Add link, images (resource)

This is still some messy code that needs cleaning up, but it adds support for
links and images, of the resource kind (`[a](b)`).
References (`[a][b]`) are parsed and will soon be supported, but need matching.

*   Fix bug to pad percent-encoded bytes when normalizing urls
*   Fix bug with escapes counting as balancing in destination
*   Add `space_or_tab_one_line_ending`, to parse whitespace including up to
    one line ending (but not a blank line)
*   Add `ParserState` to share codes, definitions, etc

1 files changed, 47 insertions, 0 deletions

diff --git a/src/construct/label_start_image.rs b/src/construct/label_start_image.rs
new file mode 100644
index 0000000..2e96977
--- /dev/null
+++ b/src/construct/label_start_image.rs
@@ -0,0 +1,47 @@
+//! To do
+
+use super::label_end::resolve_media;
+use crate::tokenizer::{Code, LabelStart, State, StateFnResult, TokenType, Tokenizer};
+
+/// Start of label (image) start.
+///
+/// ```markdown
+/// a |![ b
+/// ```
+pub fn start(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    match code {
+        Code::Char('!') => {
+            tokenizer.enter(TokenType::LabelImage);
+            tokenizer.enter(TokenType::LabelImageMarker);
+            tokenizer.consume(code);
+            tokenizer.exit(TokenType::LabelImageMarker);
+            (State::Fn(Box::new(open)), None)
+        }
+        _ => (State::Nok, None),
+    }
+}
+
+/// After `!`, before a `[`.
+///
+/// ```markdown
+/// a !|[ b
+/// ```
+pub fn open(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    match code {
+        Code::Char('[') => {
+            tokenizer.enter(TokenType::LabelMarker);
+            tokenizer.consume(code);
+            tokenizer.exit(TokenType::LabelMarker);
+            tokenizer.exit(TokenType::LabelImage);
+            let end = tokenizer.events.len() - 1;
+            tokenizer.label_start_stack.push(LabelStart {
+                start: (end - 5, end),
+                balanced: false,
+                inactive: false,
+            });
+            tokenizer.register_resolver("media".to_string(), Box::new(resolve_media));
+            (State::Ok, None)
+        }
+        _ => (State::Nok, None),
+    }
+}