import { baseUrl, bit, id, normalizeConfig, ossSettings, qualified, sha256 } from './core.mjs';

const RUNS_TABLE = 'infra_file_oss_migration_runs';
const RESTORED_FIELDS = [
  'sourceConfigIds', 'targetConfigId', 'sourceMode', 'downloadBaseUrl', 'oldDomains',
  'objectPrefix', 'imagesOnly', 'referenceSchemas', 'excludeReferenceTables', 'targetUrlMode'
];
const hasValue = (value, key) => Object.prototype.hasOwnProperty.call(value, key) && value[key] !== undefined;
const sortedIds = values => [...new Set(values.map(id))].sort((left, right) => BigInt(left) < BigInt(right) ? -1 : BigInt(left) > BigInt(right) ? 1 : 0);

function assertIdentity(expected, current) {
  if (!expected || expected.server !== current.server || expected.schema !== current.schema) {
    throw new Error('数据库身份与原迁移配置不一致，请检查数据库连接和批次编号');
  }
}

function parseRunSettings(value) {
  let settings;
  try {
    settings = typeof value === 'string' ? JSON.parse(value) : value;
  } catch {
    throw new Error('迁移批次的配置记录损坏，不能自动恢复');
  }
  if (!settings || typeof settings !== 'object' || !settings.binding || typeof settings.binding !== 'object') {
    throw new Error('迁移批次缺少原始配置绑定，不能自动恢复');
  }
  return settings;
}

function selectRun(rows, requestedRunId) {
  if (requestedRunId !== undefined) return rows.find(row => row.run_id === requestedRunId);
  const unfinished = rows.filter(row => !['complete', 'rolled_back'].includes(row.status));
  if (unfinished.length > 1) throw new Error('存在多个未完成迁移批次，请使用 --run-id 指定要继续的批次');
  if (unfinished.length === 1) return unfinished[0];
  if (rows.length > 1) throw new Error('存在多个历史迁移批次，请使用 --run-id 指定批次，或指定新的批次编号');
  return rows[0];
}

function contentId(value) {
  if ((typeof value === 'number' && !Number.isSafeInteger(value)) || !/^\d+$/.test(String(value))) {
    throw new Error('迁移批次的内容上界无效，不能安全判断增量数据');
  }
  return BigInt(value);
}

/**
 * Read-only discovery of storage configuration and a stable migration run.
 * This function never emits logs, persists configuration, or returns the OSS
 * credentials read from infra_file_config. Explicit input fields take priority
 * over a restored binding; loadSettings/runApply validate the final fingerprint.
 */
export async function discoverStorageConfig(db, input, { command = 'plan' } = {}) {
  if (!input?.mysql?.database) throw new Error('缺少本地数据库名称，无法自动识别文件存储');
  const schema = input.mysql.database;
  const [[serverRow]] = await db.execute('SELECT @@server_uuid AS server_uuid');
  if (!serverRow?.server_uuid) throw new Error('无法读取数据库服务器身份');
  const identity = { server: serverRow.server_uuid, schema };
  if (hasValue(input, '_databaseIdentity')) assertIdentity(input._databaseIdentity, identity);

  const [runTable] = await db.execute(
    "SELECT 1 AS present FROM information_schema.TABLES WHERE TABLE_SCHEMA=? AND TABLE_NAME=? AND TABLE_TYPE='BASE TABLE' LIMIT 1",
    [schema, RUNS_TABLE]
  );
  let history = [];
  if (runTable.length) {
    [history] = await db.execute(`SELECT run_id,settings,status FROM ${qualified(schema, RUNS_TABLE)}`);
  }
  const selected = selectRun(history, input.runId);
  const settings = selected ? parseRunSettings(selected.settings) : undefined;
  const config = { ...input, mysql: { ...input.mysql } };
  if (selected) {
    assertIdentity(settings.binding, identity);
    for (const key of RESTORED_FIELDS) {
      if (!hasValue(input, key) && hasValue(settings.binding, key)) {
        config[key] = structuredClone(settings.binding[key]);
      }
    }
    if (!hasValue(input, 'targetPublicDomain') && hasValue(settings.binding, 'publicDomain')) {
      config.targetPublicDomain = settings.binding.publicDomain;
    }
    config.runId = selected.run_id;
    if (command === 'apply' && (selected.status.startsWith('rollback') || selected.status === 'rolled_back')) {
      throw new Error('该批次已开始或完成回滚，不能继续迁移；请继续 rollback，或使用 --run-id 指定新批次');
    }
  } else if (command === 'rollback') {
    throw new Error('未找到可回滚的历史迁移批次，请使用 --run-id 指定已有批次');
  }

  config._databaseIdentity = identity;
  config._autoDiscovery = true;
  delete config._projectDownloadBaseUrl;

