import { exec } from 'child_process';
import { promisify } from 'util';
import { hostname } from 'os';
import { readFile } from 'fs/promises';

const execAsync = promisify(exec);

// Paths are env-configurable so they work both in the Docker container (via
// volume mounts) and when the backend is run directly on the host for dev.
const SCRIPTS_PATH = process.env.VM_SCRIPTS_PATH
  ?? '/opt/bytelyst/learning_ai_devops_tools/scripts/VMs/HostingerVM';
const LOG_DIR = process.env.VM_LOG_DIR ?? '/var/log';

const HEALTH_SCRIPT  = `${SCRIPTS_PATH}/vm-health-check.sh`;
const CLEANUP_SCRIPT = `${SCRIPTS_PATH}/vm-cleanup.sh`;
const CLEANUP_LOG    = `${LOG_DIR}/vm-cleanup.log`;

// ---------------------------------------------------------------------------
// Health check  (vm-health-check.sh --json)
// ---------------------------------------------------------------------------

export async function runVmHealthCheck() {
  try {
    // Script exits 1 (WARN) or 2 (CRIT) but still emits valid JSON on stdout.
    const { stdout } = await execAsync(`bash "${HEALTH_SCRIPT}" --json 2>/dev/null`, {
      timeout: 30_000,
    });
    return JSON.parse(stdout);
  } catch (error: any) {
    // Non-zero exit — stdout may still contain valid JSON (WARN/CRIT result)
    if (error.stdout) {
      try { return JSON.parse(error.stdout); } catch { /* fall through */ }
    }
    return {
      timestamp: new Date().toISOString(),
      hostname: hostname(),
      overall: 'CRIT',
      checks: {},
      error: String(error.stderr || error.message || error),
    };
  }
}

// ---------------------------------------------------------------------------
// Cleanup log — raw tail
// ---------------------------------------------------------------------------

export async function getCleanupLog(lines = 50): Promise<string> {
  try {
    const { stdout } = await execAsync(
      `tail -${lines} "${CLEANUP_LOG}" 2>/dev/null || echo "(log not found)"`,
      { timeout: 5_000 }
    );
    return stdout.trim();
  } catch {
    return '(log not available)';
  }
}

// ---------------------------------------------------------------------------
// Cron status — parsed run history + next scheduled times
// ---------------------------------------------------------------------------

export interface CronRunSummary {
  timestamp: string;
  mode: 'standard' | 'full';
  diskBefore: string;
  diskAfter: string;
  freedMB: number;
  durationSecs: number;
  success: boolean;
  steps: string[];
  jsonSummary?: Record<string, unknown>;
}

export interface CronJob {
  name: string;
  schedule: string;
  description: string;
  lastRun: CronRunSummary | null;
  nextRun: string | null;
}

export async function getCronStatus(): Promise<{ jobs: CronJob[]; recentRuns: CronRunSummary[] }> {
  const [rawLog, crontab] = await Promise.all([
    readFile(CLEANUP_LOG, 'utf8').catch(() => ''),
    execAsync('crontab -l 2>/dev/null').then(r => r.stdout).catch(() => ''),
  ]);

  const recentRuns = parseCleanupLog(rawLog);
  const jobs = buildJobList(crontab, recentRuns);
  return { jobs, recentRuns: recentRuns.slice(0, 20) };
}

function parseCleanupLog(raw: string): CronRunSummary[] {
  const runs: CronRunSummary[] = [];
  // Runs are delimited by [START] lines
  const blocks = raw.split(/\[START\]/);
  for (const block of blocks.slice(1)) {
    try {
      const startLine = block.match(/\[(\d{4}-\d{2}-\d{2}T[\d:Z]+)\] mode=(\w+)/);
      if (!startLine) continue;
      const timestamp = startLine[1];
      const mode = startLine[2] === 'full' ? 'full' : 'standard';

      const diskLine  = block.match(/\[DISK\] before=([^\s]+) after=([^\s]+)/);
      const endLine   = block.match(/\[END\]/);
      const cmdLines  = [...block.matchAll(/\[CMD\] (.+)/g)].map(m => m[1]);
      const jsonMatch = block.match(/\[JSON\] ({.+})/);

