use std::{fmt, cmp};
use std::fmt::{Formatter, Debug};

/// Position in the input string
#[derive(PartialEq, Clone, Default)]
pub struct SourcePosition {
    /// The line number on which the error occurred.
    pub line: u32,
    /// The column number on which the error occurred.
    pub column: u32,
    /// The index in the given string which caused the error.
    pub index: u32,
    /// File index if there are multiple files
    pub file: u32,
}

impl fmt::Display for SourcePosition {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        write!(f, "{}:{}", self.line, self.column)
    }
}

impl SourcePosition {
    pub fn with_file(mut self, file: u32) -> Self {
        self.file = file;
        self
    }
}

impl Debug for SourcePosition {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        if f.alternate() {
            f.debug_struct("SourcePosition")
                .field("line", &self.line)
                .field("column", &self.column)
                .field("index", &self.index)
                .field("file", &self.file)
                .finish()
        } else {
            // shorter version
            write!(f, "Pos({}|{}:{})", self.file, self.line, self.column)
        }
    }
}

pub(crate) fn get_line_and_column(s: &str, pos: usize) -> SourcePosition {
    let mut line: usize = 1;
    let mut col: isize = -1;
    for c in s.chars().take(pos + 1) {
        if c == '\n' {
            line += 1;
            col = -1;
        } else {
            col += 1;
        }
    }
    SourcePosition {
        line: line as u32,
        column: cmp::max(col, 0) as u32,
        index: pos as u32,
        file: 0
    }
}

/// Build a span
pub(crate) fn spos(s: &str, pos: usize) -> SourcePosition {
    if pos >= s.len() {
        Default::default()
    } else {
        get_line_and_column(s, pos)
    }
}