use ra_db::{SourceDatabase};
use ra_syntax::{
    AstNode, ast,
    algo::find_node_at_offset,
};
use hir::{db::HirDatabase, source_binder};

use crate::{FilePosition, NavigationTarget, db::RootDatabase, RangeInfo};

pub(crate) fn goto_implementation(
    db: &RootDatabase,
    position: FilePosition,
) -> Option<RangeInfo<Vec<NavigationTarget>>> {
    let file = db.parse(position.file_id);
    let syntax = file.syntax();

    let module = source_binder::module_from_position(db, position)?;
    let krate = module.krate(db)?;

    let node = find_node_at_offset::<ast::NominalDef>(syntax, position.offset)?;
    let ty = match node.kind() {
        ast::NominalDefKind::StructDef(def) => {
            source_binder::struct_from_module(db, module, &def).ty(db)
        }
        ast::NominalDefKind::EnumDef(def) => {
            source_binder::enum_from_module(db, module, &def).ty(db)
        }
    };

    let impls = db.impls_in_crate(krate);

    let navs = impls
        .lookup_impl_blocks(db, &ty)
        .map(|(module, imp)| NavigationTarget::from_impl_block(db, module, &imp));

    Some(RangeInfo::new(node.syntax().range(), navs.collect()))
}

#[cfg(test)]
mod tests {
    use crate::mock_analysis::analysis_and_position;

    fn check_goto(fixuture: &str, expected: &[&str]) {
        let (analysis, pos) = analysis_and_position(fixuture);

        let navs = analysis.goto_implementation(pos).unwrap().unwrap().info;
        assert_eq!(navs.len(), expected.len());
        navs.into_iter()
            .enumerate()
            .for_each(|(i, nav)| nav.assert_match(expected[i]));
    }

    #[test]
    fn goto_implementation_works() {
        check_goto(
            "
            //- /lib.rs
            struct Foo<|>;
            impl Foo {}
            ",
            &["impl IMPL_BLOCK FileId(1) [12; 23)"],
        );
    }

    #[test]
    fn goto_implementation_works_multiple_blocks() {
        check_goto(
            "
            //- /lib.rs
            struct Foo<|>;
            impl Foo {}
            impl Foo {}
            ",
            &[
                "impl IMPL_BLOCK FileId(1) [12; 23)",
                "impl IMPL_BLOCK FileId(1) [24; 35)",
            ],
        );
    }

    #[test]
    fn goto_implementation_works_multiple_mods() {
        check_goto(
            "
            //- /lib.rs
            struct Foo<|>;
            mod a {
                impl super::Foo {}
            }
            mod b {
                impl super::Foo {}
            }
            ",
            &[
                "impl IMPL_BLOCK FileId(1) [24; 42)",
                "impl IMPL_BLOCK FileId(1) [57; 75)",
            ],
        );
    }

    #[test]
    fn goto_implementation_works_multiple_files() {
        check_goto(
            "
            //- /lib.rs
            struct Foo<|>;
            mod a;
            mod b;
            //- /a.rs
            impl crate::Foo {}
            //- /b.rs
            impl crate::Foo {}
            ",
            &[
                "impl IMPL_BLOCK FileId(2) [0; 18)",
                "impl IMPL_BLOCK FileId(3) [0; 18)",
            ],
        );
    }
}