// apps/server/src/lib/modules/model-loader.ts
import type { ModuleParams } from "@erp/core/api";
import type { Sequelize } from "sequelize";

import { logger } from "../logger";

type SequelizeLike = {
  sync: (options?: any) => Promise<void>;
  models: Record<string, unknown>;
};

type ModelStatic = {
  name: string;
  associate?: (sequelize: Sequelize) => void;
};

export type ModelInitializer = (sequelize: Sequelize) => ModelStatic;

type InitializerEntry = { init: ModelInitializer; moduleName: string };

type RegisteredModelEntry = {
  model: ModelStatic;
  moduleName: string;
};

const allModelInitializers: InitializerEntry[] = [];
const registeredModels: Map<string, RegisteredModelEntry> = new Map();

let modelsInitialized = false;

export const registerModels = (
  models: ModelInitializer[],
  _params?: ModuleParams,
  ctx?: { moduleName: string }
) => {
  const moduleName = ctx?.moduleName ?? "unknown";

  if (!Array.isArray(models) || models.length === 0) {
    logger.warn(`No models provided by module "${moduleName}"`, { label: "registerModels" });
    return;
  }

  for (const init of models) {
    allModelInitializers.push({ init, moduleName });
  }

  logger.info(`${models.length} model initializer(s) enqueued from "${moduleName}"`, {
    label: "registerModels",
  });
};

export const initModels = async (params: ModuleParams) => {
  if (modelsInitialized) {
    logger.warn("Models already initialized. Skipping initModels()", { label: "initModels" });
    return;
  }

  logger.info("Init models...", { label: "initModels" });

  const database = getDatabaseOrThrow(params);

  try {
    defineRegisteredModels(database);
    associateRegisteredModels(database);
    await syncDatabase(database, getDatabaseSyncMode(params));

    modelsInitialized = true;
  } catch (error) {
    registeredModels.clear();
    throw error;
  }
};

const getDatabaseOrThrow = (params: ModuleParams): SequelizeLike => {
  const { database } = params as { database?: SequelizeLike };

  if (!database) {
    const error = new Error("Database not found.");
    logger.error(error.message, { label: "initModels" });
    throw error;
  }

  return database;
};

const defineRegisteredModels = (database: SequelizeLike): void => {
  for (const entry of allModelInitializers) {
    defineModel(database, entry);
  }
};

const defineModel = (database: SequelizeLike, entry: InitializerEntry): void => {
  const { init, moduleName } = entry;

  try {
    const model = init(database as unknown as Sequelize);

    assertValidModel(model);
    assertModelNameIsAvailable(model.name, moduleName);

    registeredModels.set(model.name, { model, moduleName });

    logger.info(`Model "${model.name}" registered (sequelize)`, {
      label: "registerModel",
      module: moduleName,
    });
  } catch (err) {
    const error = err as Error;

    logger.error(`Failed to define model (module="${moduleName}") : ${error.message}`, {
      label: "initModels",
      stack: error.stack,
    });

    throw error;
  }
};

const assertValidModel = (model: ModelStatic): void => {
  if (!model || typeof model.name !== "string" || !model.name) {
    throw new Error('Invalid model initializer: missing or empty "name"');
  }
};

const assertModelNameIsAvailable = (modelName: string, moduleName: string): void => {
  const existing = registeredModels.get(modelName);

  if (!existing) {
    return;
  }

  throw new Error(
    `Model name collision: "${modelName}" from module "${moduleName}" conflicts with existing model from "${existing.moduleName}"`
  );
};

const associateRegisteredModels = (database: SequelizeLike): void => {
  for (const entry of registeredModels.values()) {
    associateModel(database, entry);
  }
};

const associateModel = (database: SequelizeLike, entry: RegisteredModelEntry): void => {
  const { model, moduleName } = entry;

  if (typeof model.associate !== "function") {
    return;
  }

  try {
    model.associate(database as unknown as Sequelize);
  } catch (err) {
    const error = err as Error;

    logger.error(
      `Failed to associate model "${model.name}" (module="${moduleName}") : ${error.message}`,
      { label: "initModels", stack: error.stack }
    );

    throw error;
  }
};

const getDatabaseSyncMode = (params: ModuleParams): string => {
  return params.config.database.syncMode;
};

const syncDatabase = async (database: SequelizeLike, syncMode: string): Promise<void> => {
  logger.info(`Database sync mode ${syncMode}`, { label: "initModels" });

  try {
    if (syncMode === "none") {
      logger.info("Database sync skipped (mode=none)", { label: "initModels" });
      return;
    }

    if (syncMode === "alter") {
      await database.sync({ force: false, alter: true });
      logger.info("Database synchronized successfully (mode=alter).", { label: "initModels" });
      return;
    }

    if (syncMode === "force") {
      await database.sync({ force: true, alter: false });
      logger.warn("Database synchronized with FORCE (mode=force).", { label: "initModels" });
      return;
    }

    logger.warn(`Unknown DB sync mode "${String(syncMode)}" → skipping`, {
      label: "initModels",
    });
  } catch (err) {
    const error = err as Error;

    logger.error("Error synchronizing database:", {
      error,
      label: "initModels",
    });

    throw error;
  }
};

export const getRegisteredModels = () =>
  Array.from(registeredModels.entries()).map(([name, { moduleName }]) => ({
    name,
    moduleName,
  }));

export const resetModelsRegistry = () => {
  allModelInitializers.length = 0;
  registeredModels.clear();
  modelsInitialized = false;

  logger.info("Model registry has been reset.", { label: "initModels" });
};