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use crate::traits::{Error, Position};

#[cfg(not(feature = "std"))]
extern crate alloc;

#[cfg(not(feature = "std"))]
use alloc::fmt::Formatter;
#[cfg(not(feature = "std"))]
use alloc::vec::Vec;

#[cfg_attr(feature = "std", derive(Debug))]
#[derive(Copy, Clone, Default, PartialEq, Eq)]
pub struct SimplePosition {
    pub index: u32,
    pub line: u32,
    pub column: u32,
}

impl SimplePosition {
    pub fn next(&self, c: char) -> Self {
        let new_line = c == '\n';
        Self {
            index: self.index + 1,
            line: if new_line { self.line + 1 } else { self.line },
            column: if new_line { 0 } else { self.column + 1 },
        }
    }
}

impl Position for SimplePosition {
    fn index(&self) -> u32 {
        self.index
    }

    fn line(&self) -> u32 {
        self.line
    }

    fn column(&self) -> u32 {
        self.column
    }
}

impl core::ops::Sub<Self> for SimplePosition {
    type Output = i32;

    fn sub(self, rhs: SimplePosition) -> Self::Output {
        if self.index > rhs.index {
            (self.index - rhs.index) as i32
        } else {
            -((rhs.index - self.index) as i32)
        }
    }
}

#[cfg_attr(feature = "std", derive(Debug, PartialEq, Eq))]
pub struct SimpleError {
    pub reasons: Vec<(SimplePosition, &'static str)>,
}

#[cfg(not(feature = "std"))]
impl core::fmt::Debug for SimpleError {
    fn fmt(&self, _f: &mut Formatter<'_>) -> core::fmt::Result {
        Ok(())
    }
}

impl Error for SimpleError {
    type Position = SimplePosition;

    fn reasons(&self) -> &[(Self::Position, &'static str)] {
        &self.reasons[..]
    }

    fn add_reason(self, position: Self::Position, reason: &'static str) -> Self {
        let mut reasons = self.reasons;
        reasons.push((position, reason));
        Self { reasons }
    }
}