/**
 * doctor.ts — il controllo generale.
 *
 * Two callers, one implementation:
 *   • session_start  → `runDoctor()` then `sessionBanner()`: one short line, only if
 *                      something is actually wrong. Silence when all is well.
 *   • `/doctor`      → `runDoctor()` then `formatReport()`: the full table.
 *
 * THREE RULES THIS FILE EXISTS TO KEEP:
 *
 *  1. IT NEVER THROWS. Every single check runs inside `check()`, which converts any
 *     exception into an ordinary "error" row. A health check that crashes is worse than
 *     no health check: it takes the whole session down at start-up.
 *
 *  2. A DISCONNECTED MODEL DISK IS A NORMAL CONDITION, NOT A FAULT. The models live on
 *     an external volume; it *will* be unplugged. We name the volume, say it is not
 *     connected, and tell him to plug it in — no stack trace, no ENOENT, no drama.
 *
 *  3. EVERY LINE HE READS IS ITALIAN, and every problem carries a concrete remedy.
 *     A check that says only "manca X" has failed at its job.
 *
 * Nothing here mutates anything except one temp file in the output directory (written
 * and deleted immediately) — that is the only honest way to answer "can I write there?".
 */

import { access, mkdir, readdir, rm, stat, statfs, writeFile } from "node:fs/promises";
import { constants as FS } from "node:fs";
import { spawn } from "node:child_process";
import { homedir } from "node:os";
import { arch, platform } from "node:process";
import { dirname, isAbsolute, join, parse as parsePath, resolve } from "node:path";
import { fileURLToPath, pathToFileURL } from "node:url";

import { configPath, loadConfig, type ImgenConfig, type ModelsConfig } from "./config.ts";
import { FONTS } from "./design/fonts.ts";
import { GRPC_SERVER_BINARY, GRPC_SERVER_URL, isPortOpen, serverPaths } from "./backends/server.ts";
import S, { bullets, errorText, fill, list, type ErrorMessage } from "./ui/strings.ts";

// ---------------------------------------------------------------------------
// Paths
// ---------------------------------------------------------------------------

/** extensions/imgen/doctor.ts -> repo root. */
const REPO_ROOT = resolve(dirname(fileURLToPath(import.meta.url)), "..", "..");

/** Where install.sh unpacks the 22 bundled families (one directory per family). */
export const FONTS_DIR = join(REPO_ROOT, "vendor", "fonts");

/** Default pi config dir, used only when the caller does not pass one. */
export const DEFAULT_PI_CONFIG_DIR = join(homedir(), ".pi", "agent");

/**
 * pi may be launched from a GUI context, where PATH is the bare
 * `/usr/bin:/bin:/usr/sbin:/sbin` and Homebrew is invisible. Same list as cpu.ts —
 * duplicated on purpose, because cpu.ts keeps its resolver private and doctor must not
 * drag the whole CPU-tools module (and sharp) into session start-up.
 */
const EXTRA_BIN_DIRS = [
  join(REPO_ROOT, "vendor", "bin"),
  "/opt/homebrew/bin",
  "/usr/local/bin",
  join(homedir(), ".cargo", "bin"),
  join(homedir(), ".local", "bin"),
];

// ---------------------------------------------------------------------------
// Thresholds
// ---------------------------------------------------------------------------

/** A "model" smaller than this is a Git LFS pointer or an interrupted download. */
const MIN_MODEL_BYTES = 64 * 1024 * 1024;

/** Below this much free space a print job (300 dpi A3 PNG + PDF) starts to be at risk. */
const LOW_DISK_BYTES = 2 * 1024 * 1024 * 1024;

/** Version probes must never hang a session start. */
const VERSION_TIMEOUT_MS = 4_000;

/** The templates are written against Typst 0.15 (see docs/typst-verified.md). */
const TYPST_MIN = [0, 15] as const;

// ---------------------------------------------------------------------------
// Local Italian strings
// ---------------------------------------------------------------------------

/**
 * Only the lines `ui/strings.ts` does not (yet) carry. `S.doctor.checks` already owns
 * every check LABEL, and `S.errors.*` owns the big remedies, so this table is
 * deliberately small: statuses and detail lines.
 *
 * TODO: fold into `S.doctor` once that table settles — kept local for now so two files
 * are not being edited for one feature.
 */
const T = {
  /** Row status when a check itself blew up. Rule 1 made visible. */
  checkFailed: "Non sono riuscito a fare questo controllo.",
  checkFailedFix: "Non è colpa tua: riprova, e se si ripete mandami quello che scrive qui sotto.",

  config: {
    ok: "Impostazioni lette.",
    okDefaults: "Nessun file di impostazioni: uso quelle standard.",
    fixDefaults: "Va benissimo così. Se vuoi cambiare cartelle o modelli, lancia ./install.sh.",
  },

  platform: {
    notMac: "Questo pacchetto disegna solo su un Mac con chip Apple.",
    notArm: "Serve un Mac con chip Apple (M1 o successivi): su Intel il motore non esiste.",
    fix: "Il resto (impaginazione, PDF, ritagli) funziona lo stesso.",
  },

