use lazy_static::lazy_static;
use regex::Regex;
use serde::{Deserialize, Serialize};

#[derive(Debug, PartialEq, Eq, Copy, Clone, Deserialize, Serialize, ts_rs::TS)]
#[ts(export)]
#[serde(rename_all = "lowercase")]
pub enum TokenType {
    Number,
    Word,
    Operator,
    String,
    Brace,
    Whitespace,
    Comma,
    Colon,
    Period,
    LineComment,
    BlockComment,
}

#[derive(Debug, PartialEq, Eq, Deserialize, Serialize, Clone, ts_rs::TS)]
#[ts(export)]
pub struct Token {
    #[serde(rename = "type")]
    pub token_type: TokenType,
    pub start: usize,
    pub end: usize,
    pub value: String,
}

impl From<Token> for crate::executor::SourceRange {
    fn from(token: Token) -> Self {
        Self([token.start, token.end])
    }
}

impl From<&Token> for crate::executor::SourceRange {
    fn from(token: &Token) -> Self {
        Self([token.start, token.end])
    }
}

lazy_static! {
    static ref NUMBER: Regex = Regex::new(r"^-?\d+(\.\d+)?").unwrap();
    static ref WHITESPACE: Regex = Regex::new(r"\s+").unwrap();
    static ref WORD: Regex = Regex::new(r"^[a-zA-Z_][a-zA-Z0-9_]*").unwrap();
    static ref STRING: Regex = Regex::new(r#"^"([^"\\]|\\.)*"|'([^'\\]|\\.)*'"#).unwrap();
    static ref OPERATOR: Regex = Regex::new(r"^(>=|<=|==|=>|!= |\|>|\*|\+|-|/|%|=|<|>|\||\^)").unwrap();
    static ref BLOCK_START: Regex = Regex::new(r"^\{").unwrap();
    static ref BLOCK_END: Regex = Regex::new(r"^\}").unwrap();
    static ref PARAN_START: Regex = Regex::new(r"^\(").unwrap();
    static ref PARAN_END: Regex = Regex::new(r"^\)").unwrap();
    static ref ARRAY_START: Regex = Regex::new(r"^\[").unwrap();
    static ref ARRAY_END: Regex = Regex::new(r"^\]").unwrap();
    static ref COMMA: Regex = Regex::new(r"^,").unwrap();
    static ref COLON: Regex = Regex::new(r"^:").unwrap();
    static ref PERIOD: Regex = Regex::new(r"^\.").unwrap();
    static ref LINECOMMENT: Regex = Regex::new(r"^//.*").unwrap();
    static ref BLOCKCOMMENT: Regex = Regex::new(r"^/\*[\s\S]*?\*/").unwrap();
}

fn is_number(character: &str) -> bool {
    NUMBER.is_match(character)
}
fn is_whitespace(character: &str) -> bool {
    WHITESPACE.is_match(character)
}
fn is_word(character: &str) -> bool {
    WORD.is_match(character)
}
fn is_string(character: &str) -> bool {
    match STRING.find(character) {
        Some(m) => m.start() == 0,
        None => false,
    }
}
fn is_operator(character: &str) -> bool {
    OPERATOR.is_match(character)
}
fn is_block_start(character: &str) -> bool {
    BLOCK_START.is_match(character)
}
fn is_block_end(character: &str) -> bool {
    BLOCK_END.is_match(character)
}
fn is_paran_start(character: &str) -> bool {
    PARAN_START.is_match(character)
}
fn is_paran_end(character: &str) -> bool {
    PARAN_END.is_match(character)
}
fn is_array_start(character: &str) -> bool {
    ARRAY_START.is_match(character)
}
fn is_array_end(character: &str) -> bool {
    ARRAY_END.is_match(character)
}
fn is_comma(character: &str) -> bool {
    COMMA.is_match(character)
}
fn is_colon(character: &str) -> bool {
    COLON.is_match(character)
}
fn is_period(character: &str) -> bool {
    PERIOD.is_match(character)
}
fn is_line_comment(character: &str) -> bool {
    LINECOMMENT.is_match(character)
}
fn is_block_comment(character: &str) -> bool {
    BLOCKCOMMENT.is_match(character)
}

fn match_first(str: &str, regex: &Regex) -> Option<String> {
    regex.find(str).map(|the_match| the_match.as_str().to_string())
}

