//! Postfix completions, like `Ok(10).ifl$0` => `if let Ok() = Ok(10) { $0 }`.

mod format_like;

use hir::{Documentation, HasAttrs};
use ide_db::{imports::insert_use::ImportScope, ty_filter::TryEnum, SnippetCap};
use syntax::{
    ast::{self, make, AstNode, AstToken},
    SyntaxKind::{BLOCK_EXPR, EXPR_STMT, FOR_EXPR, IF_EXPR, LOOP_EXPR, STMT_LIST, WHILE_EXPR},
    TextRange, TextSize,
};
use text_edit::TextEdit;

use crate::{
    completions::postfix::format_like::add_format_like_completions,
    context::{CompletionContext, DotAccess, DotAccessKind},
    item::{Builder, CompletionRelevancePostfixMatch},
    CompletionItem, CompletionItemKind, CompletionRelevance, Completions, SnippetScope,
};

pub(crate) fn complete_postfix(
    acc: &mut Completions,
    ctx: &CompletionContext<'_>,
    dot_access: &DotAccess,
) {
    if !ctx.config.enable_postfix_completions {
        return;
    }

    let (dot_receiver, receiver_ty, receiver_is_ambiguous_float_literal) = match dot_access {
        DotAccess { receiver_ty: Some(ty), receiver: Some(it), kind, .. } => (
            it,
            &ty.original,
            match *kind {
                DotAccessKind::Field { receiver_is_ambiguous_float_literal } => {
                    receiver_is_ambiguous_float_literal
                }
                DotAccessKind::Method { .. } => false,
            },
        ),
        _ => return,
    };

    let receiver_text = get_receiver_text(dot_receiver, receiver_is_ambiguous_float_literal);

    let cap = match ctx.config.snippet_cap {
        Some(it) => it,
        None => return,
    };

    let postfix_snippet = match build_postfix_snippet_builder(ctx, cap, dot_receiver) {
        Some(it) => it,
        None => return,
    };

    if let Some(drop_trait) = ctx.famous_defs().core_ops_Drop() {
        if receiver_ty.impls_trait(ctx.db, drop_trait, &[]) {
            if let &[hir::AssocItem::Function(drop_fn)] = &*drop_trait.items(ctx.db) {
                cov_mark::hit!(postfix_drop_completion);
                // FIXME: check that `drop` is in scope, use fully qualified path if it isn't/if shadowed
                let mut item = postfix_snippet(
                    "drop",
                    "fn drop(&mut self)",
                    &format!("drop($0{receiver_text})"),
                );
                item.set_documentation(drop_fn.docs(ctx.db));
                item.add_to(acc);
            }
        }
    }

    let try_enum = TryEnum::from_ty(&ctx.sema, &receiver_ty.strip_references());
    if let Some(try_enum) = &try_enum {
        match try_enum {
            TryEnum::Result => {
                postfix_snippet(
                    "ifl",
                    "if let Ok {}",
                    &format!("if let Ok($1) = {receiver_text} {{\n    $0\n}}"),
                )
                .add_to(acc);

                postfix_snippet(
                    "while",
                    "while let Ok {}",
                    &format!("while let Ok($1) = {receiver_text} {{\n    $0\n}}"),
                )
                .add_to(acc);
            }
            TryEnum::Option => {
                postfix_snippet(
                    "ifl",
                    "if let Some {}",
                    &format!("if let Some($1) = {receiver_text} {{\n    $0\n}}"),
                )
                .add_to(acc);

