// This file is part of yash, an extended POSIX shell.
// Copyright (C) 2021 WATANABE Yuki
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

//! Part of the lexer that parses raw parameter expansion.

use super::core::Lexer;
use crate::parser::core::Result;
use crate::syntax::TextUnit;

/// Tests if a character can be part of a POSIXly-portable name.
///
/// Returns true if the character is an ASCII alphanumeric or underscore.
///
/// Note that a valid name cannot start with a digit.
pub fn is_portable_name_char(c: char) -> bool {
    matches!(c, '0'..='9' | 'A'..='Z' | '_' | 'a'..='z')
}

/// Tests if a character names a special parameter.
///
/// A special parameter is one of: `@*#?-$!0`.
pub fn is_special_parameter_char(c: char) -> bool {
    matches!(c, '@' | '*' | '#' | '?' | '-' | '$' | '!' | '0')
}

/// Tests if a character is a valid single-character raw parameter name.
///
/// If this function returns true, the character is a valid parameter name for a
/// raw parameter expansion, but the next character is never treated as part of
/// the name.
///
/// This function returns true for ASCII digits and special parameter names.
pub fn is_single_char_name(c: char) -> bool {
    c.is_ascii_digit() || is_special_parameter_char(c)
}

impl Lexer<'_> {
    /// Parses a parameter expansion that is not enclosed in braces.
    ///
    /// The initial `$` must have been consumed before calling this function.
    /// This functions checks if the next character is a valid POSIXly-portable
    /// parameter name. If so, the name is consumed and returned. Otherwise, no
    /// characters are consumed and the return value is `Ok(None)`.
    ///
    /// The `start_index` parameter should be the index for the initial `$`. It is
    /// used to construct the result, but this function does not check if it
    /// actually points to the `$`.
    pub async fn raw_param(&mut self, start_index: usize) -> Result<Option<TextUnit>> {
        let name = if let Some(c) = self.consume_char_if(is_single_char_name).await? {
            c.value.to_string()
        } else if let Some(c) = self.consume_char_if(is_portable_name_char).await? {
            let mut name = c.value.to_string();
            while let Some(c) = self.consume_char_if(is_portable_name_char).await? {
                name.push(c.value);
            }
            name
        } else {
            return Ok(None);
        };
        let location = self.location_range(start_index..self.index());
        Ok(Some(TextUnit::RawParam { name, location }))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::source::Source;
    use assert_matches::assert_matches;
    use futures_util::FutureExt;

    #[test]
    fn lexer_raw_param_special_parameter() {
        let mut lexer = Lexer::from_memory("$@;", Source::Unknown);
        lexer.peek_char().now_or_never().unwrap().unwrap();
        lexer.consume_char();

        let result = lexer.raw_param(0).now_or_never().unwrap().unwrap().unwrap();
        assert_matches!(result, TextUnit::RawParam { name, location } => {
            assert_eq!(name, "@");
            assert_eq!(*location.code.value.borrow(), "$@;");
            assert_eq!(location.code.start_line_number.get(), 1);
            assert_eq!(location.code.source, Source::Unknown);
            assert_eq!(location.range, 0..2);
        });

        assert_eq!(lexer.peek_char().now_or_never().unwrap(), Ok(Some(';')));
    }

    #[test]
    fn lexer_raw_param_digit() {
        let mut lexer = Lexer::from_memory("$12", Source::Unknown);
        lexer.peek_char().now_or_never().unwrap().unwrap();
        lexer.consume_char();

        let result = lexer.raw_param(0).now_or_never().unwrap().unwrap().unwrap();
        assert_matches!(result, TextUnit::RawParam { name, location } => {
            assert_eq!(name, "1");
            assert_eq!(*location.code.value.borrow(), "$12");
            assert_eq!(location.code.start_line_number.get(), 1);
            assert_eq!(location.code.source, Source::Unknown);
            assert_eq!(location.range, 0..2);
        });

        assert_eq!(lexer.peek_char().now_or_never().unwrap(), Ok(Some('2')));
    }

    #[test]
    fn lexer_raw_param_posix_name() {
        let mut lexer = Lexer::from_memory("$az_AZ_019<", Source::Unknown);
        lexer.peek_char().now_or_never().unwrap().unwrap();
        lexer.consume_char();

        let result = lexer.raw_param(0).now_or_never().unwrap().unwrap().unwrap();
        assert_matches!(result, TextUnit::RawParam { name, location } => {
            assert_eq!(name, "az_AZ_019");
            assert_eq!(*location.code.value.borrow(), "$az_AZ_019<");
            assert_eq!(location.code.start_line_number.get(), 1);
            assert_eq!(location.code.source, Source::Unknown);
            assert_eq!(location.range, 0..10);
        });

        assert_eq!(lexer.peek_char().now_or_never().unwrap(), Ok(Some('<')));
    }

    #[test]
    fn lexer_raw_param_posix_name_line_continuations() {
        let mut lexer = Lexer::from_memory("$a\\\n\\\nb\\\n\\\nc\\\n>", Source::Unknown);
        lexer.peek_char().now_or_never().unwrap().unwrap();
        lexer.consume_char();

        let result = lexer.raw_param(0).now_or_never().unwrap().unwrap().unwrap();
        assert_matches!(result, TextUnit::RawParam { name, location } => {
            assert_eq!(name, "abc");
            assert_eq!(*location.code.value.borrow(), "$a\\\n\\\nb\\\n\\\nc\\\n>");
            assert_eq!(location.code.start_line_number.get(), 1);
            assert_eq!(location.code.source, Source::Unknown);
            assert_eq!(location.range, 0..14);
        });

        assert_eq!(lexer.peek_char().now_or_never().unwrap(), Ok(Some('>')));
    }

    #[test]
    fn lexer_raw_param_not_parameter() {
        let mut lexer = Lexer::from_memory("$;", Source::Unknown);
        lexer.peek_char().now_or_never().unwrap().unwrap();
        lexer.consume_char();
        assert_eq!(lexer.raw_param(0).now_or_never().unwrap(), Ok(None));
        assert_eq!(lexer.peek_char().now_or_never().unwrap(), Ok(Some(';')));
    }
}