import { loadConfig } from "../config";
import { isGitRepo, getRecentCommits } from "../git";
import { CHANGELOG_SYSTEM_PROMPT, buildChangelogPrompt } from "../prompt";
import { callAI } from "../ai";
import { BOLD, RED, DIM, RESET, CYAN } from "../terminal";
import { isStdinTTY } from "../tty";
import type { StreamCallbacks } from "../types";
import type { ParsedArgs } from "../cli";

export async function handleChangelog(args: ParsedArgs): Promise<number> {
  const config = await loadConfig();

  if (!config.apiKey) {
    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
    return 1;
  }

  if (!(await isGitRepo())) {
    console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
    return 1;
  }

  const from = args.flags["from"] as string | undefined;
  const to = args.flags["to"] as string | undefined;
  const countFlag = args.flags["count"] as number | undefined;
  const verbose = args.flags["verbose"] as boolean;

  // Collect commits
  let commits: string[];

  if (from) {
    // Range-based: get commits between from..to
    const range = to ? `${from}..${to}` : `${from}..HEAD`;
    try {
      const result = await Bun.$`git log --oneline ${range}`.quiet().text();
      commits = result.trim().split("\n").filter(Boolean);
    } catch {
      console.error(`\n  ${RED()}Error: Invalid range: ${range}${RESET()}\n`);
      return 1;
    }
  } else {
    // Count-based
    const count = typeof countFlag === "number" ? countFlag : 20;
    commits = await getRecentCommits(count);
  }

  if (commits.length === 0) {
    console.log(`  ${DIM()}No commits found for the specified range.${RESET()}`);
    return 0;
  }

  if (verbose) {
    console.log(`  ${DIM()}Processing ${commits.length} commits${RESET()}`);
    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
  }

  const userPrompt = buildChangelogPrompt(commits, from, to);

  const tty = isStdinTTY();
  if (tty) {
    console.log(`\n  ${BOLD()}${CYAN()}Generating changelog from ${commits.length} commits...${RESET()}\n`);
  }

  try {
    const callbacks: StreamCallbacks = tty ? {
      onToken: (token) => process.stdout.write(token),
    } : undefined;

    const result = await callAI(config, CHANGELOG_SYSTEM_PROMPT, userPrompt, callbacks);
    if (callbacks) {
      process.stdout.write("\n");
    } else {
      process.stdout.write(result + "\n");
    }
  } catch (err) {
    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
    return 1;
  }

  return 0;
}