import path from 'path';
import express from 'express';
const router = express.Router();
import multer from 'multer';
import XLSX from 'xlsx';
import { DataTypes } from 'sequelize';
import defineCase from '../../models/cases.js';
import defineStep from '../../models/steps.js';
import defineCaseStep from '../../models/caseSteps.js';
import authMiddleware from '../../middleware/auth.js';
import editableMiddleware from '../../middleware/verifyEditable.js';
import { priorities, testTypes, automationStatus, templates } from '../../config/enums.js';

const fileFilter = (req, file, cb) => {
  // Accept Excel and JSON by extension. JSON mime types vary across browsers
  // (application/json, text/plain, application/octet-stream), so rely on the extension.
  const allowedFileTypes = ['.xlsx', '.xls', '.json'];
  const extname = allowedFileTypes.includes(path.extname(file.originalname).toLowerCase());

  if (extname) {
    return cb(null, true);
  } else {
    cb(new Error('Only Excel (.xlsx, .xls) or JSON (.json) files are allowed!'));
  }
};

const storage = multer.memoryStorage();
const upload = multer({
  storage: storage,
  fileFilter,
  limits: { fileSize: 50 * 1024 * 1024 }, // 50 MB limit
});

export default function (sequelize) {
  const Case = defineCase(sequelize, DataTypes);
  const Step = defineStep(sequelize, DataTypes);
  const CaseStep = defineCaseStep(sequelize, DataTypes);
  Case.belongsToMany(Step, { through: CaseStep });
  Step.belongsToMany(Case, { through: CaseStep });
  const { verifySignedIn } = authMiddleware(sequelize);
  const { verifyProjectDeveloperFromFolderId } = editableMiddleware(sequelize);

  router.post(
    '/import',
    (req, res, next) => {
      upload.single('file')(req, res, function (err) {
        if (err) {
          return res.status(400).json({ error: err.message });
        }
        next();
      });
    },
    verifySignedIn,
    verifyProjectDeveloperFromFolderId,
    async (req, res) => {
      const { folderId } = req.query;

      if (!req.file || !req.file.buffer) {
        return res.status(400).json({ error: 'No file uploaded' });
      }

      if (!folderId) {
        return res.status(400).json({ error: 'folderId is required' });
      }

      // Parse and validate the file before opening a transaction.
      // Both parsers return the same { casesToCreate, stepsToCreate } shape,
      // or throw an Error with a user-facing validation message.
      let casesToCreate;
      let stepsToCreate;
      try {
        const ext = path.extname(req.file.originalname).toLowerCase();
        const parsed =
          ext === '.json' ? _parseJsonBuffer(req.file.buffer, folderId) : _parseExcelBuffer(req.file.buffer, folderId);
        casesToCreate = parsed.casesToCreate;
        stepsToCreate = parsed.stepsToCreate;
      } catch (error) {
        return res.status(400).json({ error: error.message });
      }

      const t = await sequelize.transaction();
      try {
        // 'Manually' create cases, steps and caseStep association.
        const createdCases = await Case.bulkCreate(casesToCreate, { transaction: t });
        for (const stepData of stepsToCreate) {
          const createdCase = createdCases[stepData.caseIndex];
          const createdStep = await Step.create(
            {
              step: stepData.step,
              result: stepData.result,
            },
            { transaction: t }
          );
          await CaseStep.create(
            {
              caseId: createdCase.id,
              stepId: createdStep.id,
              stepNo: stepData.stepNo,
            },
            { transaction: t }
          );
        }

        await t.commit();
        res.json(createdCases);
      } catch (error) {
        await t.rollback();
        console.error(error);
        if (!res.headersSent) {
          res.status(500).json({ error: 'Internal Server Error' });
        }
      }
    }
  );

  return router;
}

// Parse an Excel (.xlsx, .xls) buffer into { casesToCreate, stepsToCreate }.
// Rows sharing the same title are grouped into a single case with multiple steps.
function _parseExcelBuffer(buffer, folderId) {
  const workbook = XLSX.read(buffer, { type: 'buffer' });
  const sheetName = workbook.SheetNames[0];
  const worksheet = workbook.Sheets[sheetName];
  const jsonData = XLSX.utils.sheet_to_json(worksheet);

  let currentTitle = null;
  let previousTitle = null;
  let stepNo = 1;
  const casesToCreate = [];
  const stepsToCreate = [];
  for (const [index, row] of jsonData.entries()) {
    const errorMessage = _getRowValidationError(row, index);
    if (errorMessage) {
      throw new Error(errorMessage);
    }

