Reorganize syntax types into two modules 📦

1 files changed, 639 insertions, 0 deletions

diff --git a/src/parse/tokenizer.rs b/src/parse/tokenizer.rs
new file mode 100644
index 00000000..a251d960
--- /dev/null
+++ b/src/parse/tokenizer.rs
@@ -0,0 +1,639 @@
+//! Tokenization.
+
+use std::iter::Peekable;
+use std::str::Chars;
+use unicode_xid::UnicodeXID;
+
+use crate::length::Length;
+use crate::syntax::{Pos, Span, Spanned, Token};
+
+use Token::*;
+use TokenMode::*;
+
+/// An iterator over the tokens of a string of source code.
+#[derive(Debug)]
+pub struct Tokens<'s> {
+    src: &'s str,
+    iter: Peekable<Chars<'s>>,
+    mode: TokenMode,
+    stack: Vec<TokenMode>,
+    pos: Pos,
+    index: usize,
+}
+
+/// Whether to tokenize in header mode which yields expression, comma and
+/// similar tokens or in body mode which yields text and star, underscore,
+/// backtick tokens.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum TokenMode {
+    Header,
+    Body,
+}
+
+impl<'s> Tokens<'s> {
+    /// Create a new token iterator with the given mode.
+    pub fn new(src: &'s str, mode: TokenMode) -> Self {
+        Self {
+            src,
+            iter: src.chars().peekable(),
+            mode,
+            stack: vec![],
+            pos: Pos::ZERO,
+            index: 0,
+        }
+    }
+
+    /// Change the token mode and push the old one on a stack.
+    pub fn push_mode(&mut self, mode: TokenMode) {
+        self.stack.push(self.mode);
+        self.mode = mode;
+    }
+
+    /// Pop the old token mode from the stack. This panics if there is no mode
+    /// on the stack.
+    pub fn pop_mode(&mut self) {
+        self.mode = self.stack.pop().expect("no pushed mode");
+    }
+
+    /// The index in the string at which the last token ends and next token will
+    /// start.
+    pub fn index(&self) -> usize {
+        self.index
+    }
+
+    /// The line-colunn position in the source at which the last token ends and
+    /// next token will start.
+    pub fn pos(&self) -> Pos {
+        self.pos
+    }
+}
+
+impl<'s> Iterator for Tokens<'s> {
+    type Item = Spanned<Token<'s>>;
+
+    /// Parse the next token in the source code.
+    fn next(&mut self) -> Option<Self::Item> {
+        let start = self.pos();
+        let first = self.eat()?;
+
+        let token = match first {
+            // Comments.
+            '/' if self.peek() == Some('/') => self.read_line_comment(),
+            '/' if self.peek() == Some('*') => self.read_block_comment(),
+            '*' if self.peek() == Some('/') => {
+                self.eat();
+                Invalid("*/")
+            }
+
+            // Whitespace.
+            c if c.is_whitespace() => self.read_whitespace(start),
+
+            // Functions and blocks.
+            '[' => LeftBracket,
+            ']' => RightBracket,
+            '{' => LeftBrace,
+            '}' => RightBrace,
+
+            // Syntactic elements in function headers.
+            '(' if self.mode == Header => LeftParen,
+            ')' if self.mode == Header => RightParen,
+            ':' if self.mode == Header => Colon,
+            ',' if self.mode == Header => Comma,
+            '=' if self.mode == Header => Equals,
+            '>' if self.mode == Header && self.peek() == Some('>') => self.read_chain(),
+
+            // Expression operators.
+            '+' if self.mode == Header => Plus,
+            '-' if self.mode == Header => Hyphen,
+            '/' if self.mode == Header => Slash,
+
+            // Star serves a double purpose as a style modifier
+            // and a expression operator in the header.
+            '*' => Star,
+
+            // A hex expression.
+            '#' if self.mode == Header => self.read_hex(),
+
+            // String values.
+            '"' if self.mode == Header => self.read_string(),
+
+            // Style toggles.
+            '_' if self.mode == Body => Underscore,
+            '`' if self.mode == Body => self.read_raw_or_code(),
+
+            // Sections.
+            '#' if self.mode == Body => Hashtag,
+
+            // Non-breaking spaces.
