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use crate::source::DecodedInput;
use std::convert::TryInto;

/// Representation of any location in the given input
#[repr(C)]
#[derive(Clone, PartialEq, Eq, Copy, Default)]
pub struct Loc {
    /// Begin of the `Loc` range
    pub begin: usize,

    /// End of the `Loc` range
    pub end: usize,
}

impl Loc {
    /// Converts location to a range
    pub fn to_range(&self) -> std::ops::Range<usize> {
        self.begin..self.end
    }

    /// Returns size of the `Loc` (i.e. `end - begin`)
    pub fn size(&self) -> usize {
        self.end - self.begin
    }

    /// Returns a new `Loc` with given `begin` and current `end`
    pub fn with_begin(&self, begin: usize) -> Loc {
        Self {
            begin,
            end: self.end,
        }
    }

    /// Returns a new `Loc` with given `end` and current `begin`
    pub fn with_end(&self, end: usize) -> Loc {
        Self {
            begin: self.begin,
            end,
        }
    }

    /// Adds given `delta` to `begin`
    pub fn adjust_begin(&self, delta: i32) -> Loc {
        let begin: i32 = self
            .begin
            .try_into()
            .expect("failed to convert location to i32 (is it too big?)");
        let begin: usize = (begin + delta)
            .try_into()
            .expect("failed to convert location to usize (is it negative?)");
        Self {
            begin,
            end: self.end,
        }
    }

    /// Adds given `delta` to `end`
    pub fn adjust_end(&self, d: i32) -> Loc {
        let end: i32 = self
            .end
            .try_into()
            .expect("failed to convert location to i32 (is it too big?)");
        let end: usize = (end + d)
            .try_into()
            .expect("failed to convert location to usize (is it negative?)");
        Self {
            begin: self.begin,
            end,
        }
    }

    /// Returns a new `Loc` with the same `begin`, but adjusted `end`,
    /// so that its size is equal to given `new_size`
    pub fn resize(&self, new_size: usize) -> Loc {
        self.with_end(self.begin + new_size)
    }

    /// Joins two `Loc`s by choosing `min(begin)` + `max(end)`
    pub fn join(&self, other: &Self) -> Loc {
        Self {
            begin: std::cmp::min(self.begin, other.begin),
            end: std::cmp::max(self.end, other.end),
        }
    }

    pub(crate) fn maybe_join(&self, other: &Option<Loc>) -> Loc {
        match other.as_ref() {
            Some(other) => self.join(other),
            None => *self,
        }
    }

    /// Returns true if `Loc` is empty (i.e. `begin` == `end`)
    pub fn is_empty(&self) -> bool {
        self.begin == self.end
    }

    pub(crate) fn begin_line_col(&self, input: &DecodedInput) -> Option<(usize, usize)> {
        input.line_col_for_pos(self.begin)
    }

    pub(crate) fn expand_to_line(&self, input: &DecodedInput) -> Option<(usize, Loc)> {
        let (begin_line, _) = self.begin_line_col(input)?;
        let line_no = begin_line;
        let line = input.line_at(line_no);
        Some((
            line_no,
            Self {
                begin: line.start,
                end: line.line_end(),
            },
        ))
    }

    /// Returns source code of the current `Loc` on a given `Input`
    pub fn source(&self, input: &DecodedInput) -> Option<String> {
        let bytes = input.substr_at(self.begin, self.end)?;
        Some(String::from_utf8_lossy(bytes).into_owned())
    }

    pub(crate) fn print(&self, name: &str) {
        println!(
            "{}{} {}",
            " ".repeat(self.begin),
            "~".repeat(self.size()),
            name
        )
    }
}

impl std::fmt::Debug for Loc {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&format!("{}...{}", self.begin, self.end))
    }
}

#[test]
fn test_to_range() {
    assert_eq!(Loc { begin: 10, end: 20 }.to_range(), 10..20)
}

#[test]
fn test_fmt() {
    assert_eq!(format!("{:?}", Loc { begin: 10, end: 20 }), "10...20")
}

#[test]
fn test_is_empty() {
    assert!(Loc { begin: 1, end: 1 }.is_empty());
    assert!(!Loc { begin: 1, end: 2 }.is_empty());
}