skyscraper 0.7.0

//! <https://www.w3.org/TR/2017/REC-xpath-31-20170321/#id-string-concat-expr>

use std::fmt::Display;

use nom::{bytes::complete::tag, error::context, multi::many0, sequence::tuple};

use crate::{
    xpath::{
        grammar::{
            data_model::{AnyAtomicType, XpathItem},
            recipes::Res,
            whitespace_recipes::ws,
        },
        xpath_item_set::XpathItemSet,
        ExpressionApplyError, XpathExpressionContext,
    },
    xpath_item_set,
};

use super::{
    primary_expressions::static_function_calls::func_data,
    sequence_expressions::constructing_sequences::{range_expr, RangeExpr},
};

pub fn string_concat_expr(input: &str) -> Res<&str, StringConcatExpr> {
    // https://www.w3.org/TR/2017/REC-xpath-31-20170321/#prod-xpath31-StringConcatExpr

    context(
        "string_concat_expr",
        tuple((range_expr, many0(ws((tag("||"), range_expr))))),
    )(input)
    .map(|(next_input, res)| {
        let items = res.1.into_iter().map(|res| res.1).collect();
        (next_input, StringConcatExpr { expr: res.0, items })
    })
}

#[derive(PartialEq, Debug, Clone)]
pub struct StringConcatExpr {
    pub expr: RangeExpr,
    pub items: Vec<RangeExpr>,
}

impl Display for StringConcatExpr {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.expr)?;
        for x in &self.items {
            write!(f, " || {}", x)?;
        }

        Ok(())
    }
}

impl StringConcatExpr {
    pub(crate) fn eval<'tree>(
        &self,
        context: &XpathExpressionContext<'tree>,
    ) -> Result<XpathItemSet<'tree>, ExpressionApplyError> {
        // Evaluate the first expression.
        let result = self.expr.eval(context)?;

        // If there's only one parameter, return its eval.
        if self.items.is_empty() {
            return Ok(result);
        }

        // Atomize the first operand and cast to string.
        let atomized = func_data(&result, context.item_tree)?;
        let mut concatenated = String::new();
        for a in &atomized {
            concatenated.push_str(&a.to_string());
        }

        // Evaluate and concatenate each additional operand.
        for item in &self.items {
            let item_result = item.eval(context)?;
            let item_atomized = func_data(&item_result, context.item_tree)?;
            for a in &item_atomized {
                concatenated.push_str(&a.to_string());
            }
        }

        Ok(xpath_item_set![XpathItem::AnyAtomicType(
            AnyAtomicType::String(concatenated),
        )])
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn string_concat_expr_should_parse() {
        // arrange
        let input = "a||b||c";

        // act
        let (next_input, res) = string_concat_expr(input).unwrap();

        // assert
        assert_eq!(next_input, "");
        assert_eq!(res.to_string(), "a || b || c");
    }

    #[test]
    fn string_concat_expr_should_parse_whitespace() {
        // arrange
        let input = "a || b || c";

        // act
        let (next_input, res) = string_concat_expr(input).unwrap();

        // assert
        assert_eq!(next_input, "");
        assert_eq!(res.to_string(), "a || b || c");
    }
}