use std::ops::Deref;
use std::sync::Arc;

use ruff_source_file::LineIndex;

use crate::vfs::VfsFile;
use crate::Db;

/// Reads the content of file.
#[salsa::tracked]
pub fn source_text(db: &dyn Db, file: VfsFile) -> SourceText {
    let content = file.read(db);

    SourceText {
        inner: Arc::from(content),
    }
}

/// Computes the [`LineIndex`] for `file`.
#[salsa::tracked]
pub fn line_index(db: &dyn Db, file: VfsFile) -> LineIndex {
    let source = source_text(db, file);

    LineIndex::from_source_text(&source)
}

/// The source text of a [`VfsFile`].
///
/// Cheap cloneable in `O(1)`.
#[derive(Clone, Eq, PartialEq)]
pub struct SourceText {
    inner: Arc<str>,
}

impl SourceText {
    pub fn as_str(&self) -> &str {
        &self.inner
    }
}

impl Deref for SourceText {
    type Target = str;

    fn deref(&self) -> &str {
        self.as_str()
    }
}

impl std::fmt::Debug for SourceText {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_tuple("SourceText").field(&self.inner).finish()
    }
}

#[cfg(test)]
mod tests {
    use filetime::FileTime;
    use salsa::EventKind;

    use ruff_source_file::OneIndexed;
    use ruff_text_size::TextSize;

    use crate::file_system::FileSystemPath;
    use crate::source::{line_index, source_text};
    use crate::tests::TestDb;
    use crate::Db;

    #[test]
    fn re_runs_query_when_file_revision_changes() {
        let mut db = TestDb::new();
        let path = FileSystemPath::new("test.py");

        db.file_system_mut().write_file(path, "x = 10".to_string());

        let file = db.file(path);

        assert_eq!(&*source_text(&db, file), "x = 10");

        db.file_system_mut().write_file(path, "x = 20".to_string());
        file.set_revision(&mut db).to(FileTime::now().into());

        assert_eq!(&*source_text(&db, file), "x = 20");
    }

    #[test]
    fn text_is_cached_if_revision_is_unchanged() {
        let mut db = TestDb::new();
        let path = FileSystemPath::new("test.py");

        db.file_system_mut().write_file(path, "x = 10".to_string());

        let file = db.file(path);

        assert_eq!(&*source_text(&db, file), "x = 10");

        // Change the file permission only
        file.set_permissions(&mut db).to(Some(0o777));

        db.clear_salsa_events();
        assert_eq!(&*source_text(&db, file), "x = 10");

        let events = db.take_salsa_events();

        assert!(!events
            .iter()
            .any(|event| matches!(event.kind, EventKind::WillExecute { .. })));
    }

    #[test]
    fn line_index_for_source() {
        let mut db = TestDb::new();
        let path = FileSystemPath::new("test.py");

        db.file_system_mut()
            .write_file(path, "x = 10\ny = 20".to_string());

        let file = db.file(path);
        let index = line_index(&db, file);
        let text = source_text(&db, file);

        assert_eq!(index.line_count(), 2);
        assert_eq!(
            index.line_start(OneIndexed::from_zero_indexed(0), &text),
            TextSize::new(0)
        );
    }
}