#!/usr/bin/env npx tsx

import { execFile } from "node:child_process";
import { promises as fs } from "node:fs";
import path from "node:path";
import { promisify } from "node:util";

const execFileAsync = promisify(execFile);

const DEFAULT_QUERY = "\"Co-Authored-By: Paperclip <noreply@paperclip.ing>\"";
const DEFAULT_CACHE_FILE = path.resolve("data/paperclip-commit-metrics-cache.json");
const DEFAULT_SEARCH_START = "2008-01-01T00:00:00Z";
const SEARCH_WINDOW_LIMIT = 900;
const MIN_WINDOW_MS = 60_000;
const DEFAULT_STATS_FETCH_LIMIT = 250;
const DEFAULT_STATS_CONCURRENCY = 4;
const DEFAULT_SEARCH_FIELD = "committer-date";
const PAPERCLIP_EMAIL = "noreply@paperclip.ing";
const PAPERCLIP_NAME = "paperclip";

interface CliOptions {
  cacheFile: string;
  end: Date;
  excludeOwners: string[];
  exportFormat: "csv" | "json";
  includePrivate: boolean;
  json: boolean;
  output: string | null;
  query: string;
  refreshSearch: boolean;
  refreshStats: boolean;
  searchField: "author-date" | "committer-date";
  start: Date;
  statsConcurrency: number;
  statsFetchLimit: number;
  skipStats: boolean;
}

interface SearchCommitItem {
  author: {
    login?: string;
  } | null;
  commit: {
    author: {
      date: string;
      email: string | null;
      name: string | null;
    } | null;
    message: string;
  };
  html_url: string;
  repository: {
    full_name: string;
    html_url: string;
  };
  sha: string;
}

interface CommitStats {
  additions: number;
  deletions: number;
  total: number;
}

interface CachedCommit {
  authorEmail: string | null;
  authorLogin: string | null;
  authorName: string | null;
  committedAt: string | null;
  contributors: ContributorRecord[];
  htmlUrl: string;
  repositoryFullName: string;
  repositoryUrl: string;
  sha: string;
}

interface CachedCommitStats extends CommitStats {
  fetchedAt: string;
}

interface ContributorRecord {
  displayName: string;
  email: string | null;
  key: string;
  login: string | null;
}

interface WindowCacheEntry {
  completedAt: string;
  key: string;
  shas: string[];
  totalCount: number;
}

interface CacheFile {
  commits: Record<string, CachedCommit>;
  queryKey: string;
  searchField: CliOptions["searchField"];
  stats: Record<string, CachedCommitStats>;
  updatedAt: string | null;
  version: number;
  windows: Record<string, WindowCacheEntry>;
}

interface SearchResponse {
  incomplete_results: boolean;
  items: SearchCommitItem[];
  total_count: number;
}

interface SearchWindowResult {
  shas: Set<string>;
  totalCount: number;
}

interface Summary {
  cacheFile: string;
  contributors: {
    count: number;
    sample: ContributorRecord[];
  };
  detectedQuery: string;
  lineStats: {
    additions: number;
    complete: boolean;
    coveredCommits: number;
    deletions: number;
    missingCommits: number;
    totalChanges: number;
  };
  range: {
    end: string;
    searchField: CliOptions["searchField"];
    start: string;
  };
  filters: {
    excludedOwners: string[];
  };
  repos: {
    count: number;
    sample: string[];
  };
  statsFetch: {
    fetchedThisRun: number;
    skipped: boolean;
  };
  totals: {
    commits: number;
  };
}

async function main() {
  const options = parseArgs(process.argv.slice(2));
  const cache = await loadCache(options.cacheFile, options);
  const client = new GitHubClient(await resolveGitHubToken());

  const { shas } = await searchWindow(client, cache, options, options.start, options.end);
  const sortedShas = [...shas].sort();

  let fetchedThisRun = 0;
  if (!options.skipStats) {
    fetchedThisRun = await enrichCommitStats(client, cache, options, sortedShas);
  }