  // Rollback only restores journalled database values. Current storage rows,
  // default targets and OSS credentials are deliberately irrelevant here.
  if (command === 'rollback') return normalizeConfig(config);

  if (!hasValue(config, 'sourceMode')) config.sourceMode = 'database';
  if (!hasValue(config, 'downloadBaseUrl') && input._projectDownloadBaseUrl) {
    config.downloadBaseUrl = input._projectDownloadBaseUrl;
  }
  const [storageRows] = await db.execute(`SELECT id,storage,master,config FROM ${qualified(schema, 'infra_file_config')} WHERE deleted=0`);
  const byId = new Map(storageRows.map(row => [id(row.id), row]));
  const masters = storageRows.filter(row => bit(row.master));
  const requireDefault = !hasValue(config, 'targetConfigId') || input._autoDiscovery === true || Boolean(selected);
  if (requireDefault && masters.length !== 1) {
    throw new Error('默认文件存储配置必须唯一，请先在文件配置中设置唯一的阿里云 OSS 默认存储');
  }
  if (!hasValue(config, 'targetConfigId')) config.targetConfigId = id(masters[0].id);
  config.targetConfigId = id(config.targetConfigId);
  if (requireDefault && (id(masters[0].id) !== config.targetConfigId
      || (selected && id(masters[0].id) !== id(settings.binding.targetConfigId)))) {
    throw new Error('当前默认 OSS 与原迁移目标不同，不能自动续跑；请恢复原默认配置或使用 --run-id 建立新批次');
  }
  const target = byId.get(config.targetConfigId);
  if (!target) throw new Error('目标文件存储配置不存在或已删除');
  try {
    ossSettings(target, config);
  } catch {
    // JSON/URL parsing errors must not include raw configuration or secrets.
    throw new Error('目标默认存储不是有效的阿里云 OSS 配置，请检查类型、endpoint、Bucket 和访问凭据');
  }

  if (!hasValue(config, 'sourceConfigIds')) {
    const databaseIds = sortedIds(storageRows.filter(row => Number(row.storage) === 1).map(row => row.id));
    let contents = [];
    if (databaseIds.length) {
      [contents] = await db.execute(
        `SELECT DISTINCT config_id FROM ${qualified(schema, 'infra_file_content')} WHERE deleted=0 AND config_id IN (${databaseIds.map(() => '?').join(',')})`,
        databaseIds
      );
    }
    config.sourceConfigIds = sortedIds(contents.map(row => row.config_id));
  }
  if (!Array.isArray(config.sourceConfigIds) || !config.sourceConfigIds.length) {
    throw new Error('未发现包含未删除内容的数据库存储配置，无需迁移');
  }
  config.sourceConfigIds = [...new Set(config.sourceConfigIds.map(id))];
  for (const sourceId of config.sourceConfigIds) {
    const source = byId.get(sourceId);
    if (!source || Number(source.storage) !== 1) throw new Error('原数据库存储配置不存在、已删除或类型发生变化，请检查原迁移绑定');
    if (bit(source.master)) throw new Error('源配置仍是默认上传配置，请先切换默认配置到阿里云 OSS');
  }

  if (selected && selected.status !== 'inventory' && command === 'apply') {
    const sourceIds = settings.binding.sourceConfigIds.map(id);
    if (!sourceIds.length) throw new Error('历史迁移批次的源配置列表为空，不能安全续跑');
    const [[maximum]] = await db.execute(
      `SELECT COALESCE(MAX(id),0) AS max_id FROM ${qualified(schema, 'infra_file_content')} WHERE deleted=0 AND config_id IN (${sourceIds.map(() => '?').join(',')})`,
      sourceIds
    );
    if (contentId(maximum.max_id) > contentId(settings.maxId)) {
      throw new Error('原批次建立后出现新的数据库文件，请使用 --run-id 指定新批次，避免遗漏新增内容');
    }
  }

  if (!hasValue(config, 'oldDomains')) {
    const [domains] = await db.execute(
      `SELECT DISTINCT SUBSTRING_INDEX(url,'/admin-api/infra/file/',1) AS domain FROM ${qualified(schema, 'infra_file')} WHERE deleted=0 AND config_id IN (${config.sourceConfigIds.map(() => '?').join(',')}) AND url LIKE '%/admin-api/infra/file/%'`,
      config.sourceConfigIds
    );
    const validDomains = new Set();
    for (const row of domains) {
      try { validDomains.add(baseUrl(row.domain)); } catch { /* Ignore malformed and credential-bearing historical URLs. */ }
    }
    config.oldDomains = [...validDomains].sort();
  }

  if (!hasValue(config, 'runId')) {
    const fingerprint = { ...identity, sourceConfigIds: sortedIds(config.sourceConfigIds), targetConfigId: config.targetConfigId };
    config.runId = `db-images-${sha256(JSON.stringify(fingerprint)).slice(0, 16)}`;
  }
  return normalizeConfig(config);
}