const CONFIG_TABLE = 'h5_wechat_cursor_executor_config';
const CONFIG_SCOPE = 'global';
const POLICY_SOURCE_DEFAULT = 'default';
const POLICY_SOURCE_ADMIN_DB = 'admin-db';

const DEFAULT_INTENT_ALLOWLIST = Object.freeze(['page.generate']);
const DEFAULT_CHANNEL_ALLOWLIST = Object.freeze(['h5', 'wechat_mp']);

export const CURSOR_EXECUTOR_CHANNEL = Object.freeze({
  H5: 'h5',
  WECHAT_MP: 'wechat_mp',
});

function defaultConfigShape() {
  return {
    enabled: false,
    userAllowlist: [],
    channelAllowlist: [...DEFAULT_CHANNEL_ALLOWLIST],
    intentAllowlist: [...DEFAULT_INTENT_ALLOWLIST],
    fallbackToDeepseek: true,
    meta: {
      notes: '',
    },
  };
}

function normalizeBoolean(value, fallback = false) {
  if (value == null || value === '') return fallback;
  if (typeof value === 'boolean') return value;
  const normalized = String(value).trim().toLowerCase();
  if (['1', 'true', 'yes', 'on'].includes(normalized)) return true;
  if (['0', 'false', 'no', 'off'].includes(normalized)) return false;
  return fallback;
}

function normalizeStringList(value) {
  if (!Array.isArray(value)) {
    return String(value ?? '')
      .split(/[\n,]+/)
      .map((item) => item.trim())
      .filter(Boolean);
  }
  return value.map((item) => String(item ?? '').trim()).filter(Boolean);
}

function cloneConfig(config = null) {
  return structuredClone?.(config ?? defaultConfigShape())
    ?? JSON.parse(JSON.stringify(config ?? defaultConfigShape()));
}

function parseJsonLike(value, fallback) {
  if (value == null || value === '') return fallback;
  if (typeof value === 'string') {
    try {
      return JSON.parse(value);
    } catch {
      return fallback;
    }
  }
  if (typeof value === 'object') return value;
  return fallback;
}

function mergePatch(currentConfig, patch = {}) {
  const next = cloneConfig(currentConfig);
  if ('enabled' in patch) next.enabled = normalizeBoolean(patch.enabled, false);
  if ('userAllowlist' in patch) next.userAllowlist = normalizeStringList(patch.userAllowlist);
  if ('channelAllowlist' in patch) {
    const channels = normalizeStringList(patch.channelAllowlist);
    next.channelAllowlist = channels.length ? channels : [...DEFAULT_CHANNEL_ALLOWLIST];
  }
  if ('intentAllowlist' in patch) {
    const intents = normalizeStringList(patch.intentAllowlist);
    next.intentAllowlist = intents.length ? intents : [...DEFAULT_INTENT_ALLOWLIST];
  }
  if ('fallbackToDeepseek' in patch) {
    next.fallbackToDeepseek = normalizeBoolean(patch.fallbackToDeepseek, true);
  }
  if (patch?.meta && typeof patch.meta.notes === 'string') {
    next.meta.notes = patch.meta.notes;
  }
  return next;
}

function flattenPolicy(config, source) {
  const intentAllowlist = normalizeStringList(config.intentAllowlist);
  const channelAllowlist = normalizeStringList(config.channelAllowlist);
  return {
    source,
    enabled: Boolean(config.enabled),
    userAllowlist: normalizeStringList(config.userAllowlist),
    channelAllowlist: channelAllowlist.length ? channelAllowlist : [...DEFAULT_CHANNEL_ALLOWLIST],
    intentAllowlist: intentAllowlist.length ? intentAllowlist : [...DEFAULT_INTENT_ALLOWLIST],
    fallbackToDeepseek: config.fallbackToDeepseek !== false,
  };
}

export function isChannelAllowedByCursorPolicy(channel, policy) {
  const allowlist = normalizeStringList(policy?.channelAllowlist ?? DEFAULT_CHANNEL_ALLOWLIST)
    .map((item) => item.toLowerCase());
  if (allowlist.length === 0) return false;
  const normalized = String(channel ?? '').trim().toLowerCase();
  if (!normalized) return false;
  return allowlist.includes(normalized);
}

