#[derive(Debug, Clone)]
pub struct LexerInfo {
    pub filename: String,
    pub source: String,
    pub pos: usize,
    pub column: usize,
    pub line: usize,
}

impl LexerInfo {
    pub fn new(filename: impl Into<String>, source: impl Into<String>) -> Self {
        Self {
            filename: filename.into(),
            source: source.into(),
            pos: 0,
            column: 1,
            line: 1,
        }
    }

    fn peek(&self) -> char {
        self.source.chars().nth(self.pos).unwrap_or('\0')
    }

    fn far_peek(&self, offset: usize) -> char {
        self.source.chars().nth(self.pos + offset).unwrap_or('\0')
    }

    fn advance(&mut self) -> char {
        if self.peek() == '\n' {
            self.line += 1;
            self.column = 1;
        } else {
            self.column += 1;
        }
        self.pos += 1;
        self.peek()
    }

    fn skip_comments_and_whitespace(&mut self) {
        loop {
            let c = self.peek();
            
            // Skip comments
            if (c == '/' && self.far_peek(1) == '/') || c == '#' {
                while self.peek() != '\n' && self.peek() != '\0' {
                    self.advance();
                }
            }
            
            // Skip whitespace
            if self.peek().is_whitespace() {
                while self.peek().is_whitespace() {
                    self.advance();
                }
            } else {
                break;
            }
        }
    }
}

#[derive(Debug, Clone)]
pub struct Identifier {
    pub name: String,
    pub is_literal: bool,
}

#[derive(Debug, Clone)]
pub enum ArrayLiteral {
    _Identifiers(Vec<Identifier>),
    _I64(Vec<i64>),
    _I32(Vec<i32>),
    _I16(Vec<i16>),
    _I8(Vec<i8>),
    _U64(Vec<u64>),
    _U32(Vec<u32>),
    _U16(Vec<u16>),
    _U8(Vec<u8>),
    _Float(Vec<f32>),
    _Double(Vec<f64>),
    _Character(Vec<u8>),
    _Strings(Vec<String>),
    _Boolean(Vec<bool>),
    _TokenStrings(Vec<TokenString>),
    _TypeTuples(Vec<TypeTuple>),
    _StructInline(StructInline),
}

#[derive(Debug, Clone)]
pub struct ShapedArray {
    pub _array: ArrayLiteral,
    pub _shape: Vec<usize>,
}

#[derive(Debug, Clone)]
pub struct TokenString {
    pub tokens: Vec<Token>,
}

#[derive(Debug, Clone)]
pub struct TypeTuple {
    pub _inputs: Vec<Identifier>,
    pub _outputs: Vec<Identifier>,
}

#[derive(Debug, Clone)]
pub struct StructInline {
    pub _name: String,
    pub _values: Vec<StructValue>,
}

#[derive(Debug, Clone)]
pub enum StructValue {
    _Integer(i64),
    _Float(f32),
    _Double(f64),
    _Boolean(bool),
    _Character(u8),
    _String(String),
    _Token(Token),
}

#[derive(Debug, Clone)]
pub enum Token {
    Eof,
    Identifier(Identifier),
    I64(i64),
    I32(i32),
    I16(i16),
    I8(i8),
    U64(u64),
    U32(u32),
    U16(u16),
    U8(u8),
    Float(f32),
    Double(f64),
    Character(u8),
    StringLiteral(String),
    Boolean(bool),
    Array(ShapedArray),
    TokenString(TokenString),
    TypeTuple(TypeTuple),
}

#[derive(Debug, Clone)]
pub struct LexError {
    pub message: String,
    pub file: String,
    pub line: usize,
    pub column: usize,
}

pub type LexResult<T> = Result<T, LexError>;