  cache.updatedAt = new Date().toISOString();
  await saveCache(options.cacheFile, cache);

  const filteredShas = sortFilteredShas(cache, filterShas(cache, sortedShas, options));
  const summary = buildSummary(cache, options, filteredShas, fetchedThisRun);

  if (options.output) {
    await writeExport(options.output, options.exportFormat, cache, filteredShas, summary);
  }

  if (options.json) {
    console.log(JSON.stringify(summary, null, 2));
    return;
  }

  printSummary(summary);
}

function parseArgs(argv: string[]): CliOptions {
  const options: CliOptions = {
    cacheFile: DEFAULT_CACHE_FILE,
    end: new Date(),
    excludeOwners: [],
    exportFormat: "csv",
    includePrivate: false,
    json: false,
    output: null,
    query: DEFAULT_QUERY,
    refreshSearch: false,
    refreshStats: false,
    searchField: DEFAULT_SEARCH_FIELD,
    start: new Date(DEFAULT_SEARCH_START),
    statsConcurrency: DEFAULT_STATS_CONCURRENCY,
    statsFetchLimit: DEFAULT_STATS_FETCH_LIMIT,
    skipStats: false,
  };

  for (let index = 0; index < argv.length; index += 1) {
    const arg = argv[index];
    switch (arg) {
      case "--cache-file":
        options.cacheFile = requireValue(argv, ++index, arg);
        break;
      case "--end":
        options.end = parseDateArg(requireValue(argv, ++index, arg), arg);
        break;
      case "--exclude-owner":
        options.excludeOwners.push(requireValue(argv, ++index, arg).toLowerCase());
        break;
      case "--export-format": {
        const value = requireValue(argv, ++index, arg);
        if (value !== "csv" && value !== "json") {
          throw new Error(`Invalid --export-format value: ${value}`);
        }
        options.exportFormat = value;
        break;
      }
      case "--include-private":
        options.includePrivate = true;
        break;
      case "--json":
        options.json = true;
        break;
      case "--output":
        options.output = requireValue(argv, ++index, arg);
        break;
      case "--query":
        options.query = requireValue(argv, ++index, arg);
        break;
      case "--refresh-search":
        options.refreshSearch = true;
        break;
      case "--refresh-stats":
        options.refreshStats = true;
        break;
      case "--search-field": {
        const value = requireValue(argv, ++index, arg);
        if (value !== "author-date" && value !== "committer-date") {
          throw new Error(`Invalid --search-field value: ${value}`);
        }
        options.searchField = value;
        break;
      }
      case "--skip-stats":
        options.skipStats = true;
        break;
      case "--start":
        options.start = parseDateArg(requireValue(argv, ++index, arg), arg);
        break;
      case "--stats-concurrency":
        options.statsConcurrency = parsePositiveInt(requireValue(argv, ++index, arg), arg);
        break;
      case "--stats-fetch-limit":
        options.statsFetchLimit = parseNonNegativeInt(requireValue(argv, ++index, arg), arg);
        break;
      case "--help":
        printHelp();
        process.exit(0);
        break;
      default:
        throw new Error(`Unknown argument: ${arg}`);
    }
  }

  if (Number.isNaN(options.start.getTime()) || Number.isNaN(options.end.getTime())) {
    throw new Error("Invalid start or end date");
  }
  if (options.start >= options.end) {
    throw new Error("--start must be earlier than --end");
  }

  return options;
}

function requireValue(argv: string[], index: number, flag: string): string {
  const value = argv[index];
  if (!value) {
    throw new Error(`Missing value for ${flag}`);
  }
  return value;
}

function parseDateArg(value: string, flag: string): Date {
  const parsed = new Date(value);
  if (Number.isNaN(parsed.getTime())) {
    throw new Error(`Invalid date for ${flag}: ${value}`);
  }
  return parsed;
}