                postfix_snippet(
                    "while",
                    "while let Some {}",
                    &format!("while let Some($1) = {receiver_text} {{\n    $0\n}}"),
                )
                .add_to(acc);
            }
        }
    } else if receiver_ty.is_bool() || receiver_ty.is_unknown() {
        postfix_snippet("if", "if expr {}", &format!("if {receiver_text} {{\n    $0\n}}"))
            .add_to(acc);
        postfix_snippet("while", "while expr {}", &format!("while {receiver_text} {{\n    $0\n}}"))
            .add_to(acc);
        postfix_snippet("not", "!expr", &format!("!{receiver_text}")).add_to(acc);
    } else if let Some(trait_) = ctx.famous_defs().core_iter_IntoIterator() {
        if receiver_ty.impls_trait(ctx.db, trait_, &[]) {
            postfix_snippet(
                "for",
                "for ele in expr {}",
                &format!("for ele in {receiver_text} {{\n    $0\n}}"),
            )
            .add_to(acc);
        }
    }

    postfix_snippet("ref", "&expr", &format!("&{receiver_text}")).add_to(acc);
    postfix_snippet("refm", "&mut expr", &format!("&mut {receiver_text}")).add_to(acc);

    let mut unsafe_should_be_wrapped = true;
    if dot_receiver.syntax().kind() == BLOCK_EXPR {
        unsafe_should_be_wrapped = false;
        if let Some(parent) = dot_receiver.syntax().parent() {
            if matches!(parent.kind(), IF_EXPR | WHILE_EXPR | LOOP_EXPR | FOR_EXPR) {
                unsafe_should_be_wrapped = true;
            }
        }
    };
    let unsafe_completion_string = if unsafe_should_be_wrapped {
        format!("unsafe {{ {receiver_text} }}")
    } else {
        format!("unsafe {receiver_text}")
    };
    postfix_snippet("unsafe", "unsafe {}", &unsafe_completion_string).add_to(acc);

    // The rest of the postfix completions create an expression that moves an argument,
    // so it's better to consider references now to avoid breaking the compilation

    let (dot_receiver, node_to_replace_with) = include_references(dot_receiver);
    let receiver_text =
        get_receiver_text(&node_to_replace_with, receiver_is_ambiguous_float_literal);
    let postfix_snippet = match build_postfix_snippet_builder(ctx, cap, &dot_receiver) {
        Some(it) => it,
        None => return,
    };

    if !ctx.config.snippets.is_empty() {
        add_custom_postfix_completions(acc, ctx, &postfix_snippet, &receiver_text);
    }

    match try_enum {
        Some(try_enum) => match try_enum {
            TryEnum::Result => {
                postfix_snippet(
                    "match",
                    "match expr {}",
                    &format!("match {receiver_text} {{\n    Ok(${{1:_}}) => {{$2}},\n    Err(${{3:_}}) => {{$0}},\n}}"),
                )
                .add_to(acc);
            }
            TryEnum::Option => {
                postfix_snippet(
                    "match",
                    "match expr {}",
                    &format!(
                        "match {receiver_text} {{\n    Some(${{1:_}}) => {{$2}},\n    None => {{$0}},\n}}"
                    ),
                )
                .add_to(acc);
            }
        },
        None => {
            postfix_snippet(
                "match",
                "match expr {}",
                &format!("match {receiver_text} {{\n    ${{1:_}} => {{$0}},\n}}"),
            )
            .add_to(acc);
        }
    }

    postfix_snippet("box", "Box::new(expr)", &format!("Box::new({receiver_text})")).add_to(acc);
    postfix_snippet("dbg", "dbg!(expr)", &format!("dbg!({receiver_text})")).add_to(acc); // fixme
    postfix_snippet("dbgr", "dbg!(&expr)", &format!("dbg!(&{receiver_text})")).add_to(acc);
    postfix_snippet("call", "function(expr)", &format!("${{1}}({receiver_text})")).add_to(acc);

    if let Some(parent) = dot_receiver.syntax().parent().and_then(|p| p.parent()) {
        if matches!(parent.kind(), STMT_LIST | EXPR_STMT) {
            postfix_snippet("let", "let", &format!("let $0 = {receiver_text};")).add_to(acc);
            postfix_snippet("letm", "let mut", &format!("let mut $0 = {receiver_text};"))
                .add_to(acc);
        }
    }