+            '~' if self.mode == Body => Text("\u{00A0}"),
+
+            // An escaped thing.
+            '\\' if self.mode == Body => self.read_escaped(),
+
+            // Expressions or just strings.
+            c => {
+                let body = self.mode == Body;
+
+                let start_offset = -(c.len_utf8() as isize);
+                let mut last_was_e = false;
+
+                let (text, _) = self.read_string_until(false, start_offset, 0, |n| {
+                    let val = match n {
+                        c if c.is_whitespace() => true,
+                        '[' | ']' | '{' | '}' | '/' | '*' => true,
+                        '\\' | '_' | '`' | '#' | '~' if body => true,
+                        ':' | '=' | ',' | '"' | '(' | ')' if !body => true,
+                        '+' | '-' if !body && !last_was_e => true,
+                        _ => false,
+                    };
+
+                    last_was_e = n == 'e' || n == 'E';
+                    val
+                });
+
+                if self.mode == Header {
+                    self.read_expr(text)
+                } else {
+                    Text(text)
+                }
+            }
+        };
+
+        let end = self.pos();
+        let span = Span { start, end };
+
+        Some(Spanned { v: token, span })
+    }
+}
+
+impl<'s> Tokens<'s> {
+    fn read_line_comment(&mut self) -> Token<'s> {
+        self.eat();
+        LineComment(self.read_string_until(false, 0, 0, is_newline_char).0)
+    }
+
+    fn read_block_comment(&mut self) -> Token<'s> {
+        enum Last {
+            Slash,
+            Star,
+            Other,
+        }
+
+        let mut depth = 0;
+        let mut last = Last::Other;
+
+        // Find the first `*/` that does not correspond to a nested `/*`.
+        // Remove the last two bytes to obtain the raw inner text without `*/`.
+        self.eat();
+        let (content, _) = self.read_string_until(true, 0, -2, |c| {
+            match c {
+                '/' => match last {
+                    Last::Star if depth == 0 => return true,
+                    Last::Star => depth -= 1,
+                    _ => last = Last::Slash,
+                },
+                '*' => match last {
+                    Last::Slash => depth += 1,
+                    _ => last = Last::Star,
+                },
+                _ => last = Last::Other,
+            }
+
+            false
+        });
+
+        BlockComment(content)
+    }
+
+    fn read_chain(&mut self) -> Token<'s> {
+        assert!(self.eat() == Some('>'));
+        Chain
+    }
+
+    fn read_whitespace(&mut self, start: Pos) -> Token<'s> {
+        self.read_string_until(false, 0, 0, |n| !n.is_whitespace());
+        let end = self.pos();
+
+        Space(end.line - start.line)
+    }
+
+    fn read_string(&mut self) -> Token<'s> {
+        let (string, terminated) = self.read_until_unescaped('"');
+        Str { string, terminated }
+    }
+
+    fn read_raw_or_code(&mut self) -> Token<'s> {
+        let (raw, terminated) = self.read_until_unescaped('`');
+        if raw.is_empty() && terminated && self.peek() == Some('`') {
+            // Third tick found; this is a code block.
+            self.eat();
+
+            // Reads the lang tag (until newline or whitespace).
+            let start = self.pos();
+            let (lang, _) = self.read_string_until(false, 0, 0, |c| {
+                c == '`' || c.is_whitespace() || is_newline_char(c)
+            });
+            let end = self.pos();
+
+            let lang = if !lang.is_empty() {
+                Some(Spanned::new(lang, Span::new(start, end)))
+            } else {
+                None
+            };
+
+            // Skip to start of raw contents.
+            while let Some(c) = self.peek() {
+                if is_newline_char(c) {
+                    self.eat();
+                    if c == '\r' && self.peek() == Some('\n') {
+                        self.eat();
+                    }
+
+                    break;
+                } else if c.is_whitespace() {
+                    self.eat();
+                } else {
+                    break;
+                }
+            }
+
+            let start = self.index();
+            let mut backticks = 0u32;
+
+            while backticks < 3 {
+                match self.eat() {
+                    Some('`') => backticks += 1,
+                    // Escaping of triple backticks.
