define result-chan (make-channel))
+  (define timeout-thread
+    (thread (λ ()
+               ; Doing this instead of sync/timeout to distinguish error values,
+               ; rather than just have #f to work with.
+               (sleep timeout)
+               (channel-put timeout-chan '(error . timeout)))))
+  (define result-thread
+    (thread (λ ()
+               (define result
+                 (with-handlers
+                   ; TODO Maybe name each known errno? (exn:fail:network:errno-errno e)
+                   ([exn:fail:network?
+                      (λ (e) `(error . (net-error . ,e)))]
+                    [exn?
+                      (λ (e) `(error . (other . ,e)))])
+                   (define-values (status-line headers body-input)
+                     (http-sendrecv/url
+                       u
+                       #:headers (list (format "User-Agent: ~a" user-agent-str))))
+                   (log-debug "headers: ~v" headers)
+                   (log-debug "status-line: ~v" status-line)
+                   (define status
+                     (string->number (second (string-split (bytes->string/utf-8 status-line)))))
+                   (log-debug "status: ~v" status)
+                   (let ([result
+                           ; TODO Handle redirects.
+                           ; TODO Should a redirect update a peer URL?
+                           (match status
+                             [200
+                               `(ok . ,(url-download-http-from-port u headers body-input))]
+                             [_
+                               `(error . (http-not-ok . ,status))])])
+                     (close-input-port body-input)
+                     result)))
+               (channel-put result-chan result))))
+  (define result (sync timeout-chan result-chan))
+  (kill-thread result-thread)
+  (kill-thread timeout-thread)
+  result)
+
+(: url-download (-> Positive-Float Url Download-Result))
+(define (url-download timeout u)
+  (match (url-scheme u)
+    ; TODO Support Gopher.
+    [(or "http" "https")
+     (url-download-http timeout u)]
+    [scheme
+      `(error . (unsupported-url-scheme . ,scheme))]))
+
+(: timeline-print (-> Out-Format (Listof Msg) Void))
 (define (timeline-print out-format timeline)
-  (for ([msg timeline]
-        [i   (in-naturals)])
-    (msg-print out-format (odd? i) msg)))
-
-(define (feed->msgs feed)
-  (log-info "downloading feed nick:~a uri:~a"
-            (feed-nick feed)
-            (feed-uri feed))
-  (with-handlers
-    ([exn:fail:network?
-       (λ (e)
-          (log-error "network error nick:~a uri:~a  exn:~a"
-                     (feed-nick feed)
-                     (feed-uri feed)
-                     e)
-          #f)]
-     [integer?
-       (λ (status)
-          (log-error "http error nick:~a uri:~a  status:~a"
-                     (feed-nick feed)
-                     (feed-uri feed)
-                     status)
-          #f)])
-    (define uri (feed-uri feed))
-    (str->msgs [feed-nick feed] uri [uri-fetch uri])))
-
-; TODO timeline contract : time-sorted list of messages
-(define (timeline num_workers feeds)
-  (sort (append* (concurrent-filter-map num_workers feed->msgs feeds))
-        (λ (a b) [< (msg-ts_epoch a) (msg-ts_epoch b)])))
-
-(define (str->feed str)
-  ; TODO validation
-  (define toks (string-split str))
-  (apply feed toks))
-
-(define (str->feeds str)
-  (map str->feed (str->lines str)))
-
-(define (file->feeds filename)
-  (str->feeds (file->string filename)))
-
-(define (we-are-twtxt)
-  (define uri
-    "https://raw.githubusercontent.com/mdom/we-are-twtxt/master/we-are-twtxt.txt")
-  (str->feeds (uri-fetch uri)))
-
-(define (user-agent prog-name prog-version)
-  (let*
-    ([prog-uri       "https://github.com/xandkar/tt"]
-     [user-feed-file (expand-user-path "~/twtxt-me.txt")]
