// SPDX-License-Identifier: AGPL-3.0-or-later
// DB → Asterisk config (03). render() is pure; apply() writes changed files and reloads Asterisk.
import { createHash } from 'node:crypto';
import { copyFile, mkdir, readFile, rename, writeFile } from 'node:fs/promises';
import { join } from 'node:path';
import type { FastifyBaseLogger } from 'fastify';
import type { AmiClient } from '../ami/client.ts';
import type { Db } from '../db/client.ts';
import { eq } from 'drizzle-orm';
import { generatorRuns, settings } from '../db/schema.ts';
import { getSetting, setSetting } from '../services/settings.ts';
import { resendPauses } from '../services/queues.ts';
import { loadSnapshot, type Snapshot } from './load.ts';
import { renderPjsip, renderRtp, renderTransports } from './pjsip.ts';
import { STATIC_DIALPLAN } from './dialplan/static.ts';
import { renderGlobals, renderIvrDirect, renderLocalNumbers } from './dialplan/local.ts';
import { renderDids, renderTrunkEntries } from './dialplan/inbound.ts';
import { renderOutbound } from './dialplan/outbound.ts';
import { renderEmergency } from './dialplan/emergency.ts';
import { renderRingGroups } from './dialplan/ringgroups.ts';
import { renderQueueDialplan } from './dialplan/queues.ts';
import { renderQueues } from './queues.ts';
import { renderMoh } from './moh.ts';
import { renderConfbridge, renderConferences } from './dialplan/conferences.ts';
import { renderPaging } from './dialplan/paging.ts';
import { renderIvrs } from './dialplan/ivrs.ts';
import { renderTimeConditions } from './dialplan/timeconditions.ts';
import { renderAnnouncements } from './dialplan/announcements.ts';
import { renderVoicemail } from './voicemail.ts';

export { renderTransports };

export const HEADER = '; GENERATED BY SelfPhoneNG — DO NOT EDIT. Changes will be overwritten.\n';

/** Generated file → the AMI Command that makes Asterisk load it (03 §3). Order = reload order. */
export const RELOADS = {
  'pjsip_selfphoneng.conf': 'module reload res_pjsip.so',
  'rtp_selfphoneng.conf': 'module reload res_rtp_asterisk.so',
  'extensions_globals_selfphoneng.conf': 'dialplan reload',
  'extensions_selfphoneng.conf': 'dialplan reload',
  'voicemail_selfphoneng.conf': 'voicemail reload',
  'queues_selfphoneng.conf': 'queue reload all',
  'musiconhold_selfphoneng.conf': 'moh reload',
  'confbridge_selfphoneng.conf': 'module reload app_confbridge.so',
} as const;

export type GeneratedFileName = keyof typeof RELOADS;
export const GENERATED_FILES = Object.keys(RELOADS) as GeneratedFileName[];
export type RenderedFiles = Record<GeneratedFileName, string>;

// Each file's body; tasks fill these in (M2-T3 pjsip/rtp, M2-T4 dialplan, ...).
const BODIES: Partial<Record<GeneratedFileName, (snap: Snapshot) => string>> = {
  'pjsip_selfphoneng.conf': renderPjsip,
  'rtp_selfphoneng.conf': renderRtp,
  'musiconhold_selfphoneng.conf': renderMoh,
  'extensions_globals_selfphoneng.conf': renderGlobals,
  'voicemail_selfphoneng.conf': renderVoicemail,
  'queues_selfphoneng.conf': renderQueues,
  'confbridge_selfphoneng.conf': renderConfbridge,
  'extensions_selfphoneng.conf': (snap) =>
    [
      STATIC_DIALPLAN,
      renderLocalNumbers(snap),
      renderRingGroups(snap),
      renderQueueDialplan(snap),
      renderConferences(snap),
      renderPaging(snap),
      renderIvrs(snap),
      renderIvrDirect(snap),
      renderTimeConditions(snap),
      renderAnnouncements(snap),
      renderTrunkEntries(snap),
      renderDids(snap),
      renderOutbound(snap),
      renderEmergency(snap),
    ]
      .filter(Boolean)
      .join('\n'),
};