function parsePositiveInt(value: string, flag: string): number {
  const parsed = Number.parseInt(value, 10);
  if (!Number.isFinite(parsed) || parsed <= 0) {
    throw new Error(`Invalid positive integer for ${flag}: ${value}`);
  }
  return parsed;
}

function parseNonNegativeInt(value: string, flag: string): number {
  const parsed = Number.parseInt(value, 10);
  if (!Number.isFinite(parsed) || parsed < 0) {
    throw new Error(`Invalid non-negative integer for ${flag}: ${value}`);
  }
  return parsed;
}

function printHelp() {
  console.log(`Usage: tsx scripts/paperclip-commit-metrics.ts [options]

Options:
  --start <date>             ISO date/time lower bound (default: ${DEFAULT_SEARCH_START})
  --end <date>               ISO date/time upper bound (default: now)
  --query <search>           Commit search string (default: ${DEFAULT_QUERY})
  --search-field <field>     author-date | committer-date (default: ${DEFAULT_SEARCH_FIELD})
  --include-private          Include repos visible to the current token
  --exclude-owner <owner>    Exclude repositories owned by this GitHub owner/org (repeatable)
  --cache-file <path>        Cache path (default: ${DEFAULT_CACHE_FILE})
  --skip-stats               Skip additions/deletions enrichment
  --stats-fetch-limit <n>    Max uncached commit stats to fetch this run (default: ${DEFAULT_STATS_FETCH_LIMIT})
  --stats-concurrency <n>    Parallel commit stat requests (default: ${DEFAULT_STATS_CONCURRENCY})
  --output <path>            Write the full filtered result set to a file
  --export-format <format>   csv | json for --output exports (default: csv)
  --refresh-search           Ignore cached search windows
  --refresh-stats            Re-fetch cached commit stats
  --json                     Print JSON summary
  --help                     Show this help
`);
}

async function resolveGitHubToken(): Promise<string> {
  const envToken = process.env.GITHUB_TOKEN ?? process.env.GH_TOKEN;
  if (envToken) {
    return envToken;
  }

  const { stdout } = await execFileAsync("gh", ["auth", "token"]);
  const token = stdout.trim();
  if (!token) {
    throw new Error("Unable to resolve a GitHub token. Set GITHUB_TOKEN/GH_TOKEN or run `gh auth login`.");
  }
  return token;
}

async function loadCache(cacheFile: string, options: CliOptions): Promise<CacheFile> {
  try {
    const raw = await fs.readFile(cacheFile, "utf8");
    const parsed = JSON.parse(raw) as CacheFile;
    if (parsed.version !== 1 || parsed.queryKey !== buildQueryKey(options) || parsed.searchField !== options.searchField) {
      return createEmptyCache(options);
    }
    return parsed;
  } catch (error) {
    if ((error as NodeJS.ErrnoException).code === "ENOENT") {
      return createEmptyCache(options);
    }
    throw error;
  }
}

function createEmptyCache(options: CliOptions): CacheFile {
  return {
    commits: {},
    queryKey: buildQueryKey(options),
    searchField: options.searchField,
    stats: {},
    updatedAt: null,
    version: 1,
    windows: {},
  };
}

function buildQueryKey(options: CliOptions): string {
  const visibility = options.includePrivate ? "all" : "public";
  return JSON.stringify({
    query: options.query,
    searchField: options.searchField,
    visibility,
  });
}

async function saveCache(cacheFile: string, cache: CacheFile): Promise<void> {
  await fs.mkdir(path.dirname(cacheFile), { recursive: true });
  await fs.writeFile(cacheFile, JSON.stringify(cache, null, 2), "utf8");
}

async function searchWindow(
  client: GitHubClient,
  cache: CacheFile,
  options: CliOptions,
  start: Date,
  end: Date,
): Promise<SearchWindowResult> {
  const windowKey = makeWindowKey(start, end);
  if (!options.refreshSearch) {
    const cached = cache.windows[windowKey];
    if (cached) {
      return { shas: new Set(cached.shas), totalCount: cached.totalCount };
    }
  }

