const assert = require('node:assert/strict');
const { readFileSync } = require('node:fs');
const path = require('node:path');
const Module = require('node:module');

// Mutate only the isolated fixture process. Repository files and the production
// module cache remain unchanged; all route exports are restored after each case.
module.exports = async function employeeMutations(h, runFixture) {
  const filename = h.req.resolve('./src/services/loanLenderEmployee');
  const source = readFileSync(filename, 'utf8');
  const live = h.req('./src/services/loanLenderEmployee'); const original = { ...live };
  const mutations = [
    ['bank_permission', 'if (!fastify.hasPermission(request.employee, "employee.bank.read") &&\n      !fastify.hasPermission(request.employee, "employee.bank.manage"))', 'if (false)'],
    ['source_version', 'if (source.sourceVersion !== expectedSourceVersion)', 'if (false)'],
    ['legacy_duplicate', 'if (links.some((lender) => lender.id !== lenderId))', 'if (false)'],
    ['employee_lock', 'if (unique.length) await tx.$queryRaw', 'if (false) await tx.$queryRaw'],
    ['employee_lock_fk_compatibility', 'ORDER BY id FOR NO KEY UPDATE', 'ORDER BY id FOR UPDATE'],
    ['in_flight', 'await assertLenderNotInFlight(tx, id);', ''],
    ['lender_versions', 'assertCurrentVersion(lender.identity_version, input.expectedIdentityVersion);\n  assertCurrentVersion(lender.account_version, input.expectedAccountVersion);', ''],
    ['reuse_request_binding', 'if (!previousRequest) await auditLoan(tx, request, "LOAN_LENDER_EMPLOYEE_REUSED", lender.id, {\n            ...requestBinding, employeeSourceRequestKey: input.requestKey,\n          });', ''],
    ['required_audit', 'await auditLoan(tx, request, "LOAN_LENDER_EMPLOYEE_CREATED", created.id, {\n          ...requestBinding, employeeSourceRequestKey: input.requestKey,\n        });', ''],
  ];
  const results = [];
  for (const [name, from, to] of mutations) {
    assert.equal(source.split(from).length, 2, `mutation ${name} must have exactly one target`);
    const mutant = new Module(filename, module); mutant.filename = filename;
    mutant.paths = Module._nodeModulePaths(path.dirname(filename));
    mutant._compile(source.replace(from, to), filename);
    let failure;
    Object.assign(live, mutant.exports);
    try { await runFixture(h); } catch (error) { failure = error; }
    finally { Object.assign(live, original); }
    assert.ok(failure, `mutation ${name} survived`);
    // A generic environment, SQL or parsing failure is not a killed guard.
    const wrongAcceptance = failure.code === 'ERR_ASSERTION' && failure.actual === 200 && [403, 409, 500].includes(failure.expected);
    const duplicateIdentity = name === 'employee_lock' && failure.code === 'ERR_ASSERTION' &&
      typeof failure.actual === 'string' && typeof failure.expected === 'string' &&
      /^[0-9a-f-]{36}$/.test(failure.actual) && /^[0-9a-f-]{36}$/.test(failure.expected) && failure.actual !== failure.expected;
    const missingLock = name === 'employee_lock' && (failure.message === 'synthetic employee operation did not actually wait for the row lock' ||
      failure.code === 'EMPLOYEE_SOURCE_LOCK_NOT_HELD');
    const fkDeadlock = name === 'employee_lock_fk_compatibility' && failure.code === 'EMPLOYEE_SOURCE_FK_DEADLOCK';
    const hint = failure.code === 'ERR_ASSERTION' ? String(failure.message).split('\n')[0] : failure.name;
    assert.ok(wrongAcceptance || duplicateIdentity || missingLock || fkDeadlock, `mutation ${name} failed outside its guard: ${hint} ${failure.code ?? ''}`);
    results.push({ name, caught: true, witness: wrongAcceptance ? 'unsafe_http_acceptance' : duplicateIdentity ? 'duplicate_employee_lender' : fkDeadlock ? 'observed_postgres_deadlock' : 'missing_row_lock' });
    console.log(JSON.stringify({ stage: 'loan_employee_mutation', ...results.at(-1) }));
  }
  console.log(JSON.stringify({ stage: 'loan_employee_mutations', status: 'PASS', count: results.length, sourceFilesChanged: false }));
  return results;
};