// The Home Assistant API client — home-assistant's own code, living in the module (novox/hq
// ADR 0039). Both this module's tools and its events entrypoint import it, and nothing outside
// home-assistant does. Talks to the HA REST API (/api) with a long-lived access token.

import { readFileSync } from "node:fs";

export interface HAEntityState {
  entity_id: string;
  state: string;
  attributes: Record<string, unknown>;
  last_changed?: string;
  last_updated?: string;
}

export interface HAConfig {
  location_name?: string;
  version?: string;
  components?: string[];
  time_zone?: string;
  state?: string;
}

/** 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 {}; }
}

/** Read a secret the mesh mounted at a file path (an own-secret delivered by `secret accept`);
 *  absent or unreadable yields undefined so callers fall back rather than crash. */
function readSecret(file?: string): string | undefined {
  if (!file) return undefined;
  try { return readFileSync(file, "utf8").trim(); }
  catch { return undefined; }
}

export class HomeAssistantClient {
  readonly baseUrl: string;

  constructor(
    url: string,
    private readonly token: string,
  ) {
    this.baseUrl = url.replace(/\/$/, "");
  }

  /**
   * Build from the module's resolved environment. The URL defaults to the local server (HA runs on
   * the node); the token is the long-lived access token minted in HA's profile — required, since
   * every API call is Bearer-authenticated and there is nowhere to discover it from.
   */
  static fromEnv(env: NodeJS.ProcessEnv = process.env): HomeAssistantClient {
    const cfg = meshConfig(env.MESH_HOMEASSISTANT_CONFIG_FILE);
    const url = cfg.url ?? env.MESH_HOMEASSISTANT_URL ?? `http://127.0.0.1:${env.HOMEASSISTANT_PORT ?? "8123"}`;
    const token = cfg.token ?? readSecret(env.MESH_HOMEASSISTANT_TOKEN_FILE) ?? env.MESH_HOMEASSISTANT_TOKEN;
    if (!token) throw new Error("no Home Assistant token — set MESH_HOMEASSISTANT_TOKEN");
    return new HomeAssistantClient(url, token);
  }

  private async request(path: string, init?: RequestInit): Promise<unknown> {
    const res = await fetch(`${this.baseUrl}${path}`, {
      ...init,
      headers: {
        Authorization: `Bearer ${this.token}`,
        "Content-Type": "application/json",
        Accept: "application/json",
        ...(init?.headers ?? {}),
      },
    });
    if (!res.ok) throw new Error(`Home Assistant API ${path}: ${res.status} ${await res.text()}`);
    return res.json();
  }

  async getConfig(): Promise<HAConfig> {
    return (await this.request("/api/config")) as HAConfig;
  }

  /** All entity states, or one entity when an id is given. */
  async getStates(): Promise<HAEntityState[]> {
    return (await this.request("/api/states")) as HAEntityState[];
  }

  async getState(entityId: string): Promise<HAEntityState> {
    return (await this.request(`/api/states/${encodeURIComponent(entityId)}`)) as HAEntityState;
  }

  /** Call a service (e.g. switch.turn_on) — how "turn the light on" reaches HA. Returns the states
   *  the call changed. */
  async callService(domain: string, service: string, data: Record<string, unknown> = {}): Promise<HAEntityState[]> {
    return (await this.request(`/api/services/${encodeURIComponent(domain)}/${encodeURIComponent(service)}`, {
      method: "POST",
      body: JSON.stringify(data),
    })) as HAEntityState[];
  }
}