      // Compute freed MB from disk "used" before/after (e.g. " 70G 123G 37%")
      let freedMB = 0;
      let diskBefore = '', diskAfter = '';
      if (diskLine) {
        diskBefore = diskLine[1].trim();
        diskAfter  = diskLine[2].trim();
        const gbBefore = parseFloat(diskLine[1].match(/([\d.]+)G/)?.[1] ?? '0');
        const gbAfter  = parseFloat(diskLine[2].match(/([\d.]+)G/)?.[1] ?? '0');
        freedMB = Math.round((gbBefore - gbAfter) * 1024);
      }

      // Rough duration: time from start to end
      const startTs = new Date(timestamp).getTime();
      const endTs   = endLine
        ? (() => {
            const m = block.slice(block.indexOf('[END]') - 28, block.indexOf('[END]') - 2);
            return new Date(m.match(/\d{4}-\d{2}-\d{2}T[\d:Z]+/)?.[0] ?? timestamp).getTime();
          })()
        : startTs;
      const durationSecs = Math.round((endTs - startTs) / 1000);

      runs.push({
        timestamp,
        mode,
        diskBefore,
        diskAfter,
        freedMB,
        durationSecs: isNaN(durationSecs) ? 0 : durationSecs,
        success: !!endLine,
        steps: cmdLines,
        jsonSummary: jsonMatch ? JSON.parse(jsonMatch[1]) : undefined,
      });
    } catch {
      // Skip malformed blocks
    }
  }
  return runs.reverse(); // most recent first
}

function buildJobList(crontab: string, runs: CronRunSummary[]): CronJob[] {
  const managed = crontab.match(/# bytelyst-vm-maintenance[\s\S]+/m)?.[0] ?? '';

  const defs: Array<{ name: string; schedule: string; description: string; mode?: string }> = [
    { name: 'build-cache-prune', schedule: '0 3 * * *',   description: 'Daily build cache prune' },
    { name: 'weekly-cleanup',    schedule: '0 2 * * 0',    description: 'Weekly standard cleanup' },
    { name: 'monthly-full',      schedule: '0 1 1 * *',    description: 'Monthly full cleanup',  mode: 'full' },
    { name: 'health-check',      schedule: '0 7 * * *',    description: 'Daily health check + Telegram alert' },
  ];

  return defs.map(def => {
    const matchingRun = def.mode === 'full'
      ? runs.find(r => r.mode === 'full')
      : runs.find(r => r.mode === 'standard');

    const nextRun = computeNextRun(def.schedule);
    return { ...def, lastRun: matchingRun ?? null, nextRun };
  });
}

/** Very lightweight cron next-run calculator (handles standard 5-field expressions) */
function computeNextRun(expr: string): string {
  const [min, hr, dom, , dow] = expr.split(' ');
  const now = new Date();
  const next = new Date(now);
  next.setSeconds(0, 0);
  next.setMinutes(parseInt(min));
  next.setHours(parseInt(hr));

  if (dom === '*' && dow !== '*') {
    // Weekly: advance to correct day-of-week
    const targetDow = parseInt(dow);
    const dayDiff = (targetDow - next.getDay() + 7) % 7 || 7;
    next.setDate(next.getDate() + dayDiff);
  } else if (dom !== '*') {
    // Monthly: advance to correct day-of-month
    next.setDate(parseInt(dom));
    if (next <= now) next.setMonth(next.getMonth() + 1);
  } else {
    // Daily: just advance to tomorrow if already passed today
    if (next <= now) next.setDate(next.getDate() + 1);
  }

  return next.toISOString();
}

// ---------------------------------------------------------------------------
// Trigger cleanup  (container runs as root — no sudo needed)
// ---------------------------------------------------------------------------

export async function runVmCleanup(
  mode: 'weekly' | 'monthly' | 'dry-run',
): Promise<{ success: boolean; output: string }> {
  const args =
    mode === 'monthly'  ? '--full --quiet' :
    mode === 'dry-run'  ? '--dry-run'      :
                          '--quiet';

  try {
    const { stdout, stderr } = await execAsync(
      `bash "${CLEANUP_SCRIPT}" ${args} 2>&1`,
      { timeout: 120_000 },
    );
    return { success: true, output: (stdout + stderr).trim() };
  } catch (error: any) {
    const out = ((error.stdout ?? '') + (error.stderr ?? '')).trim();
    return { success: false, output: out || String(error.message ?? error) };
  }
}

