(import (chicken tcp)
        (chicken port)
        (chicken io)
        (chicken string)
        (chicken pathname)
        (chicken file posix)
        (chicken time posix)
        (chicken condition)
        (chicken process)
        (chicken process-context)
        srfi-13)

(define gopher-index-file-name "index")

;;; Server loop
;; We don't actually use worker threads here to handle requests,
;; the server just blocks until the first request is finished.

(define (make-server-config root-dir host port)
  (list root-dir host port))

(define (server-root-dir config) (list-ref config 0))
(define (server-host config) (list-ref config 1))
(define (server-port config) (list-ref config 2))

(define (run-server config)
  (print "Gopher server listening on port " (server-port config) " ...")
  (let ((listener (tcp-listen (server-port config))))
    (let server-loop ()
      (let-values (((in-port out-port) (tcp-accept listener)))
        (let* ((line (read-line in-port))
               (selector (string-trim-both line)))
          (let-values (((local-ip remote-ip) (tcp-addresses in-port)))
            (print "Accepted connection from " remote-ip
                   " on " (seconds->string)))
          (condition-case
              (begin
                (with-output-to-port out-port
                  (lambda ()
                    (serve-selector (if (= (string-length selector) 0)
                                        "/"
                                        selector)
                                    config)))
                (print "... served selector '" selector "'. Closing connection."))
            (o (exn)
               (print-error-message o out-port)
               (print-error-message o)
               (print "Error while attempting to serve selector " selector "."))))
        (close-input-port in-port)
        (close-output-port out-port))
      (server-loop))
    (tcp-close listener)))


;;; Selector retrieval

(define (directory-selector? selector)
  (string-suffix? "/" selector))

(define (text-selector? selector)
  (apply or (map (lambda (ext) (string-suffix? ext selector))
                 '(".txt" ".org" ".md"))))
  
(define (serve-selector selector config)
  ((cond
    ((directory-selector? selector) serve-directory)
    ((text-selector? seletor) serve-text-file)
    (else serve-binary-file))
   selector config))

(define (serve-directory path config)
  (let ((file-name (make-pathname (list (server-root-dir config) path)
                                  gopher-index-file-name)))
    (if (regular-file? file-name)
        (with-input-from-file file-name
          (lambda ()
            (let loop ((c (peek-char)))
              (if (eof-object? c)
                  'done
                  (begin
                    (if (eq? c #\,)
                        (begin
                          (read-char)
                          (serve-record (read) path config)
                          (read-line))
                        (serve-info-record (read-line)))
                    (loop (peek-char)))))))
        (error "Index file not found."))))
  
(define (serve-text-file path config)
  (let ((file-name (make-pathname (server-root-dir config) path)))
    (if (regular-file? file-name)
        (with-input-from-file file-name
          (lambda ()
            (for-each
             (lambda (line)
               (print line "\r"))
             (read-lines))))
        (error "File not found." file-name))))

(define (serve-binary-file path config)
  (let ((file-name (make-pathname (server-root-dir config) path)))
    (if (regular-file? file-name)
        (with-input-from-file file-name
          (lambda ()
            (let loop ((b (read-byte)))
              (if (eof-object? b)
                  'done
                  (begin
                    (write-byte b)
                    (loop (read-byte)))))))
        (error "File not found." file-name))))


;;; Index rendering

(define (serve-info-record info-string)
  (print "i" info-string "\tfake\tfake\t1\r"))

;;; main

(define (main)
  (let ((progname (car (argv)))
        (args (cdr (argv))))
    (if (or (< (length args) 2)
            (equal? (car args) "-h")
            (equal? (car args) "--help"))
        (print "Usage:\n"
               progname " -h/--help\n"
               progname " gopher-root-dir server-hostname server-port")
        (let ((root (car args))
              (hostname (cadr args))
              (port (if (= (length args) 3) (string->number (caddr args)) 70)))
          (if port
              (run-server (make-server-config root hostname port))
              (error "Invalid port argument." port))))))

(main)

;; (define (test)
  ;; (run-server (make-server-config "gopher-root" "localhost" 70)))

;; (test)