  disk: {
    /** The headline case: the external volume is simply unplugged. */
    volumeAbsent: "Il disco «{disco}» non è collegato.",
    volumeAbsentFix: "Collega il disco e riprova. I modelli li cerco in {dove}.",
    volumeThereFolderMissing: "Il disco «{disco}» c'è, ma dentro manca la cartella dei modelli.",
    folderMissing: "Non trovo la cartella dei modelli.",
    folderMissingFix: "Dovrebbe essere {dove}. Creala e rimettici dentro i modelli, oppure lancia ./install.sh.",
    notADir: "Il percorso dei modelli non è una cartella: {dove}",
    notReadable: "La cartella dei modelli c'è ma non riesco a leggerla: {dove}",
    notReadableFix: "Controlla i permessi della cartella (in Finder: Informazioni ▸ Autorizzazioni).",
    notAbsolute: "Il percorso dei modelli deve partire dalla radice del disco: {dove}",
    notAbsoluteFix: "Correggilo in {file} oppure rilancia ./install.sh.",
    okExternal: "Il disco «{disco}» è collegato.",
    okInternal: "I modelli stanno sul disco del computer.",
    space: "Spazio libero: {spazio}.",
  },

  models: {
    allOk: "Ci sono tutti i modelli che servono.",
    someMissing: "Manca qualche modello.",
    noneConfigured: "Non è configurato nessun modello per disegnare.",
    skippedDiskOff: "Non posso controllare i modelli finché non è sistemato il disco qui sopra.",
    remote: "si scarica da internet al primo uso",
    present: "c'è",
    missing: "manca",
    truncated: "il file è troppo piccolo: scaricato a metà",
    unusedRole: "non configurato",
    fixMissing: "Rimetti i file mancanti in {dove}, oppure rilancia ./install.sh per riscaricarli.",
    /** Roles, as he would name them. */
    roles: {
      draft: "prova veloce",
      final: "immagine definitiva",
      alt: "stile alternativo",
      edit: "modifica di un'immagine",
      upscale: "ingrandimento per la stampa",
    } as Record<keyof ModelsConfig, string>,
  },

  drawThings: {
    ok: "Trovato: {dove}",
    missing: "Non trovo il comando che disegna le immagini.",
  },

  typst: {
    ok: "Trovato: {dove}",
    okVersion: "Versione {versione}, trovato in {dove}",
    missing: "Non trovo il programma che compone le scritte.",
    tooOld: "La versione di Typst è vecchia ({versione}): le impaginazioni sono fatte per la {minima} o successive.",
    tooOldFix: "Aggiornalo con «brew upgrade typst».",
  },

  server: {
    disabled: "Il motore residente è spento nelle impostazioni: ogni immagine partirà da fredda (più lenta).",
    disabledFix: "Se vuoi riaccenderlo, metti «server.enabled: true» in {file}.",
    running: "Acceso e in ascolto sulla porta {porta}.",
    binaryMissing: "Manca il programma del motore ({nome}).",
    binaryMissingFix: "Scaricalo da {url} e mettilo in {dove}, oppure lancia ./install.sh.",
    notExecutable: "Il programma del motore c'è ma non ha il permesso di partire: {dove}",
    notExecutableFix: "Dagli il permesso con «chmod +x \"{dove}\"».",
    stopped: "Il motore c'è ma non è acceso: le immagini partiranno da fredde (più lente).",
    stoppedFix: "Lo accendo da solo quando serve. Se vuoi accenderlo a mano: {comando}",
    foreign: "Sulla porta {porta} risponde già qualcosa che non ho avviato io: lo uso com'è e non lo tocco.",
  },

  fonts: {
    ok: "Ci sono tutti i {n} caratteri, con le loro licenze.",
    empty: "La cartella dei caratteri è vuota.",
    emptyFix: "Lancia ./install.sh per scaricarli: senza caratteri non posso comporre le scritte.",
    missing: "Mancano {n} caratteri su {tot}.",
    missingFix: "Lancia ./install.sh per riscaricare quelli che mancano.",
    noLicense: "{n} caratteri sono senza file di licenza.",
    noLicenseItem: "manca la licenza",
    noLicenseFix: "Le licenze vanno distribuite insieme ai caratteri: rilancia ./install.sh.",
    dir: "Cartella: {dove}",
  },

  print: {
    label: "Gli strumenti per la stampa",
    allOk: "Ci sono tutti: posso controllare il PDF prima di darlo alla tipografia.",
    someMissing: "Ne mancano alcuni: il PDF lo preparo lo stesso, ma non posso controllarlo bene.",
    noneNeeded: "Sono facoltativi: senza di loro il PDF si fa comunque.",
    fix: "Se li vuoi: brew install poppler qpdf ghostscript",
    tools: {
      pdfinfo: "controlla le misure e il riquadro di taglio del PDF",
      pdffonts: "controlla che i caratteri siano incorporati",
      qpdf: "controlla che il PDF non sia rovinato",
      gs: "converte e comprime il PDF quando la tipografia lo chiede",
    } as Record<string, string>,
  },

  output: {
    ok: "Posso scrivere in {dove}",
    created: "Ho creato la cartella dei lavori: {dove}",
    notAbsolute: "Il percorso della cartella dei lavori deve partire dalla radice del disco: {dove}",
    volumeAbsent: "La cartella dei lavori sta sul disco «{disco}», che non è collegato: {dove}",
    volumeAbsentFix: "Collega il disco «{disco}» e riprova. Non creo niente finché non c'è, altrimenti il Mac poi rimonta il disco con un altro nome.",
    lowSpace: "Resta poco spazio sul disco ({spazio}): una locandina da stampare può occuparne parecchio.",
    lowSpaceFix: "Libera un po' di posto, oppure sposta la cartella dei lavori.",
  },

