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//! A module for AST elements that represent a position in a source file. Implementing thie Node trait allows
//! an ergonomic means of extracting line and column information from an item.

use pyo3::{PyAny, PyResult};

/// A trait for AST elements that represent a position in a source file. Implementing this trait allows
/// an ergonomic means of extracting line and column information from an item.
pub trait Node {
    /// A method for getting the starting line number of the node. This may not exist for all node types.
    fn lineno(&self) -> Option<usize> {
        None
    }

    /// A method for getting the starting column of the node. This may not exist for all node types.
    fn col_offset(&self) -> Option<usize> {
        None
    }

    /// A method for getting the ending line number of the node. This may not exist for all node types.
    fn end_lineno(&self) -> Option<usize> {
        None
    }

    /// A method for getting the ending column of the node. This may not exist for all node types.
    fn end_col_offset(&self) -> Option<usize> {
        None
    }

    /// Generate an error message for the current code, adding line and column number.
    fn error_message<S1: Into<String>, S2: Into<String>>(&self, mod_name: S1, message: S2) -> String {
        format!("{} {}:{:?}:{:?}", message.into(), mod_name.into(), self.lineno(), self.col_offset())
    }
}

// These will only work on objects of Python's ast library's nodes, but you can try them on anything.
impl Node for PyAny {
    /// A method for getting the starting line number of the node. This may not exist for all node types.
    fn lineno(&self) -> Option<usize> {
        let lineno = self.getattr("lineno");
        if let Ok(ln_any) = lineno {
            let ln: PyResult<usize> = ln_any.extract();
            if let Ok(l) = ln {
                Some(l)
            } else {
                None
            }
        }
        else { None }
    }

    /// A method for getting the starting column of the node. This may not exist for all node types.
    fn col_offset(&self) -> Option<usize> {
        let col_offset = self.getattr("col_offset");
        if let Ok(offset_any) = col_offset {
            let ln: PyResult<usize> = offset_any.extract();
            if let Ok(l) = ln {
                Some(l)
            } else {
                None
            }
        }
        else { None }
    }

    /// A method for getting the ending line number of the node. This may not exist for all node types.
    fn end_lineno(&self) -> Option<usize> {
        let lineno = self.getattr("end_lineno");
        if let Ok(ln_any) = lineno {
            let ln: PyResult<usize> = ln_any.extract();
            if let Ok(l) = ln {
                Some(l)
            } else {
                None
            }
        }
        else { None }
    }

    /// A method for getting the ending column of the node. This may not exist for all node types.
    fn end_col_offset(&self) -> Option<usize> {
        let col_offset = self.getattr("end_col_offset");
        if let Ok(offset_any) = col_offset {
            let ln: PyResult<usize> = offset_any.extract();
            if let Ok(l) = ln {
                Some(l)
            } else {
                None
            }
        }
        else { None }
    }
}