// The Mailu API client — mailu's own code, living in the module (novox/hq ADR 0039). Moved out of
// the shared hal sdk, where a change to Mailu's surface rebuilt everything; here it rebuilds only
// mailu. Both this module's tools and its events entrypoint import it, and nothing outside mailu does.
//
// hal drove Mailu through its flask CLI over `docker compose exec` into the admin container. That
// coupling was to the container, not to Mailu: it needed a shell on the box. The module's real
// coupling is the admin REST API, so that is what this client speaks — a token and a URL, no shell.
// The one exception is reading a mailbox: the admin API exposes no message reads, so that alone
// falls back to `doveadm` inside the imap container, the operation the HTTP surface cannot serve.

import { execFile } from "node:child_process";
import { readFileSync } from "node:fs";
import { promisify } from "node:util";

const run = promisify(execFile);

export interface MailuUser {
  email: string;
  displayed_name?: string;
  global_admin?: boolean;
  enabled?: boolean;
  forward_enabled?: boolean;
  forward_destination?: string[];
  quota_bytes?: number;
}

export interface MailuAlias {
  email: string;
  destination: string[];
  wildcard?: boolean;
}

export interface MailuDomain {
  name: string;
}

/** One parsed message from a doveadm fetch — the subset the read/search tools surface. */
export interface MailMessage {
  date?: string;
  from?: string;
  subject?: string;
  preview?: string;
}

// The fields we ask doveadm for, once — kept together so read and search stay identical in shape.
const FETCH_FIELDS = "date.received hdr.subject hdr.from body.snippet";

/** The settings-merged config the mesh delivers (novox/hq ADR 0046): { url, apiKey, token, password, user, ... }. */
function meshConfig(file?: string): Record<string, string> {
  if (!file) return {};
  try { return JSON.parse(readFileSync(file, "utf8")) as Record<string, string>; }
  catch { return {}; }
}

export class MailuClient {
  readonly baseUrl: string;

  constructor(
    url: string,
    private readonly apiKey: string,
    /** The container name doveadm runs in — reads bypass the API, so they need the box, not a token. */
    private readonly imapContainer: string,
  ) {
    this.baseUrl = url.replace(/\/$/, "");
  }

  /**
   * Build from the module's resolved environment. MESH_MAILU_URL points at the admin API (e.g. the
   * admin container's /api/v1), MESH_MAILU_API_KEY authenticates against it. Both are required — a
   * client with neither would only fail later, one call at a time, so it fails here instead.
   */
  static fromEnv(env: NodeJS.ProcessEnv = process.env): MailuClient {
    const cfg = meshConfig(env.MESH_MAILU_CONFIG_FILE);
    const url = cfg.url ?? env.MESH_MAILU_URL;
    const apiKey = cfg.apiKey ?? env.MESH_MAILU_API_KEY;
    if (!url || !apiKey) {
      throw new Error("Mailu is not configured — set MESH_MAILU_URL and MESH_MAILU_API_KEY");
    }
    const imapContainer = cfg.container ?? env.MESH_MAILU_IMAP_CONTAINER ?? "mailu-imap";
    return new MailuClient(url, apiKey, imapContainer);
  }

  // --- The admin REST API: users, aliases, domains. ---------------------------------------------

  private async api<T>(method: string, path: string, body?: unknown): Promise<T> {
    const res = await fetch(`${this.baseUrl}${path}`, {
      method,
      headers: {
        // Mailu's admin API takes the token directly in Authorization, no scheme prefix.
        Authorization: this.apiKey,
        Accept: "application/json",
        ...(body !== undefined ? { "Content-Type": "application/json" } : {}),
      },
      ...(body !== undefined ? { body: JSON.stringify(body) } : {}),
    });
    if (!res.ok) throw new Error(`Mailu API ${method} ${path}: ${res.status} ${await res.text()}`);
    // DELETE and some writes answer with an empty body or a bare string; guard the JSON parse.
    const text = await res.text();
    return (text ? JSON.parse(text) : undefined) as T;
  }

  async listUsers(): Promise<MailuUser[]> {
    const users = await this.api<any[]>("GET", "/user");
    return (users ?? []).map((u) => ({
      email: u.email,
      displayed_name: u.displayed_name,
      global_admin: u.global_admin,
      enabled: u.enabled,
      forward_enabled: u.forward_enabled,
      forward_destination: u.forward_destination,
      quota_bytes: u.quota_bytes,
    }));
  }

