import { join } from "jsr:@std/path@1";
import {
  readRuntimeManifest,
  type RuntimeManifest,
  type RuntimeOutcome,
} from "./runtime.ts";

export type PostContext = {
  apiUrl: string;
  repository: string;
  issueIndex: string;
  eventName: string;
};

type Anchor = {
  path: string;
  line: number;
  side: "new" | "old";
  body: string;
};

const ANSI = new RegExp(`${String.fromCharCode(27)}\\[[0-9;]*[A-Za-z]`, "g");
const stripAnsi = (text: string): string => text.replace(ANSI, "");
const VERDICTS: Record<string, [event: string, mark: string]> = {
  Approved: ["APPROVED", "✅"],
  "Changes requested": ["REQUEST_CHANGES", "🛑"],
};

function parseAnchors(text: string, sourcePath: string): Anchor[] {
  const entries: unknown = JSON.parse(text);
  if (!Array.isArray(entries)) throw new Error(`${sourcePath}: not an array`);
  return entries.map((entry: unknown, index) => {
    const at = `${sourcePath}[${index}]`;
    if (typeof entry !== "object" || entry === null) {
      throw new Error(`${at}: not an object`);
    }
    const { path, line, side = "new", body } = entry as Record<string, unknown>;
    if (typeof path !== "string" || path === "") {
      throw new Error(`${at}.path: expected a repository path`);
    }
    if (typeof line !== "number" || !Number.isInteger(line) || line < 1) {
      throw new Error(`${at}.line: expected a line number`);
    }
    if (side !== "new" && side !== "old") {
      throw new Error(`${at}.side: expected \"new\" or \"old\"`);
    }
    if (typeof body !== "string" || body.trim() === "") {
      throw new Error(`${at}.body: expected the finding`);
    }
    return { path, line, side, body };
  });
}

async function readOutcome(path: string): Promise<RuntimeOutcome> {
  const value: unknown = JSON.parse(await Deno.readTextFile(path));
  if (typeof value !== "object" || value === null || !("ok" in value)) {
    throw new Error("invalid agent outcome");
  }
  const outcome = value as Record<string, unknown>;
  if (outcome.ok === false) return { ok: false };
  if (
    outcome.ok !== true || typeof outcome.body !== "string" ||
    typeof outcome.reviewPath !== "string" ||
    typeof outcome.anchorsPath !== "string"
  ) {
    throw new Error("invalid agent outcome");
  }
  return {
    ok: true,
    body: outcome.body,
    reviewPath: outcome.reviewPath,
    anchorsPath: outcome.anchorsPath,
  };
}

async function readAgentArtifact(
  manifest: RuntimeManifest,
  path: string,
  name: string,
): Promise<string | null> {
  const profile = manifest.profiles.find((entry) =>
    join(entry.home, name) === path
  );
  if (profile === undefined) throw new Error(`${name}: outside profile home`);
  let stat: Deno.FileInfo;
  try {
    stat = await Deno.lstat(path);
  } catch (error) {
    if (error instanceof Deno.errors.NotFound) return null;
    throw error;
  }
  if (
    !stat.isFile || stat.isSymlink || stat.uid !== profile.uid ||
    (stat.mode! & 0o077) !== 0
  ) {
    throw new Error(`${name}: expected a profile-owned regular private file`);
  }
  const text = await Deno.readTextFile(path);
  return text === "" ? null : text;
}

export async function postRuntime(
  manifestPath: string,
  context: PostContext,
  fetcher: typeof fetch = fetch,
): Promise<void> {
  const manifest = await readRuntimeManifest(manifestPath);
  try {
    const reviewerToken = (await Deno.readTextFile(manifest.reviewerFile))
      .trim();
    const request = async (path: string, body: unknown): Promise<void> => {
      const response = await fetcher(`${context.apiUrl}/${path}`, {
        method: "POST",
        headers: {
          Authorization: `token ${reviewerToken}`,
          "Content-Type": "application/json",
        },
        body: JSON.stringify(body),
      });
      if (!response.ok) {
        throw new Error(`${path}: ${response.status} ${await response.text()}`);
      }
    };
    const postComment = (body: string) =>
      request(
        `repos/${context.repository}/issues/${context.issueIndex}/comments`,
        { body: stripAnsi(body) },
      );

    let outcome: RuntimeOutcome;
    try {
      outcome = await readOutcome(manifest.outcomeFile);
    } catch (error) {
      await postComment("AI bot failed.");
      throw new Error("agent phase failed", { cause: error });
    }
    if (!outcome.ok) {
      await postComment("AI bot failed.");
      throw new Error("agent phase failed");
    }

    const review = await readAgentArtifact(
      manifest,
      outcome.reviewPath,
      "review.md",
    );
    if (review === null) {
      if (context.eventName === "pull_request") {
        throw new Error("agent did not write a pull request review");
      }
      await postComment(outcome.body);
      return;
    }

    const [verdict, ...rest] = review.split("\n");
    const [event, mark] = VERDICTS[verdict.trim()] ?? ["COMMENT", "💬"];
    const anchorText = await readAgentArtifact(
      manifest,
      outcome.anchorsPath,
      "anchors.json",
    );
    const anchors = anchorText === null
      ? []
      : parseAnchors(anchorText, outcome.anchorsPath);
    const postReview = (entries: Anchor[]) =>
      request(
        `repos/${context.repository}/pulls/${context.issueIndex}/reviews`,
        {
          body: stripAnsi([`${mark} ${verdict.trim()}`, ...rest].join("\n")),
          event,
          comments: entries.map(({ path, line, side, body }) => ({
            path,
            body: stripAnsi(body),
            new_position: side === "new" ? line : 0,
            old_position: side === "old" ? line : 0,
          })),
        },
      );
    await postReview(anchors).catch(async (error: Error) => {
      if (anchors.length === 0) throw error;
      console.error(`inline comments rejected: ${error.message}`);
      await postReview([]);
    });
  } finally {
    await Deno.remove(manifest.runtimeDir, { recursive: true }).catch(
      (error) => {
        if (!(error instanceof Deno.errors.NotFound)) throw error;
      },
    );
  }
}

if (import.meta.main) {
  const required = (name: string): string => {
    const value = Deno.env.get(name);
    if (!value) throw new Error(`${name} is not set`);
    return value;
  };
  await postRuntime(required("BOT_AGENTS_MANIFEST"), {
    apiUrl: required("GITEA_API_URL"),
    repository: required("GITEA_REPOSITORY"),
    issueIndex: required("ISSUE_INDEX"),
    eventName: required("EVENT_NAME"),
  });
}