16 files changed, 795 insertions(+), 32 deletions(-)

M backend.rkt
M frontends/discord.rkt
A frontends/http/base.html
A frontends/http/favicon.ico
A frontends/http/home.html
A frontends/http/icon.svg
A frontends/http/main.rkt
A frontends/http/raw.html
A frontends/http/result.html
A frontends/http/simple.html
A frontends/http/style-in.css
A frontends/http/style.css
A frontends/http/tailwind.config.js
A frontends/http/tricks.html
M interface.rkt
A result.rkt

@@ 70,7 70,7 @@
                       enrich-context
                       (current-context-id)
                       #f "" "" #f))
-      (ev:run code ev-ctx response?))
+      (cons 'ok (ev:run code ev-ctx response?)))
 
     (define/public (call name args)
       (define ctx-id (current-context-id))


@@ 89,9 89,9 @@
                          (current-context-id)
                          trick-obj name args #f))
          (define code (trick-body trick-obj))
-         (ev:run code ev-ctx response?)]
+         (cons 'ok (ev:run code ev-ctx response?))]
         [else
-         (~a "Trick " name " doesn't exist!")]))
+         (list 'err (~a "Trick " name " doesn't exist!") 'no-such-trick)]))
 
     (define/public (delete name)
       (define ctx-id (current-context-id))


@@ 99,22 99,22 @@
       (define frontend (current-frontend))
       (cond
         [(not trick-obj)
-         (~a "Trick " name " doesn't exist!")]
+         (list 'err (~a "Trick " name " doesn't exist!") 'no-such-trick)]
         [(db:remove-trick!
           db ctx-id name
           (lambda (t) (send frontend can-modify? t)))
-         (~a "Successfully removed trick " name "!")]
+         (cons 'ok (~a "Successfully removed trick " name "!"))]
         [else
-         (~a "You cannot modify trick " name "!")]))
+         (list 'err (~a "You cannot modify trick " name "!") 'missing-permissions)]))
 
     (define/public (register name code author timestamp)
       (cond
         [(zero? (string-length code))
-         (~a "Trick " name " needs a body!")]
+         (list 'err (~a "Trick " name " needs a body!") 'needs-body)]
         [(db:add-trick!
           db (current-context-id) name
           (thunk (trick author code timestamp (make-hash) 0)))
-         (~a "Successfully registered trick " name "!")]
+         (cons 'ok (~a "Successfully registered trick " name "!"))]
         [else (update name code)]))
 
     (define/public (update name code)


@@ 123,9 123,9 @@
       (define frontend (current-frontend))
       (cond
         [(not trick-obj)
-         (~a "Trick " name " doesn't exist!")]
+         (list 'err (~a "Trick " name " doesn't exist!") 'no-such-trick)]
         [(zero? (string-length code))
-         (~a "Trick " name " needs a body!")]
+         (list 'err (~a "Trick " name " needs a body!") 'needs-body)]
         [(db:update-trick!
           db ctx-id name
           (lambda (trick-obj)


@@ 136,7 136,9 @@
                    (trick-invocations trick-obj)))
           (lambda (t)
             (send frontend can-modify? t)))
-         (~a "Successfully updated trick " name "!")]))
+         (cons 'ok (~a "Successfully updated trick " name "!"))]
+        [else
+         (list 'err (~a "You cannot modify trick " name "!") 'missing-permissions)]))
 
     (define/public (lookup name)
       (db:get-trick db (current-context-id) name))

@@ 447,15 447,16 @@
         (define (codeblock-quote result)
           (~a "```scheme\n" result "```"))
 
+        (define (error-response err)
+          (list (car err)))
+
         (define/command (call-snippet text)
           " [_code_]:  evaluate [_code_] as a Racket form"
           (with-typing-indicator
             (thunk
              (define result
                (send (current-backend) evaluate (strip-backticks text)))
-             (if (ev:run-result? result)
-                 (format-run-result result)
-                 (list result)))))
+             (result-case format-run-result error-response result))))
 
         (define/command/trick (call-trick name body)
           " [_name_] ...:  invoke the trick [_name_], evaluating its source code in a fresh sandbox"


@@ 463,17 464,16 @@
             (thunk
              (define result
                (send (current-backend) call name body))
-             (if (ev:run-result? result)
-                 (format-run-result result)
-                 (list result)))))
+             (result-case format-run-result error-response result))))
 
         (define/command/trick (register-trick name body)
           " [_name_] [_code_]:  register [_code_] as a trick with name [_name_]"
-          (list
-           (send (current-backend) register
-                 name (strip-backticks body)
-                 (message-author-id (current-message))
-                 (hash-ref (current-message) 'timestamp))))
+          (define result
+            (send (current-backend) register
+                  name (strip-backticks body)
+                  (message-author-id (current-message))
+                  (hash-ref (current-message) 'timestamp)))
+          (list (result-case cdr cadr result)))
 