    if let ast::Expr::Literal(literal) = dot_receiver.clone() {
        if let Some(literal_text) = ast::String::cast(literal.token()) {
            add_format_like_completions(acc, ctx, &dot_receiver, cap, &literal_text);
        }
    }
}

fn get_receiver_text(receiver: &ast::Expr, receiver_is_ambiguous_float_literal: bool) -> String {
    let text = if receiver_is_ambiguous_float_literal {
        let text = receiver.syntax().text();
        let without_dot = ..text.len() - TextSize::of('.');
        text.slice(without_dot).to_string()
    } else {
        receiver.to_string()
    };

    // The receiver texts should be interpreted as-is, as they are expected to be
    // normal Rust expressions. We escape '\' and '$' so they don't get treated as
    // snippet-specific constructs.
    //
    // Note that we don't need to escape the other characters that can be escaped,
    // because they wouldn't be treated as snippet-specific constructs without '$'.
    text.replace('\\', "\\\\").replace('$', "\\$")
}

fn include_references(initial_element: &ast::Expr) -> (ast::Expr, ast::Expr) {
    let mut resulting_element = initial_element.clone();

    while let Some(field_expr) = resulting_element.syntax().parent().and_then(ast::FieldExpr::cast)
    {
        resulting_element = ast::Expr::from(field_expr);
    }

    let mut new_element_opt = initial_element.clone();

    if let Some(first_ref_expr) = resulting_element.syntax().parent().and_then(ast::RefExpr::cast) {
        if let Some(expr) = first_ref_expr.expr() {
            resulting_element = expr;
        }

        while let Some(parent_ref_element) =
            resulting_element.syntax().parent().and_then(ast::RefExpr::cast)
        {
            resulting_element = ast::Expr::from(parent_ref_element);

            new_element_opt = make::expr_ref(new_element_opt, false);
        }
    } else {
        // If we do not find any ref expressions, restore
        // all the progress of tree climbing
        resulting_element = initial_element.clone();
    }

    (resulting_element, new_element_opt)
}

fn build_postfix_snippet_builder<'ctx>(
    ctx: &'ctx CompletionContext<'_>,
    cap: SnippetCap,
    receiver: &'ctx ast::Expr,
) -> Option<impl Fn(&str, &str, &str) -> Builder + 'ctx> {
    let receiver_range = ctx.sema.original_range_opt(receiver.syntax())?.range;
    if ctx.source_range().end() < receiver_range.start() {
        // This shouldn't happen, yet it does. I assume this might be due to an incorrect token mapping.
        return None;
    }
    let delete_range = TextRange::new(receiver_range.start(), ctx.source_range().end());

    // Wrapping impl Fn in an option ruins lifetime inference for the parameters in a way that
    // can't be annotated for the closure, hence fix it by constructing it without the Option first
    fn build<'ctx>(
        ctx: &'ctx CompletionContext<'_>,
        cap: SnippetCap,
        delete_range: TextRange,
    ) -> impl Fn(&str, &str, &str) -> Builder + 'ctx {
        move |label, detail, snippet| {
            let edit = TextEdit::replace(delete_range, snippet.to_string());
            let mut item =
                CompletionItem::new(CompletionItemKind::Snippet, ctx.source_range(), label);
            item.detail(detail).snippet_edit(cap, edit);
            let postfix_match = if ctx.original_token.text() == label {
                cov_mark::hit!(postfix_exact_match_is_high_priority);
                Some(CompletionRelevancePostfixMatch::Exact)
            } else {
                cov_mark::hit!(postfix_inexact_match_is_low_priority);
                Some(CompletionRelevancePostfixMatch::NonExact)
            };
            let relevance = CompletionRelevance { postfix_match, ..Default::default() };
            item.set_relevance(relevance);
            item
        }
    }
    Some(build(ctx, cap, delete_range))
}