// ---------------------------------------------------------------------------
// Unhealthy containers  (docker inspect via shell — no Docker SDK needed)
// ---------------------------------------------------------------------------

export interface UnhealthyContainer {
  name: string;
  status: string;
  restartCount: number;
  lastHealthLogs: string[];
  unhealthySince: string | null;
}

export async function getUnhealthyContainers(): Promise<UnhealthyContainer[]> {
  try {
    const { stdout } = await execAsync(
      `docker ps --filter health=unhealthy --format '{{.Names}}' 2>/dev/null`,
      { timeout: 10_000 },
    );
    const names = stdout.trim().split('\n').filter(Boolean);
    if (!names.length) return [];

    const results = await Promise.all(names.map(async name => {
      try {
        const { stdout: raw } = await execAsync(
          `docker inspect "${name}" 2>/dev/null`,
          { timeout: 5_000 },
        );
        const data = JSON.parse(raw)?.[0];
        const health = data?.State?.Health ?? {};
        const logs: string[] = (health.Log ?? [])
          .slice(-3)
          .map((l: any) => l.Output?.trim() ?? '');
        const unhealthySince = health.Log?.[0]?.Start ?? null;

        return {
          name,
          status: data?.State?.Status ?? 'unknown',
          restartCount: data?.RestartCount ?? 0,
          lastHealthLogs: logs,
          unhealthySince,
        } satisfies UnhealthyContainer;
      } catch {
        return { name, status: 'unknown', restartCount: 0, lastHealthLogs: [], unhealthySince: null };
      }
    }));

    return results;
  } catch {
    return [];
  }
}

export async function restartContainer(name: string): Promise<{ success: boolean; message: string }> {
  // Validate name — only allow alphanumeric, dash, underscore
  if (!/^[\w-]+$/.test(name)) {
    return { success: false, message: 'Invalid container name' };
  }
  try {
    await execAsync(`docker restart "${name}"`, { timeout: 30_000 });
    return { success: true, message: `${name} restarted` };
  } catch (error: any) {
    return { success: false, message: String(error.stderr || error.message || error) };
  }
}

// ---------------------------------------------------------------------------
// Ollama models
// ---------------------------------------------------------------------------

export interface OllamaModel {
  name: string;
  sizeGB: number;
  modifiedAt: string;
}

export interface OllamaRunning {
  name: string;
  sizeGB: number;
  processor: string;
  expiresAt: string;
}

// Ollama REST API base — host-gateway resolves to the Docker host,
// where ollama serve listens on port 11434.
const OLLAMA_BASE = process.env.OLLAMA_BASE_URL ?? 'http://host-gateway:11434';

async function ollamaFetch(path: string, opts?: RequestInit): Promise<unknown> {
  const res = await fetch(`${OLLAMA_BASE}${path}`, {
    signal: AbortSignal.timeout(10_000),
    ...opts,
  });
  if (!res.ok) throw new Error(`Ollama ${path}: ${res.status}`);
  return res.json();
}

export async function getOllamaModels(): Promise<{ models: OllamaModel[]; running: OllamaRunning[] }> {
  try {
    const [tagsData, psData] = await Promise.all([
      ollamaFetch('/api/tags').catch(() => ({ models: [] })),
      ollamaFetch('/api/ps').catch(()  => ({ models: [] })),
    ]);

    const models = ((tagsData as any).models ?? []).map((m: any) => ({
      name:       m.name ?? '',
      sizeGB:     parseFloat(((m.size ?? 0) / 1e9).toFixed(2)),
      modifiedAt: m.modified_at ?? '',
    }));

    const running = ((psData as any).models ?? []).map((m: any) => ({
      name:      m.name ?? '',
      sizeGB:    parseFloat(((m.size ?? 0) / 1e9).toFixed(2)),
      processor: m.details?.families?.join(', ') ?? '',
      expiresAt: m.expires_at ?? '',
    }));

    return { models, running };
  } catch {
    return { models: [], running: [] };
  }
}

export async function unloadOllamaModel(name: string): Promise<{ success: boolean; message: string }> {
  if (!/^[\w.:\-/]+$/.test(name)) return { success: false, message: 'Invalid model name' };
  try {
    // Unload by setting keep_alive to 0
    await ollamaFetch('/api/generate', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ model: name, keep_alive: 0 }),
    });
    return { success: true, message: `${name} unloaded` };
  } catch (error: any) {
    return { success: false, message: String(error.message ?? error) };
  }
}