use either::Either;
use hir::{db::AstDatabase, InFile, Type};
use ide_db::{assists::Assist, helpers::FamousDefs, source_change::SourceChange};
use rustc_hash::FxHashMap;
use stdx::format_to;
use syntax::{algo, ast::make, AstNode, SyntaxNodePtr};
use text_edit::TextEdit;

use crate::{fix, Diagnostic, DiagnosticsContext};

// Diagnostic: missing-fields
//
// This diagnostic is triggered if record lacks some fields that exist in the corresponding structure.
//
// Example:
//
// ```rust
// struct A { a: u8, b: u8 }
//
// let a = A { a: 10 };
// ```
pub(crate) fn missing_fields(ctx: &DiagnosticsContext<'_>, d: &hir::MissingFields) -> Diagnostic {
    let mut message = String::from("missing structure fields:\n");
    for field in &d.missed_fields {
        format_to!(message, "- {}\n", field);
    }

    let ptr = InFile::new(
        d.file,
        d.field_list_parent_path
            .clone()
            .map(SyntaxNodePtr::from)
            .unwrap_or_else(|| d.field_list_parent.clone().either(|it| it.into(), |it| it.into())),
    );

    Diagnostic::new("missing-fields", message, ctx.sema.diagnostics_display_range(ptr).range)
        .with_fixes(fixes(ctx, d))
}

fn fixes(ctx: &DiagnosticsContext<'_>, d: &hir::MissingFields) -> Option<Vec<Assist>> {
    // Note that although we could add a diagnostics to
    // fill the missing tuple field, e.g :
    // `struct A(usize);`
    // `let a = A { 0: () }`
    // but it is uncommon usage and it should not be encouraged.
    if d.missed_fields.iter().any(|it| it.as_tuple_index().is_some()) {
        return None;
    }

    let root = ctx.sema.db.parse_or_expand(d.file)?;
    let field_list_parent = match &d.field_list_parent {
        Either::Left(record_expr) => record_expr.to_node(&root),
        // FIXE: patterns should be fixable as well.
        Either::Right(_) => return None,
    };
    let old_field_list = field_list_parent.record_expr_field_list()?;

    let new_field_list = old_field_list.clone_for_update();
    let mut locals = FxHashMap::default();
    ctx.sema.scope(field_list_parent.syntax()).process_all_names(&mut |name, def| {
        if let hir::ScopeDef::Local(local) = def {
            locals.insert(name, local);
        }
    });
    let missing_fields = ctx.sema.record_literal_missing_fields(&field_list_parent);

    let generate_default_expr = |ty: &Type| {
        let krate = ctx.sema.to_module_def(d.file.original_file(ctx.sema.db))?.krate();
        let default_trait = FamousDefs(&ctx.sema, Some(krate)).core_default_Default();

        match default_trait {
            Some(default_trait) if ty.impls_trait(ctx.sema.db, default_trait, &[]) => {
                Some(make::ext::expr_default())
            }
            _ => Some(make::ext::expr_todo()),
        }
    };

    for (f, ty) in missing_fields.iter() {
        let field_expr = if let Some(local_candidate) = locals.get(&f.name(ctx.sema.db)) {
            cov_mark::hit!(field_shorthand);
            let candidate_ty = local_candidate.ty(ctx.sema.db);
            if ty.could_unify_with(ctx.sema.db, &candidate_ty) {
                None
            } else {
                generate_default_expr(ty)
            }
        } else {
            generate_default_expr(ty)
        };
        let field =
            make::record_expr_field(make::name_ref(&f.name(ctx.sema.db).to_smol_str()), field_expr)
                .clone_for_update();
        new_field_list.add_field(field);
    }

    let mut builder = TextEdit::builder();
    if d.file.is_macro() {
        // we can't map the diff up into the macro input unfortunately, as the macro loses all
        // whitespace information so the diff wouldn't be applicable no matter what
        // This has the downside that the cursor will be moved in macros by doing it without a diff
        // but that is a trade off we can make.
        // FIXE: this also currently discards a lot of whitespace in the input... we really need a formatter here
        let range = ctx.sema.original_range_opt(old_field_list.syntax())?;
        builder.replace(range.range, new_field_list.to_string());
    } else {
        algo::diff(old_field_list.syntax(), new_field_list.syntax()).into_text_edit(&mut builder);
    }
    let edit = builder.finish();
    Some(vec![fix(
        "fill_missing_fields",
        "Fill struct fields",
        SourceChange::from_text_edit(d.file.original_file(ctx.sema.db), edit),
        ctx.sema.original_range(field_list_parent.syntax()).range,
    )])
}

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

    #[test]
    fn missing_record_pat_field_diagnostic() {
        check_diagnostics(
            r#"
struct S { foo: i32, bar: () }
fn baz(s: S) {
    let S { foo: _ } = s;
      //^ error: missing structure fields:
      //| - bar
}
"#,
        );
    }

    #[test]
    fn missing_record_pat_field_no_diagnostic_if_not_exhaustive() {
        check_diagnostics(
            r"
struct S { foo: i32, bar: () }
fn baz(s: S) -> i32 {
    match s {
        S { foo, .. } => foo,
    }
}
",
        )
    }

    #[test]
    fn missing_record_pat_field_box() {
        check_diagnostics(
            r"
struct S { s: Box<u32> }
fn x(a: S) {
    let S { box s } = a;
}
",
        )
    }

    #[test]
    fn missing_record_pat_field_ref() {
        check_diagnostics(
            r"
struct S { s: u32 }
fn x(a: S) {
    let S { ref s } = a;
}
",
        )
    }