  /** Report chrome. */
  report: {
    heading: "Controllo generale",
    detailPrefix: "dettaglio: ",
  },
} as const;

// ---------------------------------------------------------------------------
// Public shape
// ---------------------------------------------------------------------------

export type CheckId =
  | "config"
  | "platform"
  | "modelsDisk"
  | "models"
  | "drawThings"
  | "server"
  | "typst"
  | "fonts"
  | "printTools"
  | "outputDir";

/**
 * - `ok`    tutto a posto
 * - `info`  a posto, ma c'è qualcosa da sapere (roba facoltativa che manca)
 * - `warn`  si lavora lo stesso, ma peggio / più lentamente
 * - `error` non si lavora finché non lo sistemi
 */
export type CheckLevel = "ok" | "info" | "warn" | "error";

/** One line inside a check: a model, a font family, an optional tool. */
export interface CheckItem {
  name: string;
  ok: boolean;
  /** Italian, short: "c'è", "manca", "si scarica al primo uso"… */
  status: string;
  detail?: string;
}

export interface CheckResult {
  id: CheckId;
  /** Italian label — from `S.doctor.checks` wherever that table has one. */
  label: string;
  level: CheckLevel;
  /** One Italian sentence: what the situation is. */
  message: string;
  /** One Italian sentence: what to do about it. Absent when there is nothing to do. */
  fix?: string;
  /** Technical detail (path, port, version). Never the whole message. */
  detail?: string;
  items?: CheckItem[];
}

export interface DoctorReport {
  /** True when nothing is blocking: no `error` rows. Warnings do not clear this flag. */
  ok: boolean;
  /** True when at least one `warn` row is present. */
  warnings: boolean;
  checks: CheckResult[];
  /** Every warn/error message, ready for `bullets()` or a `Backend.probe()` shape. */
  problems: string[];
  /** The config the checks were run against (defaults when the file was unreadable). */
  config: ImgenConfig;
  configFile: string;
  elapsedMs: number;
}

export interface DoctorOptions {
  /** Where `pi-imgen.json` lives. Defaults to `~/.pi/agent`. */
  piConfigDir?: string;
  /** Pre-loaded config, when the caller already has one (session_start does). */
  config?: ImgenConfig;
  /** Problems already found while loading that config. */
  configProblems?: string[];
  /** Skip the external `--version` calls. session_start passes true to stay instant. */
  fast?: boolean;
}

// ---------------------------------------------------------------------------
// Never-throwing primitives
// ---------------------------------------------------------------------------

async function statOf(path: string): Promise<import("node:fs").Stats | null> {
  try {
    return await stat(path);
  } catch {
    return null;
  }
}

async function canAccess(path: string, mode: number): Promise<boolean> {
  try {
    await access(path, mode);
    return true;
  } catch {
    return false;
  }
}

async function listDir(path: string): Promise<string[]> {
  try {
    return await readdir(path);
  } catch {
    return [];
  }
}

/** Resolves an executable by name, searching the GUI-invisible dirs first. Never throws. */
async function findExecutable(name: string): Promise<string | null> {
  if (name.includes("/")) return (await canAccess(name, FS.X_OK)) ? name : null;
  const pathDirs = (process.env["PATH"] ?? "").split(":").filter(Boolean);
  for (const dir of [...EXTRA_BIN_DIRS, ...pathDirs]) {
    const candidate = join(dir, name);
    const st = await statOf(candidate);
    if (st?.isFile() && (await canAccess(candidate, FS.X_OK))) return candidate;
  }
  return null;
}

/** Runs a short command for its stdout. Returns null on any failure or timeout. */
function runBriefly(bin: string, args: string[], timeoutMs = VERSION_TIMEOUT_MS): Promise<string | null> {
  return new Promise((resolveOut) => {
    let done = false;
    const finish = (value: string | null): void => {
      if (done) return;
      done = true;
      clearTimeout(timer);
      resolveOut(value);
    };
    let child: ReturnType<typeof spawn> | null = null;
    const timer = setTimeout(() => {
      try { child?.kill("SIGKILL"); } catch { /* already gone */ }
      finish(null);
    }, timeoutMs);
    try {
      child = spawn(bin, args, { stdio: ["ignore", "pipe", "pipe"] });
    } catch {
      finish(null);
      return;
    }
    let out = "";
    child.stdout?.on("data", (b: Buffer) => { out += b.toString("utf8"); });
    child.stderr?.on("data", (b: Buffer) => { out += b.toString("utf8"); });
    child.on("error", () => finish(null));
    child.on("close", (code) => finish(code === 0 ? out : out.trim() === "" ? null : out));
  });
}

/** "1,2 GB" — sizes as he would read them, with the Italian decimal comma. */
export function humanBytes(bytes: number): string {
  const units = ["B", "kB", "MB", "GB", "TB"];
  let value = bytes;
  let unit = 0;
  while (value >= 1024 && unit < units.length - 1) {
    value /= 1024;
    unit += 1;
  }
  const text = unit === 0 ? String(Math.round(value)) : value.toFixed(1).replace(".", ",");
  return `${text} ${units[unit]}`;
}

/** Free bytes on the filesystem holding `path`, or null when it cannot be measured. */
async function freeBytes(path: string): Promise<number | null> {
  try {
    const fsStat = await statfs(path);
    return Number(fsStat.bavail) * Number(fsStat.bsize);
  } catch {
    return null;
  }
}

