use either::Either;
use hir::{AssocItem, HasVisibility, Module, ModuleDef, Name, PathResolution, ScopeDef};
use ide_db::{
    defs::{Definition, NameRefClass},
    search::SearchScope,
};
use stdx::never;
use syntax::{
    ast::{self, make},
    ted, AstNode, Direction, SyntaxNode, SyntaxToken, T,
};

use crate::{
    assist_context::{AssistContext, Assists},
    AssistId, AssistKind,
};

// Assist: expand_glob_import
//
// Expands glob imports.
//
// ```
// mod foo {
//     pub struct Bar;
//     pub struct Baz;
// }
//
// use foo::*$0;
//
// fn qux(bar: Bar, baz: Baz) {}
// ```
// ->
// ```
// mod foo {
//     pub struct Bar;
//     pub struct Baz;
// }
//
// use foo::{Bar, Baz};
//
// fn qux(bar: Bar, baz: Baz) {}
// ```
pub(crate) fn expand_glob_import(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
    let star = ctx.find_token_syntax_at_offset(T![*])?;
    let use_tree = star.parent().and_then(ast::UseTree::cast)?;
    let (parent, mod_path) = find_parent_and_path(&star)?;
    let target_module = match ctx.sema.resolve_path(&mod_path)? {
        PathResolution::Def(ModuleDef::Module(it)) => it,
        _ => return None,
    };

    let current_scope = ctx.sema.scope(&star.parent()?)?;
    let current_module = current_scope.module();

    let refs_in_target = find_refs_in_mod(ctx, target_module, current_module)?;
    let imported_defs = find_imported_defs(ctx, star)?;

    let target = parent.either(|n| n.syntax().clone(), |n| n.syntax().clone());
    acc.add(
        AssistId("expand_glob_import", AssistKind::RefactorRewrite),
        "Expand glob import",
        target.text_range(),
        |builder| {
            let use_tree = builder.make_mut(use_tree);

            let names_to_import = find_names_to_import(ctx, refs_in_target, imported_defs);
            let expanded = make::use_tree_list(names_to_import.iter().map(|n| {
                let path = make::ext::ident_path(&n.to_string());
                make::use_tree(path, None, None, false)
            }))
            .clone_for_update();

            match use_tree.star_token() {
                Some(star) => {
                    let needs_braces = use_tree.path().is_some() && names_to_import.len() != 1;
                    if needs_braces {
                        ted::replace(star, expanded.syntax())
                    } else {
                        let without_braces = expanded
                            .syntax()
                            .children_with_tokens()
                            .filter(|child| !matches!(child.kind(), T!['{'] | T!['}']))
                            .collect();
                        ted::replace_with_many(star, without_braces)
                    }
                }
                None => never!(),
            }
        },
    )
}

fn find_parent_and_path(
    star: &SyntaxToken,
) -> Option<(Either<ast::UseTree, ast::UseTreeList>, ast::Path)> {
    return star.parent_ancestors().find_map(|n| {
        find_use_tree_list(n.clone())
            .map(|(u, p)| (Either::Right(u), p))
            .or_else(|| find_use_tree(n).map(|(u, p)| (Either::Left(u), p)))
    });

    fn find_use_tree_list(n: SyntaxNode) -> Option<(ast::UseTreeList, ast::Path)> {
        let use_tree_list = ast::UseTreeList::cast(n)?;
        let path = use_tree_list.parent_use_tree().path()?;
        Some((use_tree_list, path))
    }

    fn find_use_tree(n: SyntaxNode) -> Option<(ast::UseTree, ast::Path)> {
        let use_tree = ast::UseTree::cast(n)?;
        let path = use_tree.path()?;
        Some((use_tree, path))
    }
}

fn def_is_referenced_in(def: Definition, ctx: &AssistContext<'_>) -> bool {
    let search_scope = SearchScope::single_file(ctx.file_id());
    def.usages(&ctx.sema).in_scope(search_scope).at_least_one()
}

#[derive(Debug, Clone)]
struct Ref {
    // could be alias
    visible_name: Name,
    def: Definition,
}

impl Ref {
    fn from_scope_def(name: Name, scope_def: ScopeDef) -> Option<Self> {
        match scope_def {
            ScopeDef::ModuleDef(def) => {
                Some(Ref { visible_name: name, def: Definition::from(def) })
            }
            _ => None,
        }
    }
}

