; 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

#lang racket

(require openssl/sha1)
(require racket/date)

(require http-client)
(require rfc3339-old)

(module+ test
  (require rackunit))

(struct msg  (ts_epoch ts_rfc3339 nick uri text))
(struct feed (nick uri))

(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 (work)
         (thread-send parent (cons 'next self))
         (match (thread-receive)
           ['done          (thread-send parent (cons 'exit id))]
           [(cons 'unit x) (begin
                             (define y (f x))
                             (when y (thread-send parent (cons 'result y)))
                             (work))]))
       (work)))
  (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))
  (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))))))

(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)))

(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
  (let*
    ([prog-name      "tt"]
     [prog-version   "0.3.4"]
     [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)))

(module+ main
  (define (setup-logging)
    (define logger (make-logger #f #f 'debug #f))
    (define log-chan (make-log-receiver logger 'debug))
    (void (thread (λ ()
                     [date-display-format 'iso-8601]
                     [let loop ()
                       (define data  (sync log-chan))
                       (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))

  (setup-logging)
  (current-http-response-auto #f)
  (current-http-user-agent user-agent)
  (date-display-format 'rfc2822)

  (define args (current-command-line-arguments))
  (define feeds
    (if (vector-empty? args)
      (we-are-twtxt)
      (file->feeds (vector-ref args 0))))
  (define out-format 'multi-line)
  (define num_workers 15) ; 15 was fastest out of the tried 1, 5, 10, 15 and 20.
  (timeline-print out-format (timeline num_workers feeds)))