// ---------------------------------------------------------------------------
// Volumes — the check that makes an unplugged disk a sentence, not a crash
// ---------------------------------------------------------------------------

export interface VolumeInfo {
  /** The path we were asked about. */
  path: string;
  /** Mount point of the volume that (should) hold it, e.g. `/Volumes/Foto` or `/`. */
  root: string;
  /** Volume name as it appears in Finder, when the path is on an external disk. */
  name: string | null;
  /** True when the path is NOT on the boot disk. */
  external: boolean;
  /** True when the volume is actually mounted right now. */
  mounted: boolean;
  /** Deepest ancestor of `path` that exists. Useful to explain what is missing. */
  deepestExisting: string | null;
}

/**
 * Works out whether the model volume is mounted, without ever asking the OS a question
 * it can answer with an exception.
 *
 * macOS mounts external disks under `/Volumes/<Nome>`, so the volume NAME is simply the
 * second path segment — that is what lets us say «Il disco "Foto" non è collegato»
 * instead of printing an ENOENT. Two traps handled:
 *   • an unmounted disk usually leaves NO `/Volumes/<Nome>` entry at all;
 *   • sometimes it leaves an empty stub directory on the boot volume. We catch that by
 *     comparing st_dev with `/`: same device means the mount point is a plain folder,
 *     i.e. the real disk is not there.
 * Off macOS the same st_dev walk still finds the mount point, so this is portable.
 */
export async function volumeOf(path: string): Promise<VolumeInfo> {
  const info: VolumeInfo = {
    path,
    root: "/",
    name: null,
    external: false,
    mounted: true,
    deepestExisting: null,
  };

  // Deepest existing ancestor: also tells us where a missing tree stops existing.
  let cursor = path;
  for (;;) {
    const st = await statOf(cursor);
    if (st) { info.deepestExisting = cursor; break; }
    const parent = dirname(cursor);
    if (parent === cursor) break;
    cursor = parent;
  }

  const segments = path.split("/").filter(Boolean);
  const underVolumes = path.startsWith("/Volumes/") && segments.length >= 2;
  if (underVolumes) {
    info.name = segments[1] ?? null;
    info.root = `/Volumes/${info.name}`;
    info.external = true;
  }

  const rootStat = await statOf(info.root);
  const bootStat = await statOf("/");

  if (info.external) {
    if (!rootStat) {
      info.mounted = false;
    } else if (bootStat && rootStat.dev === bootStat.dev) {
      // Empty stub left behind by an ejected disk: the folder exists, the disk does not.
      const entries = await listDir(info.root);
      info.mounted = entries.length > 0;
    }
    return info;
  }

  // Not under /Volumes: walk up from the deepest existing ancestor to its mount point,
  // so a path on any other mounted filesystem is still described correctly.
  if (info.deepestExisting) {
    let current = info.deepestExisting;
    let currentStat = await statOf(current);
    for (;;) {
      const parent = dirname(current);
      if (parent === current) break;
      const parentStat = await statOf(parent);
      if (!parentStat || !currentStat || parentStat.dev !== currentStat.dev) break;
      current = parent;
      currentStat = parentStat;
    }
    info.root = current;
    if (bootStat && currentStat && currentStat.dev !== bootStat.dev) {
      info.external = true;
      info.name = parsePath(current).base || current;
    }
  }
  return info;
}

// ---------------------------------------------------------------------------
// The checks
// ---------------------------------------------------------------------------

type CheckBody = Omit<CheckResult, "id" | "label">;

/** Rule 1, in one function: no check can ever escape with an exception. */
async function check(id: CheckId, label: string, body: () => Promise<CheckBody>): Promise<CheckResult> {
  try {
    return { id, label, ...(await body()) };
  } catch (e) {
    return {
      id,
      label,
      level: "error",
      message: T.checkFailed,
      fix: T.checkFailedFix,
      detail: (e as Error)?.message ?? String(e),
    };
  }
}

/** Turns an `S.errors.*` entry into a check body, so remedies stay in one place. */
function fromError(level: CheckLevel, e: ErrorMessage): CheckBody {
  return {
    level,
    message: e.message,
    ...(e.fix ? { fix: e.fix } : {}),
    ...(e.detail ? { detail: e.detail } : {}),
  };
}

function isRemoteModelRef(ref: string): boolean {
  return /^hf:\/\//i.test(ref) || /^https?:\/\//i.test(ref);
}

async function checkConfig(configFile: string, problems: string[]): Promise<CheckBody> {
  const present = (await statOf(configFile)) !== null;
  if (problems.length > 0) {
    return { ...fromError("warn", S.errors.configBroken(configFile, problems.join("; "))), detail: configFile };
  }
  if (!present) {
    return { level: "info", message: T.config.okDefaults, fix: T.config.fixDefaults, detail: configFile };
  }
  return { level: "ok", message: T.config.ok, detail: configFile };
}

async function checkPlatform(): Promise<CheckBody> {
  if (platform !== "darwin") {
    return { level: "error", message: T.platform.notMac, fix: T.platform.fix, detail: `${platform}/${arch}` };
  }
  if (arch !== "arm64") {
    return { level: "error", message: T.platform.notArm, fix: T.platform.fix, detail: `${platform}/${arch}` };
  }
  return { level: "ok", message: "macOS · Apple Silicon", detail: `${platform}/${arch}` };
}

async function checkModelsDisk(cfg: ImgenConfig, configFile: string): Promise<CheckBody & { usable: boolean }> {
  const path = cfg.modelsPath;

  if (!isAbsolute(path)) {
    return {
      usable: false,
      level: "error",
      message: fill(T.disk.notAbsolute, { dove: path }),
      fix: fill(T.disk.notAbsoluteFix, { file: configFile }),
      detail: path,
    };
  }

  const vol = await volumeOf(path);

