// Escorted NPCs stay on the hero's follower list (2026-10-26, docs/quests.md).
// "Furchtbares Verbrechen" (quest 9008) did not go on at its target point:
// the NPC walked after the hero, but the script's test there ("@npc", 0x498aa0
// case 0x40) looks the NPC up in the hero's follower list (hero +0x39c), and
// that list was empty (measured on Borf's save: NPC 0x1fa with leader 1 and
// the follow bit, no followers on the hero). The NPC keeps its side of the
// escort (leader +0x251, status bit 4) across a load; the hero's list does
// not come back. The mod adds every NPC that follows a hero but is missing
// from its list back with the game's own AddFollower (0x54b070), with the
// entry the follow order uses ({id, 1, 1}), once after loading.

#include <cstdint>

#include "game/engine/events.h"
#include "game/engine/objects.h"
#include "game/engine/orders.h"
#include "re/log.h"

namespace mods::followers {
namespace {

constexpr int kTicksAfterStart = 30;

// Small town NPCs run after the hero for a few seconds (status 0x404, leader
// the hero) without joining his list (measured 2026-10-26: types 0x2be,
// 0x2c0); they are not escorts.
constexpr int32_t kStatusTagAlong = 0x400;

int g_ticksToCheck = -1;

int32_t Field(const void* creature, size_t offset) {
    return *reinterpret_cast<const int32_t*>(static_cast<const uint8_t*>(creature) + offset);
}

void RepairFollowers() {
    for (uint32_t id = 1; id < game::ObjectIdEnd(); ++id) {
        if (game::IsPlayerHeroId(id) || !game::GetObjectById(id)) {
            continue;
        }
        void* creature = game::GetCreature(id);
        const int32_t status = creature ? Field(creature, game::kCreatureStatus) : 0;
        if (!(status & game::kStatusFollowing) || (status & kStatusTagAlong)) {
            continue;
        }
        const auto leaderId = static_cast<uint32_t>(Field(creature, game::kCreatureLeader));
        void* leader = game::IsPlayerHeroId(leaderId) ? game::GetCreature(leaderId) : nullptr;
        if (!leader || game::HasFollower(leader, id)) {
            continue;
        }
        game::AddFollower(leader, {id, 1, 1});
        re::Log("followers: %x back on the follower list of hero %x", id, leaderId);
    }
}

void OnTick(uint8_t*) {
    if (g_ticksToCheck > 0 && --g_ticksToCheck == 0) {
        RepairFollowers();
    }
}

void OnStart() {
    g_ticksToCheck = kTicksAfterStart;
}

struct Registration {
    Registration() {
        game::OnEngineTick(&OnTick);
        game::OnGameStart(&OnStart);
    }
} g_registration;

} // namespace
} // namespace mods::followers