// app/api/onboarding/submit/route.ts
// POST /api/onboarding/submit
//
// Public endpoint — anyone with a valid `access_token` can submit once.
//
// Flow:
//   1. Parse + validate the multipart form (payload + documents).
//   2. Hash the token and check if a row with this hash already exists.
//      If yes → 409 (link already used).
//   3. Build the full submission record (reference_no, hash, payload,
//      uploads, status='submitted', submitted_at=now) and POST it to PB.
//      PB's UNIQUE INDEX on access_token_hash is the source of truth —
//      two concurrent submits race for the index, one wins, the other
//      gets a 400 from PB which we surface as 409.
//   4. Return the reference_no so the wizard can show it to the client.
//
// PB rules are all-locked so the browser cannot write directly; this
// endpoint is the only path that creates a submission.

import { NextRequest, NextResponse } from "next/server";
import { createHash, randomBytes } from "node:crypto";
import {
  createRecordMultipart,
  fetchCollection,
  type PBRecord,
} from "@/lib/pb";
import type {
  OnboardingSubmissionPayload,
  OnboardingDirectorPayload,
  OnboardingShareholderPayload,
  OnboardingCompany,
} from "@/lib/types";

export const dynamic = "force-dynamic";

const COLLECTION = "ysterbaard_onboarding_submissions";

function mintReferenceNo(): string {
  const today = new Date().toISOString().slice(0, 10).replace(/-/g, "");
  const suffix = randomBytes(2).toString("hex").toUpperCase();
  return `ONB-${today}-${suffix}`;
}

interface SubmissionLookup extends PBRecord {
  reference_no: string;
  status: string;
}

function hashToken(token: string): string {
  return createHash("sha256").update(token + ":" + COLLECTION).digest("hex");
}

async function findExistingByToken(token: string): Promise<SubmissionLookup | null> {
  const hash = hashToken(token);
  try {
    const result = await fetchCollection<SubmissionLookup>(COLLECTION, {
      filter: `access_token_hash = "${hash}"`,
      perPage: 1,
      fields: "id,reference_no,status",
    });
    return result.items[0] ?? null;
  } catch {
    // If the lookup itself fails, fall through — the create step below
    // will still fail with the unique-index constraint if there's a row.
    return null;
  }
}

function parsePayload(raw: string): OnboardingSubmissionPayload | null {
  try {
    const parsed = JSON.parse(raw) as OnboardingSubmissionPayload;
    if (!parsed.client_name?.trim() || !parsed.client_email?.trim()) {
      return null;
    }
    if (!parsed.company || !Array.isArray(parsed.directors)) {
      return null;
    }
    return parsed;
  } catch {
    return null;
  }
}

function validateCompany(c: OnboardingCompany): string | null {
  if (!c || typeof c !== "object") return "Invalid company payload";
  if (!Array.isArray(c.proposed_names) || c.proposed_names.length !== 3) {
    return "Company must have a 3-slot proposed_names array";
  }
  if (!c.proposed_names[0].trim()) return "At least one proposed name required";
  if (!c.physical_address_line_1?.trim()) return "Physical address line 1 required";
  if (!c.physical_town_city?.trim()) return "Physical town/city required";
  if (!c.physical_province?.trim()) return "Physical province required";
  if (!c.physical_postal_code?.trim()) return "Physical postal code required";
  if (!c.postal_address_line_1?.trim()) return "Postal address line 1 required";
  if (!c.postal_town_city?.trim()) return "Postal town/city required";
  if (!c.postal_province?.trim()) return "Postal province required";
  if (!c.postal_postal_code?.trim()) return "Postal postal code required";
  if (!c.company_email?.trim()) return "Company email required";
  return null;
}

function validateDirector(d: OnboardingDirectorPayload): string | null {
  if (!d.first_names?.trim()) return "Director first names required";
  if (!d.surname?.trim()) return "Director surname required";
  if (!/^\d{13}$/.test(d.id_no ?? "")) return "Director ID must be 13 digits";
  if (!d.date_of_birth) return "Director date of birth required";
  if (!d.residential_address_line_1?.trim()) return "Director residential address line 1 required";
  if (!d.residential_town_city?.trim()) return "Director residential town/city required";
  if (!d.residential_province?.trim()) return "Director residential province required";
  if (!d.residential_postal_code?.trim()) return "Director residential postal code required";
  if (!d.postal_address_line_1?.trim()) return "Director postal address line 1 required";
  if (!d.postal_town_city?.trim()) return "Director postal town/city required";
  if (!d.postal_province?.trim()) return "Director postal province required";
  if (!d.postal_postal_code?.trim()) return "Director postal postal code required";
  if (!d.email?.trim()) return "Director email required";
  return null;
}

function validateShareholder(s: OnboardingShareholderPayload): string | null {
  if (!s.name?.trim()) return "Shareholder name required";
  if (!s.id_or_company_no?.trim()) return "Shareholder ID / reg no. required";
  if (typeof s.share_percent !== "number" || s.share_percent <= 0 || s.share_percent > 100) {
    return "Shareholder share % out of range";
  }
  return null;
}

