IronCalc/base/src/expressions/lexer/structured_references.rs

// Grammar:
// structured references -> table_name "[" arguments "]"
//  arguments -> table_reference | "["specifier"]"  "," table_reference
//  specifier > "#All"      |
//              "#This Row" |
//              "#Data"     |
//              "#Headers"  |
//              "#Totals"
// table_reference -> column_reference | range_reference
// column reference -> column_name | "["column_name"]"
// range_reference -> column_reference":"column_reference

use crate::expressions::token::TokenType;
use crate::expressions::token::{TableReference, TableSpecifier};

use super::Result;
use super::{Lexer, LexerError};

impl Lexer {
    fn consume_table_specifier(&mut self) -> Result<Option<TableSpecifier>> {
        if self.peek_char() == Some('#') {
            // It's a specifier
            // TODO(TD): There are better ways of doing this :)
            let rest_of_formula: String = self.chars[self.position..self.len].iter().collect();
            let specifier = if rest_of_formula.starts_with("#This Row]") {
                self.position += "#This Row]".bytes().len();
                TableSpecifier::ThisRow
            } else if rest_of_formula.starts_with("#All]") {
                self.position += "#All]".bytes().len();
                TableSpecifier::All
            } else if rest_of_formula.starts_with("#Data]") {
                self.position += "#Data]".bytes().len();
                TableSpecifier::Data
            } else if rest_of_formula.starts_with("#Headers]") {
                self.position += "#Headers]".bytes().len();
                TableSpecifier::Headers
            } else if rest_of_formula.starts_with("#Totals]") {
                self.position += "#Totals]".bytes().len();
                TableSpecifier::Totals
            } else {
                return Err(LexerError {
                    position: self.position,
                    message: "Invalid structured reference".to_string(),
                });
            };
            Ok(Some(specifier))
        } else {
            Ok(None)
        }
    }

    fn consume_column_reference(&mut self) -> Result<String> {
        self.consume_whitespace();
        let end_char = if self.peek_char() == Some('[') {
            self.position += 1;
            ']'
        } else {
            ')'
        };

        let mut position = self.position;
        while position < self.len {
            let next_char = self.chars[position];
            if next_char != end_char {
                position += 1;
                if next_char == '\'' {
                    if position == self.len {
                        return Err(LexerError {
                            position: self.position,
                            message: "Invalid column name".to_string(),
                        });
                    }
                    // skip next char
                    position += 1
                }
            } else {
                break;
            }
        }
        let chars: String = self.chars[self.position..position].iter().collect();
        if end_char == ']' {
            position += 1;
        }
        self.position = position;
        Ok(chars
            .replace("'[", "[")
            .replace("']", "]")
            .replace("'#", "#")
            .replace("'@", "@")
            .replace("''", "'"))
    }

    // Possibilities:
    //  1. MyTable[#Totals] or MyTable[#This Row]
    //  2. MyTable[MyColumn]
    //  3. MyTable[[My Column]]
    //  4. MyTable[[#This Row], [My Column]]
    //  5. MyTable[[#Totals], [MyColumn]]
    //  6. MyTable[[#This Row], [Jan]:[Dec]]
    //  7. MyTable[]
    //
    // Multiple specifiers are not supported yet:
    //  1. MyTable[[#Data], [#Totals], [MyColumn]]
    //
    // In particular note that names of columns are escaped only when they are in the first argument
    // We use '[' and ']'
    // When there is only a specifier but not a reference the specifier is not in brackets
    //
    // Invalid:
    // * MyTable[#Totals, [Jan]:[March]] => MyTable[[#Totals], [Jan]:[March]]
    //
    // NOTES:
    // * MyTable[[#Totals]] is translated into MyTable[#Totals]
    // * Excel shows '@' instead of '#This Row':
    //     MyTable[[#This Row], [Jan]:[Dec]] => MyTable[@[Jan]:[Dec]]
    //   But this is only a UI thing that we will ignore for now.
    pub(crate) fn consume_structured_reference(&mut self, table_name: &str) -> Result<TokenType> {
        self.expect(TokenType::LeftBracket)?;
        let peek_char = self.peek_char();
        if peek_char == Some(']') {
            // This is just a reference to the full table
            self.expect(TokenType::RightBracket)?;
            return Ok(TokenType::Ident(table_name.to_string()));
        }
        if peek_char == Some('#') {
            // Expecting MyTable[#Totals]
            if let Some(specifier) = self.consume_table_specifier()? {
                return Ok(TokenType::StructuredReference {
                    table_name: table_name.to_string(),
                    specifier: Some(specifier),
                    table_reference: None,
                });
            } else {
                return Err(LexerError {
                    position: self.position,
                    message: "Invalid structured reference".to_string(),
                });
            }
        } else if peek_char != Some('[') {
            // Expecting MyTable[MyColumn]
            self.position -= 1;
            let column_name = self.consume_column_reference()?;
            return Ok(TokenType::StructuredReference {
                table_name: table_name.to_string(),
                specifier: None,
                table_reference: Some(TableReference::ColumnReference(column_name)),
            });
        }
        self.expect(TokenType::LeftBracket)?;
        let specifier = self.consume_table_specifier()?;
        if specifier.is_some() {
            let peek_token = self.peek_token();
            if peek_token == TokenType::Comma {
                self.advance_token();
                self.expect(TokenType::LeftBracket)?;
            } else if peek_token == TokenType::RightBracket {
                return Ok(TokenType::StructuredReference {
                    table_name: table_name.to_string(),
                    specifier,
                    table_reference: None,
                });
            }
        }

        // Now it's either:
        // [Column Name]
        // [Column Name]:[Column Name]
        self.position -= 1;
        let column_reference = self.consume_column_reference()?;
        let table_reference = if self.peek_char() == Some(':') {
            self.position += 1;
            let column_reference_right = self.consume_column_reference()?;
            self.expect(TokenType::RightBracket)?;
            Some(TableReference::RangeReference((
                column_reference,
                column_reference_right,
            )))
        } else {
            self.expect(TokenType::RightBracket)?;
            Some(TableReference::ColumnReference(column_reference))
        };
        Ok(TokenType::StructuredReference {
            table_name: table_name.to_string(),
            specifier,
            table_reference,
        })
    }
}