use std::error::Error as StdError;
use std::fmt::{Display, Formatter, Result};

/// Type representing a TOML parse error
#[derive(Debug, Clone, Eq, PartialEq, Hash)]
pub struct TomlError {
    message: String,
    raw: Option<String>,
    keys: Vec<String>,
    span: Option<std::ops::Range<usize>>,
}

impl TomlError {
    #[cfg(feature = "parse")]
    pub(crate) fn new(
        error: winnow::error::ParseError<
            crate::parser::prelude::Input<'_>,
            winnow::error::ContextError,
        >,
        mut raw: crate::parser::prelude::Input<'_>,
    ) -> Self {
        use winnow::stream::Stream;

        let offset = error.offset();
        let span = if offset == raw.len() {
            offset..offset
        } else {
            offset..(offset + 1)
        };

        let message = error.inner().to_string();
        let raw = raw.finish();

        Self {
            message,
            raw: Some(String::from_utf8(raw.to_owned()).expect("original document was utf8")),
            keys: Vec::new(),
            span: Some(span),
        }
    }

    #[cfg(any(feature = "serde", feature = "parse"))]
    pub(crate) fn custom(message: String, span: Option<std::ops::Range<usize>>) -> Self {
        Self {
            message,
            raw: None,
            keys: Vec::new(),
            span,
        }
    }

    #[cfg(feature = "serde")]
    pub(crate) fn add_key(&mut self, key: String) {
        self.keys.insert(0, key);
    }

    /// What went wrong
    pub fn message(&self) -> &str {
        &self.message
    }

    /// The start/end index into the original document where the error occurred
    pub fn span(&self) -> Option<std::ops::Range<usize>> {
        self.span.clone()
    }

    #[cfg(feature = "serde")]
    pub(crate) fn set_span(&mut self, span: Option<std::ops::Range<usize>>) {
        self.span = span;
    }

    #[cfg(feature = "serde")]
    pub(crate) fn set_raw(&mut self, raw: Option<String>) {
        self.raw = raw;
    }
}

/// Displays a TOML parse error
///
/// # Example
///
/// TOML parse error at line 1, column 10
///   |
/// 1 | 00:32:00.a999999
///   |          ^
/// Unexpected `a`
/// Expected `digit`
/// While parsing a Time
/// While parsing a Date-Time
impl Display for TomlError {
    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
        let mut context = false;
        if let (Some(raw), Some(span)) = (&self.raw, self.span()) {
            context = true;

            let (line, column) = translate_position(raw.as_bytes(), span.start);
            let line_num = line + 1;
            let col_num = column + 1;
            let gutter = line_num.to_string().len();
            let content = raw.split('\n').nth(line).expect("valid line number");
            let highlight_len = span.end - span.start;
            // Allow highlight to go one past the line
            let highlight_len = highlight_len.min(content.len().saturating_sub(column));

            writeln!(
                f,
                "TOML parse error at line {}, column {}",
                line_num, col_num
            )?;
            //   |
            for _ in 0..=gutter {
                write!(f, " ")?;
            }
            writeln!(f, "|")?;

            // 1 | 00:32:00.a999999
            write!(f, "{} | ", line_num)?;
            writeln!(f, "{}", content)?;

            //   |          ^
            for _ in 0..=gutter {
                write!(f, " ")?;
            }
            write!(f, "|")?;
            for _ in 0..=column {
                write!(f, " ")?;
            }
            // The span will be empty at eof, so we need to make sure we always print at least
            // one `^`
            write!(f, "^")?;
            for _ in 1..highlight_len {
                write!(f, "^")?;
            }
            writeln!(f)?;
        }
        writeln!(f, "{}", self.message)?;
        if !context && !self.keys.is_empty() {
            writeln!(f, "in `{}`", self.keys.join("."))?;
        }

        Ok(())
    }
}

impl StdError for TomlError {
    fn description(&self) -> &'static str {
        "TOML parse error"
    }
}

fn translate_position(input: &[u8], index: usize) -> (usize, usize) {
    if input.is_empty() {
        return (0, index);
    }

    let safe_index = index.min(input.len() - 1);
    let column_offset = index - safe_index;
    let index = safe_index;

    let nl = input[0..index]
        .iter()
        .rev()
        .enumerate()
        .find(|(_, b)| **b == b'\n')
        .map(|(nl, _)| index - nl - 1);
    let line_start = match nl {
        Some(nl) => nl + 1,
        None => 0,
    };
    let line = input[0..line_start].iter().filter(|b| **b == b'\n').count();

    let column = std::str::from_utf8(&input[line_start..=index])
        .map(|s| s.chars().count() - 1)
        .unwrap_or_else(|_| index - line_start);
    let column = column + column_offset;

    (line, column)
}

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

    #[test]
    fn empty() {
        let input = b"";
        let index = 0;
        let position = translate_position(&input[..], index);
        assert_eq!(position, (0, 0));
    }

    #[test]
    fn start() {
        let input = b"Hello";
        let index = 0;
        let position = translate_position(&input[..], index);
        assert_eq!(position, (0, 0));
    }

    #[test]
    fn end() {
        let input = b"Hello";
        let index = input.len() - 1;
        let position = translate_position(&input[..], index);
        assert_eq!(position, (0, input.len() - 1));
    }

    #[test]
    fn after() {
        let input = b"Hello";
        let index = input.len();
        let position = translate_position(&input[..], index);
        assert_eq!(position, (0, input.len()));
    }

    #[test]
    fn first_line() {
        let input = b"Hello\nWorld\n";
        let index = 2;
        let position = translate_position(&input[..], index);
        assert_eq!(position, (0, 2));
    }

    #[test]
    fn end_of_line() {
        let input = b"Hello\nWorld\n";
        let index = 5;
        let position = translate_position(&input[..], index);
        assert_eq!(position, (0, 5));
    }

    #[test]
    fn start_of_second_line() {
        let input = b"Hello\nWorld\n";
        let index = 6;
        let position = translate_position(&input[..], index);
        assert_eq!(position, (1, 0));
    }

    #[test]
    fn second_line() {
        let input = b"Hello\nWorld\n";
        let index = 8;
        let position = translate_position(&input[..], index);
        assert_eq!(position, (1, 2));
    }
}