// Expression lowering split from builder.rs to keep files lean
use super::{MirInstruction, ConstValue, ValueId};
use crate::ast::ASTNode;

impl super::MirBuilder {
    // Main expression dispatcher
    pub(super) fn build_expression_impl(&mut self, ast: ASTNode) -> Result<ValueId, String> {
        if matches!(ast,
            ASTNode::Program { .. }
            | ASTNode::Print { .. }
            | ASTNode::If { .. }
            | ASTNode::Loop { .. }
            | ASTNode::TryCatch { .. }
            | ASTNode::Throw { .. }
        ) {
            return self.build_expression_impl_legacy(ast);
        }
        match ast {
            ASTNode::Literal { value, .. } => self.build_literal(value),

            ASTNode::BinaryOp { left, operator, right, .. } =>
                self.build_binary_op(*left, operator, *right),

            ASTNode::UnaryOp { operator, operand, .. } => {
                let op_string = match operator {
                    crate::ast::UnaryOperator::Minus => "-".to_string(),
                    crate::ast::UnaryOperator::Not => "not".to_string(),
                };
                self.build_unary_op(op_string, *operand)
            }

            ASTNode::Variable { name, .. } => self.build_variable_access(name.clone()),

            ASTNode::Me { .. } => self.build_me_expression(),

            ASTNode::MethodCall { object, method, arguments, .. } => {
                if (method == "is" || method == "as") && arguments.len() == 1 {
                    if let Some(type_name) = Self::extract_string_literal(&arguments[0]) {
                        let obj_val = self.build_expression_impl(*object.clone())?;
                        let ty = Self::parse_type_name_to_mir(&type_name);
                        let dst = self.value_gen.next();
                        let op = if method == "is" { crate::mir::TypeOpKind::Check } else { crate::mir::TypeOpKind::Cast };
                        self.emit_instruction(MirInstruction::TypeOp { dst, op, value: obj_val, ty })?;
                        return Ok(dst);
                    }
                }
                self.build_method_call(*object.clone(), method.clone(), arguments.clone())
            }

            ASTNode::FromCall { parent, method, arguments, .. } =>
                self.build_from_expression(parent.clone(), method.clone(), arguments.clone()),

            ASTNode::Assignment { target, value, .. } => {
                if let ASTNode::FieldAccess { object, field, .. } = target.as_ref() {
                    self.build_field_assignment(*object.clone(), field.clone(), *value.clone())
                } else if let ASTNode::Variable { name, .. } = target.as_ref() {
                    self.build_assignment(name.clone(), *value.clone())
                } else {
                    Err("Complex assignment targets not yet supported".to_string())
                }
            }

            ASTNode::FunctionCall { name, arguments, .. } =>
                self.build_function_call(name.clone(), arguments.clone()),

            ASTNode::Call { callee, arguments, .. } =>
                self.build_indirect_call_expression(*callee.clone(), arguments.clone()),

            ASTNode::QMarkPropagate { expression, .. } =>
                self.build_qmark_propagate_expression(*expression.clone()),

            ASTNode::PeekExpr { scrutinee, arms, else_expr, .. } =>
                self.build_peek_expression(*scrutinee.clone(), arms.clone(), *else_expr.clone()),

            ASTNode::Lambda { params, body, .. } =>
                self.build_lambda_expression(params.clone(), body.clone()),

            ASTNode::Return { value, .. } => self.build_return_statement(value.clone()),

            // Control flow: break/continue are handled inside LoopBuilder context

            ASTNode::Local { variables, initial_values, .. } =>
                self.build_local_statement(variables.clone(), initial_values.clone()),

            ASTNode::BoxDeclaration { name, methods, is_static, fields, constructors, weak_fields, .. } => {
                if is_static && name == "Main" {
                    self.build_static_main_box(name.clone(), methods.clone())
                } else {
                    self.user_defined_boxes.insert(name.clone());
                    self.build_box_declaration(name.clone(), methods.clone(), fields.clone(), weak_fields.clone())?;
                    for (ctor_key, ctor_ast) in constructors.clone() {
                        if let ASTNode::FunctionDeclaration { params, body, .. } = ctor_ast {
                            let func_name = format!("{}.{}", name, ctor_key);
                            self.lower_method_as_function(func_name, name.clone(), params.clone(), body.clone())?;
                        }
                    }
                    for (method_name, method_ast) in methods.clone() {
                        if let ASTNode::FunctionDeclaration { params, body, is_static, .. } = method_ast {
                            if !is_static {
                                let func_name = format!("{}.{}{}", name, method_name, format!("/{}", params.len()));
                                self.lower_method_as_function(func_name, name.clone(), params.clone(), body.clone())?;
                            }
                        }
                    }
                    let void_val = self.value_gen.next();
                    self.emit_instruction(MirInstruction::Const { dst: void_val, value: ConstValue::Void })?;
                    Ok(void_val)
                }
            }

            ASTNode::FieldAccess { object, field, .. } =>
                self.build_field_access(*object.clone(), field.clone()),

            ASTNode::New { class, arguments, .. } =>
                self.build_new_expression(class.clone(), arguments.clone()),

            ASTNode::Nowait { variable, expression, .. } =>
                self.build_nowait_statement(variable.clone(), *expression.clone()),

            ASTNode::AwaitExpression { expression, .. } =>
                self.build_await_expression(*expression.clone()),

            ASTNode::Include { filename, .. } =>
                self.build_include_expression(filename.clone()),

            ASTNode::Program { statements, .. } =>
                self.build_block(statements.clone()),

            ASTNode::Print { expression, .. } =>
                self.build_print_statement(*expression.clone()),

            ASTNode::If { condition, then_body, else_body, .. } => {
                let else_ast = if let Some(else_statements) = else_body {
                    Some(ASTNode::Program { statements: else_statements.clone(), span: crate::ast::Span::unknown() })
                } else { None };
                self.build_if_statement(
                    *condition.clone(),
                    ASTNode::Program { statements: then_body.clone(), span: crate::ast::Span::unknown() },
                    else_ast,
                )
            }

            ASTNode::Loop { condition, body, .. } =>
                self.build_loop_statement(*condition.clone(), body.clone()),

            ASTNode::TryCatch { try_body, catch_clauses, finally_body, .. } =>
                self.build_try_catch_statement(try_body.clone(), catch_clauses.clone(), finally_body.clone()),

            ASTNode::Throw { expression, .. } =>
                self.build_throw_statement(*expression.clone()),

            _ => Err(format!("Unsupported AST node type: {:?}", ast)),
        }
    }
}