  const firstPage = await searchPage(client, options, start, end, 1, 100);
  if (firstPage.incomplete_results) {
    throw new Error(`GitHub returned incomplete search results for window ${windowKey}`);
  }

  if (firstPage.total_count > SEARCH_WINDOW_LIMIT) {
    const durationMs = end.getTime() - start.getTime();
    if (durationMs <= MIN_WINDOW_MS) {
      throw new Error(
        `Search window ${windowKey} still has ${firstPage.total_count} results after splitting to ${durationMs}ms.`,
      );
    }

    const midpoint = new Date(start.getTime() + Math.floor(durationMs / 2));
    const left = await searchWindow(client, cache, options, start, midpoint);
    const right = await searchWindow(client, cache, options, new Date(midpoint.getTime() + 1), end);
    const shas = new Set([...left.shas, ...right.shas]);

    cache.windows[windowKey] = {
      completedAt: new Date().toISOString(),
      key: windowKey,
      shas: [...shas],
      totalCount: shas.size,
    };

    return { shas, totalCount: shas.size };
  }

  const pageCount = Math.ceil(firstPage.total_count / 100);
  const shas = new Set<string>();
  ingestSearchItems(cache, firstPage.items, shas);

  for (let page = 2; page <= pageCount; page += 1) {
    const response = await searchPage(client, options, start, end, page, 100);
    if (response.incomplete_results) {
      throw new Error(`GitHub returned incomplete search results for window ${windowKey} on page ${page}`);
    }
    ingestSearchItems(cache, response.items, shas);
  }

  cache.windows[windowKey] = {
    completedAt: new Date().toISOString(),
    key: windowKey,
    shas: [...shas],
    totalCount: firstPage.total_count,
  };

  return { shas, totalCount: firstPage.total_count };
}

async function searchPage(
  client: GitHubClient,
  options: CliOptions,
  start: Date,
  end: Date,
  page: number,
  perPage: number,
): Promise<SearchResponse> {
  const searchQuery = buildSearchQuery(options, start, end);
  const params = new URLSearchParams({
    page: String(page),
    per_page: String(perPage),
    q: searchQuery,
  });

  return client.getJson<SearchResponse>(`/search/commits?${params.toString()}`);
}

function buildSearchQuery(options: CliOptions, start: Date, end: Date): string {
  const qualifiers = [`${options.searchField}:${formatQueryDate(start)}..${formatQueryDate(end)}`];
  if (!options.includePrivate) {
    qualifiers.push("is:public");
  }
  return `${options.query} ${qualifiers.join(" ")}`.trim();
}

function filterShas(cache: CacheFile, shas: string[], options: CliOptions): string[] {
  if (options.excludeOwners.length === 0) {
    return shas;
  }

  const excludedOwners = new Set(options.excludeOwners);
  return shas.filter((sha) => {
    const commit = cache.commits[sha];
    if (!commit) {
      return false;
    }
    return !excludedOwners.has(getRepoOwner(commit.repositoryFullName));
  });
}

function sortFilteredShas(cache: CacheFile, shas: string[]): string[] {
  return [...shas].sort((leftSha, rightSha) => {
    const left = cache.commits[leftSha];
    const right = cache.commits[rightSha];
    const leftTime = left?.committedAt ? Date.parse(left.committedAt) : 0;
    const rightTime = right?.committedAt ? Date.parse(right.committedAt) : 0;
    if (rightTime !== leftTime) {
      return rightTime - leftTime;
    }

    const repoCompare = (left?.repositoryFullName ?? "").localeCompare(right?.repositoryFullName ?? "");
    if (repoCompare !== 0) {
      return repoCompare;
    }
    return leftSha.localeCompare(rightSha);
  });
}

