From 52203a49aa544b2c11c96445d8732893160c436b Mon Sep 17 00:00:00 2001
From: Asko Nõmm <asko@bien.ee>
Date: Tue, 19 Apr 2022 17:50:19 +0300
Subject: WIP #16

Pretty much done. Needs more testing. And new documentation.
---
 src/clarktown/renderers/list_block.clj | 121 +++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 src/clarktown/renderers/list_block.clj

(limited to 'src/clarktown/renderers/list_block.clj')

diff --git a/src/clarktown/renderers/list_block.clj b/src/clarktown/renderers/list_block.clj
new file mode 100644
index 0000000..2a40b06
--- /dev/null
+++ b/src/clarktown/renderers/list_block.clj
@@ -0,0 +1,121 @@
+(ns clarktown.renderers.list-block
+  (:require
+    [clojure.string :as string]))
+
+
+(defn string->indent-n
+  "Returns the indentation count from left of `str`, which must be
+  in spaces and not tabs."
+  [str]
+  (count (take-while #{\space} str)))
+
+
+(defn compose-items-with-indent-guides
+  "Composes a vector of maps from given `block` that adds a unique
+  ID to each line as well as its `indent-n` which is used later
+  on to determine hierarchies. "
+  [block]
+  (->> (string/split-lines block)
+       (mapv
+         (fn [line]
+           {:id (random-uuid)
+            :indent-n (string->indent-n line)
+            :value (-> line
+                       string/trim)}))))
+
+
+(defn find-parent-id
+  "Assuming a 1-level `items`, will attempt to find the parent `id`
+  of the item at given `index`. Will return `nil` otherwise."
+  [items index]
+  (let [indent-n-at-index (:indent-n (nth items index))]
+    (-> (->> (split-at index items)
+             first
+             reverse
+             (remove #(or (> (:indent-n %) indent-n-at-index)
+                          (= (:indent-n %) indent-n-at-index)))
+             first
+             :id))))
+
+
+(defn compose-items-with-parents
+  "Composes a 1-level list of items from `block` and adds parent
+  information to each if they belong to another item. The result
+  of this is used to build the final data tree."
+  [block]
+  (let [items (compose-items-with-indent-guides block)]
+    (->> items
+         (map-indexed
+           (fn [index line]
+             (merge line {:parent (find-parent-id items index)}))))))
+
+
+(defn add-to-parent
+  "Recursively scans `items`, which can be multiple levels deep,
+  and tries to find a home for `item` according to its parent ID."
+  [items item]
+  (->> items
+       (mapv
+         (fn [i]
+           (if (= (:id i) (:parent item))
+             (if (:items i)
+               (assoc i :items (concat (:items i) [item]))
+               (assoc i :items [item]))
+             (if (:items i)
+               (assoc i :items (add-to-parent (:items i) item))
+               i))))))
+
+
+(defn compose-item-tree
+  "Given a `block`, composes a data representation of it based on
+  the indentation of each line."
+  [block]
+  (loop [result []
+         items (compose-items-with-parents block)]
+    (if (empty? items)
+      result
+      (let [item (first items)
+            parent (:parent item)
+            new-item {:id (:id item)
+                      :value (:value item)}]
+        (recur (if parent
+                 (add-to-parent result item)
+                 (concat result [new-item]))
+               (drop 1 items))))))
+
+
+(defn render-items
+  "Renders an ordered/un-ordered list hierarchy from given `items`."
+  [items]
+  (loop [result ""
+         inner-items items]
+    (if (empty? inner-items)
+      (if (or (string/starts-with? (:value (first items)) "*")
+              (string/starts-with? (:value (first items)) "-"))
+        (str "<ul>" result "</ul>")
+        (str "<ol>" result "</ol>"))
+      (let [inner-item (first inner-items)
+            value (cond
+                    ; * unordered list
+                    (string/starts-with? (:value inner-item) "*")
+                    (-> (string/replace-first (:value inner-item) "*" "")
+                        string/trim)
+                    ; - unordered list
+                    (string/starts-with? (:value inner-item) "-")
+                    (-> (string/replace-first (:value inner-item) "-" "")
+                        string/trim)
+                    ; ordered list
+                    :else
+                    (-> (string/replace-first (:value inner-item) #"\d\." "")
+                        string/trim))]
+        (recur (if (:items inner-item)
+                 (str result "<li>" value (render-items (:items inner-item)) "</li>")
+                 (str result "<li>" value "</li>"))
+               (drop 1 inner-items))))))
+
+
+(defn render
+  "Renders the list block"
+  [block _]
+  (-> (compose-item-tree block)
+      (render-items)))
\ No newline at end of file
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