// lib/email.ts
// SERVER-ONLY email sender for resolution letters.
//
// Phase 6 — wires himalaya CLI into the resolution workflow.
//
// Two public functions:
//
//   sendSignerEmail({to, signer_name, resolution_title, sign_url})
//     → used by:
//        - app/api/resolutions/[id]/attendees/route.ts (send_for_signature)
//        - app/api/resolutions/[id]/resend/route.ts      (resend to pending)
//
//   sendFinalLetterEmail({to, signer_name, resolution_title, pdf_path, pdf_filename})
//     → used by:
//        - app/api/resolutions/sign/[token]/route.ts (last signer triggers
//          finalizeAndDistribute which emails the final signed PDF to every
//          signer + the company's primary contact)
//
// Both functions shell out to `himalaya message send` with a raw RFC 5322
// message body (via stdin). Attachments are base64-inlined per the spec
// (Content-Type: application/pdf; name="..."  +  Content-Transfer-Encoding:
// base64 + base64 body).
//
// Failure mode: if himalaya exits non-zero, we LOG the error + return a
// {ok:false, error} object — we do NOT throw. Email send failures must
// not block the sign flow or the resolution from being marked "signed".
// The caller stores the failure reason on the signer row for later retry.

import "server-only";
import { spawn } from "node:child_process";
import { promises as fs } from "node:fs";
import { HIMALAYA_BIN } from "@/lib/himalaya";

const HIMALAYA_ACCOUNT = process.env.HIMALAYA_ACCOUNT ?? "dyfins";
const FROM_ADDRESS =
  process.env.RESOLUTION_FROM_EMAIL ?? "resolutions@dyfins.co.za";

export interface SendSignerEmailInput {
  to: string;
  signer_name: string;
  resolution_title: string;
  /** Absolute URL where the signer can review + sign. */
  sign_url: string;
  /** Company name shown in body copy. */
  company_name: string;
}

export interface SendFinalLetterInput {
  to: string;
  signer_name: string;
  resolution_title: string;
  company_name: string;
  /** Absolute path to the PDF on disk. */
  pdf_path: string;
  pdf_filename: string;
}

export interface EmailResult {
  ok: boolean;
  /** himalaya's exit code (0 = sent) */
  exit_code: number;
  /** Truncated stderr from himalaya, if any */
  error?: string;
}

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

export async function sendSignerEmail(
  input: SendSignerEmailInput,
  /** Optional PDF to attach — the resolution letter itself. */
  attachment?: { filename: string; base64: string }
): Promise<EmailResult> {
  const subject = `Action required — sign resolution: ${input.resolution_title}`;
  const body = buildSignerEmailBody(input);
  const raw = buildRawMessage({
    from: FROM_ADDRESS,
    to: input.to,
    subject,
    body,
    attachments: attachment
      ? [{ filename: attachment.filename, contentType: "application/pdf", base64: attachment.base64 }]
      : [],
  });
  return runHimalaya(raw);
}

export async function sendFinalLetterEmail(
  input: SendFinalLetterInput
): Promise<EmailResult> {
  const subject = `Signed resolution: ${input.resolution_title}`;
  const body = buildFinalLetterBody(input);
  const pdfBase64 = await fs.readFile(input.pdf_path, "base64");
  const raw = buildRawMessage({
    from: FROM_ADDRESS,
    to: input.to,
    subject,
    body,
    attachments: [
      {
        filename: input.pdf_filename,
        contentType: "application/pdf",
        base64: pdfBase64,
      },
    ],
  });
  return runHimalaya(raw);
}

// ─── Email bodies ────────────────────────────────────────────────────────

function buildSignerEmailBody(input: SendSignerEmailInput): string {
  return [
    `Dear ${input.signer_name},`,
    "",
    `You are listed as an attendee on the following shareholder resolution for ${input.company_name}:`,
    "",
    `    ${input.resolution_title}`,
    "",
    "Please review and sign the resolution by opening the secure link below:",
    "",
    `    ${input.sign_url}`,
    "",
    "The link is unique to you. Do not forward it — anyone with the link can sign on your behalf.",
    "",
    "If you have any questions about the resolution, contact the company secretary.",
    "",
    "Kind regards,",
    "Ysterbaard Resolutions",
  ].join("\r\n");
}

function buildFinalLetterBody(input: SendFinalLetterInput): string {
  return [
    `Dear ${input.signer_name},`,
    "",
    `The resolution you signed for ${input.company_name} is now complete.`,
    "",
    `    ${input.resolution_title}`,
    "",
    "A copy of the fully-signed resolution is attached as a PDF. Please keep it on file for your records.",
    "",
    "If any details are incorrect, reply to this email within 7 days.",
    "",
    "Kind regards,",
    "Ysterbaard Resolutions",
  ].join("\r\n");
}

// ─── RFC 5322 message builder ────────────────────────────────────────────

interface RawAttachment {
  filename: string;
  contentType: string;
  base64: string;
}

interface BuildRawOpts {
  from: string;
  to: string;
  subject: string;
  body: string;
  attachments: RawAttachment[];
}

function buildRawMessage(opts: BuildRawOpts): string {
  const boundary = `mixed_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`;
  const headers = [
    `From: ${opts.from}`,
    `To: ${opts.to}`,
    `Subject: ${opts.subject}`,
    `Date: ${new Date().toUTCString()}`,
    `MIME-Version: 1.0`,
    `Content-Type: multipart/mixed; boundary="${boundary}"`,
    "",
    `--${boundary}`,
    `Content-Type: text/plain; charset=utf-8`,
    `Content-Transfer-Encoding: 7bit`,
    "",
    opts.body,
  ];

  const parts: string[] = [headers.join("\r\n")];

  for (const att of opts.attachments) {
    parts.push(
      [
        `--${boundary}`,
        `Content-Type: ${att.contentType}; name="${att.filename}"`,
        `Content-Disposition: attachment; filename="${att.filename}"`,
        `Content-Transfer-Encoding: base64`,
        "",
        // base64-wrap at 76 cols per RFC 2045
        att.base64.match(/.{1,76}/g)!.join("\r\n"),
      ].join("\r\n")
    );
  }

  parts.push(`--${boundary}--`);
  parts.push("");
  return parts.join("\r\n");
}

// ─── Himalaya runner ─────────────────────────────────────────────────────

function runHimalaya(rawMessage: string): Promise<EmailResult> {
  return new Promise((resolve) => {
    // v1.x: `-a` is a per-subcommand flag, so it must FOLLOW `message send`.
    // `himalaya -a acct message send` fails with "unexpected argument '-a'".
    //
    // Also: a bare "himalaya" relies on process PATH, which a Next.js server
    // captures at STARTUP. HIMALAYA_BIN resolves an absolute path at call
    // time, so this works without restarting the dev server.
    const args = [
      "message",
      "send",
      "-a",
      HIMALAYA_ACCOUNT,
    ];
    const child = spawn(HIMALAYA_BIN, args, { stdio: ["pipe", "pipe", "pipe"] });
    let stderr = "";
    child.stdout.on("data", () => {});
    child.stderr.on("data", (b) => (stderr += b.toString()));
    child.on("error", (err) => {
      resolve({ ok: false, exit_code: -1, error: err.message });
    });
    child.on("close", (code) => {
      if (code === 0) {
        resolve({ ok: true, exit_code: 0 });
      } else {
        resolve({
          ok: false,
          exit_code: code ?? -1,
          error: stderr.slice(0, 500),
        });
      }
    });
    // Write the raw RFC 5322 message to stdin
    child.stdin.write(rawMessage);
    child.stdin.end();
  });
}