         (define/command/trick (show-trick name _body)
           " [_name_]:  show metadata and source for the trick [_name_]"


@@ 494,11 494,11 @@
 
         (define/command/trick (update-trick name body)
           " [_name_] [_code_]:  change the source of the trick [_name_]; requires ownership or administrator"
-          (list (send (current-backend) update name (strip-backticks body))))
+          (list (result-case cdr cadr (send (current-backend) update name (strip-backticks body)))))
 
         (define/command/trick (delete-trick name _body)
           " [_name_]:  delete the trick [_name_]; requires ownership or administrator and cannot be undone!"
-          (list (send (current-backend) delete name)))
+          (list (result-case cdr cadr (send (current-backend) delete name))))
 
         (define/command (popular text)
           ":  show a leaderboard of popular tricks"

@@ 0,0 1,43 @@
+@; Inputs: 'title 'navbar? 'body
+<!DOCTYPE html>
+<html lang="en" class="text-[16px] text-slate-700 bg-neutral-50">
+  <head>
+    <meta charset="utf-8"/>
+    <meta name="viewport" content="width=device-width, initial-scale=1"/>
+    <title>@|title|</title>
+    <link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons"/>
+    <link rel="stylesheet" href="/style.css"></style>
+  </head>
+  <body>
+    @when[navbar?]{
+    @list{
+    <navbar class="bg-neutral-700 text-white flex items-stretch min-h-[3.25rem]"
+            role="navigation"
+            aria-label="main navigation">
+      <div class="flex items-stretch">
+        <p class="flex items-center py-2 px-3">
+          <img class="w-8 h-8" src="/icon.svg"></img>
+        </p>
+      </div>
+      <div class="flex items-stretch grow">
+        <div class="flex items-stretch justify-start mr-auto">
+          <a class="flex items-center py-2 px-3 hover:bg-neutral-800" href="/">Home</a>
+          <a class="flex items-center py-2 px-3 hover:bg-neutral-800" href="/tricks">Tricks</a>
+        </div>
+        <div class="flex items-stretch justify-end ml-auto">
+          <a class="flex items-center py-2 px-3 hover:bg-neutral-800" href="https://sr.ht/~williewillus/r16">Source</a>
+        </div>
+      </div>
+    </navbar>
+    }
+    }
+    <div class="w-full bg-white">
+      <div class="mx-auto 2xl:max-w-screen-xl xl:max-w-screen-lg lg:max-w-screen-md">@|body|</div>
+    </div>
+    <footer class="bg-neutral-50">
+      <div class="p-12 text-center">
+        @(format-for-html (send (current-backend) about))
+      </div>
+    </footer>
+  </body>
+</html>

@@ 0,0 1,5 @@
+@; No inputs
+<div class="p-12">
+  <h1 class="text-3xl font-bold mb-6">Stats</h1>
+  @(format-for-html (send (current-backend) stats))
+</div>

@@ 0,0 1,194 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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+           sodipodi:nodetypes="cccccccc" /></g></g></g></svg>

