}

/**
 * Fetches all comments for a specific user from the Reddit API.
 * Handles pagination by making multiple requests until all comments are retrieved.
 * @param username The Reddit username.
 * @returns A promise that resolves to an array of comment objects.
 */
async function fetchAllComments(username: string): Promise<RedditComment[]> {
  const allComments: RedditComment[] = [];
  let after: string | null = null;
  let pageCount = 0;

  console.log(`Starting to fetch comments for user: ${username}`);

  do {
    // Construct the URL with the 'after' parameter for pagination
    const url = new URL(`${REDDIT_API_BASE}/user/${username}/comments.json`);
    url.searchParams.set("limit", "100"); // Max limit is 100 per page
    if (after) {
      url.searchParams.set("after", after);
    }

    console.log(`Fetching page ${++pageCount}...`);

    const response = await fetch(url, {
      headers: { "User-Agent": USER_AGENT },
    });

    if (!response.ok) {
      if (response.status === 404) {
        throw new Error(`User "${username}" not found. (Status: ${response.status})`);
      }
      throw new Error(`Failed to fetch data from Reddit. Status: ${response.status}`);
    }

    const data = await response.json();
    const children = data?.data?.children;

    if (!children || children.length === 0) {
      // No more comments to fetch
      break;
    }

    for (const child of children) {
      if (child.kind === "t1") { // 't1' is the Reddit API's kind for a comment
        const commentData = child.data;
        allComments.push({
          subreddit: commentData.subreddit,
          created_utc: commentData.created_utc,
          score: commentData.score,
          // Prepend the base URL to make the permalink a full, clickable URL
          permalink: `${REDDIT_API_BASE}${commentData.permalink}`,
          // Clean up the body text by replacing newlines with spaces for better CSV compatibility
          body: commentData.body.replace(/(\r\n|\n|\r)/gm, " "),
        });
      }
    }

    // Get the 'after' token for the next page
    after = data.data.after;

    // Be a good API citizen and wait a moment between requests
    await new Promise(resolve => setTimeout(resolve, 1000));

  } while (after);

  console.log(`\nFinished fetching. Found a total of ${allComments.length} comments.`);
  return allComments;
}

/**
 * Main execution function
 */
async function main() {
  const username = Deno.args[0];

  if (!username) {
    console.error("Error: Reddit username is required.");
    console.error("Usage: deno run --allow-net --allow-write download_comments.ts <username>");
    Deno.exit(1);
  }

  try {
    const comments = await fetchAllComments(username);

    if (comments.length === 0) {
      console.log(`No comments found for user "${username}".`);
      return;
    }

    const outputFilename = `${username}_comments.csv`;

    // Define the headers and the order of columns in the CSV
    const headers = [
      "created_utc",
      "subreddit",
      "score",
      "permalink",
      "body",
    ];

    // The `stringify` function converts an array of objects into a CSV string.
    // The `columns` option ensures the columns are in the correct order.
    const csvString = await stringify(comments, {
      headers: true, // Include the header row
      columns: headers,
    });

    console.log(`Writing ${comments.length} comments to ${outputFilename}...`);
    await Deno.writeTextFile(outputFilename, csvString);

    console.log(`✅ Success! File saved as ${outputFilename}`);
  } catch (error) {
    console.error(`\nAn error occurred: ${error.message}`);
    Deno.exit(1);
  }
}

// Run the main function
main();