fn make_token(token_type: TokenType, value: &str, start: usize) -> Token {
    Token {
        token_type,
        value: value.to_string(),
        start,
        end: start + value.len(),
    }
}

fn return_token_at_index(str: &str, start_index: usize) -> Option<Token> {
    let str_from_index = &str[start_index..];
    if is_string(str_from_index) {
        return Some(make_token(
            TokenType::String,
            &match_first(str_from_index, &STRING)?,
            start_index,
        ));
    }
    let is_line_comment_bool = is_line_comment(str_from_index);
    if is_line_comment_bool || is_block_comment(str_from_index) {
        return Some(make_token(
            if is_line_comment_bool {
                TokenType::LineComment
            } else {
                TokenType::BlockComment
            },
            &match_first(
                str_from_index,
                if is_line_comment_bool {
                    &LINECOMMENT
                } else {
                    &BLOCKCOMMENT
                },
            )?,
            start_index,
        ));
    }
    if is_paran_end(str_from_index) {
        return Some(make_token(
            TokenType::Brace,
            &match_first(str_from_index, &PARAN_END)?,
            start_index,
        ));
    }
    if is_paran_start(str_from_index) {
        return Some(make_token(
            TokenType::Brace,
            &match_first(str_from_index, &PARAN_START)?,
            start_index,
        ));
    }
    if is_block_start(str_from_index) {
        return Some(make_token(
            TokenType::Brace,
            &match_first(str_from_index, &BLOCK_START)?,
            start_index,
        ));
    }
    if is_block_end(str_from_index) {
        return Some(make_token(
            TokenType::Brace,
            &match_first(str_from_index, &BLOCK_END)?,
            start_index,
        ));
    }
    if is_array_start(str_from_index) {
        return Some(make_token(
            TokenType::Brace,
            &match_first(str_from_index, &ARRAY_START)?,
            start_index,
        ));
    }
    if is_array_end(str_from_index) {
        return Some(make_token(
            TokenType::Brace,
            &match_first(str_from_index, &ARRAY_END)?,
            start_index,
        ));
    }
    if is_comma(str_from_index) {
        return Some(make_token(
            TokenType::Comma,
            &match_first(str_from_index, &COMMA)?,
            start_index,
        ));
    }
    if is_number(str_from_index) {
        return Some(make_token(
            TokenType::Number,
            &match_first(str_from_index, &NUMBER)?,
            start_index,
        ));
    }
    if is_operator(str_from_index) {
        return Some(make_token(
            TokenType::Operator,
            &match_first(str_from_index, &OPERATOR)?,
            start_index,
        ));
    }
    if is_word(str_from_index) {
        return Some(make_token(
            TokenType::Word,
            &match_first(str_from_index, &WORD)?,
            start_index,
        ));
    }
    if is_colon(str_from_index) {
        return Some(make_token(
            TokenType::Colon,
            &match_first(str_from_index, &COLON)?,
            start_index,
        ));
    }
    if is_period(str_from_index) {
        return Some(make_token(
            TokenType::Period,
            &match_first(str_from_index, &PERIOD)?,
            start_index,
        ));
    }
    if is_whitespace(str_from_index) {
        return Some(make_token(
            TokenType::Whitespace,
            &match_first(str_from_index, &WHITESPACE)?,
            start_index,
        ));
    }
    None
}

pub fn lexer(str: &str) -> Vec<Token> {
    fn recursively_tokenise(str: &str, current_index: usize, previous_tokens: Vec<Token>) -> Vec<Token> {
        if current_index >= str.len() {
            return previous_tokens;
        }
        let token = return_token_at_index(str, current_index);
        let Some(token) = token else {
            return recursively_tokenise(str, current_index + 1, previous_tokens);
        };
        let mut new_tokens = previous_tokens;
        let token_length = token.value.len();
        new_tokens.push(token);
        recursively_tokenise(str, current_index + token_length, new_tokens)
    }
    recursively_tokenise(str, 0, Vec::new())
}

#[cfg(test)]
mod tests {
    use pretty_assertions::assert_eq;

    use super::*;