@@ 0,0 1,265 @@
+#lang racket/base
+
+(require
+ racket/class
+ racket/list
+ racket/match
+ racket/function
+ racket/string
+ racket/include
+ racket/port
+
+ "../../common.rkt"
+ "../../config.rkt"
+ "../../log.rkt"
+ (prefix-in ev: "../../evaluator.rkt")
+ "../../interface.rkt"
+
+ xml
+ net/base64
+ file/sha1
+ net/url-structs
+ web-server/web-server
+ web-server/servlet-dispatch
+ web-server/templates
+ web-server/http/request-structs
+ web-server/http/response-structs
+
+ (for-syntax racket/base
+             racket/port
+             syntax/location))
+
+(provide r16-make-frontend)
+
+(define-for-syntax use-reincludes?
+  (environment-variables-ref
+   (current-environment-variables)
+   #"R16_REINCLUDE_TEMPLATES"))
+
+(define-syntax (syntax-relative-path stx)
+  (syntax-case stx ()
+    [(_ path)
+     (quasisyntax/loc stx
+       (build-path
+        #,(syntax-source-directory stx)
+        path))]))
+
+(define-syntax (include-bytes stx)
+  (syntax-case stx ()
+    [(_ path)
+     (if use-reincludes?
+         (quasisyntax/loc stx
+           (with-input-from-file (syntax-relative-path path) port->bytes))
+         (quasisyntax/loc stx
+           (include/reader
+            path
+            (lambda (_ port)
+              (if (port-closed? port)
+                  eof
+                  (datum->syntax
+                   #'#,stx
+                   (port->bytes port #:close? #t)))))))]))
+
+(define-syntax (maybe-define-namespace-anchor stx)
+  (syntax-case stx ()
+    [(_ name)
+     (if use-reincludes?
+         (quasisyntax/loc stx
+           (define-namespace-anchor name))
+         #'(begin))]))
+
+(maybe-define-namespace-anchor anchor)
+
+(define-syntax (include-template* stx)
+  (syntax-case stx ()
+    [(_ path args ...)
+     (if use-reincludes?
+         (quasisyntax/loc stx
+           (let ([namespace (namespace-anchor->namespace anchor)])
+             (namespace-set-variable-value!
+              'args args
+              #f namespace) ...
+             (eval #'(include-template path)
+                   namespace)))
+         (quasisyntax/loc stx
+           (include-template path)))]))
+
+(struct image (bytes))
+
+(define (simple-response code msg)
+  (define title msg)
+  (define navbar? #t)
+  (define body (include-template* "simple.html" msg))
+  (response/full
+   code #f
+   (current-seconds) TEXT/HTML-MIME-TYPE
+   null
+   (list
+    (string->bytes/utf-8
+     (include-template* "base.html" title navbar? body)))))
+
+(define (format-for-html str)
+  (include-template* "raw.html" str))
+
+(define (response/html #:title title #:navbar? [navbar? #f] . body)
+  (response/full
+   200 #f
+   (current-seconds) TEXT/HTML-MIME-TYPE
+   null
+   (list (string->bytes/utf-8 (include-template* "base.html" title navbar? body)))))
+
+(define http-frontend
+  (class* object% [r16-frontend<%>]
+    (init-field port)
+
+    (define trick-modify-mutex (make-semaphore 1))
+    (define current-password-hash (make-parameter #f))
+    (define/public (response? v) (image? v))
+    (define/public (get-enrich-context)
+      (define (enrich-context base _trick _args _parent-ctx)
+        (define (make-image png-bytes)
+          (image png-bytes))
+        `(((make-image . ,make-image)
+           ,@(car base))
+          ,@(cdr base)))
+      enrich-context)
+    (define/public (can-modify? trick)
+      (equal? (trick-author trick) (current-password-hash)))
+    (define/public (start)
+      (log-r16-debug "Starting server on port ~a" port)
+      (parameterize ([current-frontend this])
+        (serve
+         #:dispatch (dispatch/servlet handle-request)
+         #:port port)
+        (do-not-return)))
+
+    (define (handle-request req)
+        (define req-uri (request-uri req))
+        (define path (takef (url-path req-uri) (compose1 non-empty-string? path/param-path)))
+        (match* [(request-method req) path]
+          [[#"POST" (list (path/param "tricks" _)
+                          (path/param "submit" _))]
+           (define bindings (request-bindings/raw req))
+           (match* [(bindings-assq #"name" bindings)
+                    (bindings-assq #"code" bindings)
+                    (bindings-assq #"password" bindings)]
+             [[(binding:form _ (and name-bytes
+                                    (pregexp "^[a-zA-Z_\\-0-9]+$")
+                                    (app bytes->string/utf-8 name)))
+               (binding:form _ (app bytes->string/utf-8 code))
+               (binding:form _ password)]
+              (call-with-semaphore
+               ;; protect against concurrent modification of the body
+               trick-modify-mutex
+               (thunk
+                ;; hash the password, using the sha256sum of the trick name as salt;
+                ;; this is not completely secure because the salt *should*
+                ;; be generated randomly so as not to be predictable,
+                ;; but the risk factor is estimated to be low;
+                ;; this hash is then used as the "author" field of the trick
+                ;; and checked against for modification perms
+                (define salt (sha256-bytes name-bytes))
+                (define hashed-pass (bytes->hex-string (sha256-bytes (bytes-append salt password))))
+                (parameterize ([current-password-hash hashed-pass])
+                  (cond
+                    [(zero? (string-length code))
+                     (match (send (current-backend) delete name)
+                       [(cons 'ok msg) (simple-response 200 (string->bytes/utf-8 msg))]
+                       [(list* 'err msg _) (simple-response 400 (string->bytes/utf-8 msg))])]
+                    [else
+                     (match (send (current-backend) register name code hashed-pass (number->string (current-seconds)))
+                       [(cons 'ok _)
+                        (response/full
+                         303 #"See Other"
+                         (current-seconds) TEXT/HTML-MIME-TYPE
+                         (list (make-header #"Location" (string->bytes/utf-8 (format "/tricks/~a.rkt" name))))
+                         (list #"Redirecting..."))]
+                       [(list* 'err msg _)
+                        (simple-response 400 (string->bytes/utf-8 msg))])]))))]
+             [[_ _ _]
+              (simple-response 400 #"400 Bad Request")])]
+
+          [[#"GET" (list (path/param "tricks" _))]
+           (response/html
+            #:title "Tricks"
+            #:navbar? #t
+            (include-template* "tricks.html"))]
+
+          [[#"GET" (list (path/param "tricks" _)
+                         (path/param (pregexp "^([a-zA-Z_\\-0-9]+)\\.rkt$" (list _ trick-name)) _))]
+           (define trick-v (send (current-backend) lookup trick-name))
+           (response/full
+            200 #"OK"
+            (current-seconds) #"text/plain; charset=utf-8"
+            null
+            (list (string->bytes/utf-8 (trick-body trick-v))))]
+
+          [[#"GET" (list (path/param "tricks" _)
+                         (path/param (pregexp "^[a-zA-Z_\\-0-9]+$" (list trick-name)) _))]
+           (define args (assoc 'args (url-query req-uri)))
+           (define resp (send (current-backend) call trick-name (if args (cdr args) "")))
+           (match resp
+             [(cons 'ok res)
+              (define stderr (ev:run-result-stderr res))
+              (define stdout (ev:run-result-stdout res))
+              (define results (ev:run-result-results res))
+              (match* [stderr stdout results]
+                [[#f "" (list (image raw-bytes))]
+                 (response/full
+                  200 #f
+                  (current-seconds) #"image/png"
+                  null
+                  (list raw-bytes))]
+                [[_ _ _]
+                 (response/full
+                  200 #f
+                  (current-seconds) TEXT/HTML-MIME-TYPE
+                  null
+                  (list (string->bytes/utf-8
+                         (include-template*
+                          "result.html"
+                          trick-name
+                          stderr
+                          stdout
+                          results))))])]
+             [(list 'err msg 'no-such-trick)
+              (simple-response 404 (string->bytes/utf-8 msg))]
+             [(list* 'err msg _)
+              (simple-response 400 (string->bytes/utf-8 msg))])]
+
+          [[#"GET" (list (path/param (or "style.css" "error.css") _))]
+           (response/full
+            200 #f
+            (current-seconds) #"text/css"
+            null
+            (list (include-bytes "style.css")))]
+
+          [[#"GET" (list (path/param "favicon.ico" _))]
+           (response/full
+            200 #f
+            (current-seconds) #"image/x-icon"
+            null
+            (list (include-bytes "favicon.ico")))]
+
+          [[#"GET" (list (path/param "icon.svg" _))]
+           (response/full
+            200 #f
+            (current-seconds) #"image/svg+xml"
+            null
+            (list (include-bytes "icon.svg")))]
+
+          [[#"GET" (list)]
+           (response/html
+            #:title "r16"
+            #:navbar? #t
+            (include-template* "home.html"))]
+
+          [[#"GET" _]
+           (simple-response 404 #"404 Not Found")]))
+
+    (super-new)))
+
+(define (r16-make-frontend raw-config)
+  (define port (check-config exact-positive-integer? (hash-ref raw-config 'port 8080)))
+  (new http-frontend
+       [port port]))

