import { parseChangeLogOrExit } from './change-parser.js';
import { readFileSync, writeFileSync } from 'node:fs';
import type { Solution } from './plan.js';
import { planVersionBumps, saveSolution } from './plan.js';
import fsExtra from 'fs-extra';

const { readJSONSync, writeJSONSync } = fsExtra;

const changelogPreamblePattern = /#.*Changelog.*$/i;

export function updateChangelog(
  newChangelogContent: string,
  solution: Solution,
): string {
  const targetChangelogFile = './CHANGELOG.md';
  const oldChangelogContent = readFileSync(targetChangelogFile, 'utf8').split(
    '\n',
  );

  if (!changelogPreamblePattern.test(oldChangelogContent[0])) {
    process.stderr.write(
      `Cannot parse existing changelog. Expected it to match:\n${changelogPreamblePattern}\n`,
    );
    process.exit(-1);
  }

  const [firstNewLine, ...restNewLines] = newChangelogContent
    .trim()
    .split('\n');

  const newOutput =
    firstNewLine +
    '\n\n' +
    versionSummary(solution) +
    '\n' +
    restNewLines.join('\n') +
    '\n';
  writeFileSync(
    targetChangelogFile,
    oldChangelogContent[0] +
      '\n\n' +
      newOutput +
      oldChangelogContent.slice(1).join('\n'),
  );
  return newOutput;
}

function versionSummary(solution: Solution): string {
  const result: string[] = [];
  for (const [pkgName, entry] of solution) {
    if (entry.impact) {
      result.push(`* ${pkgName} ${entry.newVersion} (${entry.impact})`);
    }
  }
  return result.join('\n');
}

function updateVersions(solution: Solution) {
  for (const entry of solution.values()) {
    if (entry.impact) {
      const pkg = readJSONSync(entry.pkgJSONPath);
      pkg.version = entry.newVersion;
      writeJSONSync(entry.pkgJSONPath, pkg, { spaces: 2 });
    }
  }
}

export async function prepare(
  newChangelogContent: string,
  singlePackage?: string,
) {
  const changes = parseChangeLogOrExit(newChangelogContent);
  const solution = planVersionBumps(changes, singlePackage);
  updateVersions(solution);
  const description = updateChangelog(newChangelogContent, solution);
  saveSolution(solution, description);
  return solution;
}