-     [user
-       (if (file-exists? user-feed-file)
-         (let ([user (first (file->feeds user-feed-file))])
-           (format "+~a; @~a" (feed-uri user) (feed-nick user)))
-         (format "+~a" prog-uri))]
-     )
-    (format "~a/~a (~a)" prog-name prog-version user)))
+  (match timeline
+    ['()
+     (void)]
+    [(cons first-msg _)
+     (void (foldl (match-lambda**
+                    [((and m (Msg _ _ from _ _)) (cons prev-from i))
+                     (let ([i (if (peers-equal? prev-from from) i (+ 1 i))])
+                       (msg-print out-format i m)
+                       (cons from i))])
+                  (cons (Msg-from first-msg) 0)
+                  timeline))]))
+
+(: peer->msgs (-> Peer (Listof Msg)))
+(define (peer->msgs peer)
+  (match-define (Peer nick url url-str _) peer)
+  (log-debug "Reading peer nick:~v url:~v" nick url-str)
+  (define msgs-data (url-read-cached url))
+  ; TODO Expire cache
+  (if msgs-data
+      (str->msgs peer msgs-data)
+      '()))
+
+(: peer-download
+   (-> Positive-Float Peer
+       (Result (U 'skipped-cached 'downloaded-new)
+               Any)))
+(define (peer-download timeout peer)
+  (match-define (Peer nick url u _) peer)
+  (log-info "Download BEGIN URL:~a" u)
+  (define-values (results _tm-cpu-ms tm-real-ms _tm-gc-ms)
+    (time-apply url-download (list timeout url)))
+  (define result (car results))
+  (log-info "Download END in ~a seconds, URL:~a, result:~s"
+            (/ tm-real-ms 1000.0)
+            u
+            result)
+  result)
+
+(: timeline-download (-> Integer Positive-Float (Listof Peer) Void))
+(define (timeline-download num-workers timeout peers)
+  (define results
+    (concurrent-filter-map num-workers
+                           (λ (p) (cons p (peer-download timeout p)))
+                           peers))
+  (define peers-ok
+    (filter-map (match-lambda
+                  [(cons p (cons 'ok _)) p]
+                  [(cons _ (cons 'error e)) #f])
+                results))
+  (define peers-err
+    (filter-map (match-lambda
+                  [(cons _ (cons 'ok _))
+                   #f]
+                  [(cons p (cons 'error e))
+                   (struct-copy Peer p [comment (format "~s" e)])])
+                results))
+  (peers->file peers-ok (build-path tt-home-dir "peers-last-downloaded-ok.txt"))
+  (peers->file peers-err (build-path tt-home-dir "peers-last-downloaded-err.txt")))
+
+(: peers->timeline (-> (Listof Peer) (Listof Msg)))
+(define (peers->timeline peers)
+  (append* (filter-map peer->msgs peers)))
+
+(: timeline-sort (-> (Listof Msg) timeline-order (Listof Msgs)))
+(define (timeline-sort msgs order)
+  (define cmp (match order
+                ['old->new <]
+                ['new->old >]))
+  (sort msgs (λ (a b) (cmp (Msg-ts-epoch a)
+                           (Msg-ts-epoch b)))))
+
+(: paths->peers (-> (Listof String) (Listof Peer)))
+(define (paths->peers paths)
+  (let* ([paths (match paths
+                  ['()
+                   (let ([peer-refs-file (build-path tt-home-dir "following.txt")])
+                     (log-debug
+                       "No peer ref file paths provided, defaulting to ~v"
+                       (path->string peer-refs-file))
+                     (list peer-refs-file))]
+                  [paths
+                    (log-debug "Peer ref file paths provided: ~v" paths)
+                    (map string->path paths)])]
+         [peers (apply peers-merge (map file->peers paths))])
+    (log-info "Read-in ~a peers." (length peers))
+    peers))
+
+(: cache-filename->peer (-> Path-String (Option Peer)))
+(define (cache-filename->peer filename)
+  (define nick #f) ; TODO Look it up in the nick-db when it exists.
+  (define url-str (uri-decode (path->string filename))) ; TODO Can these crash?
