#! /usr/bin/env racket
; vim: filetype=racket

; TODO write
; TODO caching (use cache by default, unless explicitly asked for update)
; TODO timeline limits
; TODO user-defined feed sets (a la twitter lists)
; TODO feed set operations
; TODO timeline as a result of a query (feed set op + filter expressions)
; TODO named timelines
; TODO CLI params
; TODO config files
; 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 concurrency
; TODO console logger colors by level ('error)
; TODO file logger ('debug)
; TODO commands:
; - r | read
;   - see timeline ops above
; - w | write
;   - nick expand to URI
; - q | query
;   - see timeline ops above
;   - see hashtag and channels above

#lang racket

(require racket/date)

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

(struct msg  (tm_epoch tm_rfc3339 nick text))
(struct feed (nick uri))

(define (msg-print odd m)
  (printf "~a \033[1;37m<~a>\033[0m \033[0;~am~a\033[0m~n"
          (date->string (seconds->date [msg-tm_epoch m]) #t)
          [msg-nick m]
          [if odd 36 33]
          [msg-text m]))

(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 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*
          ([tm_rfc3339 (list-ref toks 0)]
           [tok_text   (list-ref toks 1)]
           [t (string->rfc3339-record tm_rfc3339)]
           ; TODO handle tz offset
           [tm_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 tm_epoch tm_rfc3339 nick tok_text))))))

(define (str->lines str)
  (string-split str (regexp "[\r\n]+")))

(define (str->msgs nick str)
  (filter-map (λ (line) (str->msg nick line)) (str->lines str)))

(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) body (raise status)))

(define (timeline-print timeline)
  (for ([msg timeline]
        [i   (in-naturals)])
    (msg-print (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)])
    (str->msgs [feed-nick feed] [uri-fetch (feed-uri feed)])))

; TODO timeline contract : time-sorted list of messages
(define (timeline feeds)
  (sort (append* (filter-map feed->msgs feeds))
        (λ (a b) [< (msg-tm_epoch a) (msg-tm_epoch b)])))

(define (we-are-twtxt)
  (let* ([uri
           "https://raw.githubusercontent.com/mdom/we-are-twtxt/master/we-are-twtxt.txt"]
         [payload
           (uri-fetch uri)]
         [lines
           (str->lines payload)]
         [feeds
           (map (λ (line)
                   ; TODO validation
                   (define toks (string-split line))
                   (feed
                     [list-ref toks 0]
                     [list-ref toks 1]))
                lines)])
    feeds))

(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))

(define (main)
  (setup-logging)
  (current-http-response-auto #f)
  (current-http-user-agent "xandkar/tt 0.0.0")
  (date-display-format 'rfc2822)

  (define feeds (we-are-twtxt))
  (timeline-print (timeline feeds)))

(main)