+                    Some('\\') if backticks == 1 && self.peek() == Some('`') => {
+                        backticks = 0;
+                    }
+                    Some(_) => {}
+                    None => break,
+                }
+            }
+
+            let terminated = backticks == 3;
+            let end = self.index() - if terminated { 3 } else { 0 };
+
+            Code {
+                lang,
+                raw: &self.src[start .. end],
+                terminated,
+            }
+        } else {
+            Raw { raw, terminated }
+        }
+    }
+
+    fn read_until_unescaped(&mut self, end: char) -> (&'s str, bool) {
+        let mut escaped = false;
+        self.read_string_until(true, 0, -1, |c| {
+            match c {
+                c if c == end && !escaped => return true,
+                '\\' => escaped = !escaped,
+                _ => escaped = false,
+            }
+
+            false
+        })
+    }
+
+    fn read_escaped(&mut self) -> Token<'s> {
+        fn is_escapable(c: char) -> bool {
+            match c {
+                '[' | ']' | '\\' | '/' | '*' | '_' | '`' | '"' | '#' | '~' => true,
+                _ => false,
+            }
+        }
+
+        match self.peek() {
+            Some('u') => {
+                self.eat();
+                if self.peek() == Some('{') {
+                    self.eat();
+                    let (sequence, _) =
+                        self.read_string_until(false, 0, 0, |c| !c.is_ascii_hexdigit());
+
+                    let terminated = self.peek() == Some('}');
+                    if terminated {
+                        self.eat();
+                    }
+
+                    UnicodeEscape { sequence, terminated }
+                } else {
+                    Text("\\u")
+                }
+            }
+            Some(c) if is_escapable(c) => {
+                let index = self.index();
+                self.eat();
+                Text(&self.src[index .. index + c.len_utf8()])
+            }
+            Some(c) if c.is_whitespace() => Backslash,
+            Some(_) => Text("\\"),
+            None => Backslash,
+        }
+    }
+
+    fn read_hex(&mut self) -> Token<'s> {
+        // This will parse more than the permissable 0-9, a-f, A-F character
+        // ranges to provide nicer error messages later.
+        Hex(self.read_string_until(false, 0, 0, |n| !n.is_ascii_alphanumeric()).0)
+    }
+
+    fn read_expr(&mut self, text: &'s str) -> Token<'s> {
+        if let Ok(b) = text.parse::<bool>() {
+            Bool(b)
+        } else if let Ok(num) = text.parse::<f64>() {
+            Number(num)
+        } else if let Some(num) = parse_percentage(text) {
+            Number(num / 100.0)
+        } else if let Ok(length) = text.parse::<Length>() {
+            Length(length)
+        } else if is_identifier(text) {
+            Ident(text)
+        } else {
+            Invalid(text)
+        }
+    }
+
+    /// Will read the input stream until `f` evaluates to `true`. When
+    /// `eat_match` is true, the token for which `f` was true is consumed.
+    /// Returns the string from the index where this was called offset by
+    /// `offset_start` to the end offset by `offset_end`. The end is before or
+    /// after the match depending on `eat_match`.
+    fn read_string_until(
+        &mut self,
+        eat_match: bool,
+        offset_start: isize,
+        offset_end: isize,
+        mut f: impl FnMut(char) -> bool,
+    ) -> (&'s str, bool) {
+        let start = ((self.index() as isize) + offset_start) as usize;
+        let mut matched = false;
+
+        while let Some(c) = self.peek() {
+            if f(c) {
+                matched = true;
+                if eat_match {
+                    self.eat();
+                }
+                break;
+            }
+
+            self.eat();
+        }
+
+        let mut end = self.index();
+        if matched {
+            end = ((end as isize) + offset_end) as usize;
+        }
+
+        (&self.src[start .. end], matched)
+    }
+
+    fn eat(&mut self) -> Option<char> {
+        let c = self.iter.next()?;
+        self.index += c.len_utf8();
+
+        if is_newline_char(c) && !(c == '\r' && self.peek() == Some('\n')) {
+            self.pos.line += 1;
+            self.pos.column = 0;
+        } else {
+            self.pos.column += 1;
+        }
+
+        Some(c)
+    }
+
+    fn peek(&mut self) -> Option<char> {
+        self.iter.peek().copied()
+    }
+}
+
+fn parse_percentage(text: &str) -> Option<f64> {
+    if text.ends_with('%') {
+        text[.. text.len() - 1].parse::<f64>().ok()
+    } else {
+        None
+    }
+}
+
+/// Whether this character denotes a newline.