    #[test]
    fn is_number_test() {
        assert!(is_number("1"));
        assert!(is_number("1 abc"));
        assert!(is_number("1abc"));
        assert!(is_number("1.1"));
        assert!(is_number("1.1 abc"));
        assert!(!is_number("a"));

        assert!(is_number("1"));
        assert!(is_number("5?"));
        assert!(is_number("5 + 6"));
        assert!(is_number("5 + a"));
        assert!(is_number("-5"));
        assert!(is_number("5.5"));
        assert!(is_number("-5.5"));

        assert!(!is_number("a"));
        assert!(!is_number("?"));
        assert!(!is_number("?5"));
    }

    #[test]
    fn is_whitespace_test() {
        assert!(is_whitespace(" "));
        assert!(is_whitespace("  "));
        assert!(is_whitespace(" a"));
        assert!(is_whitespace("a "));

        assert!(!is_whitespace("a"));
        assert!(!is_whitespace("?"));
    }

    #[test]
    fn is_word_test() {
        assert!(is_word("a"));
        assert!(is_word("a "));
        assert!(is_word("a5"));
        assert!(is_word("a5a"));

        assert!(!is_word("5"));
        assert!(!is_word("5a"));
        assert!(!is_word("5a5"));
    }

    #[test]
    fn is_string_test() {
        assert!(is_string("\"\""));
        assert!(is_string("\"a\""));
        assert!(is_string("\"a\" "));
        assert!(is_string("\"a\"5"));
        assert!(is_string("'a'5"));
        assert!(is_string("\"with escaped \\\" backslash\""));

        assert!(!is_string("\""));
        assert!(!is_string("\"a"));
        assert!(!is_string("a\""));
        assert!(!is_string(" \"a\""));
        assert!(!is_string("5\"a\""));
        assert!(!is_string("a + 'str'"));
    }

    #[test]
    fn is_operator_test() {
        assert!(is_operator("+"));
        assert!(is_operator("+ "));
        assert!(is_operator("-"));
        assert!(is_operator("<="));
        assert!(is_operator("<= "));
        assert!(is_operator(">="));
        assert!(is_operator(">= "));
        assert!(is_operator("> "));
        assert!(is_operator("< "));
        assert!(is_operator("| "));
        assert!(is_operator("|> "));
        assert!(is_operator("^ "));
        assert!(is_operator("% "));
        assert!(is_operator("+* "));

        assert!(!is_operator("5 + 5"));
        assert!(!is_operator("a"));
        assert!(!is_operator("a+"));
        assert!(!is_operator("a+5"));
        assert!(!is_operator("5a+5"));
        assert!(!is_operator(", newVar"));
        assert!(!is_operator(","));
    }

    #[test]
    fn is_block_start_test() {
        assert!(is_block_start("{"));
        assert!(is_block_start("{ "));
        assert!(is_block_start("{5"));
        assert!(is_block_start("{a"));
        assert!(is_block_start("{5 "));

        assert!(!is_block_start("5"));
        assert!(!is_block_start("5 + 5"));
        assert!(!is_block_start("5{ + 5"));
        assert!(!is_block_start("a{ + 5"));
        assert!(!is_block_start(" { + 5"));
    }

    #[test]
    fn is_block_end_test() {
        assert!(is_block_end("}"));
        assert!(is_block_end("} "));
        assert!(is_block_end("}5"));
        assert!(is_block_end("}5 "));

        assert!(!is_block_end("5"));
        assert!(!is_block_end("5 + 5"));
        assert!(!is_block_end("5} + 5"));
        assert!(!is_block_end(" } + 5"));
    }

    #[test]
    fn is_paran_start_test() {
        assert!(is_paran_start("("));
        assert!(is_paran_start("( "));
        assert!(is_paran_start("(5"));
        assert!(is_paran_start("(5 "));
        assert!(is_paran_start("(5 + 5"));
        assert!(is_paran_start("(5 + 5)"));
        assert!(is_paran_start("(5 + 5) "));

        assert!(!is_paran_start("5"));
        assert!(!is_paran_start("5 + 5"));
        assert!(!is_paran_start("5( + 5)"));
        assert!(!is_paran_start(" ( + 5)"));
    }

    #[test]
    fn is_paran_end_test() {
        assert!(is_paran_end(")"));
        assert!(is_paran_end(") "));
        assert!(is_paran_end(")5"));
        assert!(is_paran_end(")5 "));

        assert!(!is_paran_end("5"));
        assert!(!is_paran_end("5 + 5"));
        assert!(!is_paran_end("5) + 5"));
        assert!(!is_paran_end(" ) + 5"));
    }

