likes, mention parsing, lots of stuff

Signed-off-by: William Casarin <jb55@jb55.com>

damus/Util/Parser.swift

@@ -0,0 +1,42 @@
+//
+//  Parser.swift
+//  damus
+//
+//  Created by William Casarin on 2022-05-04.
+//
+
+import Foundation
+
+func parse_str(_ p: Parser, _ s: String) -> Bool {
+    let sub = substring(p.str, start: p.pos, end: p.pos + s.count)
+    if sub == s {
+        p.pos += s.count
+        return true
+    }
+    return false
+}
+
+func parse_char(_ p: Parser, _ c: Character) -> Bool{
+    let ind = p.str.index(p.str.startIndex, offsetBy: p.pos)
+    
+    if p.str[ind] == c {
+        p.pos += 1
+        return true
+    }
+    
+    return false
+}
+
+func parse_digit(_ p: Parser) -> Int? {
+    let ind = p.str.index(p.str.startIndex, offsetBy: p.pos)
+    
+    if let c = p.str[ind].unicodeScalars.first {
+        let d = Int(c.value) - 48
+        if d >= 0 && d < 10 {
+            p.pos += 1
+            return Int(d)
+        }
+    }
+    
+    return 0
+}