54 lines
1.8 KiB
Racket
54 lines
1.8 KiB
Racket
#lang racket
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(require racket/tcp)
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(require json)
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(define serial-port-device "/dev/ttyUSB0")
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(define port 4444)
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(define hostname "127.0.0.1")
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; Print the to-print string on the printer
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; TODO add synchronization to avoid race conditions
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(define (printer-print to-print)
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(let ((file (open-output-file serial-port-device #:exists 'append)))
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(display (string-replace to-print "\n" "\n\n") file) ; always add an extra newline because the printer is a little messed up
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(close-output-port file)))
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; Format the pizzas array from the JSON in a human-readable way
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(define (format-pizza pizzas-list)
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(let ((str ""))
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(for-each (lambda (pizza-hashmap)
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(set! str (string-append str (format "~a : ~s\n" (hash-ref pizza-hashmap 'quantity) (hash-ref pizza-hashmap 'name)))))
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pizzas-list)
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str))
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; Parse the commands given in the JSON
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(define (parse-json message)
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(let ((parsed-json (with-input-from-string message (lambda () (read-json))))) ; parse the JSON
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(case (hash-ref parsed-json 'command)
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(("print") (printer-print (hash-ref parsed-json 'text)))
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(("pizza") (printer-print (format-pizza (hash-ref parsed-json 'pizzas)))))))
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; Receive the JSON message and execute the specified command
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(define (get-message input)
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(let ((message ""))
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(let loop-until-eof ((str (read-string 1 input)))
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(if (eof-object? str)
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(begin
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(close-input-port input)
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(parse-json message))
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(begin
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(set! message (string-append message str))
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(loop-until-eof (read-string 1 input)))))))
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; Wait on a port and spawn new threads on each connection
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(define (wait-for-connection)
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(let ((listener (tcp-listen port 4 #t hostname)))
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(let infinite-loop ()
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(let-values (((input output) (tcp-accept listener)))
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(close-output-port output) ; we don't need it
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(thread (lambda () (get-message input)))
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(infinite-loop)))))
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(wait-for-connection)
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