@@ 0,0 1,23 @@
+@; Inputs: 'str
+@(define url-regex #px"(([^:/?#]+):)(//([^/?#]*))([^?#]*)(\\?([^#]*))?(#(.*))?")
+<div>
+  @in[line (in-list (string-split str "\n"))]{
+  @(define urls (regexp-match-positions* url-regex line #:match-select car))
+  <div class="mb-6 last:mb-0">
+  @(cond
+     [(null? urls) (list line)]
+     [else
+      (define positions
+        (append*
+         (for/list ([url-pos (in-list urls)])
+           (list (car url-pos) (cdr url-pos)))))
+      (for/list ([start (in-list `(0 ,@positions))]
+                 [end (in-list `(,@positions ,(string-length line)))]
+                 [is-link? (in-cycle (in-list '(#f #t)))])
+        (define v (substring line start end))
+        (if is-link?
+            (xexpr->string `(a ((href ,v) (class "text-blue-500 hover:text-blue-700")) ,v))
+            v))])
+  </div>
+  }
+</div>

@@ 0,0 1,40 @@
+@; Inputs: 'trick-name 'stderr 'stdout 'results
+@; TODO: limits on output length
+@(define trick-name-esc (xexpr->string trick-name))
+@(local-require racket/port)
+@(define description
+   (with-output-to-string
+     (lambda ()
+       (when stderr
+         (display stderr))
+       (unless (zero? (string-length stdout))
+         (display stdout))
+       (for ([r (in-list results)])
+         (unless (image? r)
+           (displayln r))))))
+@(define head
+   @list{
+     <title>@|trick-name-esc|</title>
+     <meta name="viewport" content="width=device-width, initial-scale=1"/>
+     <meta property="og:title" content="@(xml-attribute-encode trick-name)">
+     <meta property="og:type" content="website">
+     <meta property="og:description" content="@(xml-attribute-encode description)">
+     @(when stderr
+        @list{<meta name="theme-color" content="#FF0000">})
+   })
+@(define body
+   (list
+    (when stderr @list{<pre style="color:red;">@(xexpr->string stderr)</pre>})
+    (unless (zero? (string-length stdout)) @list{<pre>@(xexpr->string stdout)</pre>})
+    (for/list ([r (in-list results)])
+      (cond
+        [(image? r) @list{<img src="data:image/png;base64,@(base64-encode (image-bytes r))"></img>}]
+        [else @list{<pre>@(xexpr->string r)</pre>}]))))
+
+<!DOCTYPE html>
+<head>
+@|head|
+</head>
+<body>
+@|body|
+</body>