+pub fn is_newline_char(character: char) -> bool {
+    match character {
+        // Line Feed, Vertical Tab, Form Feed, Carriage Return.
+        '\x0A' ..= '\x0D' => true,
+        // Next Line, Line Separator, Paragraph Separator.
+        '\u{0085}' | '\u{2028}' | '\u{2029}' => true,
+        _ => false,
+    }
+}
+
+/// Whether this word is a valid identifier.
+pub fn is_identifier(string: &str) -> bool {
+    fn is_extra_allowed(c: char) -> bool {
+        c == '.' || c == '-' || c == '_'
+    }
+
+    let mut chars = string.chars();
+    match chars.next() {
+        Some(c) if UnicodeXID::is_xid_start(c) || is_extra_allowed(c) => {}
+        _ => return false,
+    }
+
+    for c in chars {
+        match c {
+            c if UnicodeXID::is_xid_continue(c) || is_extra_allowed(c) => {}
+            _ => return false,
+        }
+    }
+
+    true
+}
+
+#[cfg(test)]
+#[allow(non_snake_case)]
+mod tests {
+    use super::*;
+    use crate::length::Length;
+    use crate::parse::tests::{check, s};
+
+    use Token::{
+        BlockComment as BC, Bool, Chain, Hex, Hyphen as Min, Ident as Id,
+        LeftBrace as LB, LeftBracket as L, LeftParen as LP, Length as Len,
+        LineComment as LC, Number as Num, Plus, RightBrace as RB, RightBracket as R,
+        RightParen as RP, Slash, Space as S, Star, Text as T,
+    };
+
+    fn Str(string: &str, terminated: bool) -> Token {
+        Token::Str { string, terminated }
+    }
+    fn Raw(raw: &str, terminated: bool) -> Token {
+        Token::Raw { raw, terminated }
+    }
+    fn Code<'a>(
+        lang: Option<Spanned<&'a str>>,
+        raw: &'a str,
+        terminated: bool,
+    ) -> Token<'a> {
+        Token::Code { lang, raw, terminated }
+    }
+    fn Lang<'a, T: Into<Spanned<&'a str>>>(lang: T) -> Option<Spanned<&'a str>> {
+        Some(Into::<Spanned<&str>>::into(lang))
+    }
+    fn UE(sequence: &str, terminated: bool) -> Token {
+        Token::UnicodeEscape { sequence, terminated }
+    }
+
+    macro_rules! t { ($($tts:tt)*) => {test!(@spans=false, $($tts)*)} }
+    macro_rules! ts { ($($tts:tt)*) => {test!(@spans=true, $($tts)*)} }
+    macro_rules! test {
+        (@spans=$spans:expr, $mode:expr, $src:expr => $($token:expr),*) => {
+            let exp = vec![$(Into::<Spanned<Token>>::into($token)),*];
+            let found = Tokens::new($src, $mode).collect::<Vec<_>>();
+            check($src, exp, found, $spans);
+        }
+    }
+
+    #[test]
+    fn tokenize_whitespace() {
+        t!(Body, ""             => );
+        t!(Body, " "            => S(0));
+        t!(Body, "    "         => S(0));
+        t!(Body, "\t"           => S(0));
+        t!(Body, "  \t"         => S(0));
+        t!(Body, "\n"           => S(1));
+        t!(Body, "\n "          => S(1));
+        t!(Body, "  \n"         => S(1));
+        t!(Body, "  \n   "      => S(1));
+        t!(Body, "\r\n"         => S(1));
+        t!(Body, "  \n\t \n  "  => S(2));
+        t!(Body, "\n\r"         => S(2));
+        t!(Body, " \r\r\n \x0D" => S(3));
+        t!(Body, "a~b"          => T("a"), T("\u{00A0}"), T("b"));
+    }
+
+    #[test]
+    fn tokenize_comments() {
+        t!(Body, "a // bc\n "        => T("a"), S(0), LC(" bc"),  S(1));
+        t!(Body, "a //a//b\n "       => T("a"), S(0), LC("a//b"), S(1));