  // THE expected condition: the external disk is simply not plugged in.
  if (vol.external && !vol.mounted) {
    const err = S.errors.modelsDiskMissing(path);
    return {
      usable: false,
      level: "error",
      message: fill(T.disk.volumeAbsent, { disco: vol.name ?? vol.root }),
      fix: fill(T.disk.volumeAbsentFix, { dove: path }),
      detail: `${vol.root} — ${err.detail ?? path}`,
    };
  }

  const st = await statOf(path);
  if (!st) {
    return {
      usable: false,
      level: "error",
      message: vol.external
        ? fill(T.disk.volumeThereFolderMissing, { disco: vol.name ?? vol.root })
        : T.disk.folderMissing,
      fix: fill(T.disk.folderMissingFix, { dove: path }),
      detail: vol.deepestExisting ? `esiste fino a ${vol.deepestExisting}` : path,
    };
  }
  if (!st.isDirectory()) {
    return { usable: false, level: "error", message: fill(T.disk.notADir, { dove: path }), detail: path };
  }
  if (!(await canAccess(path, FS.R_OK | FS.X_OK))) {
    return {
      usable: false,
      level: "error",
      message: fill(T.disk.notReadable, { dove: path }),
      fix: T.disk.notReadableFix,
      detail: path,
    };
  }

  const free = await freeBytes(path);
  const space = free === null ? "" : ` ${fill(T.disk.space, { spazio: humanBytes(free) })}`;
  return {
    usable: true,
    level: "ok",
    message: (vol.external
      ? fill(T.disk.okExternal, { disco: vol.name ?? vol.root })
      : T.disk.okInternal) + space,
    detail: path,
  };
}

async function checkModels(cfg: ImgenConfig, diskUsable: boolean): Promise<CheckBody> {
  const roles: (keyof ModelsConfig)[] = ["draft", "final", "alt", "edit", "upscale"];
  const blocking = new Set<keyof ModelsConfig>(["draft", "final"]);

  if (!diskUsable) {
    return { level: "warn", message: T.models.skippedDiskOff, detail: cfg.modelsPath };
  }

  const items: CheckItem[] = [];
  const missing: string[] = [];
  let blockingMissing = false;

  for (const role of roles) {
    const file = cfg.models[role];
    const roleLabel = T.models.roles[role];
    if (!file) {
      if (blocking.has(role)) {
        blockingMissing = true;
        items.push({ name: roleLabel, ok: false, status: T.models.unusedRole });
      }
      continue;
    }
    if (isRemoteModelRef(file)) {
      items.push({ name: `${roleLabel} — ${file}`, ok: true, status: T.models.remote });
      continue;
    }
    const full = join(cfg.modelsPath, file);
    const st = await statOf(full);
    if (!st?.isFile()) {
      items.push({ name: `${roleLabel} — ${file}`, ok: false, status: T.models.missing, detail: full });
      missing.push(file);
      if (blocking.has(role)) blockingMissing = true;
      continue;
    }
    if (st.size < MIN_MODEL_BYTES) {
      // A 4-6GB checkpoint that weighs a few kB is an LFS pointer or a killed download.
      items.push({
        name: `${roleLabel} — ${file}`,
        ok: false,
        status: T.models.truncated,
        detail: `${full} (${humanBytes(st.size)})`,
      });
      missing.push(file);
      if (blocking.has(role)) blockingMissing = true;
      continue;
    }
    items.push({ name: `${roleLabel} — ${file}`, ok: true, status: `${T.models.present} (${humanBytes(st.size)})` });
  }

  if (items.length === 0) {
    return { level: "error", message: T.models.noneConfigured, fix: fill(T.models.fixMissing, { dove: cfg.modelsPath }) };
  }
  if (missing.length === 0 && !blockingMissing) {
    return { level: "ok", message: T.models.allOk, items };
  }
  // One missing model gets the fully specific remedy from strings.ts; several get the
  // generic one, because five identical paragraphs are not a better message.
  const single = missing.length === 1 ? S.errors.modelMissing(missing[0]!, cfg.modelsPath) : null;
  return {
    level: blockingMissing ? "error" : "warn",
    message: single ? single.message : T.models.someMissing,
    fix: single?.fix ?? fill(T.models.fixMissing, { dove: cfg.modelsPath }),
    items,
  };
}

async function checkDrawThings(): Promise<CheckBody> {
  const bin = await findExecutable("draw-things-cli");
  if (!bin) return fromError("error", S.errors.drawThingsMissing);
  return { level: "ok", message: fill(T.drawThings.ok, { dove: bin }), detail: bin };
}

async function checkTypst(fast: boolean): Promise<CheckBody> {
  const bin = await findExecutable("typst");
  if (!bin) return fromError("error", S.errors.typstMissing);
  if (fast) return { level: "ok", message: fill(T.typst.ok, { dove: bin }), detail: bin };

