/*

 * Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <LibJS/Interpreter.h>

#include <LibJS/Runtime/DeclarativeEnvironment.h>

#include <LibJS/Runtime/Error.h>

#include <LibJS/Runtime/FunctionObject.h>

#include <LibJS/Runtime/GlobalObject.h>

#include <LibJS/Runtime/Value.h>

namespace JS {

DeclarativeEnvironment* DeclarativeEnvironment::create_for_per_iteration_bindings(Badge<ForStatement>, DeclarativeEnvironment& other, size_t bindings_size)

{

    auto bindings = other.m_bindings.span().slice(0, bindings_size);

    auto* parent_environment = other.outer_environment();

    return parent_environment->heap().allocate_without_global_object<DeclarativeEnvironment>(parent_environment, bindings);

}

DeclarativeEnvironment::DeclarativeEnvironment()

    : Environment(nullptr)

{

}

DeclarativeEnvironment::DeclarativeEnvironment(Environment* parent_environment)

    : Environment(parent_environment)

{

}

DeclarativeEnvironment::DeclarativeEnvironment(Environment* parent_environment, Span<Binding const> bindings)

    : Environment(parent_environment)

    , m_bindings(bindings)

{

}

void DeclarativeEnvironment::visit_edges(Visitor& visitor)

{

    Base::visit_edges(visitor);

    for (auto& binding : m_bindings)

        visitor.visit(binding.value);

}

// 9.1.1.1.1 HasBinding ( N ), https://tc39.es/ecma262/#sec-declarative-environment-records-hasbinding-n

ThrowCompletionOr<bool> DeclarativeEnvironment::has_binding(FlyString const& name, Optional<size_t>* out_index) const

{

    auto index = find_binding_index(name);

    if (!index.has_value())

        return false;

    if (!is_permanently_screwed_by_eval() && out_index)

        *out_index = *index;

    return true;

}

// 9.1.1.1.2 CreateMutableBinding ( N, D ), https://tc39.es/ecma262/#sec-declarative-environment-records-createmutablebinding-n-d

ThrowCompletionOr<void> DeclarativeEnvironment::create_mutable_binding(GlobalObject&, FlyString const& name, bool can_be_deleted)

{

    // 1. Assert: envRec does not already have a binding for N.

    // NOTE: We skip this to avoid O(n) traversal of m_bindings.

    // 2. Create a mutable binding in envRec for N and record that it is uninitialized. If D is true, record that the newly created binding may be deleted by a subsequent DeleteBinding call.

    m_bindings.append(Binding {

        .name = name,

        .value = {},

        .strict = false,

        .mutable_ = true,

        .can_be_deleted = can_be_deleted,

        .initialized = false,

    });

    // 3. Return unused.

    return {};

}

// 9.1.1.1.3 CreateImmutableBinding ( N, S ), https://tc39.es/ecma262/#sec-declarative-environment-records-createimmutablebinding-n-s

ThrowCompletionOr<void> DeclarativeEnvironment::create_immutable_binding(GlobalObject&, FlyString const& name, bool strict)

{

    // 1. Assert: envRec does not already have a binding for N.

    // NOTE: We skip this to avoid O(n) traversal of m_bindings.

    // 2. Create an immutable binding in envRec for N and record that it is uninitialized. If S is true, record that the newly created binding is a strict binding.

    m_bindings.append(Binding {

        .name = name,

        .value = {},

        .strict = strict,

        .mutable_ = false,

        .can_be_deleted = false,

        .initialized = false,

    });

    // 3. Return unused.

    return {};

}

// 9.1.1.1.4 InitializeBinding ( N, V ), https://tc39.es/ecma262/#sec-declarative-environment-records-initializebinding-n-v

ThrowCompletionOr<void> DeclarativeEnvironment::initialize_binding(GlobalObject& global_object, FlyString const& name, Value value)

{

    auto index = find_binding_index(name);

    VERIFY(index.has_value());

    return initialize_binding_direct(global_object, *index, value);

}

ThrowCompletionOr<void> DeclarativeEnvironment::initialize_binding_direct(GlobalObject&, size_t index, Value value)

{

    auto& binding = m_bindings[index];

    // 1. Assert: envRec must have an uninitialized binding for N.

