1 files changed, 63 insertions, 1 deletions

diff --git a/src/construct/block_quote.rs b/src/construct/block_quote.rs
index cd5b872..048ff53 100644
--- a/src/construct/block_quote.rs
+++ b/src/construct/block_quote.rs
@@ -1,14 +1,57 @@
-//! To do.
+//! Block quote is a construct that occurs in the [document][] content type.
+//!
+//! It forms with the following BNF:
+//!
+//! ```bnf
+//! block_quote_start ::= '>' [ space_or_tab ]
+//! block_quote_cont ::= '>' [ space_or_tab ]
+//! ```
+//!
+//! Further lines that are not prefixed with `block_quote_cont` cause the block
+//! quote to be exited, except when those lines are lazy continuation.
+//! Like so many things in markdown, block quotes too, are very complex.
+//! See [*§ Phase 1: block structure*][commonmark-block] for more on parsing
+//! details.
+//!
+//! Block quote relates to the `<blockquote>` element in HTML.
+//! See [*§ 4.4.4 The `blockquote` element*][html-blockquote] in the HTML spec
+//! for more info.
+//!
+//! ## Tokens
+//!
+//! *   [`BlockQuote`][TokenType::BlockQuote]
+//! *   [`BlockQuotePrefix`][TokenType::BlockQuotePrefix]
+//! *   [`BlockQuoteMarker`][TokenType::BlockQuoteMarker]
+//! *   [`BlockQuotePrefixWhitespace`][TokenType::BlockQuotePrefixWhitespace]
+//!
+//! ## References
+//!
+//! *   [`block-quote.js` in `micromark`](https://github.com/micromark/micromark/blob/main/packages/micromark-core-commonmark/dev/lib/block-quote.js)
+//! *   [*§ 5.1 Block quotes* in `CommonMark`](https://spec.commonmark.org/0.30/#block-quotes)
+//!
+//! [document]: crate::content::document
+//! [html-blockquote]: https://html.spec.whatwg.org/multipage/grouping-content.html#the-blockquote-element
+//! [commonmark-block]: https://spec.commonmark.org/0.30/#phase-1-block-structure
 
 use crate::constant::TAB_SIZE;
 use crate::construct::partial_space_or_tab::space_or_tab_min_max;
 use crate::tokenizer::{Code, State, StateFnResult, TokenType, Tokenizer};
 
+/// Start of block quote.
+///
+/// ```markdown
+/// | > a
+/// ```
 pub fn start(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
     // To do: allow arbitrary when code (indented) is turned off.
     tokenizer.go(space_or_tab_min_max(0, TAB_SIZE - 1), before)(tokenizer, code)
 }
 
+/// Start of block quote, after whitespace, before `>`.
+///
+/// ```markdown
+/// |> a
+/// ```
 fn before(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
     match code {
         Code::Char('>') => {
@@ -19,11 +62,23 @@ fn before(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
     }
 }
 
+/// Start of block quote continuation.
+///
+/// ```markdown
+/// > a
+/// |> b
+/// ```
 pub fn cont(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
     // To do: allow arbitrary when code (indented) is turned off.
     tokenizer.go(space_or_tab_min_max(0, TAB_SIZE - 1), cont_before)(tokenizer, code)
 }
 
+/// After whitespace, before `>`.
+///
+/// ```markdown
+/// > a
+/// |> b
+/// ```
 fn cont_before(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
     match code {
         Code::Char('>') => {
@@ -37,6 +92,12 @@ fn cont_before(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
     }
 }
 
+/// After `>`, before optional whitespace.
+///
+/// ```markdown
+/// >| a
+/// >|b
+/// ```
 fn cont_after(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
     match code {
         Code::VirtualSpace | Code::Char('\t' | ' ') => {
@@ -53,6 +114,7 @@ fn cont_after(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
     }
 }
 
+/// End of a block quote.
 pub fn end() -> Vec<TokenType> {
     vec![TokenType::BlockQuote]
 }