    // Add step to the same case if the current row title is equal to previous row title
    // This handle cases with multiple steps :)
    currentTitle = row['title'].trim();
    previousTitle = casesToCreate[casesToCreate.length - 1]?.title.trim();
    if (casesToCreate.length > 0 && previousTitle === currentTitle) {
      stepNo += 1;
      stepsToCreate.push({
        caseIndex: casesToCreate.length - 1,
        stepNo: stepNo,
        step: row['step'] || '',
        result: row['expectedStepResult'] || '',
      });
    } else {
      stepNo = 1;
      casesToCreate.push({
        folderId: folderId,
        title: currentTitle,
        description: row['description'] || '',
        state: 0, // default state
        priority: row['priority'] ? priorities.indexOf(row['priority']) : priorities.indexOf('medium'),
        type: row['type'] ? testTypes.indexOf(row['type']) : testTypes.indexOf('other'),
        preConditions: row['preConditions'],
        expectedResults: row['expectedResults'],
        automationStatus: row['automationStatus']
          ? automationStatus.indexOf(row['automationStatus'])
          : automationStatus.indexOf('automation-not-required'),
        template: row['template'] ? templates.indexOf(row['template']) : templates.indexOf('text'),
      });
      stepsToCreate.push({
        caseIndex: casesToCreate.length - 1,
        stepNo: stepNo,
        step: row['step'] || '',
        result: row['expectedStepResult'] || '',
      });
    }
  }

  return { casesToCreate, stepsToCreate };
}

// Parse a JSON buffer into { casesToCreate, stepsToCreate }.
// Accepts the same shape produced by the JSON export (`/cases/download?type=json`):
// either an array of case objects, or an object map keyed by id.
// `id`, `folderId`, `folder` and `state` are ignored; cases are created in the
// target folder with the default `new` state.
function _parseJsonBuffer(buffer, folderId) {
  let parsed;
  try {
    parsed = JSON.parse(buffer.toString('utf-8'));
  } catch {
    throw new Error('Invalid JSON file');
  }

  const rawCases = Array.isArray(parsed) ? parsed : parsed && typeof parsed === 'object' ? Object.values(parsed) : null;
  if (!rawCases || rawCases.length === 0) {
    throw new Error('No cases found in JSON file');
  }

  const casesToCreate = [];
  const stepsToCreate = [];
  for (const [index, c] of rawCases.entries()) {
    const errorMessage = _getJsonCaseValidationError(c, index);
    if (errorMessage) {
      throw new Error(errorMessage);
    }

    casesToCreate.push({
      folderId: folderId,
      title: String(c.title).trim(),
      description: c.description || '',
      state: 0, // default state
      priority: priorities.indexOf(c.priority),
      type: testTypes.indexOf(c.type),
      preConditions: c.preConditions || '',
      expectedResults: c.expectedResults || '',
      automationStatus: c.automationStatus
        ? automationStatus.indexOf(c.automationStatus)
        : automationStatus.indexOf('automation-not-required'),
      template: templates.indexOf(c.template),
    });

    const steps = Array.isArray(c.Steps) ? c.Steps : [];
    steps.forEach((s, stepIndex) => {
      stepsToCreate.push({
        caseIndex: casesToCreate.length - 1,
        stepNo: stepIndex + 1,
        step: s?.step || '',
        result: s?.expectedStepResult || s?.result || '',
      });
    });
  }

  return { casesToCreate, stepsToCreate };
}

function _getRowValidationError(row, index) {
  const requiredFields = ['title', 'priority', 'type', 'template'];
  const rowNumber = index + 2;

  for (const field of requiredFields) {
    if (!row[field]) {
      return `Row ${rowNumber} is missing required field: ${field}`;
    }
  }

  // Validate priority if provided
  if (row['priority']) {
    const priorityIndex = priorities.indexOf(row['priority']?.toLowerCase());
    if (priorityIndex === -1) {
      return `Row ${rowNumber} has invalid priority: ${row['priority']}`;
    }
  }

  // Validate type if provided
  if (row['type']) {
    const typeIndex = testTypes.indexOf(row['type']?.toLowerCase());
    if (typeIndex === -1) {
      return `Row ${rowNumber} has invalid type: ${row['type']}`;
    }
  }

  // Validate automationStatus if provided
  if (row['automationStatus']) {
    const automationStatusIndex = automationStatus.indexOf(row['automationStatus']?.toLowerCase());
    if (automationStatusIndex === -1) {
      return `Row ${rowNumber} has invalid automationStatus: ${row['automationStatus']}`;
    }
  }

  // Validate template if provided
  if (row['template']) {
    const templateIndex = templates.indexOf(row['template']?.toLowerCase());
    if (templateIndex === -1) {
      return `Row ${rowNumber} has invalid template: ${row['template']}`;
    }
  }

  return null;
}

function _getJsonCaseValidationError(c, index) {
  const caseNumber = index + 1;

  if (!c || typeof c !== 'object') {
    return `Case ${caseNumber} is not a valid object`;
  }

  const requiredFields = ['title', 'priority', 'type', 'template'];
  for (const field of requiredFields) {
    if (!c[field]) {
      return `Case ${caseNumber} is missing required field: ${field}`;
    }
  }

  // Values are human-readable labels, matching the JSON export format.
  if (priorities.indexOf(c.priority) === -1) {
    return `Case ${caseNumber} has invalid priority: ${c.priority}`;
  }

  if (testTypes.indexOf(c.type) === -1) {
    return `Case ${caseNumber} has invalid type: ${c.type}`;
  }

  if (templates.indexOf(c.template) === -1) {
    return `Case ${caseNumber} has invalid template: ${c.template}`;
  }

  if (c.automationStatus && automationStatus.indexOf(c.automationStatus) === -1) {
    return `Case ${caseNumber} has invalid automationStatus: ${c.automationStatus}`;
  }

  return null;
}