import PayloadValidator from '../validation/PayloadValidator.js';
import QueryBuilder from './QueryBuilder.js';

export default class SchemaBuilder {

  constructor() {
    this.errorSchemas = new Map();
  }

  requestSchema(s) { this.reqSchema = s; return this; }
  responseSchema(s) { this.resSchema = s; return this; }
  requestTranslator(f) { this.reqT = f; return this; }
  responseTranslator(f) { this.resT = f; return this; }
  preProcess(f) { this.pre = f; return this; }
  postProcess(f) { this.post = f; return this; }
  onError(c, s) { this.errorSchemas.set(c, s); return this; }
  defaultError(s) { this.defErr = s; return this; }
  pathSchema(schema) { this._pathSchema = schema; return this; }
  querySchema(schema) { this._querySchema = schema; return this; }
  headerSchema(schema) { this._headerSchema = schema; return this; }

  getErrorSchema(statusCode) {
    return this.errorSchemas.has(statusCode)
      ? this.errorSchemas.get(statusCode)
      : this.defErr;
  }

  log(req, level, message, meta = {}) {
    const requestId = req?.requestId || 'unknown';
    console[level](
      `[SchemaBuilder] [${level.toUpperCase()}] [req:${requestId}] ${message}`,
      Object.keys(meta).length ? meta : ''
    );
  }

  async execute(req, res, dbClient) {
    const start = Date.now();

    try {
      this.log(req, 'info', 'Execution started');

      // -----------------------------
      // PATH PARAM VALIDATION
      // -----------------------------
      if (this._pathSchema) {
        this.log(req, 'debug', 'Validating path params');
        const vPath = PayloadValidator.validate(this._pathSchema, req.params);
        if (!vPath.valid) {
          this.log(req, 'warn', 'Path validation failed', vPath);
          return res.status(400).json(vPath);
        }
      }

      // -----------------------------
      // QUERY PARAM VALIDATION
      // -----------------------------
      if (this._querySchema) {
        this.log(req, 'debug', 'Validating query params');
        const vQuery = PayloadValidator.validate(this._querySchema, req.query);
        if (!vQuery.valid) {
          this.log(req, 'warn', 'Query validation failed', vQuery);
          return res.status(400).json(vQuery);
        }
      }

      // -----------------------------
      // HEADER VALIDATION
      // -----------------------------
      if (this._headerSchema) {
        this.log(req, 'debug', 'Validating headers');
        const vHeader = PayloadValidator.validate(this._headerSchema, req.headers);
        if (!vHeader.valid) {
          this.log(req, 'warn', 'Header validation failed', vHeader);
          return res.status(400).json(vHeader);
        }
      }

      // -----------------------------
      // BODY VALIDATION
      // -----------------------------
      if (this.reqSchema) {
        this.log(req, 'debug', 'Validating request body');
        const vReq = PayloadValidator.validate(this.reqSchema, req.body);
        if (!vReq.valid) {
          this.log(req, 'warn', 'Body validation failed', vReq);
          return res.status(400).json(vReq);
        }
      }

      // -----------------------------
      // PRE-PROCESS
      // -----------------------------
      if (this.pre) {
        this.log(req, 'debug', 'Running pre-process hook');
        const c = await this.pre(req.headers, req.params, req.query, req.body);
        if (c !== 200) {
          this.log(req, 'warn', 'Pre-process failed', { status: c });
          return res.status(c).json(this.getErrorSchema(c));
        }
      }

      // -----------------------------
      // REQUEST TRANSLATION
      // -----------------------------
      this.log(req, 'debug', 'Translating request to query');
      const q = this.reqT(req.headers, req.params, req.query, req.body);

      // -----------------------------
      // DB EXECUTION
      // -----------------------------
      this.log(req, 'info', 'Executing DB query', { type: q?.type });
      const qb = new QueryBuilder().fromJSON(q);
      const dbResp = await qb.execute(dbClient);

      // -----------------------------
      // RESPONSE TRANSLATION
      // -----------------------------
      this.log(req, 'debug', 'Translating DB response');
      const resp = this.resT(dbResp, this.resSchema);

      // -----------------------------
      // RESPONSE VALIDATION
      // -----------------------------
      this.log(req, 'debug', 'Validating response');
      const vResp = PayloadValidator.validate(this.resSchema, resp);
      if (!vResp.valid) {
        this.log(req, 'error', 'Response validation failed', vResp);
        return res.status(500).json(vResp);
      }

      // -----------------------------
      // POST-PROCESS
      // -----------------------------
      if (this.post) {
        this.log(req, 'debug', 'Running post-process hook');
        const c = await this.post(req, resp);
        if (c !== 200) {
          this.log(req, 'warn', 'Post-process failed', { status: c });
          return res.status(c).json(this.getErrorSchema(c));
        }
      }

      const duration = Date.now() - start;
      this.log(req, 'info', 'Execution completed', { durationMs: duration });

      res.json(resp);

    } catch (e) {
      this.log(req, 'error', 'Unhandled exception', {
        message: e.message,
        stack: e.stack
      });
      res.status(500).json(this.defErr);
    }
  }
}