use crate::token::*;

pub use rules::*;

peg::parser! {
	pub grammar rules() for str {
		pub rule token_stream() -> TokenStream<'input>
			= _ tokens:(token() ** _) _ { TokenStream(tokens) }

		pub rule token() -> Token<'input>
			= number:number() { Token::Number(number) }
			/ string:string() { Token::String(string) }
			/ ident:ident() { Token::Ident(ident) }
			/ punct:punct() { Token::Punct(punct) }

		rule ident() -> &'input str
			= $(
				['a'..='z' | 'A' ..='Z' | '_' ]
				['a'..='z' | 'A' ..='Z' | '_' | '0'..='9']*
			)

		rule punct() -> Punct
			= ch:punct_char() spacing:spacing() { Punct(ch, spacing) }

		rule punct_char() -> char
			= !number() !string() !ident() !__ ch:[_] { ch }

		rule spacing() -> Spacing
			= &punct_char() { Spacing::Joint }
			/ { Spacing::Alone }

		rule number() -> &'input str
			= $(['0'..='9'] ['0'..='9' | 'a'..='z' | 'A'..='Z' | '_']*)

		rule string() -> String<'input>
			= "\"" pieces:string_piece()* "\"" {
				String {
					pieces,
					kind: StringKind::String,
				}
			}
			/ "r\"" chars:$([^'"']*) "\"" {
				String {
					pieces: vec![StringPiece::Chars(chars)],
					kind: StringKind::RawString,
				}
			}
			/ "```" newline() pieces:script_string_piece()* "```" {
				String {
					pieces,
					kind: StringKind::ScriptString,
				}
			}

		rule string_piece() -> StringPiece<'input>
			= chars:$((!"{{" [^'"' | '\\'])+) { StringPiece::Chars(chars) }
			/ "\\" escape:string_escape() { StringPiece::Escape(escape) }
			/ string_interp()

		rule string_escape() -> char
			= "n" { '\n' }
			/ "r" { '\r' }
			/ "t" { '\t' }
			/ "\\" { '\\' }
			/ "\"" { '"' }
			/ "0" { '\0' }
			/ "x" digits:$(['0'..='7'] hex_digit()) {
				u8::from_str_radix(digits, 16).unwrap().into()
			}
			/ "u{" digits:$(hex_digit()*<1,6>) "}" { ?
				u32::from_str_radix(digits, 16).unwrap().try_into().or(Err("Invalid unicode escape"))
			}

		rule script_string_piece() -> StringPiece<'input>
			= chars:$((!"{{" !"```" [_])+) { StringPiece::Chars(chars) }
			/ string_interp()

		rule string_interp() -> StringPiece<'input>
			= "{{" _ tokens:(subtoken() ++ _) _ "}}" {
				StringPiece::Interp(TokenStream(tokens))
			}

		rule subtoken() -> Token<'input>
			= !"}}" token:token() { token }

		rule hex_digit()
			= ['0'..='9' | 'a'..='f' | 'A'..='F']

		/// Mandatory whitespace
		rule __
			= ([' ' | '\t'] / quiet!{newline()} / quiet!{comment()})+

		/// Optional whitespace
		rule _
			= quiet!{__?}

		rule comment()
			= "//" (!newline() [_])* (newline() / ![_])
			/ "/*" (!"*/" [_])* "*/"

		rule newline()
			= ['\n' | '\r']
	}
}