@@ 0,0 1,4 @@
+@; Inputs: msg
+<div class="p-12">
+  <span class="text-2xl font-bold mb-2">@|msg|</span>
+</div>

@@ 0,0 1,20 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+.toggled .togglable { display: none; }
+.togglable-inverse { display: none; }
+.toggled .togglable-inverse { display: inline; }
+
+.trick > .trick-info {
+    max-width: 0;
+    max-height: 0;
+    overflow: hidden;
+    opacity: 0;
+}
+
+.trick:hover > .trick-info {
+    max-width: 2000px;
+    max-height: 300px;
+    opacity: 1;
+}

@@ 0,0 1,1 @@
+/*! tailwindcss v3.0.24 | MIT License | https://tailwindcss.com*/*,:after,:before{box-sizing:border-box;border:0 solid #e5e7eb}:after,:before{--tw-content:""}html{line-height:1.5;-webkit-text-size-adjust:100%;-moz-tab-size:4;-o-tab-size:4;tab-size:4;font-family:ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{margin:0;line-height:inherit}hr{height:0;color:inherit;border-top-width:1px}abbr:where([title]){-webkit-text-decoration:underline dotted;text-decoration:underline dotted}h1,h2,h3,h4,h5,h6{font-size:inherit;font-weight:inherit}a{color:inherit;text-decoration:inherit}b,strong{font-weight:bolder}code,kbd,pre,samp{font-family:ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,Liberation Mono,Courier 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;--tw-pan-y: ;--tw-pinch-zoom: ;--tw-scroll-snap-strictness:proximity;--tw-ordinal: ;--tw-slashed-zero: ;--tw-numeric-figure: ;--tw-numeric-spacing: ;--tw-numeric-fraction: ;--tw-ring-inset: ;--tw-ring-offset-width:0px;--tw-ring-offset-color:#fff;--tw-ring-color:#3b82f680;--tw-ring-offset-shadow:0 0 #0000;--tw-ring-shadow:0 0 #0000;--tw-shadow:0 0 #0000;--tw-shadow-colored:0 0 #0000;--tw-blur: ;--tw-brightness: ;--tw-contrast: ;--tw-grayscale: ;--tw-hue-rotate: ;--tw-invert: ;--tw-saturate: ;--tw-sepia: ;--tw-drop-shadow: ;--tw-backdrop-blur: ;--tw-backdrop-brightness: ;--tw-backdrop-contrast: ;--tw-backdrop-grayscale: ;--tw-backdrop-hue-rotate: ;--tw-backdrop-invert: ;--tw-backdrop-opacity: ;--tw-backdrop-saturate: ;--tw-backdrop-sepia: }.absolute{position:absolute}.-m-3{margin:-.75rem}.-m-6{margin:-1.5rem}.mx-auto{margin-left:auto}.mr-auto,.mx-auto{margin-right:auto}.ml-auto{margin-left:auto}.mb-6{margin-bottom:1.5rem}.mb-3{margin-bottom:.75rem}.mb-2{margin-bottom:.5rem}.mr-2{margin-right:.5rem}.mb-0{margin-bottom:0}.mb-1{margin-bottom:.25rem}.mb-4{margin-bottom:1rem}.mb-5{margin-bottom:1.25rem}.block{display:block}.flex{display:flex}.inline-flex{display:inline-flex}.hidden{display:none}.h-1{height:.25rem}.h-5{height:1.25rem}.h-2{height:.5rem}.h-12{height:3rem}.h-4{height:1rem}.h-8{height:2rem}.min-h-\[3\.25rem\]{min-height:3.25rem}.w-full{width:100%}.w-12{width:3rem}.w-4{width:1rem}.w-8{width:2rem}.shrink{flex-shrink:1}.grow{flex-grow:1}.basis-0{flex-basis:0px}.cursor-pointer{cursor:pointer}.flex-col{flex-direction:column}.flex-wrap{flex-wrap:wrap}.content-center{align-content:center}.items-center{align-items:center}.items-stretch{align-items:stretch}.justify-start{justify-content:flex-start}.justify-end{justify-content:flex-end}.justify-center{justify-content:center}.rounded{border-radius:.25rem}.rounded-lg{border-radius:.5rem}.rounded-t-lg{border-top-left-radius:.5rem;border-top-right-radius:.5rem}.border{border-width:1px}.border-neutral-100{--tw-border-opacity:1;border-color:rgb(245 245 245/var(--tw-border-opacity))}.bg-neutral-50{--tw-bg-opacity:1;background-color:rgb(250 250 250/var(--tw-bg-opacity))}.bg-neutral-700{--tw-bg-opacity:1;background-color:rgb(64 64 64/var(--tw-bg-opacity))}.bg-white{--tw-bg-opacity:1;background-color:rgb(255 255 255/var(--tw-bg-opacity))}.bg-green-400{--tw-bg-opacity:1;background-color:rgb(74 222 