#[derive(Debug, Clone, Copy)]
enum NumericLiteralType {
    Binary,
    Octal,
    Decimal,
    Hexadecimal,
    Float,
}

impl LexerInfo {
    fn make_error(&self, message: impl Into<String>, start_line: usize, start_col: usize) -> LexError {
        LexError {
            message: message.into(),
            file: self.filename.clone(),
            line: start_line,
            column: start_col,
        }
    }

    fn is_identifier_continue(&self, c: char) -> bool {
        if !c.is_ascii() || !c.is_ascii_graphic() {
            return false;
        }
        if c == '/' && self.far_peek(1) == '/' {
            return false;
        }
        !matches!(c, '{' | '}' | '[' | ']' | '(' | ')' | '\'' | '"' | '#') && !c.is_whitespace()
    }

    fn is_identifier_start(&self) -> bool {
        let mut c = self.peek();
        if c == ':' && self.far_peek(1) == ':' {
            c = self.far_peek(2);
        }
        !c.is_ascii_digit() && self.is_identifier_continue(c)
    }

    fn parse_identifiers_and_booleans(&mut self, _start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut c = self.peek();
        let mut literal = false;

        // Skip leading `::` for identifier literals
        if c == ':' && self.far_peek(1) == ':' {
            literal = true;
            self.advance();
            c = self.advance();
        }

        // Read the name
        let name_start = self.pos;
        while self.is_identifier_continue(c) {
            if c == ':' {
                return Err(self.make_error("Invalid identifier: ':' is not allowed in identifiers.", start_line, start_col));
            }
            if c == '.' {
                return Err(self.make_error("Invalid identifier: '.' is not allowed in identifiers.", start_line, start_col));
            }
            c = self.advance();
        }

        let name = self.source[name_start..self.pos].to_string();

        // Check for booleans
        match name.as_str() {
            "false" => Ok(Token::Boolean(false)),
            "true" => Ok(Token::Boolean(true)),
            _ => Ok(Token::Identifier(Identifier { name, is_literal: literal })),
        }
    }

    fn parse_character_literal(&mut self, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut c = self.peek();

        if c == '\'' {
            return Err(self.make_error("Invalid character literal: empty character literal.", start_line, start_col));
        }

        let value = if c == '\\' {
            c = self.advance();
            match c {
                'n' => b'\n',
                'r' => b'\r',
                't' => b'\t',
                '\\' => b'\\',
                '\'' => b'\'',
                '0' => b'\0',
                _ => return Err(self.make_error(format!("Invalid character literal: unknown escape sequence '\\{}'.", c), start_line, start_col)),
            }
        } else if c == '\n' || c == '\r' {
            return Err(self.make_error("Invalid character literal: unclosed character literal.", start_line, start_col));
        } else {
            c as u8
        };

        c = self.advance();

        if c.is_whitespace() || c == '/' || c == '\0' {
            return Err(self.make_error("Invalid character literal: unclosed character literal.", start_line, start_col));
        } else if c != '\'' {
            return Err(self.make_error(format!("Invalid character literal: unexpected '{}' in character.", c), start_line, start_col));
        }

        self.advance();
        Ok(Token::Character(value))
    }

    fn parse_token_string(&mut self, _start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut tokens = Vec::new();
        self.advance(); // skip '{'

        loop {
            self.skip_comments_and_whitespace();
            let c = self.peek();

            if c == '}' {
                self.advance();
                return Ok(Token::TokenString(TokenString { tokens }));
            }

            if c == '\0' {
                return Err(self.make_error("Unclosed token string: missing closing brace '}'.", start_line, start_col));
            }

            match get_token(self) {
                Some(token) => {
                    if matches!(token, Token::Eof) {
                        break;
                    }
                    tokens.push(token);
                }
                None => return Err(self.make_error("Failed to parse token in token string.", start_line, start_col)),
            }
        }

        Err(self.make_error("Unclosed token string: missing closing brace '}'.", start_line, start_col))
    }

    fn parse_numeric_literal(&mut self, start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut c = self.peek();

        if c == '-' {
            c = self.advance();
        }

        if c == '0' {
            c = self.advance();
            match c {
                'b' | 'B' => {
                    self.advance();
                    return self.parse_binary_integer(start, start_line, start_col);
                }
                'o' | 'O' => {
                    self.advance();
                    return self.parse_octal_integer(start, start_line, start_col);
                }
                'x' | 'X' => {
                    self.advance();
                    return self.parse_hexadecimal_integer(start, start_line, start_col);
                }
                _ => {}
            }
        }

