// Runs a coding agent for one Gitea issue or pull request event and posts its
// final response back. The agent works as the author account through
// GITEA_TOKEN; everything this script posts goes through the reviewer token,
// so it appears as the bot account.
import { TextLineStream } from "jsr:@std/streams@1/text-line-stream";

type GiteaUser = { login: string; email: string };
type GiteaComment = { user: GiteaUser; created_at: string; body: string };

const env = (name: string): string => {
  const value = Deno.env.get(name);
  if (value === undefined) throw new Error(`${name} is not set`);
  return value;
};

const API = env("GITEA_API_URL");
const REPO = env("GITEA_REPOSITORY");
const INDEX = env("ISSUE_INDEX");
const EVENT = env("EVENT_NAME");
const AUTHOR_TOKEN = env("GITEA_TOKEN");
const REVIEWER_TOKEN = env("REVIEWER_TOKEN");
const RULES_PATH = "repos/commons/code-rules/raw/README.md";

// The reviewer token is withheld so the agent cannot approve as the bot.
const { REVIEWER_TOKEN: _, ...agentEnv } = Deno.env.toObject();

async function gitea(
  token: string,
  path: string,
  body?: unknown,
): Promise<Response> {
  const response = await fetch(`${API}/${path}`, {
    method: body === undefined ? "GET" : "POST",
    headers: {
      Authorization: `token ${token}`,
      "Content-Type": "application/json",
    },
    body: body === undefined ? undefined : JSON.stringify(body),
  });
  if (!response.ok) {
    throw new Error(`${path}: ${response.status} ${await response.text()}`);
  }
  return response;
}

const ANSI = new RegExp(`${String.fromCharCode(27)}\\[[0-9;]*[A-Za-z]`, "g");
const stripAnsi = (text: string): string => text.replace(ANSI, "");

async function postComment(body: string): Promise<void> {
  await gitea(REVIEWER_TOKEN, `repos/${REPO}/issues/${INDEX}/comments`, {
    body: stripAnsi(body),
  });
}

// A pull request event is a review request, so the response becomes a review:
// changes are requested when the agent asked @bot to fix something, a failed
// run only comments, and anything else approves.
async function postResult(body: string): Promise<void> {
  if (EVENT !== "pull_request") return postComment(body);
  const event = body.includes("@bot")
    ? "REQUEST_CHANGES"
    : body.startsWith("Bot failed:")
    ? "COMMENT"
    : "APPROVED";
  await gitea(REVIEWER_TOKEN, `repos/${REPO}/pulls/${INDEX}/reviews`, {
    body: stripAnsi(body),
    event,
  });
}

// Commits belong to the same account as the pull request they end up in.
async function configureGitAuthor(): Promise<void> {
  const user: GiteaUser = await (await gitea(AUTHOR_TOKEN, "user")).json();
  for (const [key, value] of [["name", user.login], ["email", user.email]]) {
    await new Deno.Command("git", {
      args: ["config", "--global", `user.${key}`, value],
    }).output();
  }
}

async function renderPrompt(): Promise<string> {
  const comments: GiteaComment[] = await (await gitea(
    REVIEWER_TOKEN,
    `repos/${REPO}/issues/${INDEX}/comments?limit=100`,
  )).json();
  const values: Record<string, string> = {
    COMMENT: env("COMMENT"),
    ISSUE_COMMENTS: comments
      .map((c) => `## ${c.user.login} at ${c.created_at}\n\n${c.body}\n`)
      .join("\n"),
    CODE_RULES: await (await gitea(REVIEWER_TOKEN, RULES_PATH)).text(),
    EVENT_NAME: EVENT,
    GITEA_API_URL: API,
    GITEA_REPOSITORY: REPO,
    ISSUE_INDEX: INDEX,
  };
  const template = await Deno.readTextFile(
    new URL("prompt.md", import.meta.url),
  );
  return template.replace(
    /\$\{(\w+)\}/g,
    (match, name) => values[name] ?? match,
  );
}

async function runClaude(prompt: string): Promise<string> {
  const token = Deno.env.get("BOT_TOKEN");
  if (!token) {
    await postComment(
      "Run `claude setup-token` locally and set the `bot-token` action input.",
    );
    Deno.exit(1);
  }
  const claude = new Deno.Command("claude", {
    args: [
      "--print",
      "--dangerously-skip-permissions",
      "--model",
      "claude-fable-5",
      "--output-format",
      "stream-json",
      "--verbose",
      prompt,
    ],
    // Claude refuses --dangerously-skip-permissions as root outside a sandbox.
    env: { ...agentEnv, CLAUDE_CODE_OAUTH_TOKEN: token, IS_SANDBOX: "1" },
    clearEnv: true,
    stdout: "piped",
  }).spawn();
  let result = "Bot failed: no result";
  // Print events as they stream so the runner does not kill the job as a zombie.
  const lines = claude.stdout
    .pipeThrough(new TextDecoderStream())
    .pipeThrough(new TextLineStream());
  for await (const line of lines) {
    if (!line) continue;
    const event = JSON.parse(line);
    for (const part of event.message?.content ?? []) {
      const text = part.thinking ?? part.text ?? part.name;
      if (text) console.log(text);
    }
    if (event.type === "result") {
      result = event.result ?? `Bot failed: ${event.subtype}`;
    }
  }
  await claude.status;
  return result;
}

// Posts the device code so a human can finish the login on the persisted home.
async function codexDeviceLogin(): Promise<void> {
  const login = new Deno.Command("codex", {
    args: ["login", "--device-auth"],
    stdout: "piped",
    stderr: "piped",
  }).spawn();
  let shown = "";
  const collect = (stream: ReadableStream<Uint8Array>): Promise<void> =>
    stream.pipeThrough(new TextDecoderStream()).pipeTo(
      new WritableStream({ write: (chunk) => void (shown += chunk) }),
    );
  const drained = Promise.all([collect(login.stdout), collect(login.stderr)]);
  await new Promise((resolve) => setTimeout(resolve, 3000));
  await postComment(shown);
  await Promise.all([login.status, drained]);
  const status = await new Deno.Command("codex", { args: ["login", "status"] })
    .output();
  await postComment(new TextDecoder().decode(status.stdout));
}

async function runCodex(prompt: string): Promise<string> {
  const loggedIn = await new Deno.Command("codex", {
    args: ["login", "status"],
  })
    .output();
  if (!loggedIn.success) await codexDeviceLogin();
  const file = await Deno.makeTempFile();
  const status = await new Deno.Command("codex", {
    args: [
      "exec",
      "--model",
      "gpt-5.5",
      "--dangerously-bypass-approvals-and-sandbox",
      "--output-last-message",
      file,
      prompt,
    ],
    env: agentEnv,
    clearEnv: true,
    stdout: "inherit",
    stderr: "inherit",
  }).spawn().status;
  if (!status.success) throw new Error(`codex exited with ${status.code}`);
  return await Deno.readTextFile(file);
}

await configureGitAuthor();
const prompt = await renderPrompt();
const result = env("BOT_TYPE") === "claude"
  ? await runClaude(prompt)
  : await runCodex(prompt);
await postResult(result);