+  (match (str->url url-str)
+    [#f #f]
+    [url (Peer nick url url-str #f)]))
+
+(: peers-cached (-> (Listof Peer)))
+(define (peers-cached)
+  ; TODO Expire cache?
+  (filter-map cache-filename->peer (directory-list cache-object-dir)))
+
+(: peers-mentioned (-> (Listof Msg) (Listof Peer)))
+(define (peers-mentioned msgs)
+  (append* (map Msg-mentions msgs)))
+
+(: peers-filter-denied-domains (-> (Listof Peer) (Listof Peer)))
+(define (peers-filter-denied-domains peers)
+  (define deny-file (build-path tt-home-dir "domains-deny.txt"))
+  (define denied-hosts
+    (list->set (map string-trim (filter-comments (file->lines deny-file)))))
+  (define denied-domain-patterns
+    (set-map denied-hosts (λ (h) (pregexp (string-append "\\." h "$")))))
+  (filter
+    (λ (p)
+       (define host (url-host (Peer-url p)))
+       (not (or (set-member? denied-hosts host)
+                (ormap (λ (d) (regexp-match? d host)) denied-domain-patterns))))
+    peers))
+
+(: log-writer-stop (-> Thread Void))
+(define (log-writer-stop log-writer)
+  (log-message (current-logger) 'fatal 'stop "Exiting." #f)
+  (thread-wait log-writer))
+
+(: log-writer-start (-> Log-Level Thread))
+(define (log-writer-start level)
+  (let* ([logger
+           (make-logger #f #f level #f)]
+         [log-receiver
+           (make-log-receiver logger level)]
+         [log-writer
+           (thread
+             (λ ()
+                (parameterize
+                  ([date-display-format 'iso-8601])
+                  (let loop ()
+                    (match-define (vector level msg _ topic) (sync log-receiver))
+                    (unless (equal? topic 'stop)
+                      (eprintf "~a [~a] ~a~n" (date->string (current-date) #t) level msg)
+                      (loop))))))])
+    (current-logger logger)
+    log-writer))
+
+(: msgs->nick-hist (-> (Listof Msg) Url-Nick-Hist))
+(define (msgs->nick-hist msgs)
+  (foldl
+    (λ (msg url->nick->hist)
+       (match-define (Msg curr _ from _ mentions) msg)
+       (foldl
+         (λ (peer url->nick->hist)
+            (match-define (Peer nick url _ _) peer)
+            (if nick
+                (hash-update url->nick->hist
+                             url
+                             (λ (nick->hist)
+                                (hash-update nick->hist
+                                             nick
+                                             (match-lambda
+                                               [(Hist freq prev)
+                                                (Hist (+ 1 freq) (max prev curr))])
+                                             (Hist 0 0)))
+                             (hash))
+                url->nick->hist))
+         url->nick->hist
+         (cons from mentions)))
+    (hash)
+    msgs))
+
+(: url-nick-hist->file (-> Url-Nick-Hist Path-String Void))
+(define (url-nick-hist->file unh filepath)
+  (define out (open-output-file filepath #:exists 'replace))
+  (for-each
+    (match-lambda
+      [(cons url nick->hist)
+       (displayln (url->string url) out)
+       (for-each (match-lambda
+                   [(cons nick (Hist freq last))
+                    (displayln (format "    ~a ~a ~a" nick freq last) out)])
+                 (sort (hash->list nick->hist)
+                       (match-lambda**
+                         [((cons _ (Hist a _)) (cons _ (Hist b _)))
+                          (> a b)])))])
+    (sort
+      (hash->list unh)
+      (λ (a b) (string<? (url-host (car a))
+                         (url-host (car b))))))
+  (close-output-port out))
+
+(: url-nick-hist->dir (-> Url-Nick-Hist Path-String Void))