        self.parse_decimal_integer(start, start_line, start_col)
    }

    fn parse_binary_integer(&mut self, start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut c = self.peek();
        while c == '0' || c == '1' || c == '_' {
            c = self.advance();
        }

        if c == ':' {
            return self.parse_numeric_type(start, start_line, start_col, NumericLiteralType::Binary);
        }

        let value = self.create_binary_integer(start);
        Ok(Token::I64(value as i64))
    }

    fn parse_octal_integer(&mut self, start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut c = self.peek();
        while c.is_ascii_digit() && c != '8' && c != '9' || c == '_' {
            c = self.advance();
        }

        if c == ':' {
            return self.parse_numeric_type(start, start_line, start_col, NumericLiteralType::Octal);
        }

        let value = self.create_octal_integer(start);
        Ok(Token::I64(value as i64))
    }

    fn parse_decimal_integer(&mut self, start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut c = self.peek();
        while c.is_ascii_digit() || c == '_' {
            c = self.advance();
        }

        if c == '.' {
            self.advance();
            return self.parse_float(start, start_line, start_col);
        }

        if c == ':' {
            return self.parse_numeric_type(start, start_line, start_col, NumericLiteralType::Decimal);
        }

        let value = self.create_decimal_integer(start);
        Ok(Token::I64(value as i64))
    }

    fn parse_hexadecimal_integer(&mut self, start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut c = self.peek();
        while c.is_ascii_hexdigit() || c == '_' {
            c = self.advance();
        }

        if c == ':' {
            return self.parse_numeric_type(start, start_line, start_col, NumericLiteralType::Hexadecimal);
        }

        let value = self.create_hexadecimal_integer(start);
        Ok(Token::I64(value as i64))
    }

    fn parse_float(&mut self, start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let mut c = self.peek();
        while c.is_ascii_digit() || c == '_' {
            c = self.advance();
        }

        if c == ':' {
            return self.parse_numeric_type(start, start_line, start_col, NumericLiteralType::Float);
        }

        let value = self.create_float(start);
        Ok(Token::Double(value))
    }

    fn parse_numeric_type(&mut self, start: usize, start_line: usize, start_col: usize, literal_type: NumericLiteralType) -> LexResult<Token> {
        let mut c = self.advance(); // skip ':'

        let mut is_float = false;
        let mut is_unsigned = false;
        let bit_size: u32;

        if c == 'f' {
            is_float = true;
            if !matches!(literal_type, NumericLiteralType::Decimal | NumericLiteralType::Float) {
                return Err(self.make_error("Invalid numeric literal: float type not allowed.", start_line, start_col));
            }
            c = self.advance();
            if c == '6' && self.far_peek(1) == '4' {
                bit_size = 64;
                self.advance();
                self.advance();
            } else if c == '3' && self.far_peek(1) == '2' {
                bit_size = 32;
                self.advance();
                self.advance();
            } else {
                return Err(self.make_error("Invalid float type: must be of type 'f64' or 'f32'.", start_line, start_col));
            }
        } else if c == 'i' || c == 'u' {
            if matches!(literal_type, NumericLiteralType::Float) {
                return Err(self.make_error("Invalid float type: must be of type 'f64' or 'f32'.", start_line, start_col));
            }
            is_unsigned = c == 'u';
            c = self.advance();
            if c == '6' && self.far_peek(1) == '4' {
                bit_size = 64;
                self.advance();
                self.advance();
            } else if c == '3' && self.far_peek(1) == '2' {
                bit_size = 32;
                self.advance();
                self.advance();
            } else if c == '1' && self.far_peek(1) == '6' {
                bit_size = 16;
                self.advance();
                self.advance();
            } else if c == '8' {
                bit_size = 8;
                self.advance();
            } else {
                let type_name = if is_unsigned { "unsigned" } else { "signed" };
                return Err(self.make_error(
                    format!("Invalid {} integer type: must be of type '{}64', '{}32', '{}16', or '{}8'.",
                        type_name, if is_unsigned { "u" } else { "i" },
                        if is_unsigned { "u" } else { "i" },
                        if is_unsigned { "u" } else { "i" },
                        if is_unsigned { "u" } else { "i" }),
                    start_line, start_col));
            }
        } else {
            return Err(self.make_error("Invalid numeric type: type must start with 'f', 'i', or 'u'.", start_line, start_col));
        }

