/*
 * Copyright (c) 2024, stelar7 <dudedbz@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/ArrayBuffer.h>
#include <LibJS/Runtime/DataView.h>
#include <LibJS/Runtime/Date.h>
#include <LibJS/Runtime/TypedArray.h>
#include <LibJS/Runtime/VM.h>
#include <LibWeb/DOM/EventDispatcher.h>
#include <LibWeb/HTML/EventNames.h>
#include <LibWeb/IndexedDB/IDBDatabase.h>
#include <LibWeb/IndexedDB/IDBRequest.h>
#include <LibWeb/IndexedDB/IDBVersionChangeEvent.h>
#include <LibWeb/IndexedDB/Internal/Algorithms.h>
#include <LibWeb/IndexedDB/Internal/ConnectionQueueHandler.h>
#include <LibWeb/IndexedDB/Internal/Database.h>
#include <LibWeb/StorageAPI/StorageKey.h>
#include <LibWeb/WebIDL/AbstractOperations.h>

namespace Web::IndexedDB {

// https://w3c.github.io/IndexedDB/#open-a-database-connection
WebIDL::ExceptionOr<GC::Ref<IDBDatabase>> open_a_database_connection(JS::Realm& realm, StorageAPI::StorageKey storage_key, String name, Optional<u64> maybe_version, GC::Ref<IDBRequest> request)
{
    // 1. Let queue be the connection queue for storageKey and name.
    auto& queue = ConnectionQueueHandler::for_key_and_name(storage_key, name);

    // 2. Add request to queue.
    queue.append(request);

    // 3. Wait until all previous requests in queue have been processed.
    HTML::main_thread_event_loop().spin_until(GC::create_function(realm.vm().heap(), [queue, request]() {
        return queue.all_previous_requests_processed(request);
    }));

    // 4. Let db be the database named name in storageKey, or null otherwise.
    auto maybe_db = Database::for_key_and_name(storage_key, name);
    GC::Ptr<Database> db;

    // 5. If version is undefined, let version be 1 if db is null, or db’s version otherwise.
    auto version = maybe_version.value_or(maybe_db.has_value() ? maybe_db.value()->version() : 1);

    // 6. If db is null, let db be a new database with name name, version 0 (zero), and with no object stores.
    // If this fails for any reason, return an appropriate error (e.g. a "QuotaExceededError" or "UnknownError" DOMException).
    if (!maybe_db.has_value()) {
        auto maybe_database = Database::create_for_key_and_name(realm, storage_key, name);

        if (maybe_database.is_error()) {
            return WebIDL::OperationError::create(realm, "Unable to create a new database"_string);
        }

        db = maybe_database.release_value();
    }

    // 7. If db’s version is greater than version, return a newly created "VersionError" DOMException and abort these steps.
    if (db->version() > version) {
        return WebIDL::VersionError::create(realm, "Database version is greater than the requested version"_string);
    }

    // 8. Let connection be a new connection to db.
    auto connection = IDBDatabase::create(realm, *db);

    // 9. Set connection’s version to version.
    connection->set_version(version);

    // 10. If db’s version is less than version, then:
    if (db->version() < version) {
        // 1. Let openConnections be the set of all connections, except connection, associated with db.
        auto open_connections = db->associated_connections_except(connection);

        // FIXME: 2. For each entry of openConnections that does not have its close pending flag set to true,
        //    queue a task to fire a version change event named versionchange at entry with db’s version and version.
        for (auto& entry : open_connections) {
            if (!entry->close_pending()) {
                HTML::queue_a_task(HTML::Task::Source::DatabaseAccess, nullptr, nullptr, GC::create_function(realm.vm().heap(), [&realm, entry, db, version]() {
                    fire_a_version_change_event(realm, HTML::EventNames::versionchange, *entry, db->version(), version);
                }));
            }
        }

        // FIXME: 3. Wait for all of the events to be fired.

        // FIXME: 4. If any of the connections in openConnections are still not closed,
        //    queue a task to fire a version change event named blocked at request with db’s version and version.
        for (auto& entry : open_connections) {
            if (entry->state() != IDBDatabase::ConnectionState::Closed) {
                HTML::queue_a_task(HTML::Task::Source::DatabaseAccess, nullptr, nullptr, GC::create_function(realm.vm().heap(), [&realm, entry, db, version]() {
                    fire_a_version_change_event(realm, HTML::EventNames::blocked, *entry, db->version(), version);
                }));
            }
        }

        // 5. Wait until all connections in openConnections are closed.
        HTML::main_thread_event_loop().spin_until(GC::create_function(realm.vm().heap(), [open_connections]() {
            for (auto const& entry : open_connections) {
                if (entry->state() != IDBDatabase::ConnectionState::Closed) {
                    return false;
                }
            }

            return true;
        }));

        // FIXME: 6. Run upgrade a database using connection, version and request.
        // NOTE: upgrade a database sets this flag, so we set it manually temporarily.
        request->set_processed(true);

        // 7. If connection was closed, return a newly created "AbortError" DOMException and abort these steps.
        if (connection->state() == IDBDatabase::ConnectionState::Closed) {
            return WebIDL::AbortError::create(realm, "Connection was closed"_string);
        }

        // FIXME: 8. If the upgrade transaction was aborted, run the steps to close a database connection with connection,
        // return a newly created "AbortError" DOMException and abort these steps.
    }

    // 11. Return connection.
    return connection;
}

bool fire_a_version_change_event(JS::Realm& realm, FlyString const& event_name, GC::Ref<DOM::EventTarget> target, u64 old_version, Optional<u64> new_version)
{
    IDBVersionChangeEventInit event_init = {};
    // 4. Set event’s oldVersion attribute to oldVersion.
    event_init.old_version = old_version;
    // 5. Set event’s newVersion attribute to newVersion.
    event_init.new_version = new_version;

