more mention progress

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

damus/Util/Parser.swift

@@ -7,7 +7,41 @@
 
 import Foundation
 
+class Parser {
+    var pos: Int
+    var str: String
+    
+    init(pos: Int, str: String) {
+        self.pos = pos
+        self.str = str
+    }
+}
+
+func consume_until(_ p: Parser, match: (Character) -> Bool) -> Bool {
+    var i: Int = 0
+    let sub = substring(p.str, start: p.pos, end: p.str.count)
+    for c in sub {
+        if match(c) {
+            p.pos += i
+            return true
+        }
+        i += 1
+    }
+    
+    return false
+}
+
+func substring(_ s: String, start: Int, end: Int) -> Substring {
+    let ind = s.index(s.startIndex, offsetBy: start)
+    let end = s.index(s.startIndex, offsetBy: end)
+    return s[ind..<end]
+}
+
+
 func parse_str(_ p: Parser, _ s: String) -> Bool {
+    if p.pos + s.count > p.str.count {
+        return false
+    }
     let sub = substring(p.str, start: p.pos, end: p.pos + s.count)
     if sub == s {
         p.pos += s.count
@@ -16,7 +50,7 @@ func parse_str(_ p: Parser, _ s: String) -> Bool {
     return false
 }
 
-func parse_char(_ p: Parser, _ c: Character) -> Bool{
+func parse_char(_ p: Parser, _ c: Character) -> Bool {
     let ind = p.str.index(p.str.startIndex, offsetBy: p.pos)
     
     if p.str[ind] == c {
@@ -40,3 +74,19 @@ func parse_digit(_ p: Parser) -> Int? {
     
     return 0
 }
+
+
+func parse_hex_char(_ p: Parser) -> Character? {
+    let ind = p.str.index(p.str.startIndex, offsetBy: p.pos)
+    
+    if let c = p.str[ind].unicodeScalars.first {
+        // hex chars
+        let d = c.value
+        if (d >= 48 && d <= 57) || (d >= 97 && d <= 102) || (d >= 65 && d <= 70) {
+            p.pos += 1
+            return p.str[ind]
+        }
+    }
+    
+    return nil
+}