/** Health state machine: HEALTHY / DEGRADED / UNAVAILABLE. */

import { existsSync, readFileSync } from "fs";
import { resolve } from "path";
import type { ObsidianRagConfig } from "../utils/config.js";

export type HealthState = "healthy" | "degraded" | "unavailable";

export interface HealthStatus {
  state: HealthState;
  ollama_up: boolean;
  index_exists: boolean;
  vault_exists: boolean;
  total_docs: number;
  total_chunks: number;
  last_sync: string | null;
  active_job: { id: string; mode: string; progress: number } | null;
}

export interface ProbeResult {
  ollama_up: boolean;
  index_exists: boolean;
  vault_exists: boolean;
  total_docs: number;
  total_chunks: number;
  last_sync: string | null;
}

const REPROBE_INTERVAL_MS = 30_000;

export function createHealthMachine(_config: ObsidianRagConfig) {
  let currentState: HealthState = "unavailable";
  let status: ProbeResult = {
    ollama_up: false,
    index_exists: false,
    vault_exists: false,
    total_docs: 0,
    total_chunks: 0,
    last_sync: null,
  };
  let activeJob: { id: string; mode: string; progress: number } | null = null;
  let reprobeTimer: ReturnType<typeof setInterval> | null = null;

  function transition(probe: ProbeResult): void {
    status = probe;
    const prev = currentState;
    if (!probe.index_exists || !probe.vault_exists) {
      currentState = "unavailable";
    } else if (!probe.ollama_up) {
      currentState = "degraded";
    } else {
      currentState = "healthy";
    }
    if (prev !== currentState) {
      console.log(`[obsidian-rag] Health: ${prev} → ${currentState}`);
    }
  }

  function get(): HealthStatus {
    return { state: currentState, ...status, active_job: activeJob };
  }

  function setActiveJob(job: { id: string; mode: string; progress: number } | null): void {
    activeJob = job;
  }

  function startReprobing(fn: () => Promise<ProbeResult>): void {
    if (reprobeTimer) clearInterval(reprobeTimer);
    reprobeTimer = setInterval(async () => {
      const probe = await fn();
      transition(probe);
    }, REPROBE_INTERVAL_MS);
  }

  function stop(): void {
    if (reprobeTimer) {
      clearInterval(reprobeTimer);
      reprobeTimer = null;
    }
  }

  return { get, transition, setActiveJob, startReprobing, stop };
}

export async function probeAll(config: ObsidianRagConfig): Promise<ProbeResult> {
  const { resolveVectorDbPath } = await import("../utils/lancedb.js");

  const vaultPath = resolve(process.cwd(), config.vault_path);
  const dbPath = resolveVectorDbPath(config);

  const vaultExists = existsSync(vaultPath);
  const indexExists = existsSync(String(dbPath));
  const ollamaUp = await probeOllama(config.embedding.base_url);

  let totalDocs = 0;
  let totalChunks = 0;
  let lastSync: string | null = null;

  if (indexExists) {
    try {
      const dataDir = resolveDataDir();
      const syncPath = resolve(dataDir, "sync-result.json");
      if (existsSync(syncPath)) {
        const data = JSON.parse(readFileSync(syncPath, "utf-8"));
        lastSync = data.timestamp ?? null;
        totalDocs = data.indexed_files ?? 0;
        totalChunks = data.total_chunks ?? 0;
      }
    } catch {
      // ignore
    }
  }

  return {
    ollama_up: ollamaUp,
    index_exists: indexExists,
    vault_exists: vaultExists,
    total_docs: totalDocs,
    total_chunks: totalChunks,
    last_sync: lastSync,
  };
}

function resolveDataDir(): string {
  const cwd = process.cwd();
  const devDataDir = resolve(cwd, ".obsidian-rag");
  const devVaultMarker = resolve(cwd, "KnowledgeVault");
  if (existsSync(devDataDir) || existsSync(devVaultMarker)) {
    return devDataDir;
  }
  const home = process.env.HOME ?? process.env.USERPROFILE ?? "";
  return resolve(home, ".obsidian-rag");
}

async function probeOllama(baseUrl: string): Promise<boolean> {
  try {
    const res = await fetch(`${baseUrl}/api/tags`, { signal: AbortSignal.timeout(3000) });
    return res.ok;
  } catch {
    return false;
  }
}