Add parse subcommand

Co-Authored-By: Timothy Clem <timothy.clem@gmail.com>

cli/src/main.rs

@@ -86,6 +86,15 @@ fn run() -> error::Result<()> {
             eprintln!("No language found");
         }
     }
+
+    if let Some(matches) = matches.subcommand_matches("parse") {
+        loader.find_parsers(&vec![home_dir.join("github")])?;
+        let source_path = Path::new(matches.value_of("path").unwrap());
+        if let Some((language, _)) = loader.language_for_file_name(source_path)? {
+            parse::parse_file_at_path(language, source_path)?;
+        } else {
+            eprintln!("No language found");
+        }
     }
 
     Ok(())

cli/src/parse.rs

@@ -0,0 +1,69 @@
+use super::error::Result;
+use std::fs;
+use std::path::Path;
+use tree_sitter::{Language, Parser};
+use std::io::{self, Write};
+
+pub fn parse_file_at_path(language: Language, path: &Path) -> Result<()> {
+    let mut parser = Parser::new();
+    parser.set_language(language)?;
+    let source_code = fs::read_to_string(path)?;
+    let tree = parser
+        .parse_str(&source_code, None)
+        .expect("Incompatible language version");
+
+    let stdout = io::stdout();
+    let mut stdout = stdout.lock();
+    let mut cursor = tree.walk();
+    let mut needs_newline = false;
+    let mut indent_level = 0;
+    let mut did_visit_children = false;
+    loop {
+        let node = cursor.node();
+        let is_named = node.is_named();
+        if did_visit_children {
+            if is_named {
+                stdout.write(b")")?;
+                needs_newline = true;
+            }
+            if cursor.goto_next_sibling() {
+                did_visit_children = false;
+            } else if cursor.goto_parent() {
+                did_visit_children = true;
+                indent_level -= 1;
+            } else {
+                break;
+            }
+        } else {
+            if is_named {
+                if needs_newline {
+                    stdout.write(b"\n")?;
+                }
+                for _ in 0..indent_level {
+                    stdout.write(b"  ")?;
+                }
+                let start = node.start_position();
+                let end = node.end_position();
+                write!(
+                    &mut stdout,
+                    "({} [{}, {}] - [{}, {}]",
+                    node.kind(),
+                    start.row,
+                    start.column,
+                    end.row,
+                    end.column
+                )?;
+                needs_newline = true;
+            }
+            if cursor.goto_first_child() {
+                did_visit_children = false;
+                indent_level += 1;
+            } else {
+                did_visit_children = true;
+            }
+        }
+    }
+
+    println!("");
+    Ok(())
+}