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use std::borrow::ToOwned;
use types::MalError::{ErrString, ErrMalVal};
use types::{MalVal, MalRet,
_nil, _true, _false, _int, symbol, string, list, vector, hash_mapv,
err_str, err_string, err_val};
use super::printer::unescape_str;
#[derive(Debug, Clone)]
struct Reader {
tokens: Vec<String>,
position: usize,
}
impl Reader {
fn next(&mut self) -> Option<String> {
if self.position < self.tokens.len() {
self.position += 1;
Some(self.tokens[self.position-1].to_string())
} else {
None
}
}
fn peek(&self) -> Option<String> {
if self.position < self.tokens.len() {
Some(self.tokens[self.position].to_string())
} else {
None
}
}
}
fn tokenize(str: String) -> Vec<String> {
let mut results = vec![];
let re = regex!(r###"[\s,]*(~@|[\[\]{}()'`~^@]|"(?:\\.|[^\\"])*"|;.*|[^\s\[\]{}('"`,;)]*)"###);
for cap in re.captures_iter(&str) {
let group = cap.at(1).unwrap_or("");
if group == "" { break; }
if group.starts_with(";") { continue; }
results.push(group.to_owned());
}
results
}
fn read_atom(rdr : &mut Reader) -> MalRet {
let otoken = rdr.next();
//println!("read_atom: {}", otoken);
if otoken.is_none() { return err_str("read_atom underflow"); }
let stoken = otoken.unwrap();
let token = &stoken[..];
if regex!(r"^-?[0-9]+$").is_match(token) {
let num : Option<isize> = token.parse().ok();
Ok(_int(num.unwrap()))
} else if regex!(r#"^".*"$"#).is_match(token) {
let new_str = &token[1..token.len()-1];
Ok(string(unescape_str(new_str)))
} else if regex!(r#"^:"#).is_match(token) {
Ok(string(format!("\u{29e}{}", &token[1..])))
} else if token == "nil" {
Ok(_nil())
} else if token == "true" {
Ok(_true())
} else if token == "false" {
Ok(_false())
} else {
Ok(symbol(token))
}
}
fn read_seq(rdr : &mut Reader, start: &str, end: &str) -> Result<Vec<MalVal>,String> {
let otoken = rdr.next();
if otoken.is_none() {
return Err("read_atom underflow".to_string());
}
let stoken = otoken.unwrap();
let token = &stoken[..];
if token != start {
return Err(format!("expected '{}'", start))
}
let mut ast_vec : Vec<MalVal> = vec![];
loop {
let otoken = rdr.peek();
if otoken.is_none() {
return Err(format!("expected '{}', got EOF", end));
}
let stoken = otoken.unwrap();
let token = &stoken[..];
if token == end { break; }
match read_form(rdr) {
Ok(mv) => ast_vec.push(mv),
Err(ErrString(es)) => return Err(es),
Err(ErrMalVal(_)) => return Err("read_seq exception".to_string()),
}
}
rdr.next();
Ok(ast_vec)
}
fn read_list(rdr : &mut Reader) -> MalRet {
match read_seq(rdr, "(", ")") {
Ok(seq) => Ok(list(seq)),
Err(es) => err_string(es),
}
}
fn read_vector(rdr : &mut Reader) -> MalRet {
match read_seq(rdr, "[", "]") {
Ok(seq) => Ok(vector(seq)),
Err(es) => err_string(es),
}
}
fn read_hash_map(rdr : &mut Reader) -> MalRet {
match read_seq(rdr, "{", "}") {
Ok(seq) => hash_mapv(seq),
Err(es) => err_string(es),
}
}
fn read_form(rdr : &mut Reader) -> MalRet {
let otoken = rdr.peek();
//println!("read_form: {}", otoken);
let stoken = otoken.unwrap();
let token = &stoken[..];
match token {
"'" => {
let _ = rdr.next();
match read_form(rdr) {
Ok(f) => Ok(list(vec![symbol("quote"), f])),
Err(e) => Err(e),
}
},
"`" => {
let _ = rdr.next();
match read_form(rdr) {
Ok(f) => Ok(list(vec![symbol("quasiquote"), f])),
Err(e) => Err(e),
}
},
"~" => {
let _ = rdr.next();
match read_form(rdr) {
Ok(f) => Ok(list(vec![symbol("unquote"), f])),
Err(e) => Err(e),
}
},
"~@" => {
let _ = rdr.next();
match read_form(rdr) {
Ok(f) => Ok(list(vec![symbol("splice-unquote"), f])),
Err(e) => Err(e),
}
},
"^" => {
let _ = rdr.next();
match read_form(rdr) {
Ok(meta) => {
match read_form(rdr) {
Ok(f) => Ok(list(vec![symbol("with-meta"), f, meta])),
Err(e) => Err(e),
}
},
Err(e) => Err(e),
}
},
"@" => {
let _ = rdr.next();
match read_form(rdr) {
Ok(f) => Ok(list(vec![symbol("deref"), f])),
Err(e) => Err(e),
}
},
")" => err_str("unexected ')'"),
"(" => read_list(rdr),
"]" => err_str("unexected ']'"),
"[" => read_vector(rdr),
"}" => err_str("unexected '}'"),
"{" => read_hash_map(rdr),
_ => read_atom(rdr)
}
}
pub fn read_str(str :String) -> MalRet {
let tokens = tokenize(str);
if tokens.len() == 0 {
// any malval as the error slot means empty line
return err_val(_nil())
}
//println!("tokens: {}", tokens);
let rdr = &mut Reader{tokens: tokens, position: 0};
read_form(rdr)
}
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