fn add_custom_postfix_completions(
    acc: &mut Completions,
    ctx: &CompletionContext<'_>,
    postfix_snippet: impl Fn(&str, &str, &str) -> Builder,
    receiver_text: &str,
) -> Option<()> {
    if ImportScope::find_insert_use_container(&ctx.token.parent()?, &ctx.sema).is_none() {
        return None;
    }
    ctx.config.postfix_snippets().filter(|(_, snip)| snip.scope == SnippetScope::Expr).for_each(
        |(trigger, snippet)| {
            let imports = match snippet.imports(ctx) {
                Some(imports) => imports,
                None => return,
            };
            let body = snippet.postfix_snippet(receiver_text);
            let mut builder =
                postfix_snippet(trigger, snippet.description.as_deref().unwrap_or_default(), &body);
            builder.documentation(Documentation::new(format!("```rust\n{body}\n```")));
            for import in imports.into_iter() {
                builder.add_import(import);
            }
            builder.add_to(acc);
        },
    );
    None
}

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

    use crate::{
        tests::{check_edit, check_edit_with_config, completion_list, TEST_CONFIG},
        CompletionConfig, Snippet,
    };

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

    #[test]
    fn postfix_completion_works_for_trivial_path_expression() {
        check(
            r#"
fn main() {
    let bar = true;
    bar.$0
}
"#,
            expect![[r#"
                sn box    Box::new(expr)
                sn call   function(expr)
                sn dbg    dbg!(expr)
                sn dbgr   dbg!(&expr)
                sn if     if expr {}
                sn let    let
                sn letm   let mut
                sn match  match expr {}
                sn not    !expr
                sn ref    &expr
                sn refm   &mut expr
                sn unsafe unsafe {}
                sn while  while expr {}
            "#]],
        );
    }

    #[test]
    fn postfix_completion_works_for_function_calln() {
        check(
            r#"
fn foo(elt: bool) -> bool {
    !elt
}

fn main() {
    let bar = true;
    foo(bar.$0)
}
"#,
            expect![[r#"
                sn box    Box::new(expr)
                sn call   function(expr)
                sn dbg    dbg!(expr)
                sn dbgr   dbg!(&expr)
                sn if     if expr {}
                sn match  match expr {}
                sn not    !expr
                sn ref    &expr
                sn refm   &mut expr
                sn unsafe unsafe {}
                sn while  while expr {}
            "#]],
        );
    }

    #[test]
    fn postfix_type_filtering() {
        check(
            r#"
fn main() {
    let bar: u8 = 12;
    bar.$0
}
"#,
            expect![[r#"
                sn box    Box::new(expr)
                sn call   function(expr)
                sn dbg    dbg!(expr)
                sn dbgr   dbg!(&expr)
                sn let    let
                sn letm   let mut
                sn match  match expr {}
                sn ref    &expr
                sn refm   &mut expr
                sn unsafe unsafe {}
            "#]],
        )
    }

    #[test]
    fn let_middle_block() {
        check(
            r#"
fn main() {
    baz.l$0
    res
}
"#,
            expect![[r#"
                sn box    Box::new(expr)
                sn call   function(expr)
                sn dbg    dbg!(expr)
                sn dbgr   dbg!(&expr)
                sn if     if expr {}
                sn let    let
                sn letm   let mut
                sn match  match expr {}
                sn not    !expr
                sn ref    &expr
                sn refm   &mut expr
                sn unsafe unsafe {}
                sn while  while expr {}
            "#]],
        );
    }

    #[test]
    fn option_iflet() {
        check_edit(
            "ifl",
            r#"
//- minicore: option
fn main() {
    let bar = Some(true);
    bar.$0
}
"#,
            r#"
fn main() {
    let bar = Some(true);
    if let Some($1) = bar {
    $0
}
}
"#,
        );
    }