  const out = (await runBriefly(bin, ["--version"])) ?? "";
  const m = /(\d+)\.(\d+)\.(\d+)/.exec(out);
  if (!m) return { level: "ok", message: fill(T.typst.ok, { dove: bin }), detail: bin };

  const version = `${m[1]}.${m[2]}.${m[3]}`;
  const major = Number(m[1]);
  const minor = Number(m[2]);
  const old = major < TYPST_MIN[0] || (major === TYPST_MIN[0] && minor < TYPST_MIN[1]);
  if (old) {
    return {
      level: "warn",
      message: fill(T.typst.tooOld, { versione: version, minima: `${TYPST_MIN[0]}.${TYPST_MIN[1]}` }),
      fix: T.typst.tooOldFix,
      detail: bin,
    };
  }
  return { level: "ok", message: fill(T.typst.okVersion, { versione: version, dove: bin }), detail: bin };
}

/**
 * The daemon. NOTE: nothing here is an `error`. `draw-things-cli` works perfectly well
 * cold — it just reloads 6GB of weights on every single call, which turns a draft loop
 * into a coffee break. So: warn, never block.
 */
async function checkServer(cfg: ImgenConfig, piConfigDir: string): Promise<CheckBody> {
  const paths = serverPaths(cfg, piConfigDir);
  const configFile = configPath(piConfigDir);
  const listening = await isPortOpen(cfg.server.port);

  if (!cfg.server.enabled) {
    return {
      level: listening ? "info" : "warn",
      message: T.server.disabled,
      fix: fill(T.server.disabledFix, { file: configFile }),
      detail: paths.binary,
    };
  }

  // A binary on PATH is just as good as our own copy under the pi config dir.
  const own = await statOf(paths.binary);
  const bin = own?.isFile() ? paths.binary : await findExecutable(GRPC_SERVER_BINARY);

  if (!bin) {
    return {
      level: listening ? "info" : "warn",
      message: listening
        ? fill(T.server.foreign, { porta: cfg.server.port })
        : fill(T.server.binaryMissing, { nome: GRPC_SERVER_BINARY }),
      ...(listening
        ? {}
        : { fix: fill(T.server.binaryMissingFix, { url: GRPC_SERVER_URL, dove: paths.stateDir }) }),
      detail: paths.binary,
    };
  }

  if (!(await canAccess(bin, FS.X_OK))) {
    return {
      level: "warn",
      message: fill(T.server.notExecutable, { dove: bin }),
      fix: fill(T.server.notExecutableFix, { dove: bin }),
      detail: bin,
    };
  }

  if (listening) {
    return { level: "ok", message: fill(T.server.running, { porta: cfg.server.port }), detail: `${bin} :${cfg.server.port}` };
  }

  const command =
    `"${bin}" "${cfg.modelsPath}" --no-tls --port ${cfg.server.port}` +
    (cfg.server.cpuOffload ? " --cpu-offload" : "");
  return {
    level: "warn",
    message: T.server.stopped,
    fix: fill(T.server.stoppedFix, { comando: command }),
    detail: bin,
  };
}

// -- fonts -------------------------------------------------------------------

const FONT_EXT = /\.(ttf|otf|ttc|woff2?)$/i;
const LICENSE_FILE = /^(license|licence|ofl|ufl|copying|apache)/i;

const normalise = (s: string): string => s.toLowerCase().replace(/[^a-z0-9]/g, "");

/**
 * vendor/fonts is written by install.sh from Fontsource
 * (`api.fontsource.org/v1/download/{id}` ships the TTFs *and* the LICENSE), so the
 * expected layout is one directory per family named after its Fontsource id. We accept
 * the google/fonts slug and the family name too, plus a flat dump of files, because a
 * doctor that only recognises one spelling reports false alarms.
 */
async function checkFonts(): Promise<CheckBody> {
  const entries = await listDir(FONTS_DIR);
  const real = entries.filter((e) => !e.startsWith("."));
  if (real.length === 0) {
    return { level: "error", message: T.fonts.empty, fix: T.fonts.emptyFix, detail: FONTS_DIR };
  }

  // Index the tree once: directories with their files, plus any files at the top level.
  const dirs = new Map<string, string[]>();
  const flat: string[] = [];
  for (const entry of real) {
    const full = join(FONTS_DIR, entry);
    const st = await statOf(full);
    if (st?.isDirectory()) dirs.set(normalise(entry), await listDir(full));
    else if (st?.isFile()) flat.push(entry);
  }

  const items: CheckItem[] = [];
  const missing: string[] = [];
  const unlicensed: string[] = [];

  for (const font of FONTS) {
    const keys = [font.id, font.slug, font.family].map(normalise);
    const dirKey = keys.find((k) => dirs.has(k));
    let files: string[] = [];
    if (dirKey) {
      files = dirs.get(dirKey) ?? [];
    } else {
      // Flat layout: match "Anton-Regular.ttf", "anton-latin-400-normal.woff2", …
      files = flat.filter((f) => keys.some((k) => normalise(f).startsWith(k)));
    }

    const faces = files.filter((f) => FONT_EXT.test(f));
    const hasLicense = files.some((f) => LICENSE_FILE.test(f));

