Send correctors to each render as well

1 files changed, 140 insertions, 0 deletions

diff --git a/src/clarktown/engine.clj b/src/clarktown/engine.clj
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+++ b/src/clarktown/engine.clj
@@ -0,0 +1,140 @@
+(ns clarktown.engine
+  (:require
+    [clojure.string :as string]))
+
+
+(defn- stitch-code-blocks
+  "Since code blocks can span multiple blocks (a block is separated by
+  two line breaks from another block) , we need to stitch them together
+  into one block in order for a block parser to be able to do anything
+  with it."
+  [blocks]
+  (loop [stitched-blocks []
+         code-block-started? false
+         blocks blocks]
+    (if (empty? blocks)
+      stitched-blocks
+      (let [block (first blocks)]
+        (if (and (string/starts-with? (string/trim block) "```")
+                 (not (string/ends-with? (string/trim block) "```")))
+          (recur (conj stitched-blocks block)
+                 true
+                 (drop 1 blocks))
+          (if code-block-started?
+            (let [last-block (last stitched-blocks)
+                  last-block-index (- (count stitched-blocks) 1)]
+              (if (string/ends-with? (string/trim block) "```")
+                (recur (assoc stitched-blocks last-block-index (str last-block "\n\n" block))
+                       false
+                       (drop 1 blocks))
+                (recur (assoc stitched-blocks last-block-index (str last-block "\n\n" block))
+                       true
+                       (drop 1 blocks))))
+            (recur (conj stitched-blocks block)
+                   false
+                   (drop 1 blocks))))))))
+
+
+(defn- correct-block-separations
+  "Corrects block separations and adds newlines above or
+  below a block where needed."
+  [correctors lines]
+  (->> lines
+       (map-indexed
+         (fn [index line]
+           (let [add-line-above? (some #(true? (% lines line index)) (:empty-line-above? correctors))
+                 add-line-below? (some #(true? (% lines line index)) (:empty-line-below? correctors))]
+             (cond
+               ; If code block starts but there is no empty newline
+               ; above, let's fix that
+               (and add-line-above?
+                    (not add-line-below?))
+               (str \newline line)
+
+               ; If the code block ends, but there is no empty newline
+               ; below, let's fix that.
+               (and add-line-below?
+                    (not add-line-above?))
+               (str line \newline)
+
+               ; If the code block needs a newline both above and below,
+               ; let's fix that.
+               (and add-line-above?
+                    add-line-below?)
+               (str \newline line \newline)
+
+               ; otherwise is what it is
+               :else line))))))
+
+
+(defn- correct-markdown
+  "Corrects invalid Markdown for the parser."
+  [markdown given-correctors]
+  (let [lines (string/split-lines markdown)]
+    (->> lines
+         (correct-block-separations (:block-separations given-correctors))
+         (string/join \newline))))
+
+
+(defn- find-parser-by-block
+  "Find a parser from `parsers` that matches the given `block`."
+  [parsers block]
+  (->> parsers
+       (filter
+         (fn [{:keys [matcher]}]
+           (when matcher
+             (matcher block))))
+       first))
+
+
+(defn- parse-block-with-known-parser
+  "Parses a given `block` with a known `parser`."
+  [parser given-parsers given-correctors block]
+  (loop [block block
+         renderers (:renderers parser)]
+    (if (empty? renderers)
+      block
+      (let [renderer (first renderers)]
+        (recur (renderer block given-parsers given-correctors)
+               (drop 1 renderers))))))
+
+
+(defn- parse-block-with-unknown-parsers
+  "Parses the given `block` with all the parsers that do not have
+  a matcher function, useful for any fallback parsing one might want
+  to do."
+  [given-parsers given-correctors block]
+  (loop [block block
+         parsers (filter #(= nil (:matcher %)) given-parsers)]
+    (if (empty? parsers)
+      block
+      (recur (loop [block block
+                    renderers (:renderers (first parsers))]
+               (if (empty? renderers)
+                 block
+                 (let [renderer (first renderers)]
+                   (recur (renderer block parsers given-correctors)
+                          (drop 1 renderers)))))
+             (drop 1 parsers)))))
+
+
+(defn- parse-blocks
+  "Parses each individual Markdown block, given as `blocks`, with
+  the list of `parsers`."
+  [blocks given-parsers given-correctors]
+  (for [block blocks]
+    (if-let [parser (find-parser-by-block given-parsers block)]
+      (->> (string/trim block)
+           (parse-block-with-known-parser parser given-parsers given-correctors))
+      (->> (string/trim block)
+           (parse-block-with-unknown-parsers given-parsers given-correctors)))))
+
+
+(defn render
+  "Parses given `markdown` with `parsers`."
+  [markdown given-parsers given-correctors]
+  (let [blocks (-> (correct-markdown markdown given-correctors)
+                   (string/split #"\n\n")
+                   stitch-code-blocks)
+        parsed-blocks (parse-blocks blocks given-parsers given-correctors)]
+    (string/join "\n\n" parsed-blocks)))
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