//! Provides validations for unsafe code. Currently checks if unsafe functions are missing
//! unsafe blocks.

use std::sync::Arc;

use hir_def::{DefWithBodyId, FunctionId};
use hir_expand::diagnostics::DiagnosticSink;

use crate::{
    db::HirDatabase, diagnostics::MissingUnsafe, lower::CallableDef, ApplicationTy,
    InferenceResult, Ty, TypeCtor,
};

use rustc_hash::FxHashSet;

pub use hir_def::{
    body::{
        scope::{ExprScopes, ScopeEntry, ScopeId},
        Body, BodySourceMap, ExprPtr, ExprSource, PatPtr, PatSource,
    },
    expr::{
        ArithOp, Array, BinaryOp, BindingAnnotation, CmpOp, Expr, ExprId, Literal, LogicOp,
        MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField, Statement, UnaryOp,
    },
    LocalFieldId, VariantId,
};

pub struct UnsafeValidator<'a, 'b: 'a> {
    func: FunctionId,
    infer: Arc<InferenceResult>,
    sink: &'a mut DiagnosticSink<'b>,
}

impl<'a, 'b> UnsafeValidator<'a, 'b> {
    pub fn new(
        func: FunctionId,
        infer: Arc<InferenceResult>,
        sink: &'a mut DiagnosticSink<'b>,
    ) -> UnsafeValidator<'a, 'b> {
        UnsafeValidator { func, infer, sink }
    }

    pub fn validate_body(&mut self, db: &dyn HirDatabase) {
        let def = self.func.into();
        let unsafe_expressions = unsafe_expressions(db, self.infer.as_ref(), def);
        let func_data = db.function_data(self.func);
        if func_data.is_unsafe
            || unsafe_expressions
                .iter()
                .filter(|unsafe_expr| !unsafe_expr.inside_unsafe_block)
                .count()
                == 0
        {
            return;
        }

        let (_, body_source) = db.body_with_source_map(def);
        for unsafe_expr in unsafe_expressions {
            if !unsafe_expr.inside_unsafe_block {
                if let Ok(in_file) = body_source.as_ref().expr_syntax(unsafe_expr.expr) {
                    self.sink.push(MissingUnsafe { file: in_file.file_id, expr: in_file.value })
                }
            }
        }
    }
}

pub struct UnsafeExpr {
    pub expr: ExprId,
    pub inside_unsafe_block: bool,
}

impl UnsafeExpr {
    fn new(expr: ExprId) -> Self {
        Self { expr, inside_unsafe_block: false }
    }
}

pub fn unsafe_expressions(
    db: &dyn HirDatabase,
    infer: &InferenceResult,
    def: DefWithBodyId,
) -> Vec<UnsafeExpr> {
    let mut unsafe_exprs = vec![];
    let mut unsafe_block_exprs = FxHashSet::default();
    let body = db.body(def);
    for (id, expr) in body.exprs.iter() {
        match expr {
            Expr::Unsafe { .. } => {
                unsafe_block_exprs.insert(id);
            }
            Expr::Call { callee, .. } => {
                let ty = &infer[*callee];
                if let &Ty::Apply(ApplicationTy {
                    ctor: TypeCtor::FnDef(CallableDef::FunctionId(func)),
                    ..
                }) = ty
                {
                    if db.function_data(func).is_unsafe {
                        unsafe_exprs.push(UnsafeExpr::new(id));
                    }
                }
            }
            Expr::MethodCall { .. } => {
                if infer
                    .method_resolution(id)
                    .map(|func| db.function_data(func).is_unsafe)
                    .unwrap_or(false)
                {
                    unsafe_exprs.push(UnsafeExpr::new(id));
                }
            }
            Expr::UnaryOp { expr, op: UnaryOp::Deref } => {
                if let Ty::Apply(ApplicationTy { ctor: TypeCtor::RawPtr(..), .. }) = &infer[*expr] {
                    unsafe_exprs.push(UnsafeExpr::new(id));
                }
            }
            _ => {}
        }
    }

    'unsafe_exprs: for unsafe_expr in &mut unsafe_exprs {
        let mut child = unsafe_expr.expr;
        while let Some(parent) = body.parent_map.get(child) {
            if unsafe_block_exprs.contains(parent) {
                unsafe_expr.inside_unsafe_block = true;
                continue 'unsafe_exprs;
            }
            child = *parent;
        }
    }

    unsafe_exprs
}