use crate::utils::StrUtils;
use crate::{ControlWord, Token};

pub struct Lexer;

impl Lexer {
    pub fn scan(src: &str) -> Vec<Token> {
        let mut it = src.chars();
        let mut tokens: Vec<Token> = vec![];
        let mut slice_start_index = 0;
        let mut current_index = 0;
        let mut previous_char = ' ';
        while let Some(c) = it.next() {
            match c {
                // Handle Escaped chars
                // TODO: Handle char over code 127 for escaped chars
                '{' | '}' | '\\' if previous_char == '\\' => {}
                '{' | '}' | '\\' => {
                    // End of slice chars
                    if slice_start_index < current_index {
                        // Close slice
                        let slice = &src[slice_start_index..current_index];
                        // Get the corresponding token(s)
                        let slice_tokens = Self::tokenize(slice);
                        for slice_token in slice_tokens {
                            tokens.push(slice_token);
                        }
                        slice_start_index = current_index;
                    }
                }
                // Others chars
                _ => {}
            }
            current_index += 1;
            previous_char = c;
        }
        // Manage last token (should always be "}")
        if slice_start_index < current_index {
            let slice = &src[slice_start_index..current_index];
            assert_eq!(slice, "}", "[Lexer] Invalid last char, should be '}}'");
            tokens.push(Token::ClosingBracket);
        }
        return tokens;
    }

    fn tokenize(slice: &str) -> Vec<Token> {
        let mut starting_chars = slice.trim_matches(' ').chars().take(2);
        return match (starting_chars.next(), starting_chars.next()) {
            // If it start with \ : escaped text or control word
            (Some('\\'), Some(c)) => match c {
                '{' | '}' | '\\' => {
                    // Handle escaped chars
                    let tail = slice.get(1..).unwrap_or("");
                    return vec![Token::PlainText(tail)];
                }
                '\n' => {
                    // CRLF
                    let mut ret = vec![Token::CRLF];
                    if let Some(tail) = slice.get(2..) {
                        if tail != "" {
                            ret.push(Token::PlainText(tail))
                        }
                    }
                    return ret;
                }
                'a'..='z' => {
                    // Identify control word
                    // ex: parse "\b Words in bold" -> (Token::ControlWord(ControlWord::Bold), Token::ControlWordArgument("Words in bold")
                    let (ident, tail) = slice.split_first_whitespace();
                    let mut ret = vec![Token::ControlSymbol(ControlWord::from(ident))];
                    if tail.len() > 0 {
                        ret.push(Token::PlainText(tail));
                    }
                    return ret;
                }
                '*' => vec![Token::IgnorableDestination],
                _ => vec![],
            },
            // Handle brackets
            (Some('{'), None) => vec![Token::OpeningBracket],
            (Some('}'), None) => vec![Token::ClosingBracket],
            (Some('{'), Some(_)) => vec![Token::OpeningBracket, Token::PlainText(&slice[1..])],
            (Some('}'), Some(_)) => vec![Token::ClosingBracket, Token::PlainText(&slice[1..])],
            (None, None) => panic!("[Lexer] : Empty token {}", &slice),
            // Else, it's plain text
            _ => {
                let text = slice.trim();
                if text == "" {
                    return vec![];
                }
                return vec![Token::PlainText(slice.trim())];
            }
        };
    }
}

#[cfg(test)]
pub(crate) mod tests {
    use crate::lexer::Lexer;
    use crate::ControlWord::{Ansi, Bold, FontNumber, FontSize, FontTable, Rtf, Unknown};
    use crate::Property::*;
    use crate::Token::*;

    #[test]
    fn simple_tokenize_test() {
        let tokens = Lexer::tokenize(r"\b Words in bold");
        assert_eq!(tokens, vec![ControlSymbol((Bold, None)), PlainText("Words in bold"),]);
    }

    #[test]
    fn scan_entire_file_test() {
        let tokens = Lexer::scan(r#"{ \rtf1\ansi{\fonttbl\f0\fswiss Helvetica;}\f0\pard Voici du texte en {\b gras}.\par }"#);
        assert_eq!(
            tokens,
            vec![
                OpeningBracket,
                ControlSymbol((Rtf, Value(1))),
                ControlSymbol((Ansi, None)),
                OpeningBracket,
                ControlSymbol((FontTable, None)),
                ControlSymbol((FontNumber, Value(0))),
                ControlSymbol((Unknown("\\fswiss"), None)),
                PlainText("Helvetica;"),
                ClosingBracket,
                ControlSymbol((FontNumber, Value(0))),
                ControlSymbol((Unknown("\\pard"), None)),
                PlainText("Voici du texte en "),
                OpeningBracket,
                ControlSymbol((Bold, None)),
                PlainText("gras"),
                ClosingBracket,
                PlainText("."),
                ControlSymbol((Unknown("\\par"), None)),
                ClosingBracket,
            ]
        );
    }

    #[test]
    fn scan_escaped_text() {
        let tokens = Lexer::scan(
            r#"\f0\fs24 \cf0 test de code \
if (a == b) \{\
    test();\
\} else \{\
    return;\
\}}"#,
        );
        assert_eq!(
            tokens,
            vec![
                ControlSymbol((FontNumber, Value(0))),
                ControlSymbol((FontSize, Value(24))),
                ControlSymbol((Unknown("\\cf"), Value(0))),
                PlainText("test de code "),
                CRLF,
                PlainText("if (a == b) "),
                PlainText("{"),
                CRLF,
                PlainText("    test();"),
                CRLF,
                PlainText("} else "),
                PlainText("{"),
                CRLF,
                PlainText("    return;"),
                CRLF,
                PlainText("}"),
                ClosingBracket
            ],
        );
    }

    #[test]
    fn scan_ignorable_destination() {
        let text = r"{\*\expandedcolortbl;;}";
        let tokens = Lexer::scan(text);
        assert_eq!(tokens, vec![
            OpeningBracket,
            IgnorableDestination,
            ControlSymbol((Unknown(r"\expandedcolortbl;;"), None)),
            ClosingBracket,
        ])
    }
}