import { tap, expect } from '@git.zone/tstest/tapbundle';
import { VersionResolver, SmartMigrationError } from '../ts/index.js';
import type { IMigrationStepDefinition } from '../ts/index.js';

const noopHandler = async () => {};

function makeStep(id: string, from: string, to: string): IMigrationStepDefinition {
  return { id, fromVersion: from, toVersion: to, isResumable: false, handler: noopHandler };
}

tap.test('equals / lessThan / greaterThan', async () => {
  expect(VersionResolver.equals('1.0.0', '1.0.0')).toBeTrue();
  expect(VersionResolver.equals('1.0.0', '1.0.1')).toBeFalse();
  expect(VersionResolver.lessThan('1.0.0', '1.0.1')).toBeTrue();
  expect(VersionResolver.greaterThan('2.0.0', '1.99.99')).toBeTrue();
});

tap.test('assertValid: throws on garbage', async () => {
  let caught: SmartMigrationError | undefined;
  try {
    VersionResolver.assertValid('not-a-version', 'test');
  } catch (err) {
    caught = err as SmartMigrationError;
  }
  expect(caught).toBeInstanceOf(SmartMigrationError);
  expect(caught!.code).toEqual('INVALID_VERSION');
});

tap.test('validateChain: empty chain is valid', async () => {
  VersionResolver.validateChain([]);
});

tap.test('validateChain: catches duplicate ids', async () => {
  let caught: SmartMigrationError | undefined;
  try {
    VersionResolver.validateChain([
      makeStep('a', '1.0.0', '1.1.0'),
      makeStep('a', '1.1.0', '1.2.0'),
    ]);
  } catch (err) {
    caught = err as SmartMigrationError;
  }
  expect(caught!.code).toEqual('DUPLICATE_STEP_ID');
});

tap.test('validateChain: catches non-increasing step', async () => {
  let caught: SmartMigrationError | undefined;
  try {
    VersionResolver.validateChain([makeStep('a', '1.5.0', '1.5.0')]);
  } catch (err) {
    caught = err as SmartMigrationError;
  }
  expect(caught!.code).toEqual('NON_INCREASING_STEP');
});

tap.test('validateChain: catches gap in chain', async () => {
  let caught: SmartMigrationError | undefined;
  try {
    VersionResolver.validateChain([
      makeStep('a', '1.0.0', '1.1.0'),
      makeStep('b', '1.2.0', '1.3.0'), // gap! a.to=1.1.0, b.from=1.2.0
    ]);
  } catch (err) {
    caught = err as SmartMigrationError;
  }
  expect(caught!.code).toEqual('CHAIN_GAP');
});

tap.test('validateChain: contiguous chain passes', async () => {
  VersionResolver.validateChain([
    makeStep('a', '1.0.0', '1.1.0'),
    makeStep('b', '1.1.0', '1.5.0'),
    makeStep('c', '1.5.0', '2.0.0'),
  ]);
});

tap.test('computePlan: returns empty when current === target', async () => {
  const steps = [makeStep('a', '1.0.0', '1.1.0')];
  expect(VersionResolver.computePlan(steps, '1.0.0', '1.0.0')).toEqual([]);
});

tap.test('computePlan: returns full chain when starting from beginning', async () => {
  const steps = [
    makeStep('a', '1.0.0', '1.1.0'),
    makeStep('b', '1.1.0', '1.5.0'),
    makeStep('c', '1.5.0', '2.0.0'),
  ];
  const plan = VersionResolver.computePlan(steps, '1.0.0', '2.0.0');
  expect(plan.map((s) => s.id)).toEqual(['a', 'b', 'c']);
});

tap.test('computePlan: returns partial chain when starting in the middle', async () => {
  const steps = [
    makeStep('a', '1.0.0', '1.1.0'),
    makeStep('b', '1.1.0', '1.5.0'),
    makeStep('c', '1.5.0', '2.0.0'),
  ];
  const plan = VersionResolver.computePlan(steps, '1.1.0', '2.0.0');
  expect(plan.map((s) => s.id)).toEqual(['b', 'c']);
});

tap.test('computePlan: returns sub-slice when target is mid-chain', async () => {
  const steps = [
    makeStep('a', '1.0.0', '1.1.0'),
    makeStep('b', '1.1.0', '1.5.0'),
    makeStep('c', '1.5.0', '2.0.0'),
  ];
  const plan = VersionResolver.computePlan(steps, '1.0.0', '1.5.0');
  expect(plan.map((s) => s.id)).toEqual(['a', 'b']);
});

tap.test('computePlan: throws when current does not match any step from', async () => {
  const steps = [
    makeStep('a', '1.0.0', '1.1.0'),
    makeStep('b', '1.1.0', '2.0.0'),
  ];
  let caught: SmartMigrationError | undefined;
  try {
    VersionResolver.computePlan(steps, '1.0.5', '2.0.0');
  } catch (err) {
    caught = err as SmartMigrationError;
  }
  expect(caught!.code).toEqual('CHAIN_NOT_AT_CURRENT');
});

tap.test('computePlan: throws when target overshoots', async () => {
  const steps = [
    makeStep('a', '1.0.0', '1.1.0'),
    makeStep('b', '1.1.0', '2.0.0'),
  ];
  let caught: SmartMigrationError | undefined;
  try {
    VersionResolver.computePlan(steps, '1.0.0', '1.5.0');
  } catch (err) {
    caught = err as SmartMigrationError;
  }
  expect(caught!.code).toEqual('TARGET_NOT_REACHABLE');
});

tap.test('computePlan: rejects downgrade', async () => {
  const steps = [makeStep('a', '1.0.0', '2.0.0')];
  let caught: SmartMigrationError | undefined;
  try {
    VersionResolver.computePlan(steps, '2.0.0', '1.0.0');
  } catch (err) {
    caught = err as SmartMigrationError;
  }
  expect(caught!.code).toEqual('DOWNGRADE_NOT_SUPPORTED');
});

export default tap.start();