    VERIFY(binding.initialized == false);

    // 2. Set the bound value for N in envRec to V.

    binding.value = value;

    // 3. Record that the binding for N in envRec has been initialized.

    binding.initialized = true;

    // 4. Return unused.

    return {};

}

// 9.1.1.1.5 SetMutableBinding ( N, V, S ), https://tc39.es/ecma262/#sec-declarative-environment-records-setmutablebinding-n-v-s

ThrowCompletionOr<void> DeclarativeEnvironment::set_mutable_binding(GlobalObject& global_object, FlyString const& name, Value value, bool strict)

{

    // 1. If envRec does not have a binding for N, then

    auto index = find_binding_index(name);

    if (!index.has_value()) {

        // a. If S is true, throw a ReferenceError exception.

        if (strict)

            return vm().throw_completion<ReferenceError>(global_object, ErrorType::UnknownIdentifier, name);

        // FIXME: Should be `! envRec.CreateMutableBinding(N, true)` (see https://github.com/tc39/ecma262/pull/2764)

        // b. Perform envRec.CreateMutableBinding(N, true).

        MUST(create_mutable_binding(global_object, name, true));

        // c. Perform ! envRec.InitializeBinding(N, V).

        MUST(initialize_binding(global_object, name, value));

        // d. Return unused.

        return {};

    }

    // 2-5. (extracted into a non-standard function below)

    TRY(set_mutable_binding_direct(global_object, *index, value, strict));

    // 6. Return unused.

    return {};

}

ThrowCompletionOr<void> DeclarativeEnvironment::set_mutable_binding_direct(GlobalObject& global_object, size_t index, Value value, bool strict)

{

    auto& binding = m_bindings[index];

    if (binding.strict)

        strict = true;

    if (!binding.initialized)

        return vm().throw_completion<ReferenceError>(global_object, ErrorType::BindingNotInitialized, binding.name);

    if (binding.mutable_) {

        binding.value = value;

    } else {

        if (strict)

            return vm().throw_completion<TypeError>(global_object, ErrorType::InvalidAssignToConst);

    }

    return {};

}

// 9.1.1.1.6 GetBindingValue ( N, S ), https://tc39.es/ecma262/#sec-declarative-environment-records-getbindingvalue-n-s

ThrowCompletionOr<Value> DeclarativeEnvironment::get_binding_value(GlobalObject& global_object, FlyString const& name, bool strict)

{

    // 1. Assert: envRec has a binding for N.

    auto index = find_binding_index(name);

    VERIFY(index.has_value());

    // 2-3. (extracted into a non-standard function below)

    return get_binding_value_direct(global_object, *index, strict);

}

ThrowCompletionOr<Value> DeclarativeEnvironment::get_binding_value_direct(GlobalObject& global_object, size_t index, bool)

{

    auto& binding = m_bindings[index];

    // 2. If the binding for N in envRec is an uninitialized binding, throw a ReferenceError exception.

    if (!binding.initialized)

        return vm().throw_completion<ReferenceError>(global_object, ErrorType::BindingNotInitialized, binding.name);

    // 3. Return the value currently bound to N in envRec.

    return binding.value;

}

// 9.1.1.1.7 DeleteBinding ( N ), https://tc39.es/ecma262/#sec-declarative-environment-records-deletebinding-n

ThrowCompletionOr<bool> DeclarativeEnvironment::delete_binding(GlobalObject&, FlyString const& name)

{

    // 1. Assert: envRec has a binding for the name that is the value of N.

    auto index = find_binding_index(name);

    VERIFY(index.has_value());

    auto& binding = m_bindings[*index];

    // 2. If the binding for N in envRec cannot be deleted, return false.

    if (!binding.can_be_deleted)

        return false;

    // 3. Remove the binding for N from envRec.

    // NOTE: We keep the entries in m_bindings to avoid disturbing indices.

    binding = {};

    // 4. Return true.

    return true;

}

ThrowCompletionOr<void> DeclarativeEnvironment::initialize_or_set_mutable_binding(GlobalObject& global_object, FlyString const& name, Value value)

{

    auto index = find_binding_index(name);

    VERIFY(index.has_value());

    auto& binding = m_bindings[*index];

    if (!binding.initialized)

        TRY(initialize_binding(global_object, name, value));

    else

        TRY(set_mutable_binding(global_object, name, value, false));

    return {};

}

void DeclarativeEnvironment::initialize_or_set_mutable_binding(Badge<ScopeNode>, GlobalObject& global_object, FlyString const& name, Value value)

{

    MUST(initialize_or_set_mutable_binding(global_object, name, value));

}

}