    #[test]
    fn result_match() {
        check_edit(
            "match",
            r#"
//- minicore: result
fn main() {
    let bar = Ok(true);
    bar.$0
}
"#,
            r#"
fn main() {
    let bar = Ok(true);
    match bar {
    Ok(${1:_}) => {$2},
    Err(${3:_}) => {$0},
}
}
"#,
        );
    }

    #[test]
    fn postfix_completion_works_for_ambiguous_float_literal() {
        check_edit("refm", r#"fn main() { 42.$0 }"#, r#"fn main() { &mut 42 }"#)
    }

    #[test]
    fn works_in_simple_macro() {
        check_edit(
            "dbg",
            r#"
macro_rules! m { ($e:expr) => { $e } }
fn main() {
    let bar: u8 = 12;
    m!(bar.d$0)
}
"#,
            r#"
macro_rules! m { ($e:expr) => { $e } }
fn main() {
    let bar: u8 = 12;
    m!(dbg!(bar))
}
"#,
        );
    }

    #[test]
    fn postfix_completion_for_references() {
        check_edit("dbg", r#"fn main() { &&42.$0 }"#, r#"fn main() { dbg!(&&42) }"#);
        check_edit("refm", r#"fn main() { &&42.$0 }"#, r#"fn main() { &&&mut 42 }"#);
        check_edit(
            "ifl",
            r#"
//- minicore: option
fn main() {
    let bar = &Some(true);
    bar.$0
}
"#,
            r#"
fn main() {
    let bar = &Some(true);
    if let Some($1) = bar {
    $0
}
}
"#,
        )
    }

    #[test]
    fn postfix_completion_for_unsafe() {
        check_edit("unsafe", r#"fn main() { foo.$0 }"#, r#"fn main() { unsafe { foo } }"#);
        check_edit("unsafe", r#"fn main() { { foo }.$0 }"#, r#"fn main() { unsafe { foo } }"#);
        check_edit(
            "unsafe",
            r#"fn main() { if x { foo }.$0 }"#,
            r#"fn main() { unsafe { if x { foo } } }"#,
        );
        check_edit(
            "unsafe",
            r#"fn main() { loop { foo }.$0 }"#,
            r#"fn main() { unsafe { loop { foo } } }"#,
        );
        check_edit(
            "unsafe",
            r#"fn main() { if true {}.$0 }"#,
            r#"fn main() { unsafe { if true {} } }"#,
        );
        check_edit(
            "unsafe",
            r#"fn main() { while true {}.$0 }"#,
            r#"fn main() { unsafe { while true {} } }"#,
        );
        check_edit(
            "unsafe",
            r#"fn main() { for i in 0..10 {}.$0 }"#,
            r#"fn main() { unsafe { for i in 0..10 {} } }"#,
        );
        check_edit(
            "unsafe",
            r#"fn main() { let x = if true {1} else {2}.$0 }"#,
            r#"fn main() { let x = unsafe { if true {1} else {2} } }"#,
        );

        // completion will not be triggered
        check_edit(
            "unsafe",
            r#"fn main() { let x = true else {panic!()}.$0}"#,
            r#"fn main() { let x = true else {panic!()}.unsafe}"#,
        );
    }

    #[test]
    fn custom_postfix_completion() {
        let config = CompletionConfig {
            snippets: vec![Snippet::new(
                &[],
                &["break".into()],
                &["ControlFlow::Break(${receiver})".into()],
                "",
                &["core::ops::ControlFlow".into()],
                crate::SnippetScope::Expr,
            )
            .unwrap()],
            ..TEST_CONFIG
        };

        check_edit_with_config(
            config.clone(),
            "break",
            r#"
//- minicore: try
fn main() { 42.$0 }
"#,
            r#"
use core::ops::ControlFlow;

fn main() { ControlFlow::Break(42) }
"#,
        );