function formatQueryDate(value: Date): string {
  return new Date(Math.floor(value.getTime() / 1000) * 1000).toISOString().replace(".000Z", "Z");
}

function ingestSearchItems(cache: CacheFile, items: SearchCommitItem[], shas: Set<string>) {
  for (const item of items) {
    shas.add(item.sha);
    cache.commits[item.sha] = {
      authorEmail: item.commit.author?.email ?? null,
      authorLogin: item.author?.login ?? null,
      authorName: item.commit.author?.name ?? null,
      committedAt: item.commit.author?.date ?? null,
      contributors: extractContributors(item),
      htmlUrl: item.html_url,
      repositoryFullName: item.repository.full_name,
      repositoryUrl: item.repository.html_url,
      sha: item.sha,
    };
  }
}

function extractContributors(item: SearchCommitItem): ContributorRecord[] {
  const contributors = new Map<string, ContributorRecord>();

  const primaryAuthor = normalizeContributor({
    email: item.commit.author?.email ?? null,
    login: item.author?.login ?? null,
    name: item.commit.author?.name ?? null,
  });
  if (primaryAuthor) {
    contributors.set(primaryAuthor.key, primaryAuthor);
  }

  const coAuthorPattern = /^co-authored-by:\s*(.+?)\s*<([^>]+)>\s*$/gim;
  for (const match of item.commit.message.matchAll(coAuthorPattern)) {
    const contributor = normalizeContributor({
      email: match[2] ?? null,
      login: null,
      name: match[1] ?? null,
    });
    if (contributor) {
      contributors.set(contributor.key, contributor);
    }
  }

  return [...contributors.values()];
}

function normalizeContributor(input: {
  email: string | null;
  login: string | null;
  name: string | null;
}): ContributorRecord | null {
  const email = normalizeOptional(input.email);
  const login = normalizeOptional(input.login);
  const displayName = normalizeOptional(input.name) ?? login ?? email;

  if (!displayName && !email && !login) {
    return null;
  }
  if ((email && email === PAPERCLIP_EMAIL) || (displayName && displayName.toLowerCase() === PAPERCLIP_NAME)) {
    return null;
  }

  const key = login ? `login:${login}` : email ? `email:${email}` : `name:${displayName!.toLowerCase()}`;
  return {
    displayName: displayName ?? email ?? login ?? "unknown",
    email,
    key,
    login,
  };
}

function normalizeOptional(value: string | null | undefined): string | null {
  const trimmed = value?.trim();
  return trimmed ? trimmed : null;
}

function getRepoOwner(repositoryFullName: string): string {
  return repositoryFullName.split("/", 1)[0]?.toLowerCase() ?? "";
}

async function enrichCommitStats(
  client: GitHubClient,
  cache: CacheFile,
  options: CliOptions,
  shas: string[],
): Promise<number> {
  const pending = shas.filter((sha) => options.refreshStats || !cache.stats[sha]).slice(0, options.statsFetchLimit);
  let nextIndex = 0;
  let fetched = 0;

  const workers = Array.from({ length: Math.min(options.statsConcurrency, pending.length) }, async () => {
    while (true) {
      const currentIndex = nextIndex;
      nextIndex += 1;
      const sha = pending[currentIndex];
      if (!sha) {
        return;
      }
      const commit = cache.commits[sha];
      if (!commit) {
        continue;
      }
      const stats = await fetchCommitStats(client, commit.repositoryFullName, sha);
      cache.stats[sha] = {
        ...stats,
        fetchedAt: new Date().toISOString(),
      };
      fetched += 1;
    }
  });

  await Promise.all(workers);
  return fetched;
}

async function fetchCommitStats(client: GitHubClient, repositoryFullName: string, sha: string): Promise<CommitStats> {
  const response = await client.getJson<{ stats?: CommitStats }>(
    `/repos/${repositoryFullName}/commits/${sha}`,
  );
  return {
    additions: response.stats?.additions ?? 0,
    deletions: response.stats?.deletions ?? 0,
    total: response.stats?.total ?? 0,
  };
}

