Refactor NIP19 implementation and add tests

Closes: #837

damus-c/cursor.h

@@ -0,0 +1,150 @@
+//
+//  cursor.h
+//  damus
+//
+//  Created by William Casarin on 2023-04-09.
+//
+
+#ifndef cursor_h
+#define cursor_h
+
+#include <ctype.h>
+#include <string.h>
+
+typedef unsigned char u8;
+
+struct cursor {
+    const u8 *p;
+    const u8 *start;
+    const u8 *end;
+};
+
+static inline int is_whitespace(char c) {
+    return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r';
+}
+
+static inline int is_boundary(char c) {
+    return !isalnum(c);
+}
+
+static inline int is_invalid_url_ending(char c) {
+    return c == '!' || c == '?' || c == ')' || c == '.' || c == ',' || c == ';';
+}
+
+static inline void make_cursor(struct cursor *c, const u8 *content, size_t len)
+{
+    c->start = content;
+    c->end = content + len;
+    c->p = content;
+}
+
+static inline int consume_until_boundary(struct cursor *cur) {
+    char c;
+    
+    while (cur->p < cur->end) {
+        c = *cur->p;
+        
+        if (is_boundary(c))
+            return 1;
+        
+        cur->p++;
+    }
+    
+    return 1;
+}
+
+static inline int consume_until_whitespace(struct cursor *cur, int or_end) {
+    char c;
+    int consumedAtLeastOne = 0;
+    
+    while (cur->p < cur->end) {
+        c = *cur->p;
+        
+        if (is_whitespace(c))
+            return consumedAtLeastOne;
+        
+        cur->p++;
+        consumedAtLeastOne = 1;
+    }
+    
+    return or_end;
+}
+
+static inline int parse_char(struct cursor *cur, char c) {
+    if (cur->p >= cur->end)
+        return 0;
+        
+    if (*cur->p == c) {
+        cur->p++;
+        return 1;
+    }
+    
+    return 0;
+}
+
+static inline int peek_char(struct cursor *cur, int ind) {
+    if ((cur->p + ind < cur->start) || (cur->p + ind >= cur->end))
+        return -1;
+    
+    return *(cur->p + ind);
+}
+
+static int parse_digit(struct cursor *cur, int *digit) {
+    int c;
+    if ((c = peek_char(cur, 0)) == -1)
+        return 0;
+    
+    c -= '0';
+    
+    if (c >= 0 && c <= 9) {
+        *digit = c;
+        cur->p++;
+        return 1;
+    }
+    return 0;
+}
+
+
+static inline int pull_byte(struct cursor *cur, u8 *byte) {
+    if (cur->p >= cur->end)
+        return 0;
+        
+    *byte = *cur->p;
+    cur->p++;
+    return 1;
+}
+
+static inline int pull_bytes(struct cursor *cur, int count, const u8 **bytes) {
+    if (cur->p + count > cur->end)
+        return 0;
+    
+    *bytes = cur->p;
+    cur->p += count;
+    return 1;
+}
+
+static inline int parse_str(struct cursor *cur, const char *str) {
+    int i;
+    char c, cs;
+    unsigned long len;
+    
+    len = strlen(str);
+    
+    if (cur->p + len >= cur->end)
+        return 0;
+    
+    for (i = 0; i < len; i++) {
+        c = tolower(cur->p[i]);
+        cs = tolower(str[i]);
+        
+        if (c != cs)
+            return 0;
+    }
+    
+    cur->p += len;
+    
+    return 1;
+}
+
+
+#endif /* cursor_h */