+(define (url-nick-hist->dir unh dirpath)
+  (hash-for-each
+    unh
+    (λ (url nick->hist)
+       (define filename (string-append (uri-encode (url->string url)) ".txt"))
+       (define filepath (build-path dirpath filename))
+       (make-parent-directory* filepath)
+       (display-lines-to-file
+         (map (match-lambda
+                [(cons nick (Hist freq last))
+                 (format "~a ~a ~a" nick freq last)])
+              (sort (hash->list nick->hist)
+                    (match-lambda**
+                      [((cons _ (Hist a _)) (cons _ (Hist b _)))
+                       (> a b)])))
+         filepath
+         #:exists 'replace))))
+
+(: update-nicks-history-files (-> Url-Nick-Hist Void))
+(define (update-nicks-history-files unh)
+  (define nicks-dir (build-path tt-home-dir "nicks"))
+  (url-nick-hist->file unh (build-path nicks-dir "seen.txt"))
+  (url-nick-hist->dir  unh (build-path nicks-dir "seen")))
+
+(: url-nick-hist-most-by (-> Url-Nick-Hist Url (-> Hist Nonnegative-Integer) (Option String)))
+(define (url-nick-hist-most-by url->nick->hist url by)
+  (match (hash-ref url->nick->hist url #f)
+    [#f #f]
+    [nick->hist
+      (match (sort (hash->list nick->hist)
+                   (λ (a b) (> (by (cdr a))
+                               (by (cdr b)))))
+        ['() #f]
+        [(cons (cons nick _) _) nick])]))
+
+(: url-nick-hist-latest (-> Url-Nick-Hist Url (Option String)))
+(define (url-nick-hist-latest unh url)
+  (url-nick-hist-most-by unh url Hist-last))
+
+(: url-nick-hist-common (-> Url-Nick-Hist Url (Option String)))
+(define (url-nick-hist-common unh url)
+  (url-nick-hist-most-by unh url Hist-freq))
+
+(: peers-update-nick-to-common (-> Url-Nick-Hist (Listof Peer) (Listof Peer)))
+(define (peers-update-nick-to-common unh peers)
+  (map
+    (λ (p)
+       (match (url-nick-hist-common unh (Peer-url p))
+         [#f p]
+         [n (struct-copy Peer p [nick n])]))
+    peers))
+
+(module+ test
+  (let* ([url-str  "http://foo"]
+         [url      (string->url url-str)]
+         [nick1    "a"]
+         [nick2    "b"]
+         [nick3    "c"]
+         [ts-str-1 "2021-11-29T23:29:08-0500"]
+         [ts-str-2 "2021-11-29T23:30:00-0500"]
+         [ts-1     (rfc3339->epoch ts-str-1)]
+         [ts-2     (rfc3339->epoch ts-str-2)]
+         [msgs
+           (map (match-lambda
+                  [(cons ts-str nick)
+                   (str->msg (str->peer "test http://test")
+                             (string-append ts-str "	Hi @<" nick " " url-str ">"))])
+                (list (cons ts-str-2 nick1)
+                      (cons ts-str-1 nick2)
+                      (cons ts-str-1 nick2)
+                      (cons ts-str-1 nick3)
+                      (cons ts-str-1 nick3)
+                      (cons ts-str-1 nick3)))]
+         [hist
+           (msgs->nick-hist msgs)])
+    (check-equal? (hash-ref (hash-ref hist url) nick1) (Hist 1 ts-2))
+    (check-equal? (hash-ref (hash-ref hist url) nick2) (Hist 2 ts-1))
+    (check-equal? (hash-ref (hash-ref hist url) nick3) (Hist 3 ts-1))
+    (check-equal? (url-nick-hist-common hist url) nick3)
+    (check-equal? (url-nick-hist-latest hist url) nick1)))
+
+(: crawl (-> Void))
+(define (crawl)
+  ; TODO Test the non-io parts of crawling
+  (let* ([peers-all-file
+           (build-path pub-peers-dir "all.txt")]
+         [peers-mentioned-file
+           (build-path pub-peers-dir "mentioned.txt")]
+         [peers-parsed-file
+           (build-path pub-peers-dir "downloaded-and-parsed.txt")]
+         [peers-cached-file
+           (build-path pub-peers-dir "downloaded.txt")]
+         [peers-cached
