refactor(cheddar): Set up scaffolding for Markdown rendering r/281

Generalises the two bits of the program that will be required either
way (extension parsing and syntax loading).

A dependency on Comrak is introduced as I think GitHub-flavoured
Markdown (with all its fancy extensions) is desirable!

3 files changed, 224 insertions, 13 deletions

diff --git a/tools/cheddar/Cargo.lock b/tools/cheddar/Cargo.lock
index f068c918db..227db64fef 100644
--- a/tools/cheddar/Cargo.lock
+++ b/tools/cheddar/Cargo.lock
@@ -95,6 +95,30 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "block-buffer"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "block-padding 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "byte-tools 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "byteorder 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "generic-array 0.12.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "block-padding"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "byte-tools 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "byte-tools"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "byteorder"
 version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -121,6 +145,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "cheddar"
 version = "0.1.0"
 dependencies = [
+ "comrak 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntect 3.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -149,6 +175,22 @@ dependencies = [
 ]
 
 [[package]]
+name = "comrak"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "entities 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pest 2.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pest_derive 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "twoway 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "typed-arena 1.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode_categories 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "crc32fast"
 version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -157,6 +199,19 @@ dependencies = [
 ]
 
 [[package]]
+name = "digest"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "generic-array 0.12.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "entities"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "env_logger"
 version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -177,6 +232,11 @@ dependencies = [
 ]
 
 [[package]]
+name = "fake-simd"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "flate2"
 version = "1.0.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -201,6 +261,14 @@ dependencies = [
 ]
 
 [[package]]
+name = "generic-array"
+version = "0.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "typenum 1.11.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "glob"
 version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -264,6 +332,11 @@ dependencies = [
 ]
 
 [[package]]
+name = "maplit"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "memchr"
 version = "2.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -307,11 +380,55 @@ dependencies = [
 ]
 
 [[package]]
+name = "opaque-debug"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "peeking_take_while"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "pest"
+version = "2.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "ucd-trie 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "pest_derive"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "pest 2.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pest_generator 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "pest_generator"
+version = "2.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "pest 2.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pest_meta 2.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "pest_meta"
+version = "2.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "maplit 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pest 2.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha-1 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "pkg-config"
 version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -431,6 +548,17 @@ dependencies = [
 ]
 
 [[package]]
+name = "sha-1"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "block-buffer 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fake-simd 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "opaque-debug 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "shlex"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -496,6 +624,35 @@ dependencies = [
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 [[package]]
+name = "twoway"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "memchr 2.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unchecked-index 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
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+
+[[package]]
+name = "typed-arena"
+version = "1.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "typenum"
+version = "1.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "ucd-trie"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "unchecked-index"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "unicode-width"
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 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -511,6 +668,11 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "unicode_categories"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "vec_map"
 version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
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+"checksum unicode_categories 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "39ec24b3121d976906ece63c9daad25b85969647682eee313cb5779fdd69e14e"
 "checksum vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "05c78687fb1a80548ae3250346c3db86a80a7cdd77bda190189f2d0a0987c81a"
 "checksum version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "914b1a6776c4c929a602fafd8bc742e06365d4bcbe48c30f9cca5824f70dc9dd"
 "checksum walkdir 2.2.9 (registry+https://github.com/rust-lang/crates.io-index)" = "9658c94fa8b940eab2250bd5a457f9c48b748420d71293b165c8cdbe2f55f71e"
diff --git a/tools/cheddar/Cargo.toml b/tools/cheddar/Cargo.toml
index 1ce121c025..fe936deb4c 100644
--- a/tools/cheddar/Cargo.toml
+++ b/tools/cheddar/Cargo.toml
@@ -4,5 +4,7 @@ version = "0.1.0"
 authors = ["Vincent Ambo <mail@tazj.in>"]
 edition = "2018"
 
