import type { Stats } from "node:fs";
import { lstat, readFile, rm } from "node:fs/promises";
import nodePath from "node:path";

import { field, isNotFound, isObject } from "#common";
import {
  failureFooter,
  type FailureReason,
  type ProfileFailure,
  withProfile,
} from "#profiles";
import {
  readRuntimeManifest,
  type RuntimeManifest,
  type RuntimeOutcome,
} from "#runtime";

export interface PostContext {
  apiUrl: string;
  repository: string;
  issueIndex: string;
  eventName: string;
}

interface Anchor {
  path: string;
  line: number;
  side: "NEW" | "OLD";
  body: string;
}

const ANSI = new RegExp(`${String.fromCodePoint(27)}\\[[0-9;]*[A-Za-z]`, "gu");
const stripAnsi = (text: string): string => text.replace(ANSI, "");
const VERDICTS = new Map<string, [event: string, mark: string]>([
  ["Approved", ["APPROVED", "✅"]],
  ["Changes requested", ["REQUEST_CHANGES", "🛑"]],
]);
const PROFILE_TYPES = new Set<unknown>(["CLAUDE", "CODEX", "OPENCODE"]);
const FAILURE_REASONS = new Set<unknown>([
  "SIGN_IN_FAILED",
  "USAGE_EXHAUSTED",
  "FAILED",
]);
// Anchors written before the UPPER_SNAKE switch spell sides in lowercase.
const OLD_SIDES = new Map<unknown, Anchor["side"]>([
  ["new", "NEW"],
  ["old", "OLD"],
]);
const isProfileType = (value: unknown): value is ProfileFailure["type"] =>
  PROFILE_TYPES.has(value);
const isFailureReason = (value: unknown): value is FailureReason =>
  FAILURE_REASONS.has(value);
const failureComment = (failures: ProfileFailure[]): string =>
  `AI bot failed.\n\n${failureFooter(failures)}`;

// The `fetch` subset the reviewer posts through, which tests replace.
export type Fetcher = (url: string, init: RequestInit) => Promise<Response>;

class GiteaRequestError extends Error {
  constructor(message: string, options?: ErrorOptions) {
    super(message, options);
    this.name = "GiteaRequestError";
  }
}

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

async function readOutcome(path: string): Promise<RuntimeOutcome> {
  const value: unknown = JSON.parse(await readFile(path, "utf8"));
  if (!isObject(value) || !("ok" in value)) {
    throw new Error("invalid agent outcome");
  }
  const ok = field(value, "ok");
  if (ok === false) {
    // Only known labels reach the comment, never raw agent output.
    const listed = field(value, "failures");
    const failures: unknown[] = Array.isArray(listed) ? listed : [];
    return {
      ok: false,
      failures: failures.flatMap((entry: unknown) => {
        const type = field(entry, "type");
        const model = field(entry, "model");
        const reason = field(entry, "reason");
        return isProfileType(type) &&
          typeof model === "string" &&
          isFailureReason(reason)
          ? [{ type, model, reason }]
          : [];
      }),
    };
  }
  const body = field(value, "body");
  const reviewPath = field(value, "reviewPath");
  const anchorsPath = field(value, "anchorsPath");
  const profile = field(value, "profile");
  if (
    ok !== true ||
    typeof body !== "string" ||
    typeof reviewPath !== "string" ||
    typeof anchorsPath !== "string" ||
    !isObject(profile)
  ) {
    throw new Error("invalid agent outcome");
  }
  const type = field(profile, "type");
  const model = field(profile, "model");
  if (!isProfileType(type) || typeof model !== "string") {
    throw new Error("invalid agent outcome");
  }
  return { ok: true, body, reviewPath, anchorsPath, profile: { type, model } };
}