+           (peers-cached)]
+         [cached-timeline
+           (peers->timeline peers-cached)]
+         [url-nick-hist
+           (msgs->nick-hist cached-timeline)]
+         [peers-mentioned-curr
+           (peers-mentioned cached-timeline)]
+         [peers-mentioned-prev
+           (file->peers peers-mentioned-file)]
+         [peers-all-prev
+           (file->peers peers-all-file)]
+         [peers-mentioned
+           (peers-merge peers-mentioned-prev
+                        peers-mentioned-curr)]
+         [peers-all
+           (peers-update-nick-to-common
+             url-nick-hist
+             (peers-merge peers-mentioned
+                          peers-all-prev
+                          peers-cached))]
+         [peers-discovered
+           (set->list (set-subtract (make-immutable-peers peers-all)
+                                    (make-immutable-peers peers-all-prev)))]
+         [peers-parsed
+           (filter (λ (p) (> (length (peer->msgs p)) 0)) peers-all)])
+    ; TODO Deeper de-duping
+    (log-info "Known peers cached ~a" (length peers-cached))
+    (log-info "Known peers mentioned: ~a" (length peers-mentioned))
+    (log-info "Known peers parsed ~a" (length peers-parsed))
+    (log-info "Known peers total: ~a" (length peers-all))
+    (log-info "Discovered ~a new peers:~n~a"
+              (length peers-discovered)
+              (pretty-format (map
+                               (match-lambda
+                                 [(Peer n _ u c) (list n u c)])
+                               peers-discovered)))
+    (update-nicks-history-files url-nick-hist)
+    (peers->file peers-cached
+                 peers-cached-file)
+    (peers->file peers-mentioned
+                 peers-mentioned-file)
+    (peers->file peers-parsed
+                 peers-parsed-file)
+    (peers->file peers-all
+                 peers-all-file)))
+
+(: read (-> (Listof String) Number Number Timeline-Order Out-Format Void))
+(define (read file-paths ts-min ts-max order out-format)
+  (let* ([peers
+           (paths->peers file-paths)]
+         [msgs
+           (timeline-sort (peers->timeline peers) order)]
+         [include?
+           (λ (m)
+              (and (or (not ts-min) (>= (Msg-ts-epoch m) ts-min))
+                   (or (not ts-max) (<= (Msg-ts-epoch m) ts-max))))])
+    (timeline-print out-format (filter include? msgs))))
+
+(: upload (-> Void))
+(define (upload)
+  ; FIXME Should not exit from here, but only after cleanup/logger-stoppage.
+  (if (system (path->string (build-path tt-home-dir "hooks" "upload")))
+      (exit 0)
+      (exit 1)))
+
+(: download (-> (Listof String) Positive-Integer Positive-Float Void))
+(define (download file-paths num-workers timeout)
+  (let* ([peers-given (paths->peers file-paths)]
+         [peers-kept (peers-filter-denied-domains peers-given)]
+         [peers-denied (set-subtract peers-given peers-kept)])
+    (log-info "Denied ~a peers" (length peers-denied))
+    (define-values (_res _cpu real-ms _gc)
+      (time-apply timeline-download (list num-workers timeout peers-kept)))
+    (log-info "Downloaded timelines from ~a peers in ~a seconds."
+              (length peers-kept)
+              (/ real-ms 1000.0))))
+
+(: dispatch (-> String Void))
+(define (dispatch command)
+  (match command
+    [(or "d" "download")
+     ; 20 was fastest out of the tried: 1, 5, 10, 20, 25, 30.
+     (let ([num-workers : Positive-Integer 20]
+           [timeout     : Positive-Flonum  10.0])
+       (command-line
+         #:program "tt download"
+         #:once-each
+         [("-j" "--jobs")
+          positive-integer "Number of concurrent jobs."
