//! Completes keywords.

use std::iter;

use syntax::{SyntaxKind, T};

use crate::{
    context::PathCompletionContext, patterns::ImmediateLocation, CompletionContext, CompletionItem,
    CompletionItemKind, CompletionKind, Completions,
};

pub(crate) fn complete_use_tree_keyword(acc: &mut Completions, ctx: &CompletionContext) {
    // complete keyword "crate" in use stmt
    let source_range = ctx.source_range();
    let kw_completion = move |text: &str| {
        let mut item = CompletionItem::new(CompletionKind::Keyword, source_range, text);
        item.kind(CompletionItemKind::Keyword).insert_text(text);
        item
    };

    if ctx.in_use_tree() {
        match &ctx.path_context {
            Some(PathCompletionContext { qualifier: Some(qual), use_tree_parent, .. }) => {
                if iter::successors(Some(qual.clone()), |p| p.qualifier())
                    .all(|p| p.segment().and_then(|s| s.super_token()).is_some())
                {
                    kw_completion("super::").add_to(acc);
                }
                if *use_tree_parent {
                    kw_completion("self").add_to(acc);
                }
            }
            _ => {
                kw_completion("crate::").add_to(acc);
                kw_completion("self::").add_to(acc);
                kw_completion("super::").add_to(acc);
            }
        };
    }
}

pub(crate) fn complete_expr_keyword(acc: &mut Completions, ctx: &CompletionContext) {
    if ctx.token.kind() == SyntaxKind::COMMENT {
        cov_mark::hit!(no_keyword_completion_in_comments);
        return;
    }
    if matches!(ctx.completion_location, Some(ImmediateLocation::RecordExpr(_))) {
        cov_mark::hit!(no_keyword_completion_in_record_lit);
        return;
    }
    if ctx.attribute_under_caret.is_some() {
        cov_mark::hit!(no_keyword_completion_in_attr_of_expr);
        return;
    }

    // Suggest .await syntax for types that implement Future trait
    if let Some(receiver) = ctx.dot_receiver() {
        if let Some(ty) = ctx.sema.type_of_expr(receiver) {
            if ty.impls_future(ctx.db) {
                let mut item =
                    CompletionItem::new(CompletionKind::Keyword, ctx.source_range(), "await");
                item.kind(CompletionItemKind::Keyword).detail("expr.await");
                item.add_to(acc);
            }
        };
    }

    let mut add_keyword = |kw, snippet| add_keyword(ctx, acc, kw, snippet);

    let expects_assoc_item = ctx.expects_assoc_item();
    let has_block_expr_parent = ctx.has_block_expr_parent();
    let expects_item = ctx.expects_item();

    if ctx.has_impl_or_trait_prev_sibling() {
        add_keyword("where", "where ");
        if ctx.has_impl_prev_sibling() {
            add_keyword("for", "for ");
        }
        return;
    }
    if ctx.previous_token_is(T![unsafe]) {
        if expects_item || expects_assoc_item || has_block_expr_parent {
            add_keyword("fn", "fn $1($2) {\n    $0\n}")
        }

        if expects_item || has_block_expr_parent {
            add_keyword("trait", "trait $1 {\n    $0\n}");
            add_keyword("impl", "impl $1 {\n    $0\n}");
        }

        return;
    }

    if !ctx.has_visibility_prev_sibling()
        && (expects_item || ctx.expects_non_trait_assoc_item() || ctx.expect_record_field())
    {
        add_keyword("pub(crate)", "pub(crate) ");
        add_keyword("pub", "pub ");
    }

    if expects_item || expects_assoc_item || has_block_expr_parent {
        add_keyword("unsafe", "unsafe ");
        add_keyword("fn", "fn $1($2) {\n    $0\n}");
        add_keyword("const", "const $0");
        add_keyword("type", "type $0");
    }

    if expects_item || has_block_expr_parent {
        if !ctx.has_visibility_prev_sibling() {
            add_keyword("impl", "impl $1 {\n    $0\n}");
            add_keyword("extern", "extern $0");
        }
        add_keyword("use", "use $0");
        add_keyword("trait", "trait $1 {\n    $0\n}");
        add_keyword("static", "static $0");
        add_keyword("mod", "mod $0");
    }