/** PURE: no I/O, no clock, no randomness. Same snapshot → byte-identical files. */
export function render(snap: Snapshot): RenderedFiles {
  return Object.fromEntries(
    GENERATED_FILES.map((f) => [f, HEADER + (BODIES[f]?.(snap) ?? '')]),
  ) as RenderedFiles;
}

export type ApplyResult = {
  ok: boolean;
  error: string | null;
  filesChanged: GeneratedFileName[];
  commands: string[];
  restartRequired: boolean;
};

export type GeneratorDeps = {
  db: Db;
  ami: Pick<AmiClient, 'isConnected' | 'command' | 'action'>;
  /** /etc/asterisk/selfphoneng */
  dir: string;
  log: Pick<FastifyBaseLogger, 'info' | 'error'>;
  onApplied?: (r: ApplyResult) => void;
  debounceMs?: number;
  /** RTP_PORT_START/END (config.ts). */
  rtpPorts?: { start: number; end: number };
  /** The caller-name lookup (11 §6 C4). */
  callerNames?: { url: string; token: string };
};

const sha256 = (s: string) => createHash('sha256').update(s).digest('hex');

export function createGenerator(deps: GeneratorDeps) {
  const { db, ami, dir, log } = deps;
  let chain: Promise<unknown> = Promise.resolve();
  let timer: NodeJS.Timeout | undefined;

  /** One at a time: each call waits for the previous one (process-wide mutex). */
  function locked<T>(fn: () => Promise<T>): Promise<T> {
    const run = chain.then(fn);
    chain = run.catch(() => undefined);
    return run;
  }

  async function writeAtomic(name: string, content: string) {
    const path = join(dir, name);
    await writeFile(`${path}.tmp`, content, { mode: 0o640 });
    await rename(`${path}.tmp`, path);
  }

  async function sendReloads(
    commands: string[],
  ): Promise<{ sent: string[]; error: string | null }> {
    if (!ami.isConnected()) return { sent: [], error: 'ami-disconnected' };
    const sent: string[] = [];
    for (const c of commands) {
      try {
        await ami.command(c);
        sent.push(c);
      } catch (e) {
        return { sent, error: `${c}: ${(e as Error).message}` };
      }
    }
    return { sent, error: null };
  }

  async function record(trigger: string, r: ApplyResult, t0: number) {
    await db.insert(generatorRuns).values({
      trigger,
      filesChanged: r.filesChanged,
      commands: r.commands,
      ok: r.ok,
      error: r.error,
      durationMs: Math.round(performance.now() - t0),
    });
    log[r.ok ? 'info' : 'error'](
      { trigger, filesChanged: r.filesChanged, commands: r.commands, error: r.error },
      'generator apply',
    );
    deps.onApplied?.(r);
  }

  async function doApply(trigger: string, force: boolean): Promise<ApplyResult> {
    const t0 = performance.now();
    const r: ApplyResult = {
      ok: true,
      error: null,
      filesChanged: [],
      commands: [],
      restartRequired: false,
    };
    try {
      const snap = {
        ...(await loadSnapshot(db)),
        rtpPorts: deps.rtpPorts,
        callerNames: deps.callerNames,
      };
      const files = render(snap);
      await mkdir(join(dir, '.prev'), { recursive: true });
      const current = new Map<GeneratedFileName, string | null>();
      for (const f of GENERATED_FILES) {
        current.set(f, await readFile(join(dir, f), 'utf8').catch(() => null));
        if (current.get(f) !== files[f]) r.filesChanged.push(f);
      }
      if (r.filesChanged.length === 0 && !force) {
        await record(trigger, r, t0);
        return r;
      }

      if (r.filesChanged.length) {
        // Keep exactly one previous version for rollback.
        for (const [f, content] of current)
          if (content !== null) await writeFile(join(dir, '.prev', f), content, { mode: 0o640 });
        for (const f of r.filesChanged) await writeAtomic(f, files[f]);
      }