        // Create the token based on the parsed type
        if is_float {
            let value = self.create_float(start);
            match bit_size {
                32 => Ok(Token::Float(value as f32)),
                64 => Ok(Token::Double(value)),
                _ => unreachable!()
            }
        } else {
            let value = match literal_type {
                NumericLiteralType::Binary => self.create_binary_integer(start),
                NumericLiteralType::Octal => self.create_octal_integer(start),
                NumericLiteralType::Decimal => self.create_decimal_integer(start),
                NumericLiteralType::Hexadecimal => self.create_hexadecimal_integer(start),
                NumericLiteralType::Float => return Err(self.make_error("Internal error: float literal in integer path", start_line, start_col)),
            };

            self.create_integer_token(value, is_unsigned, bit_size, start, start_line, start_col)
        }
    }

    fn create_integer_token(&self, value: u64, is_unsigned: bool, bit_size: u32, start: usize, start_line: usize, start_col: usize) -> LexResult<Token> {
        let is_negative = self.source[start..].starts_with('-');

        match (is_unsigned, bit_size) {
            (false, 64) => Ok(Token::I64(value as i64)),
            (false, 32) => {
                let signed = value as i64;
                if signed < i32::MIN as i64 || signed > i32::MAX as i64 {
                    return Err(self.make_error("Integer overflow: value exceeds range for i32.", start_line, start_col));
                }
                Ok(Token::I32(value as i32))
            }
            (false, 16) => {
                let signed = value as i64;
                if signed < i16::MIN as i64 || signed > i16::MAX as i64 {
                    return Err(self.make_error("Integer overflow: value exceeds range for i16.", start_line, start_col));
                }
                Ok(Token::I16(value as i16))
            }
            (false, 8) => {
                let signed = value as i64;
                if signed < i8::MIN as i64 || signed > i8::MAX as i64 {
                    return Err(self.make_error("Integer overflow: value exceeds range for i8.", start_line, start_col));
                }
                Ok(Token::I8(value as i8))
            }
            (true, 64) => {
                if is_negative {
                    return Err(self.make_error("Integer overflow: value exceeds range for u64.", start_line, start_col));
                }
                Ok(Token::U64(value))
            }
            (true, 32) => {
                if is_negative {
                    return Err(self.make_error("Integer overflow: value exceeds range for u32.", start_line, start_col));
                }
                if value > u32::MAX as u64 {
                    return Err(self.make_error("Integer overflow: value exceeds range for u32.", start_line, start_col));
                }
                Ok(Token::U32(value as u32))
            }
            (true, 16) => {
                if is_negative {
                    return Err(self.make_error("Integer overflow: value exceeds range for u16.", start_line, start_col));
                }
                if value > u16::MAX as u64 {
                    return Err(self.make_error("Integer overflow: value exceeds range for u16.", start_line, start_col));
                }
                Ok(Token::U16(value as u16))
            }
            (true, 8) => {
                if is_negative {
                    return Err(self.make_error("Integer overflow: value exceeds range for u8.", start_line, start_col));
                }
                if value > u8::MAX as u64 {
                    return Err(self.make_error("Integer overflow: value exceeds range for u8.", start_line, start_col));
                }
                Ok(Token::U8(value as u8))
            }
            _ => Err(self.make_error("Invalid bit size for integer type.", start_line, start_col))
        }
    }

    fn create_binary_integer(&self, start: usize) -> u64 {
        let token = &self.source[start..self.pos];
        let mut value = 0u64;
        let mut i = 2;

        if token.starts_with('-') {
            i += 1;
        }

        for c in token[i..].chars() {
            if c == '_' || c == '.' {
                continue;
            }
            if c.is_whitespace() || c == '/' || c == ':' {
                break;
            }
            value *= 2;
            if c == '1' {
                value += 1;
            }
        }