128/var(--tw-bg-opacity))}.bg-neutral-800{--tw-bg-opacity:1;background-color:rgb(38 38 38/var(--tw-bg-opacity))}.bg-gray-300{--tw-bg-opacity:1;background-color:rgb(209 213 219/var(--tw-bg-opacity))}.bg-gray-800{--tw-bg-opacity:1;background-color:rgb(31 41 55/var(--tw-bg-opacity))}.bg-neutral-900{--tw-bg-opacity:1;background-color:rgb(23 23 23/var(--tw-bg-opacity))}.p-12{padding:3rem}.p-3{padding:.75rem}.p-2{padding:.5rem}.p-6{padding:1.5rem}.py-2{padding-top:.5rem;padding-bottom:.5rem}.px-3{padding-left:.75rem;padding-right:.75rem}.px-4{padding-left:1rem;padding-right:1rem}.px-2{padding-left:.5rem;padding-right:.5rem}.py-1{padding-top:.25rem;padding-bottom:.25rem}.px-6{padding-left:1.5rem;padding-right:1.5rem}.py-4{padding-top:1rem;padding-bottom:1rem}.text-center{text-align:center}.font-mono{font-family:ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,Liberation Mono,Courier New,monospace}.text-\[16px\]{font-size:16px}.text-3xl{font-size:1.875rem;line-height:2.25rem}.text-xl{font-size:1.25rem;line-height:1.75rem}.text-2xl{font-size:1.5rem;line-height:2rem}.font-bold{font-weight:700}.text-slate-700{--tw-text-opacity:1;color:rgb(51 65 85/var(--tw-text-opacity))}.text-white{--tw-text-opacity:1;color:rgb(255 255 255/var(--tw-text-opacity))}.text-blue-500{--tw-text-opacity:1;color:rgb(59 130 246/var(--tw-text-opacity))}.opacity-0{opacity:0}.opacity-20{opacity:.2}.shadow-inner{--tw-shadow:inset 0 2px 4px 0 #0000000d;--tw-shadow-colored:inset 0 2px 4px 0 var(--tw-shadow-color)}.shadow,.shadow-inner{box-shadow:var(--tw-ring-offset-shadow,0 0 #0000),var(--tw-ring-shadow,0 0 #0000),var(--tw-shadow)}.shadow{--tw-shadow:0 1px 3px 0 #0000001a,0 1px 2px -1px #0000001a;--tw-shadow-colored:0 1px 3px 0 var(--tw-shadow-color),0 1px 2px -1px var(--tw-shadow-color)}.shadow-lg{--tw-shadow:0 10px 15px -3px #0000001a,0 4px 6px -4px #0000001a;--tw-shadow-colored:0 10px 15px -3px var(--tw-shadow-color),0 4px 6px -4px var(--tw-shadow-color);box-shadow:var(--tw-ring-offset-shadow,0 0 #0000),var(--tw-ring-shadow,0 0 #0000),var(--tw-shadow)}.transition-all{transition-property:all;transition-timing-function:cubic-bezier(.4,0,.2,1);transition-duration:.15s}.duration-500{transition-duration:.5s}.ease-out{transition-timing-function:cubic-bezier(0,0,.2,1)}.\[overflow-wrap\:break-word\]{overflow-wrap:break-word}.togglable-inverse,.toggled .togglable{display:none}.toggled .togglable-inverse{display:inline}.trick>.trick-info{max-width:0;max-height:0;overflow:hidden;opacity:0}.trick:hover>.trick-info{max-width:2000px;max-height:300px;opacity:1}.last\:mb-0:last-child{margin-bottom:0}.hover\:w-full:hover{width:100%}.hover\:grow:hover{flex-grow:1}.hover\:border-neutral-300:hover{--tw-border-opacity:1;border-color:rgb(212 212 212/var(--tw-border-opacity))}.hover\:bg-neutral-800:hover{--tw-bg-opacity:1;background-color:rgb(38 38 38/var(--tw-bg-opacity))}.hover\:bg-green-500:hover{--tw-bg-opacity:1;background-color:rgb(34 197 94/var(--tw-bg-opacity))}.hover\:bg-neutral-900:hover{--tw-bg-opacity:1;background-color:rgb(23 23 23/var(--tw-bg-opacity))}.hover\:bg-green-400:hover{--tw-bg-opacity:1;background-color:rgb(74 222 128/var(--tw-bg-opacity))}.hover\:bg-green-600:hover{--tw-bg-opacity:1;background-color:rgb(22 163 74/var(--tw-bg-opacity))}.hover\:text-blue-700:hover{--tw-text-opacity:1;color:rgb(29 78 216/var(--tw-text-opacity))}@media (min-width:768px){.md\:flex-row{flex-direction:row}.md\:text-xl{font-size:1.25rem;line-height:1.75rem}.md\:text-lg{font-size:1.125rem;line-height:1.75rem}}@media (min-width:1024px){.lg\:max-w-screen-md{max-width:768px}}@media (min-width:1280px){.xl\:max-w-screen-lg{max-width:1024px}}@media (min-width:1536px){.\32xl\:max-w-screen-xl{max-width:1280px}}<
\ No newline at end of file