function buildSummary(cache: CacheFile, options: CliOptions, shas: string[], fetchedThisRun: number): Summary {
  const repoNames = new Set<string>();
  const contributors = new Map<string, ContributorRecord>();
  let additions = 0;
  let deletions = 0;
  let coveredCommits = 0;

  for (const sha of shas) {
    const commit = cache.commits[sha];
    if (!commit) {
      continue;
    }
    repoNames.add(commit.repositoryFullName);
    for (const contributor of commit.contributors) {
      contributors.set(contributor.key, contributor);
    }

    const stats = cache.stats[sha];
    if (stats) {
      additions += stats.additions;
      deletions += stats.deletions;
      coveredCommits += 1;
    }
  }

  const contributorSample = [...contributors.values()]
    .sort((left, right) => left.displayName.localeCompare(right.displayName))
    .slice(0, 10);
  const repoSample = [...repoNames].sort((left, right) => left.localeCompare(right)).slice(0, 10);

  return {
    cacheFile: options.cacheFile,
    contributors: {
      count: contributors.size,
      sample: contributorSample,
    },
    detectedQuery: buildSearchQuery(options, options.start, options.end),
    lineStats: {
      additions,
      complete: coveredCommits === shas.length,
      coveredCommits,
      deletions,
      missingCommits: shas.length - coveredCommits,
      totalChanges: additions + deletions,
    },
    range: {
      end: options.end.toISOString(),
      searchField: options.searchField,
      start: options.start.toISOString(),
    },
    filters: {
      excludedOwners: [...options.excludeOwners].sort(),
    },
    repos: {
      count: repoNames.size,
      sample: repoSample,
    },
    statsFetch: {
      fetchedThisRun,
      skipped: options.skipStats,
    },
    totals: {
      commits: shas.length,
    },
  };
}

function printSummary(summary: Summary) {
  console.log("Paperclip commit metrics");
  console.log(`Query: ${summary.detectedQuery}`);
  console.log(`Range: ${summary.range.start} -> ${summary.range.end} (${summary.range.searchField})`);
  if (summary.filters.excludedOwners.length > 0) {
    console.log(`Excluded owners: ${summary.filters.excludedOwners.join(", ")}`);
  }
  console.log(`Commits: ${summary.totals.commits}`);
  console.log(`Distinct repos: ${summary.repos.count}`);
  console.log(`Distinct contributors: ${summary.contributors.count}`);
  console.log(
    `Line stats: +${summary.lineStats.additions} / -${summary.lineStats.deletions} / ${summary.lineStats.totalChanges} total`,
  );
  console.log(
    `Line stat coverage: ${summary.lineStats.coveredCommits}/${summary.totals.commits}` +
      (summary.lineStats.complete ? " (complete)" : " (partial; rerun to hydrate more commits)"),
  );
  console.log(`Stats fetched this run: ${summary.statsFetch.fetchedThisRun}${summary.statsFetch.skipped ? " (skipped)" : ""}`);
  console.log(`Cache: ${summary.cacheFile}`);

  if (summary.repos.sample.length > 0) {
    console.log(`Sample repos: ${summary.repos.sample.join(", ")}`);
  }
  if (summary.contributors.sample.length > 0) {
    console.log(
      `Sample contributors: ${summary.contributors.sample
        .map((contributor) => contributor.login ?? contributor.displayName)
        .join(", ")}`,
    );
  }
}

async function writeExport(
  outputPath: string,
  format: CliOptions["exportFormat"],
  cache: CacheFile,
  shas: string[],
  summary: Summary,
): Promise<void> {
  await fs.mkdir(path.dirname(outputPath), { recursive: true });
  if (format === "json") {
    const report = {
      summary,
      commits: shas.map((sha) => buildExportRow(cache, sha)),
    };
    await fs.writeFile(outputPath, JSON.stringify(report, null, 2), "utf8");
    return;
  }

