feat: redirect secondary YT channels to the YTM channel

Squashed commit of the following:

commit 88809265ead6eadfafab4b74091dd1af357b9577
Author: ThetaDev <t.testboy@gmail.com>
Date:   Sat Jan 21 22:16:23 2023 +0100

    feat: redirect secondary YT channels to the YTM channel

commit 02cc120912509f40f45da243ba5d37798b9ff411
Author: ThetaDev <t.testboy@gmail.com>
Date:   Mon Jan 9 23:57:18 2023 +0100

    add artists_no_tracks testfile

src/util/protobuf.rs

@@ -54,3 +54,85 @@ impl ProtoBuilder {
         self.bytes.append(&mut pb.bytes);
     }
 }
+
+fn parse_varint<P: Iterator<Item = u8>>(pb: &mut P) -> Option<u64> {
+    let mut result = 0;
+    let mut num_read = 0;
+
+    for b in pb.by_ref() {
+        let value = b & 0x7f;
+        result |= (value as u64) << (7 * num_read);
+        num_read += 1;
+
+        if b & 0x80 == 0 {
+            break;
+        }
+    }
+    if num_read == 0 {
+        None
+    } else {
+        Some(result)
+    }
+}
+
+fn parse_field<P: Iterator<Item = u8>>(pb: &mut P) -> Option<(u32, u8)> {
+    parse_varint(pb).map(|v| {
+        let f = (v >> 3) as u32;
+        let w = (v & 0x07) as u8;
+        (f, w)
+    })
+}
+
+pub fn string_from_pb<P: IntoIterator<Item = u8>>(pb: P, field: u32) -> Option<String> {
+    let mut pb = pb.into_iter();
+    while let Some((this_field, wire)) = parse_field(&mut pb) {
+        let to_skip = match wire {
+            // varint
+            0 => {
+                parse_varint(&mut pb);
+                0
+            }
+            // fixed 64bit
+            1 => 8,
+            // fixed 32bit
+            5 => 4,
+            // string
+            2 => {
+                let len = some_or_bail!(parse_varint(&mut pb), None);
+                if this_field == field {
+                    let mut buf = Vec::new();
+                    for _ in 0..len {
+                        buf.push(some_or_bail!(pb.next(), None));
+                    }
+                    return String::from_utf8(buf).ok();
+                } else {
+                    len
+                }
+            }
+            _ => return None,
+        };
+        for _ in 0..to_skip {
+            pb.next();
+        }
+    }
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // #[test]
+    // fn t_parse_varint() {
+
+    // }
+
+    #[test]
+    fn t_parse_proto() {
+        let p = "GhhVQzl2cnZOU0wzeGNXR1NrVjg2UkVCU2c%3D";
+        let p_bytes = base64::decode(urlencoding::decode(p).unwrap().as_bytes()).unwrap();
+
+        let res = string_from_pb(p_bytes, 3).unwrap();
+        assert_eq!(res, "UC9vrvNSL3xcWGSkV86REBSg");
+    }
+}