use std::{
    path::{Path, PathBuf},
    sync::Arc,
};

use util::paths::SanitizedPath;

/// A list of absolute paths, in a specific order.
///
/// The paths are stored in lexicographic order, so that they can be compared to
/// other path lists without regard to the order of the paths.
#[derive(Default, PartialEq, Eq, Debug, Clone)]
pub struct PathList {
    paths: Arc<[PathBuf]>,
    order: Arc<[usize]>,
}

#[derive(Debug)]
pub struct SerializedPathList {
    pub paths: String,
    pub order: String,
}

impl PathList {
    pub fn new<P: AsRef<Path>>(paths: &[P]) -> Self {
        let mut indexed_paths: Vec<(usize, PathBuf)> = paths
            .iter()
            .enumerate()
            .map(|(ix, path)| (ix, SanitizedPath::from(path).into()))
            .collect();
        indexed_paths.sort_by(|(_, a), (_, b)| a.cmp(b));
        let order = indexed_paths.iter().map(|e| e.0).collect::<Vec<_>>().into();
        let paths = indexed_paths
            .into_iter()
            .map(|e| e.1)
            .collect::<Vec<_>>()
            .into();
        Self { order, paths }
    }

    pub fn is_empty(&self) -> bool {
        self.paths.is_empty()
    }

    pub fn paths(&self) -> &[PathBuf] {
        self.paths.as_ref()
    }

    pub fn order(&self) -> &[usize] {
        self.order.as_ref()
    }

    pub fn is_lexicographically_ordered(&self) -> bool {
        self.order.iter().enumerate().all(|(i, &j)| i == j)
    }

    pub fn deserialize(serialized: &SerializedPathList) -> Self {
        let mut paths: Vec<PathBuf> = if serialized.paths.is_empty() {
            Vec::new()
        } else {
            serialized.paths.split('\n').map(PathBuf::from).collect()
        };

        let mut order: Vec<usize> = serialized
            .order
            .split(',')
            .filter_map(|s| s.parse().ok())
            .collect();

        if !paths.is_sorted() || order.len() != paths.len() {
            order = (0..paths.len()).collect();
            paths.sort();
        }

        Self {
            paths: paths.into(),
            order: order.into(),
        }
    }

    pub fn serialize(&self) -> SerializedPathList {
        use std::fmt::Write as _;

        let mut paths = String::new();
        for path in self.paths.iter() {
            if !paths.is_empty() {
                paths.push('\n');
            }
            paths.push_str(&path.to_string_lossy());
        }

        let mut order = String::new();
        for ix in self.order.iter() {
            if !order.is_empty() {
                order.push(',');
            }
            write!(&mut order, "{}", *ix).unwrap();
        }
        SerializedPathList { paths, order }
    }
}

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

    #[test]
    fn test_path_list() {
        let list1 = PathList::new(&["a/d", "a/c"]);
        let list2 = PathList::new(&["a/c", "a/d"]);

        assert_eq!(list1.paths(), list2.paths());
        assert_ne!(list1, list2);
        assert_eq!(list1.order(), &[1, 0]);
        assert_eq!(list2.order(), &[0, 1]);

        let list1_deserialized = PathList::deserialize(&list1.serialize());
        assert_eq!(list1_deserialized, list1);

        let list2_deserialized = PathList::deserialize(&list2.serialize());
        assert_eq!(list2_deserialized, list2);
    }
}