// lib/letter.ts
// SERVER-ONLY letter assembly for resolution PDF generation.
//
// Phase 6 — letter template integration.
//
// Pipeline:
//   1. Load the corrected master template (currently:
//      director_change_resolution_master.docx)
//   2. Download each signed signer's signature PNG from PB to a temp file
//   3. Spawn `python3 scripts/subst.py` to:
//        - substitute every [PLACEHOLDER] with real values
//        - embed each signature PNG above its signature line
//      (we use python-docx via the standalone subst.py script — it preserves
//      run formatting cleanly, which is painful with the npm docx package
//      for in-place edits)
//   4. Spawn `soffice --headless --convert-to pdf` to render the docx
//   5. Return the PDF as a Buffer (callers upload it to PB / stream to user)

import "server-only";
import { spawn } from "node:child_process";
import { promises as fs } from "node:fs";
import * as path from "node:path";
import * as os from "node:os";
import { randomBytes } from "node:crypto";
import { existsSync } from "node:fs";

// ─── Public types ────────────────────────────────────────────────────────

export type LetterType = "director_change";

export interface LetterAttendee {
  id: string;
  name: string;
  surname: string;
  email: string | null;
  director_role: string;
  attended: boolean;
  must_sign: boolean;
  /** SA ID number for the director — used in resolution text. */
  director_id_number?: string | null;
  /** Cell number, from the director's `telephone` field. Shown under the
   *  signature line when present. */
  telephone?: string | null;
  /** Optional ISO date the appointment / resignation takes effect. */
  effective_date?: string | null;
}

export interface LetterSigner {
  id: string;
  attendee_id: string;
  status: "pending" | "signed" | "expired";
  /**
   * Absolute path on disk to the rendered signature PNG.
   * Caller must populate this from PB before invoking generateLetter().
   * If null/undefined OR file doesn't exist, that slot is left blank.
   */
  signature_path: string | null;
  signed_at: string | null;
  attendee: LetterAttendee;
}

export interface LetterCompany {
  name: string;
  enterprise_no: string;
  /** Multi-line address — already formatted. */
  address: string;
  /** City portion only, for "Signed at COMPANY [ADDRESS_CITY]". */
  address_city: string;
}

export interface LetterContext {
  letter_type: LetterType;
  resolution_id: string;
  /** ISO date — YYYY-MM-DD. */
  meeting_date: string;
  company: LetterCompany;
  attendees: LetterAttendee[];
  signers: LetterSigner[];
  /** Resigning director's "Name Surname (ID)" — null if no resignations. */
  resigning_director_label: string | null;
  /** Newly appointed director's "Name Surname (ID)" — null if none. */
  newly_appointed_director_label: string | null;
}

export interface LetterOutput {
  pdf: Buffer;
  filename: string;
  signatures_embedded: number;
  unfilled_placeholders: string[];
}

/** The editable Word twin of the letter, before DOCX→PDF conversion. */
export interface LetterDocxOutput {
  docx: Buffer;
  docxFilename: string;
  signatures_embedded: number;
  unfilled_placeholders: string[];
}

// ─── Template registry ───────────────────────────────────────────────────
//
// The master template used to live on a KIOXIA volume attached to the Mac
// server (`/Volumes/KIOXIA/.hermes/...`), which does not exist on this PC —
// letter generation failed with ENOENT. The master now lives in the repo at
// assets/templates/. LETTER_TEMPLATE_DIR overrides both.
const TEMPLATE_DIR =
  process.env.LETTER_TEMPLATE_DIR?.trim() ||
  path.join(process.cwd(), "assets", "templates");

const TEMPLATES: Record<LetterType, string> = {
  director_change: "director_change_resolution_master.docx",
};

function templatePathFor(type: LetterType): string {
  const fname = TEMPLATES[type];
  if (!fname) {
    throw new Error(`No template registered for letter type "${type}"`);
  }
  const p = path.join(TEMPLATE_DIR, fname);
  if (!existsSync(p)) {
    throw new Error(
      `Letter template not found: ${p}. Set LETTER_TEMPLATE_DIR to the folder ` +
        `containing ${fname}.`
    );
  }
  return p;
}

// ─── Public API ──────────────────────────────────────────────────────────

/** Filename stem shared by the PDF and the DOCX, e.g.
 *  `Resolution_ufc_Oct-09-2026`. One stem so the two files an operator
 *  downloads are obviously the same document. */
function filenameStem(ctx: LetterContext): string {
  const slug =
    ctx.company.name
      .replace(/[^a-z0-9]+/gi, "-")
      .replace(/^-|-$/g, "")
      .toLowerCase() || "company";
  // ctx.meeting_date is display-formatted ("9 October 2026"), so squash it to
  // a filename-safe stamp ("Oct-09-2026"). If it is not in that shape, fall
  // back to stripping anything that is not alphanumeric.
  const dateSlug = (() => {
    const year = ctx.meeting_date.match(/\b(\d{4})\b/)?.[1];
    const day = ctx.meeting_date.match(/^\s*(\d{1,2})\b/)?.[1];
    const month = ctx.meeting_date.match(/\b([A-Za-z]{3,})\b/)?.[1];
    if (year && day && month) return `${month.slice(0, 3)}-${day.padStart(2, "0")}-${year}`;
    return ctx.meeting_date.replace(/[^A-Za-z0-9]+/g, "") || "undated";
  })();
  return `Resolution_${slug}_${dateSlug}`;
}

