feat: add support for system mentions

This change parses `0xXXXXX` as mentions such that they
can be translated to system mentions (like `@everyone`).

parser/inline.go

@@ -68,6 +68,7 @@ func (p *Parser) Inline(currBlock ast.Node, data []byte) {
 
 const pkLength = 132
 const compressedPkPrefixLen = 3
+const systemMentionLength = 7
 
 func mention(p *Parser, data []byte, offset int) (int, ast.Node) {
 	data = data[offset:]
@@ -96,10 +97,7 @@ func mention(p *Parser, data []byte, offset int) (int, ast.Node) {
 		mention.Literal = data[1 : pkLength+1]
 
 		return i, mention
-	} else if n >= compressedPkPrefixLen+1 {
-		if data[1] != 'z' || data[2] != 'Q' || data[3] != '3' {
-			return 0, nil
-		}
+	} else if n >= compressedPkPrefixLen+1 && (data[1] == 'z' || data[2] == 'Q' || data[3] == '3') {
 
 		i := 1
 		for _, c := range data[1:] {
@@ -117,6 +115,29 @@ func mention(p *Parser, data []byte, offset int) (int, ast.Node) {
 
 		mention := &ast.Mention{}
 		mention.Literal = data[1:i]
+		return i, mention
+	} else if n >= systemMentionLength+1 {
+		// need to start with 0x and can't end with 0
+		if data[1] != '0' || data[2] != 'x' || data[systemMentionLength] == '0' {
+			return 0, nil
+		}
+
+		i := 3
+		for i < systemMentionLength+1 {
+			if !isValidSystemTagChar(data[i]) {
+				return 0, nil
+			}
+			i++
+		}
+
+		// Check there's a space
+		if n != systemMentionLength+1 && !isValidTerminatingMentionChar(data[systemMentionLength+1]) {
+			return 0, nil
+		}
+
+		mention := &ast.Mention{}
+		mention.Literal = data[1 : systemMentionLength+1]
+
 		return i, mention
 	}
 

parser/parser.go

@@ -712,6 +712,11 @@ func isValidCompressedPublicKeyChar(c byte) bool {
 		c == 'R' || c == 'S' || c == 'T' || c == 'U' || c == 'V' || c == 'W' || c == 'X' || c == 'Y' || c == 'Z'
 }
 
+func isValidSystemTagChar(c byte) bool {
+  return c == '0' || c == '1' || c == '2' || c == '3' || c == '4' || c == '5' || c == '6' || c == '7' || c == '8' || c == '9'
+}
+
+
 // TODO: this is not used
 // Replace tab characters with spaces, aligning to the next TAB_SIZE column.
 // always ends output with a newline

testdata/mentions.test

@@ -85,3 +85,51 @@ Invalid char @zQ3shh7B7RWHqbcFxZXwG9H9qnproDSvcCwqmSMzdwrvzN2Of
 Not starting with zq3 @zq3shh7B7RWHqbcFxZXwG9H9qnproDSvcCwqmSMzdwrvzN2jf
 +++
 [{"type":"paragraph","children":[{"literal":"Not starting with zq3 @zq3shh7B7RWHqbcFxZXwG9H9qnproDSvcCwqmSMzdwrvzN2jf"}]}]
++++
+Valid systemMention at the end @0x00001
++++
+[{"type":"paragraph","children":[{"literal":"Valid systemMention at the end "},{"type":"mention","literal":"0x00001"}]}]
++++
+Valid systemMention comma @0x00001,
++++
+[{"type":"paragraph","children":[{"literal":"Valid systemMention comma "},{"type":"mention","literal":"0x00001"},{"literal":","}]}]
++++
+Valid systemMention dot @0x00001.
++++
+[{"type":"paragraph","children":[{"literal":"Valid systemMention dot "},{"type":"mention","literal":"0x00001"},{"literal":"."}]}]
++++
+Valid systemMention colon @0x00001:
++++
+[{"type":"paragraph","children":[{"literal":"Valid systemMention colon "},{"type":"mention","literal":"0x00001"},{"literal":":"}]}]
++++
+Valid systemMention semi-colon @0x00001;
++++
+[{"type":"paragraph","children":[{"literal":"Valid systemMention semi-colon "},{"type":"mention","literal":"0x00001"},{"literal":";"}]}]
++++
+@0x00001 at the beginning
++++
+[{"type":"paragraph","children":[{"literal":""},{"type":"mention","literal":"0x00001"},{"literal":" at the beginning"}]}]
++++
+in the middle @0x00001 middle
++++
+[{"type":"paragraph","children":[{"literal":"in the middle "},{"type":"mention","literal":"0x00001"},{"literal":" middle"}]}]
++++
+too short @0x001
++++
+[{"type":"paragraph","children":[{"literal":"too short @0x001"}]}]
++++
+too long @0x000001
++++
+[{"type":"paragraph","children":[{"literal":"too long @0x000001"}]}]
++++
+Invalid char @0x000a1
++++
+[{"type":"paragraph","children":[{"literal":"Invalid char @0x000a1"}]}]
++++
+Not starting with 0x @x00001
++++
+[{"type":"paragraph","children":[{"literal":"Not starting with 0x @x00001"}]}]
++++
+Ends with 0 @0x00000
++++
+[{"type":"paragraph","children":[{"literal":"Ends with 0 @0x00000"}]}]