export async function POST(req: NextRequest) {
  let form: FormData;
  try {
    form = await req.formData();
  } catch {
    return NextResponse.json(
      { error: "Could not parse multipart form body." },
      { status: 400 },
    );
  }

  const accessToken = form.get("access_token");
  if (typeof accessToken !== "string" || accessToken.length < 16) {
    return NextResponse.json(
      { error: "Missing or invalid access_token." },
      { status: 400 },
    );
  }

  const payloadRaw = form.get("payload");
  if (typeof payloadRaw !== "string") {
    return NextResponse.json(
      { error: "Missing payload." },
      { status: 400 },
    );
  }
  const payload = parsePayload(payloadRaw);
  if (!payload) {
    return NextResponse.json(
      { error: "Malformed payload." },
      { status: 400 },
    );
  }

  // Server-side validation (defence-in-depth — wizard also validates).
  const companyErr = validateCompany(payload.company);
  if (companyErr) {
    return NextResponse.json({ error: companyErr }, { status: 400 });
  }
  if (!payload.directors.length) {
    return NextResponse.json({ error: "At least one director required" }, { status: 400 });
  }
  for (const [idx, d] of payload.directors.entries()) {
    const err = validateDirector(d);
    if (err) {
      return NextResponse.json({ error: `Director ${idx + 1}: ${err}` }, { status: 400 });
    }
  }
  if (payload.shareholders.length) {
    const total = payload.shareholders.reduce((s, sh) => s + sh.share_percent, 0);
    if (Math.abs(total - 100) > 0.01) {
      return NextResponse.json(
        { error: `Shareholder total must equal 100% (got ${total.toFixed(2)}%).` },
        { status: 400 },
      );
    }
    for (const [idx, s] of payload.shareholders.entries()) {
      const err = validateShareholder(s);
      if (err) {
        return NextResponse.json(
          { error: `Shareholder ${idx + 1}: ${err}` },
          { status: 400 },
        );
      }
    }
  }

  // Look up by token hash — if a row already exists, this link was used.
  const existing = await findExistingByToken(accessToken);
  if (existing) {
    return NextResponse.json(
      {
        error: `This link has already been submitted (reference ${existing.reference_no}).`,
        reference_no: existing.reference_no,
      },
      { status: 409 },
    );
  }

  // Collect uploaded files.
  const files = form.getAll("documents").filter((v): v is File => v instanceof File);
  if (files.length === 0) {
    return NextResponse.json(
      { error: "At least one document (ID or proof of residence) is required." },
      { status: 400 },
    );
  }

  // Enforce per-file size limit (10 MB) — server-side guard so the PB
  // upload can't be a denial-of-service vector.
  const MAX_FILE_BYTES = 10 * 1024 * 1024;
  for (const f of files) {
    if (f.size > MAX_FILE_BYTES) {
      return NextResponse.json(
        { error: `${f.name} exceeds 10 MB limit.` },
        { status: 413 },
      );
    }
  }

  // Build the full record. PB will reject on the UNIQUE INDEX if a
  // concurrent request got in first — we surface that as 409.
  const referenceNo = mintReferenceNo();
  const hash = hashToken(accessToken);
  const clientNotes = (payload.client_notes ?? "").trim();
  const fields = {
    reference_no: referenceNo,
    access_token_hash: hash,
    client_name: payload.client_name.trim(),
    client_email: payload.client_email.trim(),
    client_telephone: payload.client_telephone?.trim() ?? "",
    company_data: JSON.stringify(payload.company),
    directors_data: JSON.stringify(payload.directors),
    shareholders_data: JSON.stringify(payload.shareholders),
    submitted_at: new Date().toISOString(),
    status: "submitted",
    // Client-supplied notes (may have been captured via the voice widget).
    // Stored under internal_notes so operators see it in PB admin alongside
    // other operator-side annotations. A dedicated client_notes PB column
    // can be added later via a superuser schema migration.
    ...(clientNotes ? { internal_notes: clientNotes } : {}),
  };

  const fileAttachments = files.map((f) => ({
    field: "documents",
    file: f,
  }));

  try {
    await createRecordMultipart(COLLECTION, fields, fileAttachments);
  } catch (err) {
    const message = err instanceof Error ? err.message : "Unknown PB error";
    console.error("[onboarding submit] createRecord failed:", message);
    // PB returns 400 on UNIQUE INDEX violation — treat as 409 (already used).
    const isDuplicate = /unique|duplicate|already/i.test(message);
    if (isDuplicate) {
      return NextResponse.json(
        { error: "This link has already been submitted." },
        { status: 409 },
      );
    }
    return NextResponse.json(
      { error: `Submission storage failed: ${message}` },
      { status: 502 },
    );
  }

  return NextResponse.json({ reference_no: referenceNo });
}