-[dependencies.syntect]
-version = "3.3"
+[dependencies]
+comrak = "0.6"
+lazy_static = "1.4"
+syntect = "3.3"
diff --git a/tools/cheddar/src/main.rs b/tools/cheddar/src/main.rs
index 9cf8538570..76bf834cb8 100644
--- a/tools/cheddar/src/main.rs
+++ b/tools/cheddar/src/main.rs
@@ -6,7 +6,8 @@ use std::path::Path;
 use syntect::easy::HighlightLines;
 use syntect::dumps::from_binary;
 use syntect::highlighting::ThemeSet;
-use syntect::parsing::{SyntaxSet, SyntaxReference};
+use syntect::parsing::SyntaxSet;
+use lazy_static::lazy_static;
 
 use syntect::html::{
     append_highlighted_html_for_styled_line,
@@ -14,7 +15,14 @@ use syntect::html::{
     IncludeBackground,
 };
 
-fn syntax_from_args(syntaxes: &SyntaxSet) -> Option<&SyntaxReference> {
+// Set up syntaxes as a lazy_static. Initialisation might not be
+// required in the case of Markdown rendering (if there's no code
+// blocks within the document).
+lazy_static! {
+    static ref SYNTAXES: SyntaxSet = from_binary(include_bytes!(env!("BAT_SYNTAXES")));
+}
+
+fn args_extension() -> Option<String> {
     // The name of the file to be formatted is usually passed in as
     // the first argument and can be used to determine a syntax set.
     let args = env::args().collect::<Vec<String>>();
@@ -22,10 +30,9 @@ fn syntax_from_args(syntaxes: &SyntaxSet) -> Option<&SyntaxReference> {
         return None
     }
 
-    Path::new(&args[1])
-        .extension()
+    Path::new(&args[1]).extension()
         .and_then(OsStr::to_str)
-        .and_then(|ext| syntaxes.find_syntax_by_extension(ext))
+        .map(|s| s.to_string())
 }
 
 fn should_continue(res: &io::Result<usize>) -> bool {
@@ -35,9 +42,11 @@ fn should_continue(res: &io::Result<usize>) -> bool {
     }
 }
 
-fn main() {
-    let syntaxes = from_binary(include_bytes!(env!("BAT_SYNTAXES")));
+fn format_markdown() {
+    unimplemented!("Not able to format Markdown just yet");
+}
 
+fn format_code(extension: String) {
     let stdin = io::stdin();
     let mut stdin = stdin.lock();
     let mut linebuf = String::new();
@@ -49,9 +58,15 @@ fn main() {
     let ts = ThemeSet::load_defaults();
     let theme = &ts.themes["InspiredGitHub"];
 
-    let syntax = syntax_from_args(&syntaxes)
-        .or_else(|| syntaxes.find_syntax_by_first_line(&linebuf))
-        .unwrap_or_else(|| syntaxes.find_syntax_plain_text());
+    let syntax = SYNTAXES.find_syntax_by_extension(&extension)
+        .or_else(|| SYNTAXES.find_syntax_by_first_line(&linebuf))
+        .unwrap_or_else(|| SYNTAXES.find_syntax_plain_text());
+
+    // We're doing a completely different thing if the file is
+    // Markdown, so lets do that thing.
+    if syntax.name == "markdown" {
+
+    }
 
     let mut hl = HighlightLines::new(syntax, theme);
     let (mut outbuf, bg) = start_highlighted_html_snippet(theme);
@@ -63,7 +78,7 @@ fn main() {
     // newlines to be efficient, and those are stripped in the lines
     // iterator.
     while should_continue(&read_result) {
-        let regions = hl.highlight(&linebuf, &syntaxes);
+        let regions = hl.highlight(&linebuf, &SYNTAXES);
 
         append_highlighted_html_for_styled_line(
             &regions[..],
@@ -83,3 +98,14 @@ fn main() {
 
     println!("</pre>");
 }
+
+fn main() {
+    let extension = args_extension()
+        .expect("cheddar should be invoked with a filename!");
+
+    if extension == "md" {
+        format_markdown();
+    } else {
+        format_code(extension);
+    }
+}