import std::map::{hashmap};
import ast_util::spanned;
import parser::parser;

type seq_sep = {
    sep: option<token::token>,
    trailing_sep_allowed: bool
};

fn seq_sep_trailing_disallowed(t: token::token) -> seq_sep {
    ret {sep: option::some(t), trailing_sep_allowed: false};
}
fn seq_sep_trailing_allowed(t: token::token) -> seq_sep {
    ret {sep: option::some(t), trailing_sep_allowed: true};
}
fn seq_sep_none() -> seq_sep {
    ret {sep: option::none, trailing_sep_allowed: false};
}

fn token_to_str(reader: reader, ++token: token::token) -> str {
    token::to_str(*reader.interner(), token)
}

// This should be done with traits, once traits work
impl parser_common for parser {

    fn unexpected_last(t: token::token) -> ! {
        self.span_fatal(
            copy self.last_span,
            "unexpected token: '" + token_to_str(self.reader, t) + "'");
    }

    fn unexpected() -> ! {
        self.fatal("unexpected token: '"
                   + token_to_str(self.reader, self.token) + "'");
    }

    fn expect(t: token::token) {
        if self.token == t {
            self.bump();
        } else {
            let mut s: str = "expecting '";
            s += token_to_str(self.reader, t);
            s += "' but found '";
            s += token_to_str(self.reader, self.token);
            self.fatal(s + "'");
        }
    }

    fn parse_ident() -> ast::ident {
        alt copy self.token {
          token::IDENT(i, _) { self.bump(); ret self.get_str(i); }
          _ { self.fatal("expecting ident, found "
                      + token_to_str(self.reader, self.token)); }
        }
    }

    fn parse_path_list_ident() -> ast::path_list_ident {
        let lo = self.span.lo;
        let ident = self.parse_ident();
        let hi = self.span.hi;
        ret spanned(lo, hi, {name: ident, id: self.get_id()});
    }

    fn parse_value_ident() -> ast::ident {
        self.check_restricted_keywords();
        ret self.parse_ident();
    }

    fn eat(tok: token::token) -> bool {
        ret if self.token == tok { self.bump(); true } else { false };
    }

    // A sanity check that the word we are asking for is a known keyword
    fn require_keyword(word: str) {
        if !self.keywords.contains_key(word) {
            self.bug(#fmt("unknown keyword: %s", word));
        }
    }

    fn token_is_keyword(word: str, ++tok: token::token) -> bool {
        self.require_keyword(word);
        alt tok {
          token::IDENT(sid, false) { str::eq(word, *self.get_str(sid)) }
          _ { false }
        }
    }

    fn is_keyword(word: str) -> bool {
        self.token_is_keyword(word, self.token)
    }

    fn eat_keyword(word: str) -> bool {
        self.require_keyword(word);

        // FIXME (#13042): this gratuitous use of @ is to
        // workaround LLVM bug.
        alt @self.token {
          @token::IDENT(sid, false) {
            if str::eq(word, *self.get_str(sid)) {
                self.bump();
                ret true;
            } else { ret false; }
          }
          _ { ret false; }
        }
    }

    fn expect_keyword(word: str) {
        self.require_keyword(word);
        if !self.eat_keyword(word) {
            self.fatal("expecting " + word + ", found " +
                    token_to_str(self.reader, self.token));
        }
    }

    fn is_restricted_keyword(word: str) -> bool {
        self.restricted_keywords.contains_key(word)
    }

    fn check_restricted_keywords() {
        alt self.token {
          token::IDENT(_, false) {
            let w = token_to_str(self.reader, self.token);
            self.check_restricted_keywords_(w);
          }
          _ { }
        }
    }

    fn check_restricted_keywords_(w: str) {
        if self.is_restricted_keyword(w) {
            self.fatal("found `" + w + "` in restricted position");
        }
    }

    fn expect_gt() {
        if self.token == token::GT {
            self.bump();
        } else if self.token == token::BINOP(token::SHR) {
            self.swap(token::GT, self.span.lo + 1u, self.span.hi);
        } else {
            let mut s: str = "expecting ";
            s += token_to_str(self.reader, token::GT);
            s += ", found ";
            s += token_to_str(self.reader, self.token);
            self.fatal(s);
        }
    }

    fn parse_seq_to_before_gt<T: copy>(sep: option<token::token>,
                                       f: fn(parser) -> T) -> [T]/~ {
        let mut first = true;
        let mut v = []/~;
        while self.token != token::GT
            && self.token != token::BINOP(token::SHR) {
            alt sep {
              some(t) { if first { first = false; }
                       else { self.expect(t); } }
              _ { }
            }
            vec::push(v, f(self));
        }

        ret v;
    }

    fn parse_seq_to_gt<T: copy>(sep: option<token::token>,
                                f: fn(parser) -> T) -> [T]/~ {
        let v = self.parse_seq_to_before_gt(sep, f);
        self.expect_gt();

        ret v;
    }

    fn parse_seq_lt_gt<T: copy>(sep: option<token::token>,
                                f: fn(parser) -> T) -> spanned<[T]/~> {
        let lo = self.span.lo;
        self.expect(token::LT);
        let result = self.parse_seq_to_before_gt::<T>(sep, f);
        let hi = self.span.hi;
        self.expect_gt();
        ret spanned(lo, hi, result);
    }

    fn parse_seq_to_end<T: copy>(ket: token::token, sep: seq_sep,
                                 f: fn(parser) -> T) -> [T]/~ {
        let val = self.parse_seq_to_before_end(ket, sep, f);
        self.bump();
        ret val;
    }


    fn parse_seq_to_before_end<T: copy>(ket: token::token, sep: seq_sep,
                                        f: fn(parser) -> T) -> [T]/~ {
        let mut first: bool = true;
        let mut v: [T]/~ = []/~;
        while self.token != ket {
            alt sep.sep {
              some(t) { if first { first = false; }
                        else { self.expect(t); } }
              _ { }
            }
            if sep.trailing_sep_allowed && self.token == ket { break; }
            vec::push(v, f(self));
        }
        ret v;
    }

    fn parse_unspanned_seq<T: copy>(bra: token::token,
                                    ket: token::token,
                                    sep: seq_sep,
                                    f: fn(parser) -> T) -> [T]/~ {
        self.expect(bra);
        let result = self.parse_seq_to_before_end::<T>(ket, sep, f);
        self.bump();
        ret result;
    }

    // NB: Do not use this function unless you actually plan to place the
    // spanned list in the AST.
    fn parse_seq<T: copy>(bra: token::token, ket: token::token, sep: seq_sep,
                          f: fn(parser) -> T) -> spanned<[T]/~> {
        let lo = self.span.lo;
        self.expect(bra);
        let result = self.parse_seq_to_before_end::<T>(ket, sep, f);
        let hi = self.span.hi;
        self.bump();
        ret spanned(lo, hi, result);
    }
}