    if (faces.length === 0) {
      missing.push(font.family);
      items.push({ name: font.family, ok: false, status: T.models.missing });
      continue;
    }
    if (!hasLicense) {
      unlicensed.push(font.family);
      items.push({ name: font.family, ok: false, status: `${T.fonts.noLicenseItem} (${font.license})` });
      continue;
    }
    items.push({ name: font.family, ok: true, status: `${faces.length} · ${font.license}` });
  }

  if (missing.length === 0 && unlicensed.length === 0) {
    return {
      level: "ok",
      message: fill(T.fonts.ok, { n: FONTS.length }),
      detail: fill(T.fonts.dir, { dove: FONTS_DIR }),
      items,
    };
  }
  if (missing.length > 0) {
    // Every family missing = install.sh never ran; a couple missing = a partial download.
    return {
      level: missing.length === FONTS.length ? "error" : "warn",
      message: fill(T.fonts.missing, { n: missing.length, tot: FONTS.length }),
      fix: T.fonts.missingFix,
      detail: list(missing),
      items,
    };
  }
  return {
    level: "warn",
    message: fill(T.fonts.noLicense, { n: unlicensed.length }),
    fix: T.fonts.noLicenseFix,
    detail: list(unlicensed),
    items,
  };
}

/**
 * Print helpers. All optional by design: the PDF is produced by Typst alone. These only
 * let us VERIFY it (TrimBox, embedded fonts, integrity) before he sends it to a printer,
 * so their absence is never worse than `info`/`warn`.
 */
async function checkPrintTools(): Promise<CheckBody> {
  const names = ["pdfinfo", "pdffonts", "qpdf", "gs"];
  const items: CheckItem[] = [];
  const found: string[] = [];

  for (const name of names) {
    const bin = await findExecutable(name);
    const what = T.print.tools[name] ?? "";
    if (bin) found.push(name);
    items.push({
      name: `${name} — ${what}`,
      ok: Boolean(bin),
      status: bin ? T.models.present : T.models.missing,
      ...(bin ? { detail: bin } : {}),
    });
  }

  if (found.length === names.length) return { level: "ok", message: T.print.allOk, items };
  return {
    level: found.length === 0 ? "info" : "warn",
    message: found.length === 0 ? T.print.noneNeeded : T.print.someMissing,
    fix: T.print.fix,
    items,
  };
}

/**
 * The only check that writes: creating the directory and putting one byte in it is the
 * only way to distinguish "writable" from "looks writable" (network shares, read-only
 * volumes, and full disks all pass a permission test and then fail on write).
 *
 * The volume test in front of the `mkdir` is not decoration. If the output directory
 * lives on the same external disk as the models and that disk is unplugged, a
 * `mkdir -p` would happily create `/Volumes/<Nome>/…` ON THE BOOT DISK — the stub that
 * makes macOS remount the real disk as "<Nome> 1" next time. We refuse to write into a
 * volume that is not there.
 */
async function checkOutputDir(cfg: ImgenConfig): Promise<CheckBody> {
  const dir = cfg.outputDir;
  if (!isAbsolute(dir)) {
    return { level: "error", message: fill(T.output.notAbsolute, { dove: dir }), detail: dir };
  }

  const vol = await volumeOf(dir);
  if (vol.external && !vol.mounted) {
    return {
      level: "error",
      message: fill(T.output.volumeAbsent, { disco: vol.name ?? vol.root, dove: dir }),
      fix: fill(T.output.volumeAbsentFix, { disco: vol.name ?? vol.root }),
      detail: vol.root,
    };
  }

  const existed = (await statOf(dir))?.isDirectory() ?? false;
  const probe = join(dir, `.imgen-doctor-${process.pid}`);
  try {
    await mkdir(dir, { recursive: true });
    await writeFile(probe, "ok", "utf8");
  } catch (e) {
    return fromError("error", S.errors.writeFailed(dir, (e as Error).message));
  } finally {
    await rm(probe, { force: true }).catch(() => { /* nothing to clean up */ });
  }

  const free = await freeBytes(dir);
  if (free !== null && free < LOW_DISK_BYTES) {
    return {
      level: "warn",
      message: fill(T.output.lowSpace, { spazio: humanBytes(free) }),
      fix: T.output.lowSpaceFix,
      detail: dir,
    };
  }
  const space = free === null ? "" : ` ${fill(T.disk.space, { spazio: humanBytes(free) })}`;
  return {
    level: "ok",
    message: (existed ? fill(T.output.ok, { dove: dir }) : fill(T.output.created, { dove: dir })) + space,
    detail: dir,
  };
}

// ---------------------------------------------------------------------------
// Runner
// ---------------------------------------------------------------------------

const LABELS = S.doctor.checks;

/**
 * Runs every check. NEVER throws, NEVER rejects: the worst it can return is a report
 * made entirely of `error` rows.
 *
 * Checks are ordered the way he would fix them: settings, machine, disk, models, tools.
 * The models check is deliberately sequenced AFTER the disk check and is fed its result,
 * so an unplugged disk produces one clear sentence instead of six ENOENTs.
 */
export async function runDoctor(opts: DoctorOptions = {}): Promise<DoctorReport> {
  const started = Date.now();
  const piConfigDir = opts.piConfigDir ?? DEFAULT_PI_CONFIG_DIR;
  const configFile = configPath(piConfigDir);
  const fast = opts.fast ?? false;

  let config: ImgenConfig;
  let configProblems: string[];
  if (opts.config) {
    config = opts.config;
    configProblems = opts.configProblems ?? [];
  } else {
    // loadConfig() is itself never-throwing and degrades to DEFAULTS.
    const loaded = loadConfig(piConfigDir);
    config = loaded.config;
    configProblems = loaded.problems;
  }

  const checks: CheckResult[] = [];
  checks.push(await check("config", LABELS.config, () => checkConfig(configFile, configProblems)));
  checks.push(await check("platform", "Il computer", () => checkPlatform()));

