import fs from 'fs';
import path from 'path';

import matter from 'gray-matter';

const projectRoot = path.resolve(import.meta.dirname, '..');
const releasesDirectory = path.join(projectRoot, 'src', 'content', 'releases');
const outputPath = path.join(
  projectRoot,
  'src',
  'lib',
  'releases',
  'generated-release-notes.ts',
);

const headingRegex = /^\s*#\s+(.+?)\s*$/m;
const imageRegex = /!\[[^\]]*\]\(([^)]+)\)/;

function normalizeFrontmatterDate(dateValue) {
  if (typeof dateValue === 'string') {
    return dateValue;
  }

  if (dateValue instanceof Date && !Number.isNaN(dateValue.getTime())) {
    return dateValue.toISOString().slice(0, 10);
  }

  return '';
}

function compareSemanticVersions(a, b) {
  return compareParsed(parseSemver(a), parseSemver(b));
}

function parseSemver(version) {
  const trimmed = version.trim().replace(/^v/i, '');
  const withoutBuild = trimmed.split('+', 1)[0] ?? '';
  const dashIndex = withoutBuild.indexOf('-');
  const coreString =
    dashIndex === -1 ? withoutBuild : withoutBuild.slice(0, dashIndex);
  const preString = dashIndex === -1 ? null : withoutBuild.slice(dashIndex + 1);
  const core = coreString.split('.').map((part) => {
    const parsed = Number.parseInt(part, 10);
    return Number.isFinite(parsed) ? parsed : 0;
  });

  return {
    core,
    pre: preString === null || preString === '' ? null : preString.split('.'),
  };
}

function compareParsed(a, b) {
  const length = Math.max(a.core.length, b.core.length);

  for (let index = 0; index < length; index += 1) {
    const left = a.core[index] ?? 0;
    const right = b.core[index] ?? 0;

    if (left !== right) {
      return left < right ? -1 : 1;
    }
  }

  if (a.pre === null && b.pre === null) {
    return 0;
  }

  if (a.pre === null) {
    return 1;
  }

  if (b.pre === null) {
    return -1;
  }

  const prereleaseLength = Math.min(a.pre.length, b.pre.length);

  for (let index = 0; index < prereleaseLength; index += 1) {
    const left = a.pre[index] ?? '';
    const right = b.pre[index] ?? '';
    const leftIsNumeric = /^\d+$/.test(left);
    const rightIsNumeric = /^\d+$/.test(right);

    if (leftIsNumeric && rightIsNumeric) {
      const leftNumber = Number.parseInt(left, 10);
      const rightNumber = Number.parseInt(right, 10);

      if (leftNumber !== rightNumber) {
        return leftNumber < rightNumber ? -1 : 1;
      }

      continue;
    }

    if (leftIsNumeric) {
      return -1;
    }

    if (rightIsNumeric) {
      return 1;
    }

    if (left !== right) {
      return left < right ? -1 : 1;
    }
  }

  if (a.pre.length === b.pre.length) {
    return 0;
  }

  return a.pre.length < b.pre.length ? -1 : 1;
}

function inferTitle(content) {
  const match = content.match(headingRegex);
  return match?.[1]?.trim() ?? '';
}

function inferPreviewImage(content) {
  const match = content.match(imageRegex);
  return match?.[1]?.trim() ?? '';
}

function readReleaseNotes() {
  const fileNames = fs
    .readdirSync(releasesDirectory)
    .filter(
      (fileName) => fileName.endsWith('.md') || fileName.endsWith('.mdx'),
    );

  const notes = fileNames.map((fileName) => {
    const fullPath = path.join(releasesDirectory, fileName);
    const raw = fs.readFileSync(fullPath, 'utf8');
    const { data, content } = matter(raw);
    const release = typeof data.release === 'string' ? data.release.trim() : '';
    const date = normalizeFrontmatterDate(data.Date ?? data.date);
    const title =
      typeof data.title === 'string' && data.title.trim()
        ? data.title.trim()
        : inferTitle(content);
    const previewImage =
      typeof data.previewImage === 'string' && data.previewImage.trim()
        ? data.previewImage.trim()
        : inferPreviewImage(content);

    if (!release) {
      throw new Error(`Missing "release" frontmatter in ${fileName}`);
    }

    if (!title) {
      throw new Error(
        `Missing release title in ${fileName}. Add "title" frontmatter or a top-level markdown heading.`,
      );
    }

    if (!previewImage) {
      throw new Error(
        `Missing preview image in ${fileName}. Add "previewImage" frontmatter or a markdown image.`,
      );
    }

    const imagePath = path.join(
      projectRoot,
      'public',
      previewImage.replace(/^\//, ''),
    );

    if (!fs.existsSync(imagePath)) {
      throw new Error(
        `Preview image "${previewImage}" referenced by ${fileName} was not found in public/.`,
      );
    }

    return {
      slug: fileName.replace(/\.mdx?$/i, ''),
      date,
      release,
      title,
      previewImage,
      content,
    };
  });

  notes.sort((left, right) =>
    compareSemanticVersions(right.release, left.release),
  );

  return notes;
}

function buildFileContent(notes) {
  const serializedNotes = JSON.stringify(notes, null, 2);

  return `/* eslint-disable */
// This file is auto-generated by scripts/generate-release-notes-manifest.mjs.
// Do not edit it manually.

import type { LocalReleaseNote } from './types';

export const GENERATED_RELEASE_NOTES: LocalReleaseNote[] = ${serializedNotes} as LocalReleaseNote[];
`;
}

function main() {
  const notes = readReleaseNotes();
  fs.writeFileSync(outputPath, buildFileContent(notes));
  process.stdout.write(
    `Generated release manifest with ${notes.length} entries at ${path.relative(projectRoot, outputPath)}\n`,
  );
}

main();