    // 1. Let event be the result of creating an event using IDBVersionChangeEvent.
    // 2. Set event’s type attribute to e.
    auto event = IDBVersionChangeEvent::create(realm, event_name, event_init);

    // 3. Set event’s bubbles and cancelable attributes to false.
    event->set_bubbles(false);
    event->set_cancelable(false);

    // 6. Let legacyOutputDidListenersThrowFlag be false.
    auto legacy_output_did_listeners_throw_flag = false;

    // 7. Dispatch event at target with legacyOutputDidListenersThrowFlag.
    DOM::EventDispatcher::dispatch(target, *event, legacy_output_did_listeners_throw_flag);

    // 8. Return legacyOutputDidListenersThrowFlag.
    return legacy_output_did_listeners_throw_flag;
}

// https://w3c.github.io/IndexedDB/#convert-value-to-key
ErrorOr<Key> convert_a_value_to_a_key(JS::Realm& realm, JS::Value input, Vector<JS::Value> seen)
{
    // 1. If seen was not given, then let seen be a new empty set.
    // NOTE: This is handled by the caller.

    // 2. If seen contains input, then return invalid.
    if (seen.contains_slow(input))
        return Error::from_string_literal("Already seen key");

    // 3. Jump to the appropriate step below:

    // - If Type(input) is Number
    if (input.is_number()) {

        // 1. If input is NaN then return invalid.
        if (input.is_nan())
            return Error::from_string_literal("NaN key");

        // 2. Otherwise, return a new key with type number and value input.
        return Key::create_number(input.as_double());
    }

    // - If input is a Date (has a [[DateValue]] internal slot)
    if (input.is_object() && is<JS::Date>(input.as_object())) {

        // 1. Let ms be the value of input’s [[DateValue]] internal slot.
        auto& date = static_cast<JS::Date&>(input.as_object());
        auto ms = date.date_value();

        // 2. If ms is NaN then return invalid.
        if (isnan(ms))
            return Error::from_string_literal("NaN key");

        // 3. Otherwise, return a new key with type date and value ms.
        return Key::create_date(ms);
    }

    // - If Type(input) is String
    if (input.is_string()) {

        // 1. Return a new key with type string and value input.
        return Key::create_string(input.as_string().utf8_string());
    }

    // - If input is a buffer source type
    if (input.is_object() && (is<JS::TypedArrayBase>(input.as_object()) || is<JS::ArrayBuffer>(input.as_object()) || is<JS::DataView>(input.as_object()))) {

        // 1. Let bytes be the result of getting a copy of the bytes held by the buffer source input. Rethrow any exceptions.
        auto data_buffer = TRY(WebIDL::get_buffer_source_copy(input.as_object()));

        // 2. Return a new key with type binary and value bytes.
        return Key::create_binary(data_buffer);
    }

    // - If input is an Array exotic object
    if (input.is_object() && is<JS::Array>(input.as_object())) {

        // 1. Let len be ? ToLength( ? Get(input, "length")).
        auto maybe_length = length_of_array_like(realm.vm(), input.as_object());
        if (maybe_length.is_error())
            return Error::from_string_literal("Failed to get length of array-like object");

        auto length = maybe_length.release_value();

        // 2. Append input to seen.
        seen.append(input);

        // 3. Let keys be a new empty list.
        Vector<Key> keys;

        // 4. Let index be 0.
        u64 index = 0;

        // 5. While index is less than len:
        while (index < length) {
            // 1. Let hop be ? HasOwnProperty(input, index).
            auto maybe_hop = input.as_object().has_own_property(index);
            if (maybe_hop.is_error())
                return Error::from_string_literal("Failed to check if array-like object has property");

            auto hop = maybe_hop.release_value();

            // 2. If hop is false, return invalid.
            if (!hop)
                return Error::from_string_literal("Array-like object has no property");

            // 3. Let entry be ? Get(input, index).
            auto maybe_entry = input.as_object().get(index);
            if (maybe_entry.is_error())
                return Error::from_string_literal("Failed to get property of array-like object");

            // 4. Let key be the result of converting a value to a key with arguments entry and seen.
            auto maybe_key = convert_a_value_to_a_key(realm, maybe_entry.release_value(), seen);

            // 5. ReturnIfAbrupt(key).
            // 6. If key is invalid abort these steps and return invalid.
            if (maybe_key.is_error())
                return maybe_key.release_error();

            auto key = maybe_key.release_value();

            // 7. Append key to keys.
            keys.append(key);

            // 8. Increase index by 1.
            index++;
        }

        // 6. Return a new array key with value keys.
        return Key::create_array(keys);
    }

    // - Otherwise
    // 1. Return invalid.
    return Error::from_string_literal("Unknown key type");
}

// https://w3c.github.io/IndexedDB/#close-a-database-connection
void close_a_database_connection(IDBDatabase& connection, bool forced)
{
    // 1. Set connection’s close pending flag to true.
    connection.set_close_pending(true);

    // FIXME: 2. If the forced flag is true, then for each transaction created using connection run abort a transaction with transaction and newly created "AbortError" DOMException.
    // FIXME: 3. Wait for all transactions created using connection to complete. Once they are complete, connection is closed.
    connection.set_state(IDBDatabase::ConnectionState::Closed);

    // 4. If the forced flag is true, then fire an event named close at connection.
    if (forced)
        connection.dispatch_event(DOM::Event::create(connection.realm(), HTML::EventNames::close));
}

}