+          (set! num-workers
+                (assert (string->number positive-integer)
+                        (conjoin exact-positive-integer?)))]
+         [("-t" "--timeout")
+          positive-float "Timeout seconds per request."
+          (set! timeout
+                (assert (string->number positive-float)
+                        (conjoin positive? flonum?)))]
+         #:args file-paths
+         (download file-paths num-workers timeout)))]
+    [(or "u" "upload")
+     (command-line
+       #:program "tt upload" #:args () (upload))]
+    [(or "r" "read")
+     (let ([out-format 'multi-line]
+           [order      'old->new]
+           [ts-min     #f]
+           [ts-max     #f])
+       (command-line
+         #:program "tt read"
+         #:once-each
+         [("-r" "--rev")
+          "Reverse displayed timeline order."
+          (set! order 'new->old)]
+         [("-m" "--min")
+          m "Earliest time to display (ignore anything before it)."
+          (set! ts-min (rfc3339->epoch m))]
+         [("-x" "--max")
+          x "Latest time to display (ignore anything after it)."
+          (set! ts-max (rfc3339->epoch x))]
+         #:once-any
+         [("-s" "--short")
+          "Short output format"
+          (set! out-format 'single-line)]
+         [("-l" "--long")
+          "Long output format"
+          (set! out-format 'multi-line)]
+         #:args file-paths
+         (read file-paths ts-min ts-max order out-format)))]
+    [(or "c" "crawl")
+     (command-line
+       #:program "tt crawl" #:args () (crawl))]
+    [command
+      (eprintf "Error: invalid command: ~v\n" command)
+      (eprintf "Please use the \"--help\" option to see a list of available commands.\n")
+      (exit 1)]))
 
 (module+ main
-  (require setup/getinfo)
-
-  (let* ([logger       (make-logger #f #f 'debug #f)]
-         [log-receiver (make-log-receiver logger 'debug)])
-    (void (thread (λ ()
-                     [date-display-format 'iso-8601]
-                     [let loop ()
-                       (define data  (sync log-receiver))
-                       (define level (vector-ref data 0))
-                       (define msg   (vector-ref data 1))
-                       (define ts    (date->string (current-date) #t))
-                       (eprintf "~a [~a] ~a~n" ts level msg)
-                       (loop)])))
-    (current-logger logger))
-  (current-http-response-auto #f)
-  (let* ([prog-name    "tt"]
-         [prog-version ((get-info (list prog-name)) 'version)]
-         [user-agent   (user-agent prog-name prog-version)])
-    (current-http-user-agent user-agent))
-  (date-display-format 'rfc2822)
-  (let ([feeds
-          (let ([args (current-command-line-arguments)])
-            (if (= 0 (vector-length args))
-              (we-are-twtxt)
-              (file->feeds (vector-ref args 0))))]
-        [out-format
-          'multi-line]
-        [num_workers
-          15]) ; 15 was fastest out of the tried 1, 5, 10, 15 and 20.
-    (timeline-print out-format (timeline num_workers feeds))))
+  (let ([log-level 'info])
+    (command-line
+      #:program
+      "tt"
+      #:once-each
+      [("-d" "--debug")
+       "Enable debug log level."
+       (set! log-level 'debug)]
+      #:help-labels
+      ""
+      "and <command> is one of"
+      "r, read     : Read the timeline (offline operation)."
+      "d, download : Download the timeline."
+      ; TODO Add path dynamically
+      "u, upload   : Upload your twtxt file (alias to execute ~/.tt/hooks/upload)."
+      "c, crawl    : Discover new peers mentioned by known peers (offline operation)."
+      ""
+      #:args (command . args)
+      (define log-writer (log-writer-start log-level))
+      (current-command-line-arguments (list->vector args))
+      (set-user-agent-str (build-path tt-home-dir "user.txt"))
+      ; TODO dispatch should return status with which we should exit after cleanups
+      (dispatch command)
+      (log-writer-stop log-writer))))