import type { FastifyInstance } from 'fastify';
import { z } from 'zod';
import { and, asc, desc, eq, inArray, sql } from 'drizzle-orm';
import {
  getDb,
  invoices,
  invoiceItems,
  clients,
  cases,
  timeEntries,
  firms,
} from '@lawdesk/db';
import { loadFirm } from '../lib/firm';
import { assertCanCreateInvoice, PlanLimitError } from '../lib/plan-limits';
import { nextInvoiceNumber } from '../lib/invoice-numbering';
import { renderInvoicePdf } from '../lib/invoice-pdf';
import { sendEmail, invoiceEmail, invoicePaidEmail } from '../lib/email';

const STATUSES = ['draft', 'sent', 'paid', 'overdue', 'void'] as const;

const itemBody = z.object({
  description: z.string().min(1).max(500),
  quantity: z.coerce.number().positive().default(1),
  rate: z.coerce.number().nonnegative(),
});

const createBody = z.object({
  clientId: z.string().uuid(),
  caseId: z.string().uuid().nullable().optional(),
  notes: z.string().max(5000).nullable().optional(),
  taxRate: z.coerce.number().min(0).max(100).default(0),
  dueAt: z.string().datetime().nullable().optional(),
  // Either provide explicit items or supply timeEntryIds to generate items from time entries.
  items: z.array(itemBody).max(200).optional(),
  timeEntryIds: z.array(z.string().uuid()).max(200).optional(),
});

const updateBody = z.object({
  notes: z.string().max(5000).nullable().optional(),
  taxRate: z.coerce.number().min(0).max(100).optional(),
  dueAt: z.string().datetime().nullable().optional(),
});

const listQuery = z.object({
  status: z.enum(STATUSES).optional(),
  clientId: z.string().uuid().optional(),
  caseId: z.string().uuid().optional(),
  limit: z.coerce.number().int().positive().max(200).default(50),
  offset: z.coerce.number().int().min(0).default(0),
});

interface ItemAccumulator {
  description: string;
  quantity: string;
  rate: string;
  amount: string;
  sortOrder: number;
  timeEntryId?: string;
}

function round2(n: number): number {
  return Math.round(n * 100) / 100;
}

function computeTotals(items: { quantity: string; rate: string; amount: string }[], taxRate: number) {
  const subtotal = items.reduce((acc, it) => acc + Number(it.amount), 0);
  const total = round2(subtotal * (1 + taxRate / 100));
  return { subtotal: round2(subtotal), total };
}

export async function invoicesRoutes(app: FastifyInstance) {
  app.addHook('preHandler', app.requireFirm);

  // List
  app.get('/api/invoices', async (req) => {
    const firmId = req.user!.firmId!;
    const { status, clientId, caseId, limit, offset } = listQuery.parse(req.query);
    const db = getDb();

    const filters = [eq(invoices.firmId, firmId)];
    if (status) filters.push(eq(invoices.status, status));
    if (clientId) filters.push(eq(invoices.clientId, clientId));
    if (caseId) filters.push(eq(invoices.caseId, caseId));
    const where = and(...filters);

    const rows = await db
      .select({
        id: invoices.id,
        number: invoices.number,
        status: invoices.status,
        total: invoices.total,
        subtotal: invoices.subtotal,
        issuedAt: invoices.issuedAt,
        dueAt: invoices.dueAt,
        paidAt: invoices.paidAt,
        createdAt: invoices.createdAt,
        clientId: invoices.clientId,
        clientName: clients.name,
        caseId: invoices.caseId,
        caseTitle: cases.title,
      })
      .from(invoices)
      .innerJoin(clients, eq(clients.id, invoices.clientId))
      .leftJoin(cases, eq(cases.id, invoices.caseId))
      .where(where)
      .orderBy(desc(invoices.createdAt))
      .limit(limit)
      .offset(offset);

    const [count] = await db
      .select({ total: sql<number>`count(*)::int` })
      .from(invoices)
      .where(where);

    return { items: rows, total: count?.total ?? 0 };
  });

  // Summary — outstanding total across sent + overdue invoices
  app.get('/api/invoices/summary', async (req) => {
    const firmId = req.user!.firmId!;
    const [row] = await getDb()
      .select({ outstanding: sql<string>`COALESCE(SUM(${invoices.total}), 0)` })
      .from(invoices)
      .where(and(eq(invoices.firmId, firmId), inArray(invoices.status, ['sent', 'overdue'])));
    return { outstanding: row?.outstanding ?? '0' };
  });