@@ 0,0 1,5 @@
+module.exports = {
+  content: [
+    "*.{html,rkt}"
+  ]
+}

@@ 0,0 1,109 @@
+@; No inputs
+@(define popular (send (current-backend) popular))
+<div class="p-12">
+  <h1 class="text-3xl font-bold mb-6">Add trick</h1>
+  <form action="/tricks/submit" method="post" target="_blank" enctype="multipart/form-data">
+    <div class="mb-3">
+      <div class="flex flex-col md:flex-row -m-3">
+        <div class="grow shrink basis-0 p-3">
+          <label class="mb-2 font-bold block" for="name">Trick Name</label>
+          <input class="p-2 border-neutral-100 hover:border-neutral-300 border rounded w-full shadow-inner" 
+                 type="text" id="name" name="name"></input>
+        </div>
+        <div class="grow shrink basis-0 p-3">
+          <label class="mb-2 font-bold block" for="password">Password</label>
+          <input class="p-2 border-neutral-100 hover:border-neutral-300 border rounded w-full shadow-inner" 
+                 type="password" id="password" name="password"></input>
+        </div>
+      </div>
+    </div>
+    <div class="mb-3">
+      <label class="mb-2 font-bold block" for="code">Code</label>
+      <textarea
+        class="font-mono p-2 border-neutral-100 hover:border-neutral-300 border rounded w-full shadow-inner"
+        id="code"
+        name="code"
+        rows="5"
+        cols="60"
+        placeholder="Enter code"
+        spellcheck="false"></textarea>
+    </div>
+    <div>
+      <input class="p-2 bg-green-400 hover:bg-green-500 rounded text-white content-center px-4 py-2 cursor-pointer"
+             type="submit" value="Add"/>
+    </div>
+  </form>
+</div>
+<div class="p-12">
+  <h1 class="text-3xl font-bold mb-6">Registered tricks</h1>
+  <script>
+    let lastTrick = null;
+    function setTrick(trick, soft) {
+      if (trick === null) trick = lastTrick;
+
+      let invocations = trick ? trick.dataset.trickInvocations : "-";
+      document.getElementById("trick-invocations").innerText = invocations;
+
+      let trickSource = document.getElementById("trick-source");
+      let trickName = document.getElementById("trick-name");
+      let trickCall = document.getElementById("trick-call");
+      if (trick) {
+        let name = trick.dataset.trickName;
+        trickSource.href = "/tricks/"+name+".rkt";
+        trickCall.action = "/tricks/"+name;
+        trickName.innerText = name;
+        if (!soft) {
+          if (trick === lastTrick) return;
+          if (lastTrick) {
+            lastTrick.classList.remove("bg-neutral-900");
+            lastTrick.classList.add("bg-neutral-700");
+          }
+          lastTrick = trick;
+          lastTrick.classList.add("bg-neutral-900");
+          lastTrick.classList.remove("bg-neutral-700");
+        }
+      } else {
+        trickSource.href = "";
+        trickCall.action = "";
+        trickName.innerText = "-";
+      }
+    }
+  </script>
+  <div class="mb-6 shadow-lg rounded-lg p-6">
+    <div class="bg-neutral-800 rounded-t-lg w-[calc(100% + 3rem)] -m-6 mb-3 px-6 py-4 text-white md:text-lg font-bold">
+      <span>Trick Name: </span>
+      <code id="trick-name">-</code>
+    </div>
+    <p class="mb-3"><span class="font-bold">Invocations</span>: <span id="trick-invocations">-</span></p>
+    <p class="mb-3"><a class="text-blue-500 hover:text-blue-700 cursor-pointer" id="trick-source">Trick Source</a></p>
+    <form id="trick-call" target="_blank" method="get">
+      <div class="mb-3">
+        <textarea class="font-mono p-2 border-neutral-100 hover:border-neutral-300 border rounded w-full shadow-inner"
+                  name="args"
+                  spellcheck="false"
+                  rows="1"
+                  placeholder="Enter arguments"></textarea>
+      </div>
+      <input class="p-2 bg-green-400 hover:bg-green-500 rounded text-white content-center px-4 py-2 cursor-pointer"
+             type="submit" value="Call"/>
+    </form>
+  </div>
+  <div id="trick-list" class="flex flex-wrap">
+    @in[trick-pair (in-list popular)]{
+    @(define name (xexpr->string (car trick-pair)))
+    @(define trick-v (cdr trick-pair))
+    <button class="mr-2 mb-2 shadow px-3 py-2 bg-neutral-700 hover:bg-neutral-800 rounded text-white trick"
+            data-trick-name="@|name|"
+            data-trick-invocations="@(trick-invocations trick-v)"
+            onmouseover="setTrick(this, true)"
+            onmouseout="setTrick(null, true)"
+            onclick="setTrick(this, false)">
+      <code class="card-header-title has-text-white">@|name|</code>
+    </button>
+  }
+  </div>
+  <script>
+    let trickList = document.getElementById("trick-list");
+    if (trickList.children.length) setTrick(trickList.children[0], false);
+  </script>
+</div>