  const header = [
    "committedAt",
    "repository",
    "repositoryUrl",
    "sha",
    "commitUrl",
    "authorLogin",
    "authorName",
    "authorEmail",
    "contributors",
    "additions",
    "deletions",
    "totalChanges",
  ];
  const rows = [header.join(",")];
  for (const sha of shas) {
    const row = buildExportRow(cache, sha);
    rows.push(
      [
        row.committedAt,
        row.repository,
        row.repositoryUrl,
        row.sha,
        row.commitUrl,
        row.authorLogin,
        row.authorName,
        row.authorEmail,
        row.contributors,
        String(row.additions),
        String(row.deletions),
        String(row.totalChanges),
      ]
        .map(escapeCsv)
        .join(","),
    );
  }
  await fs.writeFile(outputPath, `${rows.join("\n")}\n`, "utf8");
}

function buildExportRow(cache: CacheFile, sha: string) {
  const commit = cache.commits[sha];
  if (!commit) {
    throw new Error(`Missing cached commit for sha ${sha}`);
  }
  const stats = cache.stats[sha];
  return {
    additions: stats?.additions ?? 0,
    authorEmail: commit.authorEmail ?? "",
    authorLogin: commit.authorLogin ?? "",
    authorName: commit.authorName ?? "",
    commitUrl: commit.htmlUrl,
    committedAt: commit.committedAt ?? "",
    contributors: commit.contributors.map((contributor) => contributor.login ?? contributor.displayName).join(" | "),
    deletions: stats?.deletions ?? 0,
    repository: commit.repositoryFullName,
    repositoryUrl: commit.repositoryUrl,
    sha: commit.sha,
    totalChanges: stats?.total ?? 0,
  };
}

function escapeCsv(value: string): string {
  if (value.includes(",") || value.includes("\"") || value.includes("\n")) {
    return `"${value.replaceAll("\"", "\"\"")}"`;
  }
  return value;
}

function makeWindowKey(start: Date, end: Date): string {
  return `${start.toISOString()}..${end.toISOString()}`;
}

class GitHubClient {
  private readonly apiBase = "https://api.github.com";
  private readonly token: string;

  constructor(token: string) {
    this.token = token;
  }

  async getJson<T>(pathname: string): Promise<T> {
    while (true) {
      const response = await fetch(`${this.apiBase}${pathname}`, {
        headers: {
          Accept: "application/vnd.github+json",
          Authorization: `Bearer ${this.token}`,
          "User-Agent": "paperclip-commit-metrics",
          "X-GitHub-Api-Version": "2022-11-28",
        },
      });

      if (response.ok) {
        return (await response.json()) as T;
      }

      const retryAfter = response.headers.get("retry-after");
      if ((response.status === 403 || response.status === 429) && retryAfter) {
        const waitMs = Math.max(Number.parseInt(retryAfter, 10) * 1000, 1_000);
        console.error(`GitHub secondary rate limit hit for ${pathname}; waiting ${Math.ceil(waitMs / 1000)}s...`);
        await sleep(waitMs);
        continue;
      }

      const remaining = response.headers.get("x-ratelimit-remaining");
      const resetAt = response.headers.get("x-ratelimit-reset");
      if ((response.status === 403 || response.status === 429) && remaining === "0" && resetAt) {
        const waitMs = Math.max(Number.parseInt(resetAt, 10) * 1000 - Date.now() + 1_000, 1_000);
        console.error(`GitHub rate limit hit for ${pathname}; waiting ${Math.ceil(waitMs / 1000)}s...`);
        await sleep(waitMs);
        continue;
      }

      const body = await response.text();
      throw new Error(`GitHub API request failed (${response.status}) for ${pathname}: ${body}`);
    }
  }
}

function sleep(ms: number): Promise<void> {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

main().catch((error) => {
  console.error(error instanceof Error ? error.message : String(error));
  process.exit(1);
});