import { isEmpty, uniq } from 'lodash/fp';
import type {
  Diff,
  IDestinationProvider,
  ISourceProvider,
  ITransferEngine,
  ITransferEngineOptions,
} from '../../types';
import calculateSchemaDiffs from '../strategies';
import { jsonDiffs } from '../utils';

class TransferEngine implements ITransferEngine {
  sourceProvider: ISourceProvider;
  destinationProvider: IDestinationProvider;
  options: ITransferEngineOptions;

  constructor(
    sourceProvider: ISourceProvider,
    destinationProvider: IDestinationProvider,
    options: ITransferEngineOptions
  ) {
    this.sourceProvider = sourceProvider;
    this.destinationProvider = destinationProvider;
    this.options = options;
  }

  #assertStrapiVersionIntegrity(sourceVersion?: string, destinationVersion?: string) {
    const strategy = this.options.versionMatching;

    if (!sourceVersion || !destinationVersion) {
      return;
    }

    if (strategy === 'ignore') {
      return;
    }

    if (strategy === 'exact' && sourceVersion === destinationVersion) {
      return;
    }

    const sourceTokens = sourceVersion.split('.');
    const destinationTokens = destinationVersion.split('.');

    const [major, minor, patch] = sourceTokens.map(
      (value, index) => value === destinationTokens[index]
    );

    if (
      (strategy === 'major' && major) ||
      (strategy === 'minor' && major && minor) ||
      (strategy === 'patch' && major && minor && patch)
    ) {
      return;
    }

    throw new Error(
      `Strapi versions doesn't match (${strategy} check): ${sourceVersion} does not match with ${destinationVersion}`
    );
  }

  #assertSchemasMatching(sourceSchemas: any, destinationSchemas: any) {
    const chosenStrategy = this.options.schemasMatching || 'strict';
    const keys = uniq(Object.keys(sourceSchemas).concat(Object.keys(destinationSchemas)));
    const diffs: { [key: string]: Diff[] } = {};

    keys.forEach((key) => {
      const sourceSchema = sourceSchemas[key];
      const destinationSchema = destinationSchemas[key];
      const schemaDiffs = calculateSchemaDiffs(sourceSchema, destinationSchema);

      const isValid = schemaDiffs[chosenStrategy]();

      if (!isValid) {
        diffs[key] = schemaDiffs.diffs;
      }
    });

    if (!isEmpty(diffs)) {
      throw new Error(
        `Import process failed because the project doesn't have a matching data structure 
        ${JSON.stringify(diffs, null, 2)}        
        `
      );
    }
  }

  async boostrap(): Promise<void> {
    await Promise.all([
      // bootstrap source provider
      this.sourceProvider.bootstrap?.(),
      // bootstrap destination provider
      this.destinationProvider.bootstrap?.(),
    ]);
  }

  async close(): Promise<void> {
    await Promise.all([
      // close source provider
      this.sourceProvider.close?.(),
      // close destination provider
      this.destinationProvider.close?.(),
    ]);
  }

  async integrityCheck(): Promise<boolean> {
    try {
      const sourceMetadata = await this.sourceProvider.getMetadata();
      const destinationMetadata = await this.destinationProvider.getMetadata();

      if (sourceMetadata && destinationMetadata) {
        this.#assertStrapiVersionIntegrity(
          sourceMetadata?.strapi?.version,
          destinationMetadata?.strapi?.version
        );
      }

      const sourceSchemas = await this.sourceProvider.getSchemas?.();
      const destinationSchemas = await this.destinationProvider.getSchemas?.();

      if (sourceSchemas && destinationSchemas) {
        this.#assertSchemasMatching(sourceSchemas, destinationSchemas);
      }

      return true;
    } catch (error) {
      if (error instanceof Error) {
        console.error('Integrity checks failed:', error);
      }

      return false;
    }
  }

  async transfer(): Promise<void> {
    try {
      await this.boostrap();