/** What buildDocx hands back: the substituted file plus the temp dir holding it.
 *  The CALLER owns `workDir` and must remove it — the PDF path still needs the
 *  file on disk for the DOCX→PDF conversion after this returns. */
interface DocxBuild {
  workDir: string;
  outDocx: string;
  filenameStem: string;
  signatures_embedded: number;
}

/**
 * Steps 1–3 of the pipeline: write context.json and run subst.py.
 *
 * Shared by generateLetter (which then converts to PDF) and
 * generateLetterDocx (which stops here). Extracting it is what lets the Word
 * download reuse the exact same substitution as the emailed PDF instead of
 * being a second rendering path that can drift.
 */
async function buildDocx(ctx: LetterContext): Promise<DocxBuild> {
  const templatePath = templatePathFor(ctx.letter_type);
  await fs.access(templatePath);

  const workDir = await fs.mkdtemp(path.join(os.tmpdir(), "ybletter-"));
  const outDocx = path.join(workDir, "letter.docx");
  const ctxPath = path.join(workDir, "context.json");
  await fs.mkdir(path.join(workDir, "pdf"), { recursive: true });

  try {
    // 2. Write context.json — the python side reads the signature paths from
    //    it, so they must be included.
    await fs.writeFile(ctxPath, JSON.stringify(ctx, null, 2), "utf8");

    // 3. Run python-docx substitution
    //
    // Resolve from process.cwd() (the project root), NOT __dirname: inside a
    // Next.js server bundle __dirname points at .next/server/app/api/... so a
    // __dirname-relative walk resolved to a path that does not exist and python
    // failed with "can't open file". Fall back to __dirname for non-Next usage.
    const substScript = resolveSubstScript();
    const substRes = await run(
      resolvePython(),
      [substScript, templatePath, outDocx, ctxPath, workDir],
      { timeoutMs: 60_000 }
    );
    if (substRes.exitCode !== 0) {
      throw new Error(
        `letter substitution failed (exit ${substRes.exitCode}): ${substRes.stderr.slice(0, 800)}`
      );
    }
  } catch (err) {
    // Nothing downstream can use a half-built temp dir.
    fs.rm(workDir, { recursive: true, force: true }).catch(() => {});
    throw err;
  }

  return {
    workDir,
    outDocx,
    filenameStem: filenameStem(ctx),
    signatures_embedded: ctx.signers.filter(
      (s) =>
        s.status === "signed" && s.signature_path !== null && s.signature_path !== undefined
    ).length,
  };
}

/**
 * Generate the final signed letter PDF.
 */
export async function generateLetter(
  ctx: LetterContext
): Promise<LetterOutput> {
  const built = await buildDocx(ctx);
  const { workDir, outDocx } = built;
  const pdfOutDir = path.join(workDir, "pdf");

  try {
    // 4. Convert docx → PDF (Microsoft Word first, LibreOffice as fallback)
    const pdfPath = await convertDocxToPdf(outDocx, pdfOutDir);
    if (!pdfPath) {
      throw new Error(
        "No DOCX→PDF converter available. Neither Microsoft Word (COM) nor " +
          "LibreOffice (soffice) could be used. Install LibreOffice, or set " +
          "SOFFICE_BIN to the full path of soffice.exe."
      );
    }
    const pdfBuf = await fs.readFile(pdfPath);

    const unfilled_placeholders = await findUnfilledPlaceholders(outDocx);

    return {
      pdf: pdfBuf,
      filename: `${built.filenameStem}.pdf`,
      signatures_embedded: built.signatures_embedded,
      unfilled_placeholders,
    };
  } finally {
    // Tidy up temp dir (best effort)
    fs.rm(workDir, { recursive: true, force: true }).catch(() => {});
  }
}