async function readAgentArtifact(
  manifest: RuntimeManifest,
  path: string,
  name: string,
): Promise<string | null> {
  const profile = manifest.profiles.find(
    (entry) => nodePath.join(entry.home, name) === path,
  );
  if (profile === undefined) {
    throw new Error(`${name}: outside profile home`);
  }
  let stat: Stats | null = null;
  try {
    stat = await lstat(path);
  } catch (error) {
    if (isNotFound(error)) {
      return null;
    }
    throw error;
  }
  if (
    !stat.isFile() ||
    stat.isSymbolicLink() ||
    stat.uid !== profile.uid ||
    (stat.mode & 0o077) !== 0
  ) {
    throw new Error(`${name}: expected a profile-owned regular private file`);
  }
  const text = await readFile(path, "utf8");
  return text === "" ? null : text;
}

export async function postRuntime(
  manifestPath: string,
  context: PostContext,
  fetcher: Fetcher = fetch,
): Promise<void> {
  const manifest = await readRuntimeManifest(manifestPath);
  try {
    const reviewerText = await readFile(manifest.reviewerFile, "utf8");
    const reviewerToken = reviewerText.trim();
    const request = async (path: string, body: unknown): Promise<void> => {
      let response: Response | null = null;
      try {
        response = await fetcher(`${context.apiUrl}/${path}`, {
          method: "POST",
          headers: {
            Authorization: `token ${reviewerToken}`,
            "Content-Type": "application/json",
          },
          body: JSON.stringify(body),
        });
      } catch (error) {
        const detail = error instanceof Error ? error.message : String(error);
        throw new GiteaRequestError(`${path}: ${detail}`, { cause: error });
      }
      if (!response.ok) {
        throw new GiteaRequestError(
          `${path}: ${response.status} ${await response.text()}`,
        );
      }
    };
    const postComment = async (body: string): Promise<void> => {
      await request(
        `repos/${context.repository}/issues/${context.issueIndex}/comments`,
        {
          body: stripAnsi(body),
        },
      );
    };

    let outcome: RuntimeOutcome | null = null;
    try {
      outcome = await readOutcome(manifest.outcomeFile);
    } catch (error) {
      await postComment(failureComment([]));
      throw new Error("agent phase failed", { cause: error });
    }
    if (!outcome.ok) {
      await postComment(failureComment(outcome.failures));
      throw new Error("agent phase failed");
    }

    try {
      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(withProfile(outcome.body, outcome.profile));
        return;
      }

      const [verdict = "", ...rest] = review.split("\n");
      const [event, mark] = VERDICTS.get(verdict.trim()) ?? ["COMMENT", "💬"];
      const anchorText = await readAgentArtifact(
        manifest,
        outcome.anchorsPath,
        "anchors.json",
      );
      const anchors =
        anchorText === null
          ? []
          : parseAnchors(anchorText, outcome.anchorsPath);
      const postReview = async (entries: Anchor[]): Promise<void> => {
        await request(
          `repos/${context.repository}/pulls/${context.issueIndex}/reviews`,
          {
            body: stripAnsi(
              withProfile(
                [`${mark} ${verdict.trim()}`, ...rest].join("\n"),
                outcome.profile,
              ),
            ),
            event,
            comments: entries.map(({ path, line, side, body }) => ({
              path,
              body: stripAnsi(withProfile(body, outcome.profile)),
              new_position: side === "NEW" ? line : 0,
              old_position: side === "OLD" ? line : 0,
            })),
          },
        );
      };
      await postReview(anchors).catch(async (error: unknown) => {
        if (anchors.length === 0) {
          throw error;
        }
        console.error(
          `inline comments rejected: ${error instanceof Error ? error.message : String(error)}`,
        );
        await postReview([]);
      });
    } catch (error) {
      if (error instanceof GiteaRequestError) {
        throw error;
      }
      await postComment(
        failureComment([{ ...outcome.profile, reason: "FAILED" }]),
      );
      throw error;
    }
  } finally {
    await rm(manifest.runtimeDir, { recursive: true }).catch(
      (error: unknown) => {
        if (!isNotFound(error)) {
          throw error;
        }
      },
    );
  }
}