  // Disk first, then models, which need to know whether the disk answered at all.
  let diskUsable = false;
  const disk = await check("modelsDisk", LABELS.modelsDisk, async () => {
    const { usable, ...body } = await checkModelsDisk(config, configFile);
    diskUsable = usable;
    return body;
  });
  checks.push(disk);
  checks.push(await check("models", LABELS.models, () => checkModels(config, diskUsable)));

  checks.push(await check("drawThings", LABELS.drawThings, () => checkDrawThings()));
  checks.push(await check("server", LABELS.server, () => checkServer(config, piConfigDir)));
  checks.push(await check("typst", LABELS.typst, () => checkTypst(fast)));
  checks.push(await check("fonts", LABELS.fonts, () => checkFonts()));
  checks.push(await check("printTools", T.print.label, () => checkPrintTools()));
  checks.push(await check("outputDir", LABELS.outputDir, () => checkOutputDir(config)));

  const problems = checks
    .filter((c) => c.level === "warn" || c.level === "error")
    .map((c) => c.message);

  return {
    ok: !checks.some((c) => c.level === "error"),
    warnings: checks.some((c) => c.level === "warn"),
    checks,
    problems,
    config,
    configFile,
    elapsedMs: Date.now() - started,
  };
}

/** `Backend.probe()`-shaped view, for callers that only want the two fields. */
export async function probe(opts: DoctorOptions = {}): Promise<{ ok: boolean; problems: string[] }> {
  const report = await runDoctor(opts);
  return { ok: report.ok, problems: report.problems };
}

// ---------------------------------------------------------------------------
// Presentation
// ---------------------------------------------------------------------------

const MARK: Record<CheckLevel, string> = { ok: "✓", info: "·", warn: "!", error: "✗" };

export function isBlocking(c: CheckResult): boolean {
  return c.level === "error";
}

/** The full Italian report, for `/doctor`. Pure string building; cannot throw. */
export function formatReport(report: DoctorReport, opts: { verbose?: boolean } = {}): string {
  const verbose = opts.verbose ?? false;
  const lines: string[] = [S.doctor.title, ""];

  for (const c of report.checks) {
    lines.push(`${MARK[c.level]} ${c.label} — ${c.message}`);
    if (c.fix && c.level !== "ok") lines.push(`    → ${c.fix}`);
    if (c.items && (verbose || c.level !== "ok")) {
      // On a healthy row the item list is noise; on a broken one it is the diagnosis.
      const items = verbose ? c.items : c.items.filter((i) => !i.ok);
      for (const i of items) lines.push(`    ${i.ok ? "·" : "✗"} ${i.name}: ${i.status}`);
    }
    if (verbose && c.detail) lines.push(`    ${T.report.detailPrefix}${c.detail}`);
  }

  lines.push("");
  if (report.ok && !report.warnings) {
    lines.push(S.doctor.allGood);
  } else {
    lines.push(S.doctor.someProblems);
    lines.push(bullets(report.problems));
    lines.push(S.doctor.hint);
  }
  return lines.join("\n");
}

/**
 * One line for session_start. Returns null when everything is fine and there is nothing
 * worth saying — a health check that greets him every morning is a health check he stops
 * reading.
 */
export function sessionBanner(report: DoctorReport): string | null {
  if (report.ok && !report.warnings) return null;

  // One blocking fault gets the full two-line treatment: what happened, what to do.
  // Several get a list, because four remedies in a row at start-up is a wall of text.
  const blocking = report.checks.filter(isBlocking);
  if (blocking.length === 1) {
    const only = blocking[0]!;
    return errorText({ message: only.message, ...(only.fix ? { fix: only.fix } : {}) });
  }
  const shown = blocking.length > 0 ? blocking.map((c) => c.message) : report.problems;
  return `${S.doctor.someProblems}\n${bullets(shown)}\n${S.doctor.hint}`;
}

// ---------------------------------------------------------------------------
// Standalone entry point: `node --import jiti/register doctor.ts [--verbose]`
// ---------------------------------------------------------------------------

async function main(): Promise<void> {
  const argv = process.argv.slice(2);
  const verbose = argv.includes("--verbose") || argv.includes("-v");
  const dirFlag = argv.findIndex((a) => a === "--config-dir");
  const piConfigDir = dirFlag >= 0 ? argv[dirFlag + 1] : undefined;

  const report = await runDoctor({
    ...(piConfigDir ? { piConfigDir } : {}),
  });
  process.stdout.write(`${formatReport(report, { verbose })}\n`);
  process.exitCode = report.ok ? 0 : 1;
}

const invokedDirectly =
  process.argv[1] !== undefined &&
  import.meta.url === pathToFileURL(process.argv[1]).href;

if (invokedDirectly) {
  // Even the CLI path obeys rule 1: a failure here prints, it does not stack-trace.
  main().catch((e: unknown) => {
    process.stdout.write(`${errorText(S.errors.unknown((e as Error)?.message))}\n`);
    process.exitCode = 1;
  });
}

export default runDoctor;