#[derive(Debug, Clone)]
struct Refs(Vec<Ref>);

impl Refs {
    fn used_refs(&self, ctx: &AssistContext<'_>) -> Refs {
        Refs(
            self.0
                .clone()
                .into_iter()
                .filter(|r| {
                    if let Definition::Trait(tr) = r.def {
                        if tr.items(ctx.db()).into_iter().any(|ai| {
                            if let AssocItem::Function(f) = ai {
                                def_is_referenced_in(Definition::Function(f), ctx)
                            } else {
                                false
                            }
                        }) {
                            return true;
                        }
                    }

                    def_is_referenced_in(r.def, ctx)
                })
                .collect(),
        )
    }

    fn filter_out_by_defs(&self, defs: Vec<Definition>) -> Refs {
        Refs(self.0.clone().into_iter().filter(|r| !defs.contains(&r.def)).collect())
    }
}

fn find_refs_in_mod(ctx: &AssistContext<'_>, module: Module, visible_from: Module) -> Option<Refs> {
    if !is_mod_visible_from(ctx, module, visible_from) {
        return None;
    }

    let module_scope = module.scope(ctx.db(), Some(visible_from));
    let refs = module_scope.into_iter().filter_map(|(n, d)| Ref::from_scope_def(n, d)).collect();
    Some(Refs(refs))
}

fn is_mod_visible_from(ctx: &AssistContext<'_>, module: Module, from: Module) -> bool {
    match module.parent(ctx.db()) {
        Some(parent) => {
            module.visibility(ctx.db()).is_visible_from(ctx.db(), from.into())
                && is_mod_visible_from(ctx, parent, from)
        }
        None => true,
    }
}

// looks for name refs in parent use block's siblings
//
// mod bar {
//     mod qux {
//         struct Qux;
//     }
//
//     pub use qux::Qux;
// }
//
// ↓ ---------------
// use foo::*$0;
// use baz::Baz;
// ↑ ---------------
fn find_imported_defs(ctx: &AssistContext<'_>, star: SyntaxToken) -> Option<Vec<Definition>> {
    let parent_use_item_syntax = star.parent_ancestors().find_map(|n| {
        if ast::Use::can_cast(n.kind()) {
            Some(n)
        } else {
            None
        }
    })?;

    Some(
        [Direction::Prev, Direction::Next]
            .into_iter()
            .flat_map(|dir| {
                parent_use_item_syntax
                    .siblings(dir.to_owned())
                    .filter(|n| ast::Use::can_cast(n.kind()))
            })
            .flat_map(|n| n.descendants().filter_map(ast::NameRef::cast))
            .filter_map(|r| match NameRefClass::classify(&ctx.sema, &r)? {
                NameRefClass::Definition(
                    def @ (Definition::Macro(_)
                    | Definition::Module(_)
                    | Definition::Function(_)
                    | Definition::Adt(_)
                    | Definition::Variant(_)
                    | Definition::Const(_)
                    | Definition::Static(_)
                    | Definition::Trait(_)
                    | Definition::TypeAlias(_)),
                ) => Some(def),
                _ => None,
            })
            .collect(),
    )
}

fn find_names_to_import(
    ctx: &AssistContext<'_>,
    refs_in_target: Refs,
    imported_defs: Vec<Definition>,
) -> Vec<Name> {
    let used_refs = refs_in_target.used_refs(ctx).filter_out_by_defs(imported_defs);
    used_refs.0.iter().map(|r| r.visible_name.clone()).collect()
}

#[cfg(test)]
mod tests {
    use crate::tests::{check_assist, check_assist_not_applicable};

    use super::*;

    #[test]
    fn expanding_glob_import() {
        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub struct Bar;
    pub struct Baz;
    pub struct Qux;

    pub fn f() {}
}

use foo::*$0;

fn qux(bar: Bar, baz: Baz) {
    f();
}
",
            r"
mod foo {
    pub struct Bar;
    pub struct Baz;
    pub struct Qux;

    pub fn f() {}
}

use foo::{Bar, Baz, f};

fn qux(bar: Bar, baz: Baz) {
    f();
}
",
        )
    }

    #[test]
    fn expanding_glob_import_unused() {
        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub struct Bar;
    pub struct Baz;
    pub struct Qux;

    pub fn f() {}
}

use foo::*$0;

fn qux() {}
",
            r"
mod foo {
    pub struct Bar;
    pub struct Baz;
    pub struct Qux;

    pub fn f() {}
}

use foo::{};

fn qux() {}
",
        )
    }

    #[test]
    fn expanding_glob_import_with_existing_explicit_names() {
        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub struct Bar;
    pub struct Baz;
    pub struct Qux;

    pub fn f() {}
}

use foo::{*$0, f};

fn qux(bar: Bar, baz: Baz) {
    f();
}
",
            r"
mod foo {
    pub struct Bar;
    pub struct Baz;
    pub struct Qux;

    pub fn f() {}
}

use foo::{Bar, Baz, f};

fn qux(bar: Bar, baz: Baz) {
    f();
}
",
        )
    }

    #[test]
    fn expanding_glob_import_with_existing_uses_in_same_module() {
        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub struct Bar;
    pub struct Baz;
    pub struct Qux;

    pub fn f() {}
}

use foo::Bar;
use foo::{*$0, f};

fn qux(bar: Bar, baz: Baz) {
    f();
}
",
            r"
mod foo {
    pub struct Bar;
    pub struct Baz;
    pub struct Qux;

    pub fn f() {}
}

use foo::Bar;
use foo::{Baz, f};

fn qux(bar: Bar, baz: Baz) {
    f();
}
",
        )
    }

    #[test]
    fn expanding_nested_glob_import() {
        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}
    }
}

use foo::{bar::{*$0, f}, baz::*};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
}
",
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}
    }
}

use foo::{bar::{Bar, Baz, f}, baz::*};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
}
",
        );