        // The receiver texts should be escaped, see comments in `get_receiver_text()`
        // for detail.
        //
        // Note that the last argument is what *lsp clients would see* rather than
        // what users would see. Unescaping happens thereafter.
        check_edit_with_config(
            config.clone(),
            "break",
            r#"
//- minicore: try
fn main() { '\\'.$0 }
"#,
            r#"
use core::ops::ControlFlow;

fn main() { ControlFlow::Break('\\\\') }
"#,
        );

        check_edit_with_config(
            config,
            "break",
            r#"
//- minicore: try
fn main() {
    match true {
        true => "${1:placeholder}",
        false => "\$",
    }.$0
}
"#,
            r#"
use core::ops::ControlFlow;

fn main() {
    ControlFlow::Break(match true {
        true => "\${1:placeholder}",
        false => "\\\$",
    })
}
"#,
        );
    }

    #[test]
    fn postfix_completion_for_format_like_strings() {
        check_edit(
            "format",
            r#"fn main() { "{some_var:?}".$0 }"#,
            r#"fn main() { format!("{some_var:?}") }"#,
        );
        check_edit(
            "panic",
            r#"fn main() { "Panic with {a}".$0 }"#,
            r#"fn main() { panic!("Panic with {a}") }"#,
        );
        check_edit(
            "println",
            r#"fn main() { "{ 2+2 } { SomeStruct { val: 1, other: 32 } :?}".$0 }"#,
            r#"fn main() { println!("{} {:?}", 2+2, SomeStruct { val: 1, other: 32 }) }"#,
        );
        check_edit(
            "loge",
            r#"fn main() { "{2+2}".$0 }"#,
            r#"fn main() { log::error!("{}", 2+2) }"#,
        );
        check_edit(
            "logt",
            r#"fn main() { "{2+2}".$0 }"#,
            r#"fn main() { log::trace!("{}", 2+2) }"#,
        );
        check_edit(
            "logd",
            r#"fn main() { "{2+2}".$0 }"#,
            r#"fn main() { log::debug!("{}", 2+2) }"#,
        );
        check_edit("logi", r#"fn main() { "{2+2}".$0 }"#, r#"fn main() { log::info!("{}", 2+2) }"#);
        check_edit("logw", r#"fn main() { "{2+2}".$0 }"#, r#"fn main() { log::warn!("{}", 2+2) }"#);
        check_edit(
            "loge",
            r#"fn main() { "{2+2}".$0 }"#,
            r#"fn main() { log::error!("{}", 2+2) }"#,
        );
    }

    #[test]
    fn postfix_custom_snippets_completion_for_references() {
        // https://github.com/rust-lang/rust-analyzer/issues/7929

        let snippet = Snippet::new(
            &[],
            &["ok".into()],
            &["Ok(${receiver})".into()],
            "",
            &[],
            crate::SnippetScope::Expr,
        )
        .unwrap();

        check_edit_with_config(
            CompletionConfig { snippets: vec![snippet.clone()], ..TEST_CONFIG },
            "ok",
            r#"fn main() { &&42.o$0 }"#,
            r#"fn main() { Ok(&&42) }"#,
        );

        check_edit_with_config(
            CompletionConfig { snippets: vec![snippet.clone()], ..TEST_CONFIG },
            "ok",
            r#"fn main() { &&42.$0 }"#,
            r#"fn main() { Ok(&&42) }"#,
        );

        check_edit_with_config(
            CompletionConfig { snippets: vec![snippet], ..TEST_CONFIG },
            "ok",
            r#"
struct A {
    a: i32,
}

fn main() {
    let a = A {a :1};
    &a.a.$0
}
            "#,
            r#"
struct A {
    a: i32,
}

fn main() {
    let a = A {a :1};
    Ok(&a.a)
}
            "#,
        );
    }

    #[test]
    fn no_postfix_completions_in_if_block_that_has_an_else() {
        check(
            r#"
fn test() {
    if true {}.$0 else {}
}
"#,
            expect![[r#""#]],
        );
    }
}