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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

use move_symbol_pool::Symbol;
use once_cell::sync::Lazy;
use serde::{Deserialize, Serialize};
use std::{
    cmp::Ordering,
    fmt,
    hash::{Hash, Hasher},
    ops::Range,
};

//**************************************************************************************************
// Loc
//**************************************************************************************************

/// An index into a file.
/// Much like the `codespan` crate, a `u32` is used here to for space efficiency.
/// However, this assumes no file is larger than 4GB, so this might become a `usize` in the future
/// if the space concerns turn out to not be an issue.
pub type ByteIndex = u32;

#[derive(Debug, Copy, Clone, Eq, PartialEq, Serialize, Deserialize, Hash)]
/// The `Loc` struct is used to define a location in a file; where the file is considered to be a
/// vector of bytes, and the range for a given `Loc` is defined by start and end index into that
/// byte vector
pub struct Loc {
    /// The file the location points to
    file: Symbol,
    /// The start byte index into file
    start: ByteIndex,
    /// The end byte index into file
    end: ByteIndex,
}

impl Loc {
    pub fn new(file: Symbol, start: ByteIndex, end: ByteIndex) -> Loc {
        Loc { file, start, end }
    }

    pub fn file(self) -> Symbol {
        self.file
    }

    pub fn start(self) -> ByteIndex {
        self.start
    }

    pub fn end(self) -> ByteIndex {
        self.end
    }

    pub fn usize_range(self) -> Range<usize> {
        Range {
            start: self.start as usize,
            end: self.end as usize,
        }
    }
}

impl PartialOrd for Loc {
    fn partial_cmp(&self, other: &Loc) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for Loc {
    fn cmp(&self, other: &Loc) -> Ordering {
        let file_ord = self.file.cmp(&other.file);
        if file_ord != Ordering::Equal {
            return file_ord;
        }

        let start_ord = self.start.cmp(&other.start);
        if start_ord != Ordering::Equal {
            return start_ord;
        }

        self.end.cmp(&other.end)
    }
}

//**************************************************************************************************
// Spanned
//**************************************************************************************************

static NO_LOC_FILE: Lazy<Symbol> = Lazy::new(|| Symbol::from(""));

#[derive(Copy, Clone)]
pub struct Spanned<T> {
    pub loc: Loc,
    pub value: T,
}

impl<T> Spanned<T> {
    pub fn new(loc: Loc, value: T) -> Spanned<T> {
        Spanned { loc, value }
    }

    pub fn unsafe_no_loc(value: T) -> Spanned<T> {
        Spanned {
            value,
            loc: Loc::new(*NO_LOC_FILE, 0, 0),
        }
    }
}

impl<T: PartialEq> PartialEq for Spanned<T> {
    fn eq(&self, other: &Spanned<T>) -> bool {
        self.value == other.value
    }
}

impl<T: Eq> Eq for Spanned<T> {}

impl<T: Hash> Hash for Spanned<T> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.value.hash(state);
    }
}

impl<T: PartialOrd> PartialOrd for Spanned<T> {
    fn partial_cmp(&self, other: &Spanned<T>) -> Option<Ordering> {
        self.value.partial_cmp(&other.value)
    }
}

impl<T: Ord> Ord for Spanned<T> {
    fn cmp(&self, other: &Spanned<T>) -> Ordering {
        self.value.cmp(&other.value)
    }
}

impl<T: fmt::Display> fmt::Display for Spanned<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> std::fmt::Result {
        write!(f, "{}", &self.value)
    }
}

impl<T: fmt::Debug> fmt::Debug for Spanned<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{:?}", &self.value)
    }
}

/// Function used to have nearly tuple-like syntax for creating a Spanned
pub const fn sp<T>(loc: Loc, value: T) -> Spanned<T> {
    Spanned { loc, value }
}

/// Macro used to create a tuple-like pattern match for Spanned
#[macro_export]
macro_rules! sp {
    (_, $value:pat) => {
        $crate::location::Spanned { value: $value, .. }
    };
    ($loc:pat, _) => {
        $crate::location::Spanned { loc: $loc, .. }
    };
    ($loc:pat, $value:pat) => {
        $crate::location::Spanned {
            loc: $loc,
            value: $value,
        }
    };
}