@@ 3,13 3,15 @@
 (require
  racket/class
  racket/contract
+ "result.rkt"
  (only-in "evaluator.rkt" definitions? run-result?)
  "common.rkt")
 
 (provide r16-backend? r16-frontend?
          r16-backend<%> r16-frontend<%>
          current-backend current-frontend
-         current-context-id)
+         current-context-id
+         (all-from-out "result.rkt"))
 
 ;; an r16 frontend
 (define r16-frontend<%>


@@ 38,21 40,34 @@
 (define r16-backend<%>
   (interface ()
     ;; evaluate a code snippet, returning either an error message or a run result
-    [evaluate (#;code string? . ->m . (or/c string? run-result?))]
+    [evaluate (#;code string? . ->m .
+               (result/c run-result?
+                         (error/c)))]
 
-    ;; call a trick with arguments, returning either an error message or a run result
-    [call     (#;trick string? #;args string? . ->m . (or/c string? run-result?))]
+    ;; call a trick with arguments, returning either an error or a run result
+    [call     (#;trick string? #;args string? . ->m .
+               (result/c run-result?
+                         (error/c (no-such-trick))))]
 
     ;; delete a trick, returning an error or success message
-    [delete   (#;trick string? . ->m . string?)]
+    [delete   (#;trick string? . ->m .
+               (result/c string?
+                         (error/c (no-such-trick)
+                                  (missing-permissions))))]
 
     ;; register a trick, returning an error or success message
     [register (#;trick string? #;code string?
-               #;author string? #;timestamp string?
-               . ->m . string?)]
+               #;author string? #;timestamp string? . ->m .
+               (result/c string?
+                         (error/c (needs-body)
+                                  (missing-permissions))))]
 
     ;; update a trick, returning an error or success message
-    [update   (#;trick string? #;code string? . ->m . string?)]
+    [update   (#;trick string? #;code string? . ->m .
+               (result/c string?
+                         (error/c (no-such-trick)
+                                  (needs-body)
+                                  (missing-permissions))))]
 
     ;; look up a trick by name
     [lookup   (#;trick string? . ->m . (or/c trick? #f))]

@@ 0,0 1,37 @@
+#lang racket/base
+
+(require racket/contract (for-syntax racket/base syntax/parse))
+
+(provide result/c ok? err? result-case
+         error/c)
+
+;; represents a fallible computation
+;; (cons 'ok ok-value) on success
+;; (cons 'err err-value) on failure
+(define-syntax (result/c stx)
+  (syntax-parse stx
+    [(_ ok-ctc:expr err-ctc:expr)
+     (with-syntax ([name stx])
+       (syntax/loc stx
+         (rename-contract
+          (or/c (cons/c 'ok ok-ctc)
+                (cons/c 'err err-ctc))
+          'name)))]))
+
+;; represents an error, a message tagged with a type
+;; (cons message . case)
+(define-syntax (error/c stx)
+  (syntax-parse stx
+    [(_ (tag:id others ...) ...)
+     (with-syntax ([name stx])
+       (syntax/loc stx
+         (rename-contract
+          (cons/c string?
+                  (or/c (list/c 'tag others ...)
+                        ...))
+          'name)))]))
+
+(define (ok? x) (eq? 'ok (car x)))
+(define (err? x) (eq? 'err (car x)))
+(define (result-case if-ok if-err x)
+  ((if (ok? x) if-ok if-err) (cdr x)))