        if token.starts_with('-') {
            (!value).wrapping_add(1)
        } else {
            value
        }
    }

    fn create_octal_integer(&self, start: usize) -> u64 {
        let token = &self.source[start..self.pos];
        let mut value = 0u64;
        let mut i = 2;

        if token.starts_with('-') {
            i += 1;
        }

        for c in token[i..].chars() {
            if c == '_' || c == '.' {
                continue;
            }
            if c.is_whitespace() || c == '/' || c == ':' {
                break;
            }
            value *= 8;
            value += c.to_digit(8).unwrap_or(0) as u64;
        }

        if token.starts_with('-') {
            (!value).wrapping_add(1)
        } else {
            value
        }
    }

    fn create_decimal_integer(&self, start: usize) -> u64 {
        let token = &self.source[start..self.pos];
        let mut value = 0u64;
        let mut i = 0;

        if token.starts_with('-') {
            i += 1;
        }

        for c in token[i..].chars() {
            if c == '_' {
                continue;
            }
            if c.is_whitespace() || c == '/' || c == ':' {
                break;
            }
            value *= 10;
            value += c.to_digit(10).unwrap_or(0) as u64;
        }

        if token.starts_with('-') {
            (!value).wrapping_add(1)
        } else {
            value
        }
    }

    fn create_hexadecimal_integer(&self, start: usize) -> u64 {
        let token = &self.source[start..self.pos];
        let mut value = 0u64;
        let mut i = 2;

        if token.starts_with('-') {
            i += 1;
        }

        for c in token[i..].chars() {
            if c == '_' || c == '.' {
                continue;
            }
            if c.is_whitespace() || c == '/' || c == ':' {
                break;
            }
            value *= 16;
            value += c.to_digit(16).unwrap_or(0) as u64;
        }

        if token.starts_with('-') {
            (!value).wrapping_add(1)
        } else {
            value
        }
    }

    fn create_float(&self, start: usize) -> f64 {
        let token = &self.source[start..self.pos];
        let mut value = 0.0;
        let mut fractional = 0u64;
        let mut i = 0;

        if token.starts_with('-') {
            i += 1;
        }

        for c in token[i..].chars() {
            if c == '_' {
                continue;
            }
            if c.is_whitespace() || c == '/' || c == ':' {
                break;
            }
            if c == '.' {
                fractional = 1;
                continue;
            }

            if fractional == 0 {
                value *= 10.0;
            } else {
                fractional *= 10;
            }

            let digit = c.to_digit(10).unwrap_or(0) as f64;
            if fractional == 0 {
                value += digit;
            } else {
                value += digit / fractional as f64;
            }
        }

        if token.starts_with('-') {
            -value
        } else {
            value
        }
    }
}

pub fn get_token(lexer: &mut LexerInfo) -> Option<Token> {
    lexer.skip_comments_and_whitespace();

    let c = lexer.peek();
    let start = lexer.pos;
    let start_line = lexer.line;
    let start_col = lexer.column;

    if c == '\0' {
        return Some(Token::Eof);
    }

    let result = if c.is_ascii_digit() || (c == '.' && lexer.far_peek(1).is_ascii_digit()) || (c == '-' && lexer.far_peek(1).is_ascii_digit()) {
        lexer.parse_numeric_literal(start, start_line, start_col)
    } else if c == '\'' {
        lexer.advance();
        lexer.parse_character_literal(start_line, start_col)
    } else if c == '{' {
        lexer.parse_token_string(start, start_line, start_col)
    } else if lexer.is_identifier_start() {
        lexer.parse_identifiers_and_booleans(start, start_line, start_col)
    } else {
        Err(lexer.make_error(format!("Unexpected character: '{}'", c), start_line, start_col))
    };

    result.ok()
}

pub fn lexical_analysis(lexer: &mut LexerInfo) -> LexResult<Vec<Token>> {
    let mut tokens = Vec::new();

    loop {
        match get_token(lexer) {
            Some(Token::Eof) => {
                tokens.push(Token::Eof);
                break;
            }
            Some(token) => tokens.push(token),
            None => break,
        }
    }

    Ok(tokens)
}