+        t!(Body, "a //a//b\r\n"      => T("a"), S(0), LC("a//b"), S(1));
+        t!(Body, "a //a//b\n\nhello" => T("a"), S(0), LC("a//b"), S(2), T("hello"));
+        t!(Body, "/**/"              => BC(""));
+        t!(Body, "_/*_/*a*/*/"       => Underscore, BC("_/*a*/"));
+        t!(Body, "/*/*/"             => BC("/*/"));
+        t!(Body, "abc*/"             => T("abc"), Invalid("*/"));
+        t!(Body, "/***/"             => BC("*"));
+        t!(Body, "/**\\****/*/*/"    => BC("*\\***"), Invalid("*/"), Invalid("*/"));
+        t!(Body, "/*abc"             => BC("abc"));
+    }
+
+    #[test]
+    fn tokenize_body_only_tokens() {
+        t!(Body, "_*"            => Underscore, Star);
+        t!(Body, "***"           => Star, Star, Star);
+        t!(Body, "[func]*bold*"  => L, T("func"), R, Star, T("bold"), Star);
+        t!(Body, "hi_you_ there" => T("hi"), Underscore, T("you"), Underscore, S(0), T("there"));
+        t!(Body, "`raw`"         => Raw("raw", true));
+        t!(Body, "# hi"          => Hashtag, S(0), T("hi"));
+        t!(Body, "#()"           => Hashtag, T("()"));
+        t!(Body, "`[func]`"      => Raw("[func]", true));
+        t!(Body, "`]"            => Raw("]", false));
+        t!(Body, "\\ "           => Backslash, S(0));
+        t!(Body, "`\\``"         => Raw("\\`", true));
+        t!(Body, "``not code`"   => Raw("", true), T("not"), S(0), T("code"), Raw("", false));
+        t!(Body, "```rust hi```" => Code(Lang("rust"), "hi", true));
+        t!(Body, "``` hi`\\``"   => Code(None, "hi`\\``", false));
+        t!(Body, "```js   \r\n  document.write(\"go\")" => Code(Lang("js"), "  document.write(\"go\")", false));
+        t!(Header, "_`"          => Invalid("_`"));
+    }
+
+    #[test]
+    fn tokenize_header_only_tokens() {
+        t!(Body, "a: b"                => T("a:"), S(0), T("b"));
+        t!(Body, "c=d, "               => T("c=d,"), S(0));
+        t!(Header, "(){}:=,"           => LP, RP, LB, RB, Colon, Equals, Comma);
+        t!(Header, "a:b"               => Id("a"), Colon, Id("b"));
+        t!(Header, "#6ae6dd"           => Hex("6ae6dd"));
+        t!(Header, "#8A083c"           => Hex("8A083c"));
+        t!(Header, "a: true, x=1"      => Id("a"), Colon, S(0), Bool(true), Comma, S(0),
+                                          Id("x"), Equals, Num(1.0));
+        t!(Header, "=3.14"             => Equals, Num(3.14));
+        t!(Header, "12.3e5"            => Num(12.3e5));
+        t!(Header, "120%"              => Num(1.2));
+        t!(Header, "12e4%"             => Num(1200.0));
+        t!(Header, "__main__"          => Id("__main__"));
+        t!(Header, ">main"             => Invalid(">main"));
+        t!(Header, ".func.box"         => Id(".func.box"));
+        t!(Header, "arg, _b, _1"       => Id("arg"), Comma, S(0), Id("_b"), Comma, S(0), Id("_1"));
+        t!(Header, "f: arg >> g"       => Id("f"), Colon, S(0), Id("arg"), S(0), Chain, S(0), Id("g"));
+        t!(Header, "12_pt, 12pt"       => Invalid("12_pt"), Comma, S(0), Len(Length::pt(12.0)));
+        t!(Header, "1e5in"             => Len(Length::inches(100000.0)));
+        t!(Header, "2.3cm"             => Len(Length::cm(2.3)));
+        t!(Header, "12e-3in"           => Len(Length::inches(12e-3)));