    if expects_item {
        add_keyword("enum", "enum $1 {\n    $0\n}");
        add_keyword("struct", "struct $0");
        add_keyword("union", "union $1 {\n    $0\n}");
    }

    if ctx.expects_expression() {
        if !has_block_expr_parent {
            add_keyword("unsafe", "unsafe {\n    $0\n}");
        }
        add_keyword("match", "match $1 {\n    $0\n}");
        add_keyword("while", "while $1 {\n    $0\n}");
        add_keyword("while let", "while let $1 = $2 {\n    $0\n}");
        add_keyword("loop", "loop {\n    $0\n}");
        add_keyword("if", "if $1 {\n    $0\n}");
        add_keyword("if let", "if let $1 = $2 {\n    $0\n}");
        add_keyword("for", "for $1 in $2 {\n    $0\n}");
    }

    if ctx.previous_token_is(T![if]) || ctx.previous_token_is(T![while]) || has_block_expr_parent {
        add_keyword("let", "let ");
    }

    if ctx.after_if() {
        add_keyword("else", "else {\n    $0\n}");
        add_keyword("else if", "else if $1 {\n    $0\n}");
    }

    if ctx.expects_ident_pat_or_ref_expr() {
        add_keyword("mut", "mut ");
    }

    let (can_be_stmt, in_loop_body) = match ctx.path_context {
        Some(PathCompletionContext {
            is_trivial_path: true, can_be_stmt, in_loop_body, ..
        }) => (can_be_stmt, in_loop_body),
        _ => return,
    };

    if in_loop_body {
        if can_be_stmt {
            add_keyword("continue", "continue;");
            add_keyword("break", "break;");
        } else {
            add_keyword("continue", "continue");
            add_keyword("break", "break");
        }
    }

    let fn_def = match &ctx.function_def {
        Some(it) => it,
        None => return,
    };

    add_keyword(
        "return",
        match (can_be_stmt, fn_def.ret_type().is_some()) {
            (true, true) => "return $0;",
            (true, false) => "return;",
            (false, true) => "return $0",
            (false, false) => "return",
        },
    )
}

fn add_keyword(ctx: &CompletionContext, acc: &mut Completions, kw: &str, snippet: &str) {
    let mut item = CompletionItem::new(CompletionKind::Keyword, ctx.source_range(), kw);
    item.kind(CompletionItemKind::Keyword);

    match ctx.config.snippet_cap {
        Some(cap) => {
            if snippet.ends_with('}') && ctx.incomplete_let {
                cov_mark::hit!(let_semi);
                item.insert_snippet(cap, format!("{};", snippet));
            } else {
                item.insert_snippet(cap, snippet);
            }
        }
        None => {
            item.insert_text(if snippet.contains('$') { kw } else { snippet });
        }
    };
    item.add_to(acc);
}

#[cfg(test)]
mod tests {
    use expect_test::{expect, Expect};

    use crate::{
        tests::{check_edit, filtered_completion_list},
        CompletionKind,
    };

    fn check(ra_fixture: &str, expect: Expect) {
        let actual = filtered_completion_list(ra_fixture, CompletionKind::Keyword);
        expect.assert_eq(&actual)
    }

    #[test]
    fn test_keywords_in_function() {
        check(
            r"fn quux() { $0 }",
            expect![[r#"
                kw unsafe
                kw fn
                kw const
                kw type
                kw impl
                kw extern
                kw use
                kw trait
                kw static
                kw mod
                kw match
                kw while
                kw while let
                kw loop
                kw if
                kw if let
                kw for
                kw let
                kw return
            "#]],
        );
    }

    #[test]
    fn test_keywords_inside_block() {
        check(
            r"fn quux() { if true { $0 } }",
            expect![[r#"
                kw unsafe
                kw fn
                kw const
                kw type
                kw impl
                kw extern
                kw use
                kw trait
                kw static
                kw mod
                kw match
                kw while
                kw while let
                kw loop
                kw if
                kw if let
                kw for
                kw let
                kw return
            "#]],
        );
    }