      const isValidTransfer = await this.integrityCheck();

      if (!isValidTransfer) {
        throw new Error(
          `Unable to transfer the data between ${this.sourceProvider.name} and ${this.destinationProvider.name}.\nPlease refer to the log above for more information.`
        );
      }

      await this.transferSchemas();
      await this.transferEntities();
      await this.transferMedia();
      await this.transferLinks();
      await this.transferConfiguration();

      await this.close();
    } catch (e) {
      console.log('error', e);
      // Rollback the destination provider if an exception is thrown during the transfer
      // Note: This will be configurable in the future
      // await this.destinationProvider?.rollback(e);
    }
  }

  async transferSchemas(): Promise<void> {
    const inStream = await this.sourceProvider.streamSchemas?.();
    const outStream = await this.destinationProvider.getSchemasStream?.();

    if (!inStream) {
      throw new Error('Unable to transfer schemas, source stream is missing');
    }

    if (!outStream) {
      throw new Error('Unable to transfer schemas, destination stream is missing');
    }

    return new Promise((resolve, reject) => {
      inStream
        // Throw on error in the source
        .on('error', reject);

      outStream
        // Throw on error in the destination
        .on('error', reject)
        // Resolve the promise when the destination has finished reading all the data from the source
        .on('close', resolve);

      inStream.pipe(outStream);
    });
  }

  async transferEntities(): Promise<void> {
    const inStream = await this.sourceProvider.streamEntities?.();
    const outStream = await this.destinationProvider.getEntitiesStream?.();

    if (!inStream) {
      throw new Error('Unable to transfer entities, source stream is missing');
    }

    if (!outStream) {
      throw new Error('Unable to transfer entities, destination stream is missing');
    }

    return new Promise((resolve, reject) => {
      inStream
        // Throw on error in the source
        .on('error', (e) => {
          reject(e);
        });

      outStream
        // Throw on error in the destination
        .on('error', (e) => {
          reject(e);
        })
        // Resolve the promise when the destination has finished reading all the data from the source
        .on('close', resolve);

      inStream.pipe(outStream);
    });
  }

  async transferLinks(): Promise<void> {
    const inStream = await this.sourceProvider.streamLinks?.();
    const outStream = await this.destinationProvider.getLinksStream?.();

    if (!inStream) {
      throw new Error('Unable to transfer links, source stream is missing');
    }

    if (!outStream) {
      throw new Error('Unable to transfer links, destination stream is missing');
    }

    return new Promise((resolve, reject) => {
      inStream
        // Throw on error in the source
        .on('error', reject);

      outStream
        // Throw on error in the destination
        .on('error', reject)
        // Resolve the promise when the destination has finished reading all the data from the source
        .on('close', resolve);

      inStream.pipe(outStream);
    });
  }

  async transferMedia(): Promise<void> {
    console.warn('transferMedia not yet implemented');
    return new Promise((resolve) => resolve());
  }

  async transferConfiguration(): Promise<void> {
    const inStream = await this.sourceProvider.streamConfiguration?.();
    const outStream = await this.destinationProvider.getConfigurationStream?.();

    if (!inStream) {
      throw new Error('Unable to transfer configuration, source stream is missing');
    }

    if (!outStream) {
      throw new Error('Unable to transfer configuration, destination stream is missing');
    }

    return new Promise((resolve, reject) => {
      inStream
        // Throw on error in the source
        .on('error', reject);

      outStream
        // Throw on error in the destination
        .on('error', reject)
        // Resolve the promise when the destination has finished reading all the data from the source
        .on('close', resolve);

      inStream.pipe(outStream);
    });
  }
}

export const createTransferEngine = <T extends ISourceProvider, U extends IDestinationProvider>(
  sourceProvider: T,
  destinationProvider: U,
  options: ITransferEngineOptions
): TransferEngine => {
  return new TransferEngine(sourceProvider, destinationProvider, options);
};