'use strict';

/** 与 Unity / 主站 config.js BEGINNING_REAL_LVID、LevelRegistry.LEVEL_ID_BASE 一致 */
const LEVEL_ID_BASE = 91601;
const PREFAB_DIR = 'level-prefabs';

/** internalIndex 0 → 91601（首关） */
function externalLevelId(internalIndex) {
    return LEVEL_ID_BASE + internalIndex;
}

function internalLevelIndex(levelId) {
    return levelId >= LEVEL_ID_BASE ? levelId - LEVEL_ID_BASE : levelId;
}

function isGameLevelId(levelId) {
    return levelId >= LEVEL_ID_BASE;
}

function isExternalLevelId(levelId) {
    return isGameLevelId(levelId);
}

function minLevelId() {
    return LEVEL_ID_BASE;
}

function prefabResourcePath(levelId) {
    return `${PREFAB_DIR}/Level${levelId}`;
}

function normalizeDb(db) {
    if (!db.levels) db.levels = {};
    db.levelIdBase = LEVEL_ID_BASE;
    return db;
}

function nextAvailableLevelId(db) {
    const keys = Object.keys(db.levels || {});
    if (!keys.length) return LEVEL_ID_BASE;
    const ids = keys.map((k) => parseInt(k, 10)).filter((n) => !Number.isNaN(n));
    return Math.max(...ids) + 1;
}

function syncLevelEntry(cfg, levelId) {
    const out = { ...cfg };
    out.levelID = levelId;
    out.cocosPrefab = prefabResourcePath(levelId);
    if (typeof out.unityPrefab === 'string' && out.unityPrefab) {
        out.unityPrefab = out.unityPrefab.replace(/Level\d+\.prefab$/i, `Level${levelId}.prefab`);
    }
    return out;
}

function updateDbStats(db) {
    const total = Object.keys(db.levels || {}).length;
    db.stats = { ...(db.stats || {}), total, withPrefabTilemap: total };
}

function touchDatabase(db, levelId) {
    normalizeDb(db);
    const key = String(levelId);
    if (db.levels[key]) {
        db.levels[key] = syncLevelEntry(db.levels[key], levelId);
    }
    updateDbStats(db);
    db.generatedAt = new Date().toISOString();
}

function sortedLevelIds(db) {
    return Object.keys(db.levels || {})
        .map((k) => parseInt(k, 10))
        .filter((n) => !Number.isNaN(n))
        .sort((a, b) => a - b);
}

function prevLevelIdInDb(db, cur) {
    const ids = sortedLevelIds(db);
    if (!ids.length) return cur;
    const i = ids.indexOf(cur);
    if (i < 0) return ids[0];
    return ids[(i - 1 + ids.length) % ids.length];
}

function nextLevelIdInDb(db, cur) {
    const ids = sortedLevelIds(db);
    if (!ids.length) return cur;
    const i = ids.indexOf(cur);
    if (i < 0) return ids[0];
    return ids[(i + 1) % ids.length];
}

module.exports = {
    LEVEL_ID_BASE,
    PREFAB_DIR,
    externalLevelId,
    internalLevelIndex,
    isExternalLevelId,
    minLevelId,
    prefabResourcePath,
    normalizeDb,
    nextAvailableLevelId,
    syncLevelEntry,
    updateDbStats,
    touchDatabase,
    sortedLevelIds,
    prevLevelIdInDb,
    nextLevelIdInDb,
};