    #[test]
    fn test_keywords_after_if() {
        check(
            r#"fn quux() { if true { () } $0 }"#,
            expect![[r#"
                kw unsafe
                kw fn
                kw const
                kw type
                kw impl
                kw extern
                kw use
                kw trait
                kw static
                kw mod
                kw match
                kw while
                kw while let
                kw loop
                kw if
                kw if let
                kw for
                kw let
                kw else
                kw else if
                kw return
            "#]],
        );
        check_edit(
            "else",
            r#"fn quux() { if true { () } $0 }"#,
            r#"fn quux() { if true { () } else {
    $0
} }"#,
        );
    }

    #[test]
    fn test_keywords_in_match_arm() {
        check(
            r#"
fn quux() -> i32 {
    match () { () => $0 }
}
"#,
            expect![[r#"
                kw unsafe
                kw match
                kw while
                kw while let
                kw loop
                kw if
                kw if let
                kw for
                kw return
            "#]],
        );
    }

    #[test]
    fn test_keywords_in_loop() {
        check(
            r"fn my() { loop { $0 } }",
            expect![[r#"
                kw unsafe
                kw fn
                kw const
                kw type
                kw impl
                kw extern
                kw use
                kw trait
                kw static
                kw mod
                kw match
                kw while
                kw while let
                kw loop
                kw if
                kw if let
                kw for
                kw let
                kw continue
                kw break
                kw return
            "#]],
        );
    }

    #[test]
    fn test_keywords_after_unsafe_in_block_expr() {
        check(
            r"fn my_fn() { unsafe $0 }",
            expect![[r#"
                kw fn
                kw trait
                kw impl
            "#]],
        );
    }

    #[test]
    fn no_keyword_completion_in_comments() {
        cov_mark::check!(no_keyword_completion_in_comments);
        check(
            r#"
fn test() {
    let x = 2; // A comment$0
}
"#,
            expect![[""]],
        );
        check(
            r#"
/*
Some multi-line comment$0
*/
"#,
            expect![[""]],
        );
        check(
            r#"
/// Some doc comment
/// let test$0 = 1
"#,
            expect![[""]],
        );
    }

    #[test]
    fn test_completion_await_impls_future() {
        check(
            r#"
//- minicore: future
use core::future::*;
struct A {}
impl Future for A {}
fn foo(a: A) { a.$0 }
"#,
            expect![[r#"
                kw await expr.await
            "#]],
        );

        check(
            r#"
//- minicore: future
use std::future::*;
fn foo() {
    let a = async {};
    a.$0
}
"#,
            expect![[r#"
                kw await expr.await
            "#]],
        )
    }

    #[test]
    fn after_let() {
        check(
            r#"fn main() { let _ = $0 }"#,
            expect![[r#"
                kw unsafe
                kw match
                kw while
                kw while let
                kw loop
                kw if
                kw if let
                kw for
                kw return
            "#]],
        )
    }

    #[test]
    fn skip_struct_initializer() {
        cov_mark::check!(no_keyword_completion_in_record_lit);
        check(
            r#"
struct Foo {
    pub f: i32,
}
fn foo() {
    Foo {
        $0
    }
}
"#,
            expect![[r#""#]],
        );
    }

    #[test]
    fn struct_initializer_field_expr() {
        check(
            r#"
struct Foo {
    pub f: i32,
}
fn foo() {
    Foo {
        f: $0
    }
}
"#,
            expect![[r#"
                kw unsafe
                kw match
                kw while
                kw while let
                kw loop
                kw if
                kw if let
                kw for
                kw return
            "#]],
        );
    }

    #[test]
    fn let_semi() {
        cov_mark::check!(let_semi);
        check_edit(
            "match",
            r#"
fn main() { let x = $0 }
"#,
            r#"
fn main() { let x = match $1 {
    $0
}; }
"#,
        );

        check_edit(
            "if",
            r#"
fn main() {
    let x = $0
    let y = 92;
}
"#,
            r#"
fn main() {
    let x = if $1 {
    $0
};
    let y = 92;
}
"#,
        );

        check_edit(
            "loop",
            r#"
fn main() {
    let x = $0
    bar();
}
"#,
            r#"
fn main() {
    let x = loop {
    $0
};
    bar();
}
"#,
        );
    }
}