/*
 * Copyright (c) 2020, Matthew Olsson <mattco@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Function.h>
#include <LibJS/Heap/Heap.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/PrimitiveString.h>
#include <LibJS/Runtime/RegExpObject.h>
#include <LibJS/Runtime/Value.h>

namespace JS {

static Flags options_from(const String& flags)
{
    Flags options {
        // JS regexps are all 'global' by default as per our definition, but the "global" flag enables "stateful".
        // FIXME: Enable 'BrowserExtended' only if in a browser context.
        .effective_flags = { (regex::ECMAScriptFlags)regex::AllFlags::Global | (regex::ECMAScriptFlags)regex::AllFlags::SkipTrimEmptyMatches | regex::ECMAScriptFlags::BrowserExtended },
        .declared_flags = {},
    };

    for (auto ch : flags) {
        switch (ch) {
        case 'g':
            options.effective_flags |= regex::ECMAScriptFlags::Global;
            options.declared_flags |= regex::ECMAScriptFlags::Global;
            break;
        case 'i':
            options.effective_flags |= regex::ECMAScriptFlags::Insensitive;
            options.declared_flags |= regex::ECMAScriptFlags::Insensitive;
            break;
        case 'm':
            options.effective_flags |= regex::ECMAScriptFlags::Multiline;
            options.declared_flags |= regex::ECMAScriptFlags::Multiline;
            break;
        case 's':
            options.effective_flags |= regex::ECMAScriptFlags::SingleLine;
            options.declared_flags |= regex::ECMAScriptFlags::SingleLine;
            break;
        case 'u':
            options.effective_flags |= regex::ECMAScriptFlags::Unicode;
            options.declared_flags |= regex::ECMAScriptFlags::Unicode;
            break;
        case 'y':
            // Now for the more interesting flag, 'sticky' actually unsets 'global', part of which is the default.
            options.effective_flags.reset_flag(regex::ECMAScriptFlags::Global);
            // "What's the difference between sticky and global, then", that's simple.
            // all the other flags imply 'global', and the "global" flag implies 'stateful';
            // however, the "sticky" flag does *not* imply 'global', only 'stateful'.
            options.effective_flags |= (regex::ECMAScriptFlags)regex::AllFlags::Internal_Stateful;
            options.effective_flags |= regex::ECMAScriptFlags::Sticky;
            options.declared_flags |= regex::ECMAScriptFlags::Sticky;
            break;
        default:
            // RegExp flags must be validated by the parser.
            VERIFY_NOT_REACHED();
        }
    }

    return options;
}

RegExpObject* RegExpObject::create(GlobalObject& global_object, String pattern, String flags)
{
    return global_object.heap().allocate<RegExpObject>(global_object, pattern, flags, *global_object.regexp_prototype());
}

RegExpObject::RegExpObject(String pattern, String flags, Object& prototype)
    : Object(prototype)
    , m_pattern(pattern)
    , m_flags(flags)
    , m_active_flags(options_from(m_flags))
    , m_regex(pattern, m_active_flags.effective_flags)
{
    if (m_regex.parser_result.error != regex::Error::NoError) {
        vm().throw_exception<SyntaxError>(global_object(), ErrorType::RegExpCompileError, m_regex.error_string());
    }
}

void RegExpObject::initialize(GlobalObject& global_object)
{
    auto& vm = this->vm();
    Object::initialize(global_object);

    define_native_property(vm.names.lastIndex, last_index, set_last_index, Attribute::Writable);
}

RegExpObject::~RegExpObject()
{
}

static RegExpObject* regexp_object_from(VM& vm, GlobalObject& global_object)
{
    auto* this_object = vm.this_value(global_object).to_object(global_object);
    if (!this_object)
        return nullptr;
    if (!is<RegExpObject>(this_object)) {
        vm.throw_exception<TypeError>(global_object, ErrorType::NotA, "RegExp");
        return nullptr;
    }
    return static_cast<RegExpObject*>(this_object);
}

JS_DEFINE_NATIVE_GETTER(RegExpObject::last_index)
{
    auto regexp_object = regexp_object_from(vm, global_object);
    if (!regexp_object)
        return {};

    return Value((unsigned)regexp_object->regex().start_offset);
}

JS_DEFINE_NATIVE_SETTER(RegExpObject::set_last_index)
{
    auto regexp_object = regexp_object_from(vm, global_object);
    if (!regexp_object)
        return;

    auto index = value.to_i32(global_object);
    if (vm.exception())
        return;

    if (index < 0)
        index = 0;

    regexp_object->regex().start_offset = index;
}

RegExpObject* regexp_create(GlobalObject& global_object, Value pattern, Value flags)
{
    // https://tc39.es/ecma262/#sec-regexpcreate
    String p;
    if (pattern.is_undefined()) {
        p = String::empty();
    } else {
        p = pattern.to_string(global_object);
        if (p.is_null())
            return nullptr;
    }
    String f;
    if (flags.is_undefined()) {
        f = String::empty();
    } else {
        f = flags.to_string(global_object);
        if (f.is_null())
            return nullptr;
    }
    return RegExpObject::create(global_object, move(p), move(f));
}

}