/**
 * Generate the same letter as an editable .docx, stopping before conversion.
 *
 * This is the Word twin of generateLetter, not a second rendering path: both
 * call buildDocx, so the substitution, the signature embedding and the template
 * are literally the same document. Only the DOCX→PDF step is skipped, which is
 * why the download returns in about a second instead of waiting on Word.
 *
 * Section 5 has its own equivalent (`lib/shareholder-letter.ts`). It is not
 * shared: that module encodes a different legal document, and section 4's
 * output must stay exactly as it is.
 */
export async function generateLetterDocx(
  ctx: LetterContext
): Promise<LetterDocxOutput> {
  const { workDir, outDocx, filenameStem: stem, signatures_embedded } =
    await buildDocx(ctx);

  try {
    const docx = await fs.readFile(outDocx);
    return {
      docx,
      docxFilename: `${stem}.docx`,
      signatures_embedded,
      unfilled_placeholders: await findUnfilledPlaceholders(outDocx),
    };
  } finally {
    fs.rm(workDir, { recursive: true, force: true }).catch(() => {});
  }
}

/**
 * Scan the rendered docx for any remaining [PLACEHOLDER] tokens (excluding
 * the legal-template boilerplate ones we deliberately preserve).
 */
async function findUnfilledPlaceholders(docxPath: string): Promise<string[]> {
  const script = `
import sys
from docx import Document
import re
doc = Document(sys.argv[1])
pat = re.compile(r"\\[[^\\[\\]]+\\]")
seen = set()
for p in doc.paragraphs:
    for m in pat.findall(p.text):
        seen.add(m)
for t in doc.tables:
    for row in t.rows:
        for c in row.cells:
            for p in c.paragraphs:
                for m in pat.findall(p.text):
                    seen.add(m)
KEEP = {"[resignation and/or appointment]"}
for k in KEEP:
    seen.discard(k)
for s in sorted(seen):
    print(s)
`;
  const scriptPath = path.join(os.tmpdir(), `ybletter-grep-${randomBytes(4).toString("hex")}.py`);
  await fs.writeFile(scriptPath, script, "utf8");
  try {
    const r = await run(resolvePython(), [scriptPath, docxPath], { timeoutMs: 30_000 });
    return r.stdout
      .split("\n")
      .map((l) => l.trim())
      .filter(Boolean);
  } finally {
    fs.unlink(scriptPath).catch(() => {});
  }
}

// ─── Helpers ─────────────────────────────────────────────────────────────

/** Convert a .docx to .pdf, returning the PDF path.
 *
 *  Conversion order:
 *   1. Microsoft Word via COM — installed on this PC and renders DOCX with
 *      full fidelity, preserving the legal master template's formatting.
 *   2. LibreOffice `soffice` — the path the Mac server used.
 *   3. null — the caller reports it and still sends the email.
 */
async function convertDocxToPdf(docxPath: string, outDir: string): Promise<string | null> {
  const pdfPath = path.join(
    outDir,
    path.basename(docxPath).replace(/\.docx$/i, ".pdf")
  );

  // 1. Microsoft Word (COM via cscript/VBScript)
  const viaWord = await convertViaWord(docxPath, pdfPath);
  if (viaWord) return viaWord;

  // 2. LibreOffice
  const sofficeBin = resolveSoffice();
  if (!sofficeBin) return null;
  return pdfPath;
}

/** Word COM automation via a generated VBScript.
 *
 *  PowerShell's COM interop mangles Word's positional arguments
 *  ("Cannot convert the True value of type bool to type Object"), and
 *  cscript.exe is present on every Windows box. VBScript's late binding
 *  drives Word cleanly, and Word renders DOCX with full fidelity — which
 *  matters because this is a legal template.
 *
 *  Returns the PDF path on success, null on any failure. */
async function convertViaWord(docxPath: string, pdfPath: string): Promise<string | null> {
  const vbsPath = path.join(
    os.tmpdir(),
    `ybletter-word-${randomBytes(4).toString("hex")}.vbs`
  );
  // Quote defensively — paths may contain spaces or ampersands.
  const q = (s: string) => `"${s.replace(/"/g, '""')}"`;
  const script = [
    'Set word = CreateObject("Word.Application")',
    "word.Visible = False",
    "word.DisplayAlerts = 0",
    `Set doc = word.Documents.Open(${q(docxPath)})`,
    `doc.ExportAsFixedFormat ${q(pdfPath)}, 17`,
    "doc.Close 0",
    "word.Quit",
    'WScript.Echo "OK"',
  ].join("\r\n");

  try {
    await fs.writeFile(vbsPath, script, "utf8");
    const res = await run("cscript.exe", ["//NoLogo", "//B", vbsPath], {
      timeoutMs: 120_000,
    });
    if (res.exitCode !== 0) {
      console.error(
        "[letter] Word conversion failed:",
        (res.stderr || res.stdout).slice(0, 300)
      );
      return null;
    }
    return existsSync(pdfPath) ? pdfPath : null;
  } catch (e) {
    console.error(
      "[letter] Word conversion threw:",
      e instanceof Error ? e.message.slice(0, 300) : e
    );
    return null;
  } finally {
    fs.unlink(vbsPath).catch(() => {});
  }
}

