use syntax::{ast, panictry};
use syntax::ext::base::{self, *};
use syntax::parse::{self, token, DirectoryOwnership};
use syntax::print::pprust;
use syntax::ptr::P;
use syntax::symbol::Symbol;
use syntax::tokenstream::TokenStream;

use smallvec::SmallVec;
use syntax_pos::{self, Pos, Span};

use rustc_data_structures::sync::Lrc;

// These macros all relate to the file system; they either return
// the column/row/filename of the expression, or they include
// a given file into the current one.

/// line!(): expands to the current line number
pub fn expand_line(cx: &mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
                   -> Box<dyn base::MacResult+'static> {
    base::check_zero_tts(cx, sp, tts, "line!");

    let topmost = cx.expansion_cause().unwrap_or(sp);
    let loc = cx.source_map().lookup_char_pos(topmost.lo());

    base::MacEager::expr(cx.expr_u32(topmost, loc.line as u32))
}

/* column!(): expands to the current column number */
pub fn expand_column(cx: &mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
                  -> Box<dyn base::MacResult+'static> {
    base::check_zero_tts(cx, sp, tts, "column!");

    let topmost = cx.expansion_cause().unwrap_or(sp);
    let loc = cx.source_map().lookup_char_pos(topmost.lo());

    base::MacEager::expr(cx.expr_u32(topmost, loc.col.to_usize() as u32 + 1))
}

/// file!(): expands to the current filename */
/// The source_file (`loc.file`) contains a bunch more information we could spit
/// out if we wanted.
pub fn expand_file(cx: &mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
                   -> Box<dyn base::MacResult+'static> {
    base::check_zero_tts(cx, sp, tts, "file!");

    let topmost = cx.expansion_cause().unwrap_or(sp);
    let loc = cx.source_map().lookup_char_pos(topmost.lo());
    base::MacEager::expr(cx.expr_str(topmost, Symbol::intern(&loc.file.name.to_string())))
}

pub fn expand_stringify(cx: &mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
                        -> Box<dyn base::MacResult+'static> {
    let s = pprust::tts_to_string(tts);
    base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&s)))
}

pub fn expand_mod(cx: &mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
                  -> Box<dyn base::MacResult+'static> {
    base::check_zero_tts(cx, sp, tts, "module_path!");
    let mod_path = &cx.current_expansion.module.mod_path;
    let string = mod_path.iter().map(|x| x.to_string()).collect::<Vec<String>>().join("::");

    base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&string)))
}

/// include! : parse the given file as an expr
/// This is generally a bad idea because it's going to behave
/// unhygienically.
pub fn expand_include<'cx>(cx: &'cx mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
                           -> Box<dyn base::MacResult+'cx> {
    let file = match get_single_str_from_tts(cx, sp, tts, "include!") {
        Some(f) => f,
        None => return DummyResult::any(sp),
    };
    // The file will be added to the code map by the parser
    let file = cx.resolve_path(file, sp);
    let directory_ownership = DirectoryOwnership::Owned { relative: None };
    let p = parse::new_sub_parser_from_file(cx.parse_sess(), &file, directory_ownership, None, sp);

    struct ExpandResult<'a> {
        p: parse::parser::Parser<'a>,
    }
    impl<'a> base::MacResult for ExpandResult<'a> {
        fn make_expr(mut self: Box<ExpandResult<'a>>) -> Option<P<ast::Expr>> {
            Some(panictry!(self.p.parse_expr()))
        }

        fn make_items(mut self: Box<ExpandResult<'a>>) -> Option<SmallVec<[P<ast::Item>; 1]>> {
            let mut ret = SmallVec::new();
            while self.p.token != token::Eof {
                match panictry!(self.p.parse_item()) {
                    Some(item) => ret.push(item),
                    None => self.p.sess.span_diagnostic.span_fatal(self.p.token.span,
                                                           &format!("expected item, found `{}`",
                                                                    self.p.this_token_to_string()))
                                               .raise()
                }
            }
            Some(ret)
        }
    }

    Box::new(ExpandResult { p })
}

// include_str! : read the given file, insert it as a literal string expr
pub fn expand_include_str(cx: &mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
                          -> Box<dyn base::MacResult+'static> {
    let file = match get_single_str_from_tts(cx, sp, tts, "include_str!") {
        Some(f) => f,
        None => return DummyResult::any(sp)
    };
    let file = cx.resolve_path(file, sp);
    match cx.source_map().load_binary_file(&file) {
        Ok(bytes) => match std::str::from_utf8(&bytes) {
            Ok(src) => {
                let interned_src = Symbol::intern(&src);
                base::MacEager::expr(cx.expr_str(sp, interned_src))
            }
            Err(_) => {
                cx.span_err(sp, &format!("{} wasn't a utf-8 file", file.display()));
                DummyResult::any(sp)
            }
        },
        Err(e) => {
            cx.span_err(sp, &format!("couldn't read {}: {}", file.display(), e));
            DummyResult::any(sp)
        }
    }
}

pub fn expand_include_bytes(cx: &mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
                            -> Box<dyn base::MacResult+'static> {
    let file = match get_single_str_from_tts(cx, sp, tts, "include_bytes!") {
        Some(f) => f,
        None => return DummyResult::any(sp)
    };
    let file = cx.resolve_path(file, sp);
    match cx.source_map().load_binary_file(&file) {
        Ok(bytes) => {
            base::MacEager::expr(cx.expr_lit(sp, ast::LitKind::ByteStr(Lrc::new(bytes))))
        },
        Err(e) => {
            cx.span_err(sp, &format!("couldn't read {}: {}", file.display(), e));
            DummyResult::any(sp)
        }
    }
}