      // PJSIP transports can't be reloaded safely (01 §4.3). The first apply ever (no stored hash)
      // only adds transports to an Asterisk that booted with none, so a reload is fine then.
      const hash = sha256(renderTransports(snap));
      const prevHash = await getSetting(db, 'system.transportHash');
      const transportsChanged = prevHash !== null && prevHash !== hash;
      if (prevHash !== hash) await setSetting(db, 'system.transportHash', hash);
      if (transportsChanged) await setSetting(db, 'system.restartRequired', true);
      r.restartRequired = await getSetting(db, 'system.restartRequired');

      const reloadFor = force ? GENERATED_FILES : r.filesChanged;
      const commands = [...new Set(reloadFor.map((f) => RELOADS[f]))].filter(
        (c) => !(transportsChanged && c === 'module reload res_pjsip.so'),
      );
      const { sent, error } = await sendReloads(commands);
      r.commands = sent;
      if (sent.includes(RELOADS['queues_selfphoneng.conf'])) await resendPauses(db, ami);
      if (error) Object.assign(r, { ok: false, error });
    } catch (e) {
      Object.assign(r, { ok: false, error: (e as Error).message });
    }
    await record(trigger, r, t0);
    return r;
  }

  return {
    dir,
    apply: (opts: { trigger: string; force?: boolean }) =>
      locked(() => doApply(opts.trigger, opts.force ?? false)),

    /** Debounced (1 s by default): many quick changes become one apply. */
    requestApply(trigger: string) {
      clearTimeout(timer);
      timer = setTimeout(() => {
        void locked(() => doApply(trigger, false));
      }, deps.debounceMs ?? 1000);
    },

    /** POST /api/system/config/rollback: put .prev back and reload everything. */
    rollback: () =>
      locked(async () => {
        const t0 = performance.now();
        const r: ApplyResult = {
          ok: true,
          error: null,
          filesChanged: [],
          commands: [],
          restartRequired: false,
        };
        for (const f of GENERATED_FILES) {
          const prev = join(dir, '.prev', f);
          const restored = await copyFile(prev, join(dir, `${f}.tmp`)).then(
            () => true,
            () => false,
          );
          if (restored) {
            await rename(join(dir, `${f}.tmp`), join(dir, f));
            r.filesChanged.push(f);
          }
        }
        if (r.filesChanged.length === 0)
          Object.assign(r, { ok: false, error: 'no previous version' });
        else {
          const { sent, error } = await sendReloads([...new Set(Object.values(RELOADS))]);
          r.commands = sent;
          if (sent.includes(RELOADS['queues_selfphoneng.conf'])) await resendPauses(db, ami);
          if (error) Object.assign(r, { ok: false, error });
        }
        r.restartRequired = await getSetting(db, 'system.restartRequired');
        await record('rollback', r, t0);
        return r;
      }),

    /** Cancels a pending debounced apply (shutdown, tests). */
    cancelPending: () => clearTimeout(timer),
  };
}

export type Generator = ReturnType<typeof createGenerator>;

/**
 * On an AMI (re)connect: if Asterisk started after the change that needed a restart, it has
 * loaded the new transports, so the restart is no longer required (01 §4.3).
 */
export async function clearRestartIfRestarted(
  db: Db,
  ami: Pick<AmiClient, 'command'>,
  now = Date.now(),
): Promise<boolean> {
  if (!(await getSetting(db, 'system.restartRequired'))) return false;
  const uptime = /System uptime:\s*(\d+)/.exec(await ami.command('core show uptime seconds'))?.[1];
  const [row] = await db
    .select({ at: settings.updatedAt })
    .from(settings)
    .where(eq(settings.key, 'system.restartRequired'));
  if (uptime === undefined || !row) return false;
  if (now - Number(uptime) * 1000 <= row.at.getTime()) return false;
  await setSetting(db, 'system.restartRequired', false);
  return true;
}