use ra_assists::auto_import;
use ra_syntax::{ast, AstNode, SmolStr};
use ra_text_edit::TextEditBuilder;
use rustc_hash::FxHashMap;

use crate::completion::{CompletionContext, CompletionItem, CompletionKind, Completions};

pub(super) fn complete_scope(acc: &mut Completions, ctx: &CompletionContext) {
    if ctx.is_trivial_path {
        let names = ctx.analyzer.all_names(ctx.db);
        names.into_iter().for_each(|(name, res)| acc.add_resolution(ctx, name.to_string(), &res));

        // auto-import
        // We fetch ident from the original file, because we need to pre-filter auto-imports
        if ast::NameRef::cast(ctx.token.parent()).is_some() {
            let import_resolver = ImportResolver::new();
            let import_names = import_resolver.all_names(ctx.token.text());
            import_names.into_iter().for_each(|(name, path)| {
                let edit = {
                    let mut builder = TextEditBuilder::default();
                    builder.replace(ctx.source_range(), name.to_string());
                    auto_import::auto_import_text_edit(
                        &ctx.token.parent(),
                        &ctx.token.parent(),
                        &path,
                        &mut builder,
                    );
                    builder.finish()
                };

                // Hack: copied this check form conv.rs beacause auto import can produce edits
                // that invalidate assert in conv_with.
                if edit
                    .as_atoms()
                    .iter()
                    .filter(|atom| !ctx.source_range().is_subrange(&atom.delete))
                    .all(|atom| ctx.source_range().intersection(&atom.delete).is_none())
                {
                    CompletionItem::new(
                        CompletionKind::Reference,
                        ctx.source_range(),
                        build_import_label(&name, &path),
                    )
                    .text_edit(edit)
                    .add_to(acc);
                }
            });
        }
    }
}

fn build_import_label(name: &str, path: &[SmolStr]) -> String {
    let mut buf = String::with_capacity(64);
    buf.push_str(name);
    buf.push_str(" (");
    fmt_import_path(path, &mut buf);
    buf.push_str(")");
    buf
}

fn fmt_import_path(path: &[SmolStr], buf: &mut String) {
    let mut segments = path.iter();
    if let Some(s) = segments.next() {
        buf.push_str(&s);
    }
    for s in segments {
        buf.push_str("::");
        buf.push_str(&s);
    }
}

#[derive(Debug, Clone, Default)]
pub(crate) struct ImportResolver {
    // todo: use fst crate or something like that
    dummy_names: Vec<(SmolStr, Vec<SmolStr>)>,
}

impl ImportResolver {
    pub(crate) fn new() -> Self {
        let dummy_names = vec![
            (SmolStr::new("fmt"), vec![SmolStr::new("std"), SmolStr::new("fmt")]),
            (SmolStr::new("io"), vec![SmolStr::new("std"), SmolStr::new("io")]),
            (SmolStr::new("iter"), vec![SmolStr::new("std"), SmolStr::new("iter")]),
            (SmolStr::new("hash"), vec![SmolStr::new("std"), SmolStr::new("hash")]),
            (
                SmolStr::new("Debug"),
                vec![SmolStr::new("std"), SmolStr::new("fmt"), SmolStr::new("Debug")],
            ),
            (
                SmolStr::new("Display"),
                vec![SmolStr::new("std"), SmolStr::new("fmt"), SmolStr::new("Display")],
            ),
            (
                SmolStr::new("Hash"),
                vec![SmolStr::new("std"), SmolStr::new("hash"), SmolStr::new("Hash")],
            ),
            (
                SmolStr::new("Hasher"),
                vec![SmolStr::new("std"), SmolStr::new("hash"), SmolStr::new("Hasher")],
            ),
            (
                SmolStr::new("Iterator"),
                vec![SmolStr::new("std"), SmolStr::new("iter"), SmolStr::new("Iterator")],
            ),
        ];

