// Failed quests can be restarted (request of 2026-10-17): a failed quest is not
// final, the quest giver offers it again.
//
// Measured (docs/quests.md): a failed quest keeps flags 3 (triggered + done) in
// the quest table and its quest book entry gets state 101; Quest_Trigger
// (0x46de10) does nothing for a quest with flag 1, so the giver never offers it
// again. The game itself repeats only the generic quests (ids 2600..3599,
// Quest_End copies them under a new id).
//
// The mod: after Quest_End failed a quest (its failure script has run), the
// quest's flags are cleared and its book entries removed, as if it had never
// been triggered. Quests that failed before the mod are reset the same way once
// after loading.

#include <algorithm>
#include <cstdint>

#include "game/engine/events.h"
#include "game/engine/quests.h"
#include "re/hook.h"
#include "re/log.h"

namespace mods::questfail {
namespace {

constexpr uint32_t kResetFlags = game::kQuestTriggered | game::kQuestDone | game::kQuestInProgress | game::kQuestBusy;

bool g_resetAfterLoad = false;

// The quest at table `index` as if it had never been triggered.
void Restart(int index) {
    uint8_t* quest = game::Quest(index);
    const int32_t id = game::QuestId(quest);
    re::Log("questfail: restarting quest %d '%s' (flags %x)", id, game::QuestName(quest), game::QuestFlags(quest));
    game::QuestFlags(quest) &= ~kResetFlags;
    for (size_t i = game::BookCount(); i-- > 0;) {
        if (game::BookQuestId(game::BookEntry(i)) == id) {
            game::EraseBookEntry(i);
        }
    }
}

void RestartFailedInBook() {
    for (size_t i = game::BookCount(); i-- > 0;) {
        const uint8_t* entry = game::BookEntry(i);
        if (game::BookState(entry) != game::kBookFailed) {
            continue;
        }
        const int index = game::QuestIndex(game::BookQuestId(entry));
        if (index >= 0) {
            Restart(index);
        }
        i = std::min(i, game::BookCount());
    }
}

void OnTick(uint8_t*) {
    if (g_resetAfterLoad) {
        g_resetAfterLoad = false;
        RestartFailedInBook();
    }
}

void OnLoaded() {
    g_resetAfterLoad = true;
}

}  // namespace

// Quest_End (0x46ced0, quest manager thiscall (index, ?, success), ret 0xc):
// LoseQuest passes success 0, ExitQuest 1.
void __fastcall Quest_End(uint8_t* self, void* edx, int index, int a2, char success);
RE_HOOK(0x0046ced0, Quest_End);
void __fastcall Quest_End(uint8_t* self, void* edx, int index, int a2, char success) {
    Quest_End_original(self, edx, index, a2, success);
    if (!success && index >= 0 && static_cast<size_t>(index) < game::QuestCount()) {
        Restart(index);
    }
}

namespace {
struct Register {
    Register() {
        game::OnEngineTick(&OnTick);
        game::OnSaveGameLoaded(&OnLoaded);
    }
} g_register;
}  // namespace

}  // namespace mods::questfail