From a6dc7f2f92162dc9a9930c3fe676c23a03ef35b8 Mon Sep 17 00:00:00 2001
From: Alex Karle <alex@alexkarle.com>
Date: Wed, 15 Dec 2021 00:25:31 -0500
Subject: [PATCH] Add initial support for links

---
 blag.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 86 insertions(+), 17 deletions(-)

diff --git a/blag.c b/blag.c
index 08d968c..46de1e0 100644
--- a/blag.c
+++ b/blag.c
@@ -20,23 +20,13 @@
  *
  *  Inline `code`
  *
- * TODO:
+ *  Escaping via \
+ *
  *  [[url|Links]]
- *  -> if we see [[
- *      -> print out <a href="
- *  -> while in link
- *      -> push into buf
- *      -> putchar
- *  -> if we see |
- *      -> printf ">
- *      -> just putchar
- *  -> else
- *      -> printf ">url
- *  -> once we hit ]]
- *      -> </a>
  *
- *  --> error reporting for unclosed links??
- *      -> errx in closeblock() if in link parser
+ * TODO:
+ * -----
+ *  - error reporting for malformed blocks
  */
 #include <stdio.h>
 #include <err.h>
@@ -60,6 +50,10 @@ enum Block {
     OLIST_START,
     OLIST_PARSE,
     OLIST_BREAK,
+    LINK_URL_PARSE,
+    LINK_DESC_PARSE,
+    POTENTIAL_LINK,
+    POTENTIAL_LINK_END
 };
 
 int closeblock(int in, int hlvl) {
@@ -100,13 +94,47 @@ int closeblock(int in, int hlvl) {
 }
 
 int parse() {
-    /* Mini state machine */
+    /* Mini state machine (home grown spaghetti code)
+     *
+     * Key: global "line level" state in `in`, secondary mid-line states
+     * (inline code & links) use dedicated states. A newline triggers many of
+     * the line-level blocks to enter "BREAK" mode, where they can either
+     * continue or truly be broken on a second newline (PARAGRAPH, CODE,
+     * U/OLIST, etc). Several of the variable length tokens (like ordered
+     * list numbers, header level, etc) enter a "PARSE" mode where special
+     * action is taken until the parsing is done (usually on ' ', but for
+     * links on '|')
+     */
     int c;
     enum Block in = NONE;
+    enum Block in_link = NONE;
     int hlvl = 0;
     int in_code;
+    int escape = 0;
     while ((c = getchar()) != EOF) {
+        /* Handle Escapes before all else */
+        if (escape) {
+            if (in == NONE) {
+                in = PARAGRAPH;
+                printf("<p>\n");
+            }
+            putchar(c);
+            escape = 0;
+            continue;
+        }
+        
+        /* Reset special "potential" states */
+        if (c != '[' && in_link == POTENTIAL_LINK) {
+            in_link = NONE;
+        } else if (c != ']' && in_link == POTENTIAL_LINK_END) {
+            in_link = NONE;
+        }
+
+        /* Handle unique state changes by char */
         switch (c) {
+            case '\\':
+                escape = 1;
+                break;
             case '#':
                 if (in == NONE) {
                     in = HEADER_PARSE;
@@ -120,7 +148,7 @@ int parse() {
                 break;
             case ' ':
                 if (in == HEADER_PARSE) {
-                    printf("</h%d>", hlvl);
+                    printf("<h%d>", hlvl);
                     in = HEADER;
                 } else if (in == ULIST_START) {
                     printf("<ul>\n  <li>");
@@ -155,6 +183,8 @@ int parse() {
                     printf("<code><pre>\n");
                 } else if (in == CODE_BREAK) {
                     in = CODE;
+                } else {
+                    putchar(c);
                 }
                 break;
             case '>':
@@ -163,6 +193,45 @@ int parse() {
                     printf("<blockquote>\n");
                 } else if (in == QUOTE_BREAK) {
                     in = QUOTE;
+                } else {
+                    putchar(c);
+                }
+                break;
+            case '[':
+                if (in_link == NONE) {
+                    in_link = POTENTIAL_LINK;
+                } else if (in_link == POTENTIAL_LINK) {
+                    if (in == NONE) {
+                        /* Assume this is a new paragraph */
+                        in = PARAGRAPH;
+                        printf("<p>\n");
+                    }
+                    /* XXX: need to print the first link */
+                    in_link = LINK_URL_PARSE;
+                    printf("<a href=\"");
+                } else if (in_link == LINK_URL_PARSE) {
+                    /* TODO: save to linkbuf to support [[url]] links? */
+                    putchar(c);
+                } else {
+                    putchar(c);
+                }
+                break;
+            case '|':
+                if (in_link == LINK_URL_PARSE) {
+                    in_link = LINK_DESC_PARSE;
+                    printf("\">");
+                } else {
+                    putchar(c);
+                }
+                break;
+            case ']':
+                if (in_link == LINK_DESC_PARSE) {
+                    in_link = POTENTIAL_LINK_END;
+                } else if (in_link == POTENTIAL_LINK_END) {
+                    in_link = NONE;
+                    printf("</a>");
+                } else {
+                    putchar(c);
                 }
                 break;
             case '*':
--
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