        ImportResolver { dummy_names }
    }

    // Returns a map of importable items filtered by name.
    // The map associates item name with its full path.
    // todo: should return Resolutions
    pub(crate) fn all_names(&self, name: &str) -> FxHashMap<SmolStr, Vec<SmolStr>> {
        if name.len() > 1 {
            self.dummy_names.iter().filter(|(n, _)| n.contains(name)).cloned().collect()
        } else {
            FxHashMap::default()
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::completion::{do_completion, CompletionItem, CompletionKind};
    use insta::assert_debug_snapshot_matches;

    fn do_reference_completion(code: &str) -> Vec<CompletionItem> {
        do_completion(code, CompletionKind::Reference)
    }

    #[test]
    fn completes_bindings_from_let() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                fn quux(x: i32) {
                    let y = 92;
                    1 + <|>;
                    let z = ();
                }
                "
            ),
            @r###"[
    CompletionItem {
        label: "quux",
        source_range: [91; 91),
        delete: [91; 91),
        insert: "quux($0)",
        kind: Function,
        detail: "fn quux(x: i32)",
    },
    CompletionItem {
        label: "x",
        source_range: [91; 91),
        delete: [91; 91),
        insert: "x",
        kind: Binding,
        detail: "i32",
    },
    CompletionItem {
        label: "y",
        source_range: [91; 91),
        delete: [91; 91),
        insert: "y",
        kind: Binding,
        detail: "i32",
    },
]"###
        );
    }

    #[test]
    fn completes_bindings_from_if_let() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                fn quux() {
                    if let Some(x) = foo() {
                        let y = 92;
                    };
                    if let Some(a) = bar() {
                        let b = 62;
                        1 + <|>
                    }
                }
                "
            ),
            @r###"[
    CompletionItem {
        label: "a",
        source_range: [242; 242),
        delete: [242; 242),
        insert: "a",
        kind: Binding,
    },
    CompletionItem {
        label: "b",
        source_range: [242; 242),
        delete: [242; 242),
        insert: "b",
        kind: Binding,
        detail: "i32",
    },
    CompletionItem {
        label: "quux",
        source_range: [242; 242),
        delete: [242; 242),
        insert: "quux()$0",
        kind: Function,
        detail: "fn quux()",
    },
]"###
        );
    }

    #[test]
    fn completes_bindings_from_for() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                fn quux() {
                    for x in &[1, 2, 3] {
                        <|>
                    }
                }
                "
            ),
            @r###"[
    CompletionItem {
        label: "quux",
        source_range: [95; 95),
        delete: [95; 95),
        insert: "quux()$0",
        kind: Function,
        detail: "fn quux()",
    },
    CompletionItem {
        label: "x",
        source_range: [95; 95),
        delete: [95; 95),
        insert: "x",
        kind: Binding,
    },
]"###
        );
    }

    #[test]
    fn completes_generic_params() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                fn quux<T>() {
                    <|>
                }
                "
            ),
            @r###"[
    CompletionItem {
        label: "T",
        source_range: [52; 52),
        delete: [52; 52),
        insert: "T",
        kind: TypeParam,
    },
    CompletionItem {
        label: "quux",
        source_range: [52; 52),
        delete: [52; 52),
        insert: "quux()$0",
        kind: Function,
        detail: "fn quux<T>()",
    },
]"###
        );
    }

    #[test]
    fn completes_generic_params_in_struct() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                struct X<T> {
                    x: <|>
                }
                "
            ),
            @r###"[
    CompletionItem {
        label: "T",
        source_range: [54; 54),
        delete: [54; 54),
        insert: "T",
        kind: TypeParam,
    },
    CompletionItem {
        label: "X",
        source_range: [54; 54),
        delete: [54; 54),
        insert: "X",
        kind: Struct,
    },
]"###
        );
    }