    #[test]
    fn is_comma_test() {
        assert!(is_comma(","));
        assert!(is_comma(", "));
        assert!(is_comma(",5"));
        assert!(is_comma(",5 "));

        assert!(!is_comma("5"));
        assert!(!is_comma("5 + 5"));
        assert!(!is_comma("5, + 5"));
        assert!(!is_comma(" , + 5"));
    }

    #[test]
    fn is_line_comment_test() {
        assert!(is_line_comment("//"));
        assert!(is_line_comment("// "));
        assert!(is_line_comment("//5"));
        assert!(is_line_comment("//5 "));

        assert!(!is_line_comment("5"));
        assert!(!is_line_comment("5 + 5"));
        assert!(!is_line_comment("5// + 5"));
        assert!(!is_line_comment(" // + 5"));
    }

    #[test]
    fn is_block_comment_test() {
        assert!(is_block_comment("/*  */"));
        assert!(is_block_comment("/***/"));
        assert!(is_block_comment("/*5*/"));
        assert!(is_block_comment("/*5 */"));

        assert!(!is_block_comment("/*"));
        assert!(!is_block_comment("5"));
        assert!(!is_block_comment("5 + 5"));
        assert!(!is_block_comment("5/* + 5"));
        assert!(!is_block_comment(" /* + 5"));
    }

    #[test]
    fn make_token_test() {
        assert_eq!(
            make_token(TokenType::Word, "const", 56),
            Token {
                token_type: TokenType::Word,
                value: "const".to_string(),
                start: 56,
                end: 61,
            }
        );
    }

    #[test]
    fn return_token_at_index_test() {
        assert_eq!(
            return_token_at_index("const", 0),
            Some(Token {
                token_type: TokenType::Word,
                value: "const".to_string(),
                start: 0,
                end: 5,
            })
        );
        assert_eq!(
            return_token_at_index("  4554", 2),
            Some(Token {
                token_type: TokenType::Number,
                value: "4554".to_string(),
                start: 2,
                end: 6,
            })
        );
    }

    #[test]
    fn lexer_test() {
        assert_eq!(
            lexer("const a=5"),
            vec![
                Token {
                    token_type: TokenType::Word,
                    value: "const".to_string(),
                    start: 0,
                    end: 5,
                },
                Token {
                    token_type: TokenType::Whitespace,
                    value: " ".to_string(),
                    start: 5,
                    end: 6,
                },
                Token {
                    token_type: TokenType::Word,
                    value: "a".to_string(),
                    start: 6,
                    end: 7,
                },
                Token {
                    token_type: TokenType::Operator,
                    value: "=".to_string(),
                    start: 7,
                    end: 8,
                },
                Token {
                    token_type: TokenType::Number,
                    value: "5".to_string(),
                    start: 8,
                    end: 9,
                },
            ]
        );
        assert_eq!(
            lexer("54 + 22500 + 6"),
            vec![
                Token {
                    token_type: TokenType::Number,
                    value: "54".to_string(),
                    start: 0,
                    end: 2,
                },
                Token {
                    token_type: TokenType::Whitespace,
                    value: " ".to_string(),
                    start: 2,
                    end: 3,
                },
                Token {
                    token_type: TokenType::Operator,
                    value: "+".to_string(),
                    start: 3,
                    end: 4,
                },
                Token {
                    token_type: TokenType::Whitespace,
                    value: " ".to_string(),
                    start: 4,
                    end: 5,
                },
                Token {
                    token_type: TokenType::Number,
                    value: "22500".to_string(),
                    start: 5,
                    end: 10,
                },
                Token {
                    token_type: TokenType::Whitespace,
                    value: " ".to_string(),
                    start: 10,
                    end: 11,
                },
                Token {
                    token_type: TokenType::Operator,
                    value: "+".to_string(),
                    start: 11,
                    end: 12,
                },
                Token {
                    token_type: TokenType::Whitespace,
                    value: " ".to_string(),
                    start: 12,
                    end: 13,
                },
                Token {
                    token_type: TokenType::Number,
                    value: "6".to_string(),
                    start: 13,
                    end: 14,
                },
            ]
        );
    }
}