        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}
    }
}

use foo::{bar::{Bar, Baz, f}, baz::*$0};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
}
",
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}
    }
}

use foo::{bar::{Bar, Baz, f}, baz::g};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
}
",
        );

        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}

        pub mod qux {
            pub fn h() {}
            pub fn m() {}

            pub mod q {
                pub fn j() {}
            }
        }
    }
}

use foo::{
    bar::{*, f},
    baz::{g, qux::*$0}
};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
    h();
    q::j();
}
",
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}

        pub mod qux {
            pub fn h() {}
            pub fn m() {}

            pub mod q {
                pub fn j() {}
            }
        }
    }
}

use foo::{
    bar::{*, f},
    baz::{g, qux::{h, q}}
};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
    h();
    q::j();
}
",
        );

        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}

        pub mod qux {
            pub fn h() {}
            pub fn m() {}

            pub mod q {
                pub fn j() {}
            }
        }
    }
}

use foo::{
    bar::{*, f},
    baz::{g, qux::{h, q::*$0}}
};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
    h();
    j();
}
",
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}

        pub mod qux {
            pub fn h() {}
            pub fn m() {}

            pub mod q {
                pub fn j() {}
            }
        }
    }
}

use foo::{
    bar::{*, f},
    baz::{g, qux::{h, q::j}}
};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
    h();
    j();
}
",
        );

        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}

        pub mod qux {
            pub fn h() {}
            pub fn m() {}

            pub mod q {
                pub fn j() {}
            }
        }
    }
}

use foo::{
    bar::{*, f},
    baz::{g, qux::{q::j, *$0}}
};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
    h();
    j();
}
",
            r"
mod foo {
    pub mod bar {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;

        pub fn f() {}
    }

    pub mod baz {
        pub fn g() {}

        pub mod qux {
            pub fn h() {}
            pub fn m() {}

            pub mod q {
                pub fn j() {}
            }
        }
    }
}

use foo::{
    bar::{*, f},
    baz::{g, qux::{q::j, h}}
};

fn qux(bar: Bar, baz: Baz) {
    f();
    g();
    h();
    j();
}
",
        );
    }

    #[test]
    fn expanding_glob_import_with_macro_defs() {
        check_assist(
            expand_glob_import,
            r#"
//- /lib.rs crate:foo
#[macro_export]
macro_rules! bar {
    () => ()
}

pub fn baz() {}

//- /main.rs crate:main deps:foo
use foo::*$0;

fn main() {
    bar!();
    baz();
}
"#,
            r#"
use foo::{bar, baz};

fn main() {
    bar!();
    baz();
}
"#,
        );
    }

    #[test]
    fn expanding_glob_import_with_trait_method_uses() {
        check_assist(
            expand_glob_import,
            r"
//- /lib.rs crate:foo
pub trait Tr {
    fn method(&self) {}
}
impl Tr for () {}

//- /main.rs crate:main deps:foo
use foo::*$0;

fn main() {
    ().method();
}
",
            r"
use foo::Tr;

fn main() {
    ().method();
}
",
        );

        check_assist(
            expand_glob_import,
            r"
//- /lib.rs crate:foo
pub trait Tr {
    fn method(&self) {}
}
impl Tr for () {}

pub trait Tr2 {
    fn method2(&self) {}
}
impl Tr2 for () {}

//- /main.rs crate:main deps:foo
use foo::*$0;

fn main() {
    ().method();
}
",
            r"
use foo::Tr;

fn main() {
    ().method();
}
",
        );
    }

    #[test]
    fn expanding_is_not_applicable_if_target_module_is_not_accessible_from_current_scope() {
        check_assist_not_applicable(
            expand_glob_import,
            r"
mod foo {
    mod bar {
        pub struct Bar;
    }
}

use foo::bar::*$0;

fn baz(bar: Bar) {}
",
        );

        check_assist_not_applicable(
            expand_glob_import,
            r"
mod foo {
    mod bar {
        pub mod baz {
            pub struct Baz;
        }
    }
}

use foo::bar::baz::*$0;

fn qux(baz: Baz) {}
",
        );
    }

    #[test]
    fn expanding_is_not_applicable_if_cursor_is_not_in_star_token() {
        check_assist_not_applicable(
            expand_glob_import,
            r"
    mod foo {
        pub struct Bar;
        pub struct Baz;
        pub struct Qux;
    }

    use foo::Bar$0;

    fn qux(bar: Bar, baz: Baz) {}
    ",
        )
    }

    #[test]
    fn expanding_glob_import_single_nested_glob_only() {
        check_assist(
            expand_glob_import,
            r"
mod foo {
    pub struct Bar;
}

use foo::{*$0};

struct Baz {
    bar: Bar
}
",
            r"
mod foo {
    pub struct Bar;
}

use foo::{Bar};

struct Baz {
    bar: Bar
}
",
        );
    }
}