From 2204f93cf31a89dfef75fa97ffc6c9365e7f844b Mon Sep 17 00:00:00 2001
From: trivernis <trivernis@gmail.com>
Date: Sat, 30 May 2020 11:37:23 +0200
Subject: [PATCH] Add code block parsing

---
 src/elements.rs |  5 +++--
 src/parser.rs   | 53 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/tokens.rs   |  4 ++++
 3 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/src/elements.rs b/src/elements.rs
index c43696f..09bf8f0 100644
--- a/src/elements.rs
+++ b/src/elements.rs
@@ -4,6 +4,7 @@ pub enum Block {
     Paragraph(Paragraph),
     List(List),
     Table(Table),
+    CodeBlock(CodeBlock),
 }
 
 #[derive(Clone, Debug)]
@@ -69,8 +70,8 @@ pub struct Cell {
 
 #[derive(Clone, Debug)]
 pub struct CodeBlock {
-    language: String,
-    code: String,
+    pub(crate) language: String,
+    pub(crate) code: String,
 }
 
 #[derive(Clone, Debug)]
diff --git a/src/parser.rs b/src/parser.rs
index 4e033ab..374466a 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -120,10 +120,36 @@ impl Parser {
         chars.contains(&self.current_char) && !self.check_escaped()
     }
 
+    /// returns if the current character is a linebreak character
+    /// Note: No one likes CRLF
     pub fn check_linebreak(&self) -> bool {
         self.current_char == LB && !self.check_escaped()
     }
 
+    /// checks if the next characters match a special sequence
+    pub fn check_special_sequence(&mut self, sequence: &[char]) -> Result<(), ParseError> {
+        let start_index = self.index;
+        self.seek_whitespace();
+        for sq_character in sequence {
+            if !self.check_special(sq_character) {
+                let err = ParseError::new(self.index);
+                self.revert_to(start_index)?;
+                // should work
+                return Err(err);
+            }
+            if self.next_char() == None {
+                let err = ParseError::new(self.index);
+                self.revert_to(start_index)?;
+                return Err(err);
+            }
+        }
+        if self.index > 0 {
+            self.revert_to(self.index - 1)?;
+        }
+
+        Ok(())
+    }
+
     /// parses the given text into a document
     pub fn parse(&mut self) -> Document {
         let mut document = Document::new();
@@ -153,6 +179,8 @@ impl Parser {
             Block::List(list)
         } else if let Ok(table) = self.parse_table() {
             Block::Table(table)
+        } else if let Ok(code_block) = self.parse_code_block() {
+            Block::CodeBlock(code_block)
         } else if let Ok(paragraph) = self.parse_paragraph() {
             Block::Paragraph(paragraph)
         } else {
@@ -202,6 +230,7 @@ impl Parser {
         }
     }
 
+    /// parses the header of a section
     fn parse_header(&mut self) -> Result<Header, ParseError> {
         Ok(Header {
             size: 0,
@@ -209,6 +238,30 @@ impl Parser {
         })
     }
 
+    /// parses a code block
+    fn parse_code_block(&mut self) -> Result<CodeBlock, ParseError> {
+        let mut language = String::new();
+        self.check_special_sequence(&SQ_CODE_BLOCK)?;
+        while let Some(character) = self.next_char() {
+            if self.check_linebreak() {
+                break;
+            }
+            language.push(character);
+        }
+        let mut text = String::new();
+        while let Some(character) = self.next_char() {
+            if let Ok(_) = self.check_special_sequence(&SQ_CODE_BLOCK) {
+                break;
+            }
+            text.push(character);
+        }
+
+        Ok(CodeBlock {
+            language,
+            code: text,
+        })
+    }
+
     /// Parses a paragraph
     fn parse_paragraph(&mut self) -> Result<Paragraph, ParseError> {
         let mut paragraph = Paragraph::new();
diff --git a/src/tokens.rs b/src/tokens.rs
index b1d6bf7..8fac64a 100644
--- a/src/tokens.rs
+++ b/src/tokens.rs
@@ -27,3 +27,7 @@ pub(crate) const BLOCK_SPECIAL_CHARS: [char; 4] = [HASH, MINUS, BACKTICK, PIPE];
 pub(crate) const INLINE_SPECIAL_CHARS: [char; 6] = [LB, ASTERISK, UNDERSCR, TILDE, PIPE, BACKTICK];
 
 pub(crate) const LIST_SPECIAL_CHARS: [char; 4] = [MINUS, PLUS, ASTERISK, O];
+
+// sequences
+
+pub(crate) const SQ_CODE_BLOCK: [char; 3] = [BACKTICK, BACKTICK, BACKTICK];