+        t!(Header, "6.1cm + 4pt,a=1*2" => Len(Length::cm(6.1)), S(0), Plus, S(0), Len(Length::pt(4.0)),
+                                          Comma, Id("a"), Equals, Num(1.0), Star, Num(2.0));
+        t!(Header, "(5 - 1) / 2.1"     => LP, Num(5.0), S(0), Min, S(0), Num(1.0), RP,
+                                          S(0), Slash, S(0), Num(2.1));
+        t!(Header, "-1"                => Min, Num(1.0));
+        t!(Header, "--1"               => Min, Min, Num(1.0));
+        t!(Header, "- 1"               => Min, S(0), Num(1.0));
+        t!(Header, "02.4mm"            => Len(Length::mm(2.4)));
+        t!(Header, "2.4.cm"            => Invalid("2.4.cm"));
+        t!(Header, "(1,2)"             => LP, Num(1.0), Comma, Num(2.0), RP);
+        t!(Header, "{abc}"             => LB, Id("abc"), RB);
+        t!(Header, "🌓, 🌍,"          => Invalid("🌓"), Comma, S(0), Invalid("🌍"), Comma);
+    }
+
+    #[test]
+    fn tokenize_strings() {
+        t!(Body, "a \"hi\" string"           => T("a"), S(0), T("\"hi\""), S(0), T("string"));
+        t!(Header, "\"hello"                 => Str("hello", false));
+        t!(Header, "\"hello world\""         => Str("hello world", true));
+        t!(Header, "\"hello\nworld\""        => Str("hello\nworld", true));
+        t!(Header, r#"1"hello\nworld"false"# => Num(1.0), Str("hello\\nworld", true), Bool(false));
+        t!(Header, r#""a\"bc""#              => Str(r#"a\"bc"#, true));
+        t!(Header, r#""a\\"bc""#             => Str(r#"a\\"#, true), Id("bc"), Str("", false));
+        t!(Header, r#""a\tbc"#               => Str("a\\tbc", false));
+        t!(Header, "\"🌎\""                  => Str("🌎", true));
+    }
+
+    #[test]
+    fn tokenize_escaped_symbols() {
+        t!(Body, r"\\"       => T(r"\"));
+        t!(Body, r"\["       => T("["));
+        t!(Body, r"\]"       => T("]"));
+        t!(Body, r"\*"       => T("*"));
+        t!(Body, r"\_"       => T("_"));
+        t!(Body, r"\`"       => T("`"));
+        t!(Body, r"\/"       => T("/"));
+        t!(Body, r"\u{2603}" => UE("2603", true));
+        t!(Body, r"\u{26A4"  => UE("26A4", false));
+        t!(Body, r#"\""#     => T("\""));
+    }
+
+    #[test]
+    fn tokenize_unescapable_symbols() {
+        t!(Body, r"\a"     => T("\\"), T("a"));
+        t!(Body, r"\:"     => T(r"\"), T(":"));
+        t!(Body, r"\="     => T(r"\"), T("="));
+        t!(Body, r"\u{2GA4"=> UE("2", false), T("GA4"));
+        t!(Body, r"\u{ "   => UE("", false), Space(0));
+        t!(Body, r"\u"     => T(r"\u"));
+        t!(Header, r"\\\\" => Invalid(r"\\\\"));
+        t!(Header, r"\a"   => Invalid(r"\a"));
+        t!(Header, r"\:"   => Invalid(r"\"), Colon);
+        t!(Header, r"\="   => Invalid(r"\"), Equals);
+        t!(Header, r"\,"   => Invalid(r"\"), Comma);
+    }
+
+    #[test]
+    fn tokenize_with_spans() {
+        ts!(Body, "hello"          => s(0,0, 0,5, T("hello")));
+        ts!(Body, "ab\r\nc"        => s(0,0, 0,2, T("ab")), s(0,2, 1,0, S(1)), s(1,0, 1,1, T("c")));
+        ts!(Body, "// ab\r\n\nf"   => s(0,0, 0,5, LC(" ab")), s(0,5, 2,0, S(2)), s(2,0, 2,1, T("f")));
+        ts!(Body, "/*b*/_"         => s(0,0, 0,5, BC("b")), s(0,5, 0,6, Underscore));
+        ts!(Header, "a=10"         => s(0,0, 0,1, Id("a")), s(0,1, 0,2, Equals), s(0,2, 0,4, Num(10.0)));
+    }
+}