  /** Create a mailbox. Mailu wants the full address and the plaintext password it will hash. */
  async createUser(email: string, password: string): Promise<void> {
    await this.api("POST", "/user", { email, raw_password: password });
  }

  async changePassword(email: string, password: string): Promise<void> {
    await this.api("PATCH", `/user/${encodeURIComponent(email)}`, { raw_password: password });
  }

  async deleteUser(email: string): Promise<void> {
    await this.api("DELETE", `/user/${encodeURIComponent(email)}`);
  }

  async listAliases(): Promise<MailuAlias[]> {
    const aliases = await this.api<any[]>("GET", "/alias");
    return (aliases ?? []).map((a) => ({
      email: a.email,
      // The API returns destination as a comma-joined string on some versions, a list on others.
      destination: Array.isArray(a.destination)
        ? a.destination
        : String(a.destination ?? "").split(",").map((d: string) => d.trim()).filter(Boolean),
      wildcard: a.wildcard,
    }));
  }

  async createAlias(email: string, destination: string[], wildcard = false): Promise<void> {
    await this.api("POST", "/alias", { email, destination, wildcard });
  }

  async deleteAlias(email: string): Promise<void> {
    await this.api("DELETE", `/alias/${encodeURIComponent(email)}`);
  }

  async listDomains(): Promise<MailuDomain[]> {
    const domains = await this.api<any[]>("GET", "/domain");
    return (domains ?? []).map((d) => ({ name: d.name }));
  }

  // --- Reading mail: doveadm, because the admin API has no message reads. -----------------------

  /** Recent messages in a mailbox, newest last, capped to `limit`. */
  async readMail(user: string, mailbox = "INBOX", limit = 10): Promise<MailMessage[]> {
    const messages = await this.doveadmFetch(user, ["mailbox", mailbox]);
    return messages.slice(-limit);
  }

  /**
   * Search a mailbox by subject, sender and/or date. doveadm fetch takes a search query directly,
   * so we build one from whichever criteria were given — `all` when none were, to avoid an empty
   * query that would match nothing.
   */
  async searchMail(
    user: string,
    criteria: { subject?: string; from?: string; since?: string },
    limit = 10,
  ): Promise<MailMessage[]> {
    const query: string[] = [];
    if (criteria.subject) query.push("subject", criteria.subject);
    if (criteria.from) query.push("from", criteria.from);
    if (criteria.since) query.push("since", criteria.since);
    if (query.length === 0) query.push("all");
    const messages = await this.doveadmFetch(user, query);
    return messages.slice(-limit);
  }

  private async doveadmFetch(user: string, query: string[]): Promise<MailMessage[]> {
    const output = await run(
      "docker",
      ["exec", "-i", this.imapContainer, "doveadm", "fetch", "-u", user, FETCH_FIELDS, ...query],
      { timeout: 30_000 },
    )
      .then((r) => r.stdout)
      // An empty mailbox is not an error; doveadm says so on stderr and exits non-zero.
      .catch((e: { stderr?: string; message?: string }) => {
        const text = `${e.stderr ?? ""}${e.message ?? ""}`;
        if (text.includes("no matching mails")) return "";
        throw e;
      });
    return parseDoveadmFetch(output).map(toMailMessage);
  }
}

// doveadm fetch prints one record per message, records separated by a blank line (a form feed in
// some builds), each field on its own `name: value` line. A folded value continues on later lines.
function parseDoveadmFetch(output: string): Array<Record<string, string>> {
  const messages: Array<Record<string, string>> = [];
  let current: Record<string, string> = {};
  for (const line of output.split("\n")) {
    if (line === "" || line === "\f") {
      if (Object.keys(current).length) {
        messages.push(current);
        current = {};
      }
      continue;
    }
    const colonIdx = line.indexOf(": ");
    if (colonIdx > 0) {
      const key = line.slice(0, colonIdx);
      const value = line.slice(colonIdx + 2);
      current[key] = current[key] ? `${current[key]}\n${value}` : value;
    }
  }
  if (Object.keys(current).length) messages.push(current);
  return messages;
}

function toMailMessage(m: Record<string, string>): MailMessage {
  const preview = m["body.snippet"];
  return {
    date: m["date.received"]?.trim(),
    from: m["hdr.from"]?.trim(),
    subject: m["hdr.subject"]?.trim(),
    preview: preview ? preview.trim().slice(0, 200) : undefined,
  };
}