import * as plugins from "./plugins.js";

export type TChangelogBucket =
  | "Breaking Changes"
  | "Features"
  | "Fixes"
  | "Documentation"
  | "Maintenance";

export interface IChangelogEntry {
  type: string;
  scope: string;
  message: string;
  details?: string[];
}

export interface IPendingChangelog {
  block: string;
  isEmpty: boolean;
}

const bucketForCommitType = (commitType: string): TChangelogBucket => {
  switch (commitType) {
    case "BREAKING CHANGE":
      return "Breaking Changes";
    case "feat":
      return "Features";
    case "fix":
      return "Fixes";
    case "docs":
      return "Documentation";
    default:
      return "Maintenance";
  }
};

const readChangelog = async (filePath: string): Promise<string> => {
  if (!(await plugins.smartfs.file(filePath).exists())) {
    return "# Changelog\n\n";
  }
  return (await plugins.smartfs.file(filePath).encoding("utf8").read()) as string;
};

const writeChangelog = async (filePath: string, content: string): Promise<void> => {
  await plugins.smartfs.file(filePath).encoding("utf8").write(content.endsWith("\n") ? content : `${content}\n`);
};

const findPendingSection = (
  content: string,
  sectionName: string,
): { start: number; bodyStart: number; end: number } | null => {
  const headingRegex = new RegExp(`^##\\s+${sectionName.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")}\\s*$`, "m");
  const match = headingRegex.exec(content);
  if (!match || match.index === undefined) {
    return null;
  }

  const bodyStart = match.index + match[0].length;
  const rest = content.slice(bodyStart);
  const nextHeadingMatch = /^##\s+/m.exec(rest);
  const end = nextHeadingMatch ? bodyStart + nextHeadingMatch.index : content.length;
  return { start: match.index, bodyStart, end };
};

export const ensurePendingSection = async (
  filePath: string,
  sectionName = "Pending",
): Promise<string> => {
  let content = await readChangelog(filePath);
  if (findPendingSection(content, sectionName)) {
    return content;
  }

  const pendingSection = `## ${sectionName}\n\n`;
  const titleMatch = /^#\s+.+$/m.exec(content);
  if (titleMatch && titleMatch.index !== undefined) {
    const insertAt = titleMatch.index + titleMatch[0].length;
    content = `${content.slice(0, insertAt)}\n\n${pendingSection}${content.slice(insertAt).replace(/^\n+/, "")}`;
  } else {
    content = `# Changelog\n\n${pendingSection}${content}`;
  }

  await writeChangelog(filePath, content);
  return content;
};

export const appendPendingChangelogEntry = async (
  filePath: string,
  sectionName: string,
  entry: IChangelogEntry,
): Promise<void> => {
  let content = await ensurePendingSection(filePath, sectionName);
  const pendingSection = findPendingSection(content, sectionName)!;
  let pendingBody = content.slice(pendingSection.bodyStart, pendingSection.end);
  const bucket = bucketForCommitType(entry.type);
  const bucketHeading = `### ${bucket}`;

  const entryLines = [`- ${entry.message}${entry.scope ? ` (${entry.scope})` : ""}`];
  for (const detail of entry.details || []) {
    entryLines.push(`  - ${detail}`);
  }
  const renderedEntry = entryLines.join("\n");

  const bucketRegex = new RegExp(`^###\\s+${bucket.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")}\\s*$`, "m");
  const bucketMatch = bucketRegex.exec(pendingBody);
  if (!bucketMatch || bucketMatch.index === undefined) {
    pendingBody = `${pendingBody.trimEnd()}\n\n${bucketHeading}\n\n${renderedEntry}\n`;
  } else {
    const bucketBodyStart = bucketMatch.index + bucketMatch[0].length;
    const afterBucket = pendingBody.slice(bucketBodyStart);
    const nextBucketMatch = /^###\s+/m.exec(afterBucket);
    const insertAt = nextBucketMatch ? bucketBodyStart + nextBucketMatch.index : pendingBody.length;
    const beforeInsert = pendingBody.slice(0, insertAt).trimEnd();
    const afterInsert = pendingBody.slice(insertAt).replace(/^\n+/, "");
    pendingBody = `${beforeInsert}\n${renderedEntry}\n\n${afterInsert}`;
  }

  content = `${content.slice(0, pendingSection.bodyStart)}\n${pendingBody.trim()}\n\n${content.slice(pendingSection.end).replace(/^\n+/, "")}`;
  await writeChangelog(filePath, content);
};

export const readPendingChangelog = async (
  filePath: string,
  sectionName = "Pending",
): Promise<IPendingChangelog> => {
  const content = await ensurePendingSection(filePath, sectionName);
  const pendingSection = findPendingSection(content, sectionName)!;
  const block = content.slice(pendingSection.bodyStart, pendingSection.end).trim();
  return {
    block,
    isEmpty: block.length === 0,
  };
};

export const inferVersionTypeFromPending = (pendingBlock: string): "patch" | "minor" | "major" => {
  if (/^###\s+Breaking Changes\s*$/m.test(pendingBlock)) {
    return "major";
  }
  if (/^###\s+Features\s*$/m.test(pendingBlock)) {
    return "minor";
  }
  return "patch";
};

export const movePendingToVersion = async (
  filePath: string,
  sectionName: string,
  versionHeading: string,
  version: string,
  dateString: string,
): Promise<void> => {
  let content = await ensurePendingSection(filePath, sectionName);
  const pendingSection = findPendingSection(content, sectionName)!;
  const pendingBlock = content.slice(pendingSection.bodyStart, pendingSection.end).trim();
  if (!pendingBlock) {
    throw new Error("No pending changelog entries. Nothing to release.");
  }

  const renderedHeading = versionHeading
    .replaceAll("{{version}}", version)
    .replaceAll("{{date}}", dateString);
  const nextContent = content.slice(pendingSection.end).replace(/^\n+/, "");
  content = `${content.slice(0, pendingSection.bodyStart)}\n\n${renderedHeading}\n\n${pendingBlock}\n\n${nextContent}`;
  await writeChangelog(filePath, content);
};