    #[test]
    fn range_mapping_out_of_macros() {
        check_fix(
            r#"
fn some() {}
fn items() {}
fn here() {}

macro_rules! id { ($($tt:tt)*) => { $($tt)*}; }

fn main() {
    let _x = id![Foo { a: $042 }];
}

pub struct Foo { pub a: i32, pub b: i32 }
"#,
            r#"
fn some() {}
fn items() {}
fn here() {}

macro_rules! id { ($($tt:tt)*) => { $($tt)*}; }

fn main() {
    let _x = id![Foo {a:42, b: todo!() }];
}

pub struct Foo { pub a: i32, pub b: i32 }
"#,
        );
    }

    #[test]
    fn test_fill_struct_fields_empty() {
        check_fix(
            r#"
struct TestStruct { one: i32, two: i64 }

fn test_fn() {
    let s = TestStruct {$0};
}
"#,
            r#"
struct TestStruct { one: i32, two: i64 }

fn test_fn() {
    let s = TestStruct { one: todo!(), two: todo!() };
}
"#,
        );
    }

    #[test]
    fn test_fill_struct_fields_self() {
        check_fix(
            r#"
struct TestStruct { one: i32 }

impl TestStruct {
    fn test_fn() { let s = Self {$0}; }
}
"#,
            r#"
struct TestStruct { one: i32 }

impl TestStruct {
    fn test_fn() { let s = Self { one: todo!() }; }
}
"#,
        );
    }

    #[test]
    fn test_fill_struct_fields_enum() {
        check_fix(
            r#"
enum Expr {
    Bin { lhs: Box<Expr>, rhs: Box<Expr> }
}

impl Expr {
    fn new_bin(lhs: Box<Expr>, rhs: Box<Expr>) -> Expr {
        Expr::Bin {$0 }
    }
}
"#,
            r#"
enum Expr {
    Bin { lhs: Box<Expr>, rhs: Box<Expr> }
}

impl Expr {
    fn new_bin(lhs: Box<Expr>, rhs: Box<Expr>) -> Expr {
        Expr::Bin { lhs, rhs }
    }
}
"#,
        );
    }

    #[test]
    fn test_fill_struct_fields_partial() {
        check_fix(
            r#"
struct TestStruct { one: i32, two: i64 }

fn test_fn() {
    let s = TestStruct{ two: 2$0 };
}
"#,
            r"
struct TestStruct { one: i32, two: i64 }

fn test_fn() {
    let s = TestStruct{ two: 2, one: todo!() };
}
",
        );
    }

    #[test]
    fn test_fill_struct_fields_raw_ident() {
        check_fix(
            r#"
struct TestStruct { r#type: u8 }

fn test_fn() {
    TestStruct { $0 };
}
"#,
            r"
struct TestStruct { r#type: u8 }

fn test_fn() {
    TestStruct { r#type: todo!()  };
}
",
        );
    }

    #[test]
    fn test_fill_struct_fields_no_diagnostic() {
        check_diagnostics(
            r#"
struct TestStruct { one: i32, two: i64 }

fn test_fn() {
    let one = 1;
    let s = TestStruct{ one, two: 2 };
}
        "#,
        );
    }

    #[test]
    fn test_fill_struct_fields_no_diagnostic_on_spread() {
        check_diagnostics(
            r#"
struct TestStruct { one: i32, two: i64 }

fn test_fn() {
    let one = 1;
    let s = TestStruct{ ..a };
}
"#,
        );
    }

    #[test]
    fn test_fill_struct_fields_blank_line() {
        check_fix(
            r#"
struct S { a: (), b: () }

fn f() {
    S {
        $0
    };
}
"#,
            r#"
struct S { a: (), b: () }

fn f() {
    S {
        a: todo!(),
        b: todo!(),
    };
}
"#,
        );
    }

    #[test]
    fn test_fill_struct_fields_shorthand() {
        cov_mark::check!(field_shorthand);
        check_fix(
            r#"
struct S { a: &'static str, b: i32 }

fn f() {
    let a = "hello";
    let b = 1i32;
    S {
        $0
    };
}
"#,
            r#"
struct S { a: &'static str, b: i32 }

fn f() {
    let a = "hello";
    let b = 1i32;
    S {
        a,
        b,
    };
}
"#,
        );
    }

    #[test]
    fn test_fill_struct_fields_shorthand_ty_mismatch() {
        check_fix(
            r#"
struct S { a: &'static str, b: i32 }

fn f() {
    let a = "hello";
    let b = 1usize;
    S {
        $0
    };
}
"#,
            r#"
struct S { a: &'static str, b: i32 }

fn f() {
    let a = "hello";
    let b = 1usize;
    S {
        a,
        b: todo!(),
    };
}
"#,
        );
    }

    #[test]
    fn test_fill_struct_fields_shorthand_unifies() {
        check_fix(
            r#"
struct S<T> { a: &'static str, b: T }

fn f() {
    let a = "hello";
    let b = 1i32;
    S {
        $0
    };
}
"#,
            r#"
struct S<T> { a: &'static str, b: T }

fn f() {
    let a = "hello";
    let b = 1i32;
    S {
        a,
        b,
    };
}
"#,
        );
    }

    #[test]
    fn import_extern_crate_clash_with_inner_item() {
        // This is more of a resolver test, but doesn't really work with the hir_def testsuite.

        check_diagnostics(
            r#"
//- /lib.rs crate:lib deps:jwt
mod permissions;

use permissions::jwt;

fn f() {
    fn inner() {}
    jwt::Claims {}; // should resolve to the local one with 0 fields, and not get a diagnostic
}

//- /permissions.rs
pub mod jwt  {
    pub struct Claims {}
}

//- /jwt/lib.rs crate:jwt
pub struct Claims {
    field: u8,
}
        "#,
        );
    }
}