#lang racket
(require json)
(require net/http-client)
(require net/url)
(require net/rfc6455)

(define config (string->jsexpr (file->string "config.json")))

(define (get-gateway-url)
  (define-values (http-response http-headers input)
    (http-sendrecv "discordapp.com" "/api/gateway" #:ssl? #t #:version "1.1" #:method "GET"))
  (combine-url/relative (string->url (hash-ref (read-json input) 'url)) "/"))

(define gateway-url (get-gateway-url))

(define ws (ws-connect gateway-url))

(define last-seq null)

(define heartbeat-thread
  (thread
   (lambda ()
     (let loop [(interval null)]
       (cond [(null? interval) (sleep 0.1)
                               (loop (thread-receive))]
             [(number? interval) (sleep (/ interval 1000))
                                 (println "Sending heartbeat!")
                                 (ws-send! ws (jsexpr->string (hasheq 'op 1
                                                                      'd last-seq)))
                                 (loop (let [(msg (thread-try-receive))]
                                         (if msg (loop msg) (loop interval))))])))))

(define (send-message-with-file! content file-path channel-id)
  (println (string-append "https://www.rateless.net/~dormo/emotes/" (path->string file-path)))
  (http-sendrecv "discordapp.com"
                 (string-append "/api/channels/" channel-id "/messages")
                 #:ssl? #t
                 #:version "1.1"
                 #:method "POST"
                 #:headers (list (string-append "Authorization: Bot " (hash-ref config 'token))
                                 "User-Agent: RatelessBot (https://rateless.net, v0.1)"
                                 "Content-Type: application/json")
                 #:data (jsexpr->string (hasheq 'content content
                                                'embed (hasheq 'image (hasheq 'url (string-append "https://www.rateless.net/~dormo/emotes/" (path->string file-path))))
                                                'nonce (number->string (current-inexact-milliseconds))
                                                'tts #f))))

(define (send-message! content channel-id)
  (http-sendrecv "discordapp.com"
                 (string-append "/api/channels/" channel-id "/messages")
                 #:ssl? #t
                 #:version "1.1"
                 #:method "POST"
                 #:headers (list (string-append "Authorization: Bot " (hash-ref config 'token))
                                 "User-Agent: RatelessBot (https://rateless.net, v0.1)"
                                 "Content-Type: application/json")
                 #:data (jsexpr->string (hasheq 'content content
                                                'nonce (number->string (current-inexact-milliseconds))
                                                'tts #f))))

(define (handle-event res)
  (cond [(string=? "MESSAGE_CREATE" (hash-ref res 't))
         (cond [(string=? "." (substring (hash-ref (hash-ref res 'd) 'content) 0 1))
                (let* [(channel-id (hash-ref (hash-ref res 'd) 'channel_id))
                       (emote-name (substring (hash-ref (hash-ref res 'd) 'content) 1 (string-length (hash-ref (hash-ref res 'd) 'content))))
                       (files (filter (lambda (x) (string=? (path->string (path-replace-extension x "")) emote-name)) (directory-list "emotes/")))]
                  (if (< 0 (length files))
                    (send-message-with-file! (substring (hash-ref (hash-ref res 'd) 'content) 1 (string-length (hash-ref (hash-ref res 'd) 'content)))
                                             (first files)
                                             channel-id)
                    (send-message! "That emote doesn't exist" channel-id)))])]))

(define (route res)
  (set! last-seq (hash-ref res 's))
  (cond [(= 10 (hash-ref res 'op)) (ws-send! ws
                                             (jsexpr->string (hasheq 'op 2
                                                                     'd (hasheq 'token (hash-ref config 'token)
                                                                                'properties (hasheq)
                                                                                'compress #f
                                                                                'large_threshold 250))))
                                   (thread-send heartbeat-thread (hash-ref (hash-ref res 'd) 'heartbeat_interval))]
        [(= 0 (hash-ref res 'op)) (set! last-seq (hash-ref res 's))
                                  (handle-event res)]))

(define ws-listener-thread
  (thread
   (lambda ()
     (let loop ()
       (let ([m (ws-recv ws)])
         (cond [(not (eof-object? m)) (route (string->jsexpr m))]))
       (sleep 0.1) (loop)))))

; TODO:
; 1. If a client does not receive a heartbeat ack between its attempts at sending heartbeats,
; it should immediately terminate the connection with a non-1000 close code,
; reconnect, and attempt to resume.