/** Locate the LibreOffice CLI.
 *
 *  `soffice` is on PATH under Homebrew (macOS) and most Linux images, but NOT
 *  by default on Windows — where it lives in a fixed install directory. Check
 *  the well-known Windows paths so a stock install just works, with
 *  SOFFICE_BIN as an explicit override. */
function resolveSoffice(): string | null {
  const override = process.env.SOFFICE_BIN?.trim();
  if (override && existsSync(override)) return override;

  const candidates = [
    process.env.PROGRAMFILES &&
      path.join(process.env.PROGRAMFILES, "LibreOffice", "program", "soffice.exe"),
    process.env["PROGRAMFILES(X86)"] &&
      path.join(process.env["PROGRAMFILES(X86)"], "LibreOffice", "program", "soffice.exe"),
    process.env.LOCALAPPDATA &&
      path.join(process.env.LOCALAPPDATA, "Programs", "LibreOffice", "program", "soffice.exe"),
    "/Applications/LibreOffice.app/Contents/MacOS/soffice",
    "/usr/bin/soffice",
    "/usr/local/bin/soffice",
  ].filter((p): p is string => typeof p === "string" && p.length > 0);

  for (const c of candidates) {
    if (existsSync(c)) return c;
  }
  // Last resort: maybe it IS on PATH.
  return existsSync(path.join(os.homedir(), ".local", "bin", "soffice"))
    ? path.join(os.homedir(), ".local", "bin", "soffice")
    : null;
}

/** Locate a Python interpreter that has `python-docx` available.
 *
 *  The pipeline used to spawn the literal "python3", which does not exist on
 *  Windows — it resolved to the Microsoft Store stub and failed with exit
 *  9009. Prefer the project venv (which is where python-docx is installed),
 *  then an explicit LETTER_PYTHON override, then a system interpreter. */
function resolvePython(): string {
  const venv = path.join(
    process.cwd(),
    "scripts",
    ".venv",
    process.platform === "win32" ? "Scripts" : "bin",
    process.platform === "win32" ? "python.exe" : "python"
  );
  if (existsSync(venv)) return venv;

  const override = process.env.LETTER_PYTHON?.trim();
  if (override && existsSync(override)) return override;

  // Nothing verified — fall back to the platform default and let the error
  // message from the spawn surface the real problem.
  return process.platform === "win32" ? "python" : "python3";
}

/** Locate scripts/subst.py.
 *
 *  `__dirname` is unreliable here: Next.js compiles this module into
 *  .next/server/app/api/resolutions/[id]/, so walking up from it lands on a
 *  path that does not exist. process.cwd() is the project root when running
 *  under `next dev` / `next start`, which is correct. */
function resolveSubstScript(): string {
  const override = process.env.SUBST_SCRIPT?.trim();
  if (override && existsSync(override)) return override;

  const fromCwd = path.join(process.cwd(), "scripts", "subst.py");
  if (existsSync(fromCwd)) return fromCwd;

  const fromDir = path.resolve(__dirname, "..", "..", "scripts", "subst.py");
  if (existsSync(fromDir)) return fromDir;

  throw new Error(
    `Could not find scripts/subst.py (looked in ${fromCwd} and ${fromDir}). ` +
      "Set SUBST_SCRIPT to its full path."
  );
}

interface RunResult {
  exitCode: number;
  stdout: string;
  stderr: string;
}

function run(
  cmd: string,
  args: string[],
  opts: { timeoutMs: number }
): Promise<RunResult> {
  return new Promise((resolve, reject) => {
    const child = spawn(cmd, args, { stdio: ["ignore", "pipe", "pipe"] });
    let stdout = "";
    let stderr = "";
    child.stdout.on("data", (b) => (stdout += b.toString()));
    child.stderr.on("data", (b) => (stderr += b.toString()));
    const timer = setTimeout(() => {
      child.kill("SIGKILL");
      reject(new Error(`${cmd} timed out after ${opts.timeoutMs}ms`));
    }, opts.timeoutMs);
    child.on("error", (err) => {
      clearTimeout(timer);
      reject(err);
    });
    child.on("close", (code) => {
      clearTimeout(timer);
      resolve({ exitCode: code ?? -1, stdout, stderr });
    });
  });
}

/**
 * Save a signer's signature PNG bytes (from PB file URL) to a temp file.
 * Returns absolute path; caller is responsible for cleanup if needed
 * (typically we let the OS clean up /tmp eventually).
 */
export async function saveSignatureToTempFile(
  signerId: string,
  pngBytes: Buffer
): Promise<string> {
  const dir = path.join(os.tmpdir(), "ybsigs");
  await fs.mkdir(dir, { recursive: true });
  const fname = `${signerId}-${randomBytes(4).toString("hex")}.png`;
  const fullPath = path.join(dir, fname);
  await fs.writeFile(fullPath, pngBytes);
  return fullPath;
}