    #[test]
    fn completes_module_items() {
        assert_debug_snapshot_matches!(
        do_reference_completion(
            r"
                struct Foo;
                enum Baz {}
                fn quux() {
                    <|>
                }
                "
        ),
        @r###"[
    CompletionItem {
        label: "Baz",
        source_range: [105; 105),
        delete: [105; 105),
        insert: "Baz",
        kind: Enum,
    },
    CompletionItem {
        label: "Foo",
        source_range: [105; 105),
        delete: [105; 105),
        insert: "Foo",
        kind: Struct,
    },
    CompletionItem {
        label: "quux",
        source_range: [105; 105),
        delete: [105; 105),
        insert: "quux()$0",
        kind: Function,
        detail: "fn quux()",
    },
]"###
            );
    }

    #[test]
    fn completes_extern_prelude() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                //- /lib.rs
                use <|>;

                //- /other_crate/lib.rs
                // nothing here
                "
            ),
            @r#"[
    CompletionItem {
        label: "other_crate",
        source_range: [4; 4),
        delete: [4; 4),
        insert: "other_crate",
        kind: Module,
    },
]"#
        );
    }

    #[test]
    fn completes_module_items_in_nested_modules() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                struct Foo;
                mod m {
                    struct Bar;
                    fn quux() { <|> }
                }
                "
            ),
            @r###"[
    CompletionItem {
        label: "Bar",
        source_range: [117; 117),
        delete: [117; 117),
        insert: "Bar",
        kind: Struct,
    },
    CompletionItem {
        label: "quux",
        source_range: [117; 117),
        delete: [117; 117),
        insert: "quux()$0",
        kind: Function,
        detail: "fn quux()",
    },
]"###
        );
    }

    #[test]
    fn completes_return_type() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                struct Foo;
                fn x() -> <|>
                "
            ),
            @r###"[
    CompletionItem {
        label: "Foo",
        source_range: [55; 55),
        delete: [55; 55),
        insert: "Foo",
        kind: Struct,
    },
    CompletionItem {
        label: "x",
        source_range: [55; 55),
        delete: [55; 55),
        insert: "x()$0",
        kind: Function,
        detail: "fn x()",
    },
]"###
        );
    }

    #[test]
    fn dont_show_both_completions_for_shadowing() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                r"
                fn foo() {
                    let bar = 92;
                    {
                        let bar = 62;
                        <|>
                    }
                }
                "
            ),
            @r###"[
    CompletionItem {
        label: "bar",
        source_range: [146; 146),
        delete: [146; 146),
        insert: "bar",
        kind: Binding,
        detail: "i32",
    },
    CompletionItem {
        label: "foo",
        source_range: [146; 146),
        delete: [146; 146),
        insert: "foo()$0",
        kind: Function,
        detail: "fn foo()",
    },
]"###
        );
    }

    #[test]
    fn completes_self_in_methods() {
        assert_debug_snapshot_matches!(
            do_reference_completion(r"impl S { fn foo(&self) { <|> } }"),
            @r#"[
    CompletionItem {
        label: "Self",
        source_range: [25; 25),
        delete: [25; 25),
        insert: "Self",
        kind: TypeParam,
    },
    CompletionItem {
        label: "self",
        source_range: [25; 25),
        delete: [25; 25),
        insert: "self",
        kind: Binding,
        detail: "&{unknown}",
    },
]"#
        );
    }

    #[test]
    fn completes_prelude() {
        assert_debug_snapshot_matches!(
            do_reference_completion(
                "
                //- /main.rs
                fn foo() { let x: <|> }

                //- /std/lib.rs
                #[prelude_import]
                use prelude::*;

                mod prelude {
                    struct Option;
                }
                "
            ),
            @r#"[
    CompletionItem {
        label: "Option",
        source_range: [18; 18),
        delete: [18; 18),
        insert: "Option",
        kind: Struct,
    },
    CompletionItem {
        label: "foo",
        source_range: [18; 18),
        delete: [18; 18),
        insert: "foo()$0",
        kind: Function,
        detail: "fn foo()",
    },
    CompletionItem {
        label: "std",
        source_range: [18; 18),
        delete: [18; 18),
        insert: "std",
        kind: Module,
    },
]"#
        );
    }
}