export function isUserAllowedByWechatCursorPolicy(user, policy) {
  if (!policy?.enabled) return false;
  const allowlist = normalizeStringList(policy.userAllowlist).map((item) => item.toLowerCase());
  if (allowlist.length === 0) return false;
  if (allowlist.includes('*')) return true;
  const identities = [
    user?.userId,
    user?.id,
    user?.username,
    user?.slug,
    user?.displayName,
    user?.nickname,
  ]
    .map((value) => String(value ?? '').trim().toLowerCase())
    .filter(Boolean);
  return identities.some((identity) => allowlist.includes(identity));
}

export function isIntentAllowedByWechatCursorPolicy(intentKind, policy) {
  const allowlist = (policy?.intentAllowlist ?? DEFAULT_INTENT_ALLOWLIST)
    .map((item) => String(item ?? '').trim())
    .filter(Boolean);
  const normalized = String(intentKind ?? '').trim();
  if (!normalized) return false;
  return allowlist.includes(normalized);
}

async function ensureConfigTable(pool) {
  await pool.query(`
    CREATE TABLE IF NOT EXISTS ${CONFIG_TABLE} (
      config_scope VARCHAR(32) PRIMARY KEY,
      config_json JSON NOT NULL,
      updated_by CHAR(36) NULL,
      updated_at BIGINT NOT NULL
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
  `);
}

async function loadStoredState(pool) {
  await ensureConfigTable(pool);
  const [rows] = await pool.query(
    `SELECT config_json, updated_by, updated_at
       FROM ${CONFIG_TABLE}
      WHERE config_scope = ?
      LIMIT 1`,
    [CONFIG_SCOPE],
  );
  const row = rows[0];
  if (!row) return null;
  const parsed = parseJsonLike(row.config_json, {});
  return {
    config: mergePatch(defaultConfigShape(), parsed),
    updatedAt: Number(row.updated_at ?? 0) || null,
    updatedBy: row.updated_by ?? null,
  };
}

export function createWechatCursorExecutorAdminConfigService(pool) {
  async function loadEffectiveConfig() {
    const stored = await loadStoredState(pool);
    if (stored) {
      return {
        config: cloneConfig(stored.config),
        updatedAt: stored.updatedAt,
        updatedBy: stored.updatedBy,
        source: POLICY_SOURCE_ADMIN_DB,
      };
    }
    return {
      config: defaultConfigShape(),
      updatedAt: null,
      updatedBy: null,
      source: POLICY_SOURCE_DEFAULT,
    };
  }

  return {
    async getAdminConfig() {
      const state = await loadEffectiveConfig();
      return {
        config: state.config,
        updatedAt: state.updatedAt,
        updatedBy: state.updatedBy,
        source: state.source,
      };
    },

    async updateAdminConfig(patch = {}, { updatedBy = null } = {}) {
      const stored = await loadStoredState(pool);
      const base = stored?.config ?? defaultConfigShape();
      const nextConfig = mergePatch(base, patch.config ?? patch);
      await ensureConfigTable(pool);
      const now = Date.now();
      await pool.query(
        `INSERT INTO ${CONFIG_TABLE}
          (config_scope, config_json, updated_by, updated_at)
         VALUES (?, ?, ?, ?)
         ON DUPLICATE KEY UPDATE
          config_json = VALUES(config_json),
          updated_by = VALUES(updated_by),
          updated_at = VALUES(updated_at)`,
        [CONFIG_SCOPE, JSON.stringify(nextConfig), updatedBy, now],
      );
      return this.getAdminConfig();
    },

    async getRuntimeState() {
      const state = await loadEffectiveConfig();
      const policy = flattenPolicy(state.config, state.source);
      return {
        source: state.source,
        updatedAt: state.updatedAt,
        updatedBy: state.updatedBy,
        config: state.config,
        policy,
      };
    },

    async getEffectivePolicy(userId, user = null) {
      const state = await loadEffectiveConfig();
      const policy = flattenPolicy(state.config, state.source);
      const subject = user ?? { userId };
      return {
        ...policy,
        userAllowed: isUserAllowedByWechatCursorPolicy(subject, policy),
      };
    },
  };
}

export const wechatCursorExecutorAdminConfigInternals = {
  CONFIG_TABLE,
  defaultConfigShape,
  mergePatch,
  flattenPolicy,
};