  // Get with items
  app.get('/api/invoices/:id', async (req, reply) => {
    const firmId = req.user!.firmId!;
    const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
    const db = getDb();

    const [inv] = await db
      .select({
        id: invoices.id,
        number: invoices.number,
        status: invoices.status,
        subtotal: invoices.subtotal,
        taxRate: invoices.taxRate,
        total: invoices.total,
        notes: invoices.notes,
        issuedAt: invoices.issuedAt,
        dueAt: invoices.dueAt,
        paidAt: invoices.paidAt,
        createdAt: invoices.createdAt,
        clientId: invoices.clientId,
        clientName: clients.name,
        clientEmail: clients.email,
        caseId: invoices.caseId,
        caseTitle: cases.title,
      })
      .from(invoices)
      .innerJoin(clients, eq(clients.id, invoices.clientId))
      .leftJoin(cases, eq(cases.id, invoices.caseId))
      .where(and(eq(invoices.id, id), eq(invoices.firmId, firmId)))
      .limit(1);

    if (!inv) return reply.code(404).send({ error: 'not_found' });

    const items = await db
      .select()
      .from(invoiceItems)
      .where(eq(invoiceItems.invoiceId, inv.id))
      .orderBy(asc(invoiceItems.sortOrder));

    return { ...inv, items };
  });

  // Create
  app.post('/api/invoices', async (req, reply) => {
    const firmId = req.user!.firmId!;
    const firm = await loadFirm(firmId);
    if (!firm) return reply.code(403).send({ error: 'firm_missing' });

    try {
      await assertCanCreateInvoice(firmId, firm.plan);
    } catch (e) {
      if (e instanceof PlanLimitError) return reply.code(402).send({ error: e.message, plan: firm.plan });
      throw e;
    }

    const body = createBody.parse(req.body);
    const db = getDb();

    // Validate client belongs to firm
    const [client] = await db
      .select({ id: clients.id })
      .from(clients)
      .where(and(eq(clients.id, body.clientId), eq(clients.firmId, firmId)))
      .limit(1);
    if (!client) return reply.code(400).send({ error: 'invalid_client' });

    // Validate case belongs to firm (and to client) if provided
    if (body.caseId) {
      const [c] = await db
        .select({ id: cases.id })
        .from(cases)
        .where(and(eq(cases.id, body.caseId), eq(cases.firmId, firmId), eq(cases.clientId, body.clientId)))
        .limit(1);
      if (!c) return reply.code(400).send({ error: 'invalid_case' });
    }

    // Build line items
    const accumulated: ItemAccumulator[] = [];

    if (body.items && body.items.length) {
      body.items.forEach((it, i) => {
        accumulated.push({
          description: it.description,
          quantity: String(it.quantity),
          rate: String(it.rate),
          amount: String(round2(it.quantity * it.rate)),
          sortOrder: i,
        });
      });
    }

    if (body.timeEntryIds && body.timeEntryIds.length) {
      const entries = await db
        .select({
          id: timeEntries.id,
          description: timeEntries.description,
          minutes: timeEntries.minutes,
          rate: timeEntries.rate,
          billable: timeEntries.billable,
          invoiceItemId: timeEntries.invoiceItemId,
          caseId: timeEntries.caseId,
        })
        .from(timeEntries)
        .where(and(eq(timeEntries.firmId, firmId), inArray(timeEntries.id, body.timeEntryIds)));

      if (entries.length !== body.timeEntryIds.length) {
        return reply.code(400).send({ error: 'invalid_time_entries' });
      }
      for (const e of entries) {
        if (e.invoiceItemId) return reply.code(409).send({ error: 'time_entry_already_invoiced' });
        if (!e.billable) return reply.code(400).send({ error: 'time_entry_not_billable' });
        if (body.caseId && e.caseId !== body.caseId) {
          return reply.code(400).send({ error: 'time_entry_case_mismatch' });
        }
      }

      const startSort = accumulated.length;
      entries.forEach((e, i) => {
        const hours = round2(e.minutes / 60);
        const rate = Number(e.rate);
        accumulated.push({
          description: e.description,
          quantity: String(hours),
          rate: String(rate),
          amount: String(round2(hours * rate)),
          sortOrder: startSort + i,
          timeEntryId: e.id,
        });
      });
    }

    if (!accumulated.length) {
      return reply.code(400).send({ error: 'no_items' });
    }

    const taxRate = body.taxRate;
    const totals = computeTotals(accumulated, taxRate);

    const created = await db.transaction(async (tx) => {
      // Generate the number inside the transaction: the advisory lock it takes must be held
      // until this insert commits, so concurrent creates serialise and never collide.
      const number = await nextInvoiceNumber(tx, firmId);
      const [inv] = await tx
        .insert(invoices)
        .values({
          firmId,
          clientId: body.clientId,
          caseId: body.caseId ?? null,
          number,
          status: 'draft',
          subtotal: String(totals.subtotal),
          taxRate: String(taxRate),
          total: String(totals.total),
          notes: body.notes ?? null,
          dueAt: body.dueAt ? new Date(body.dueAt) : null,
        })
        .returning();
      if (!inv) throw new Error('invoice_insert_failed');

      const insertedItems = await tx
        .insert(invoiceItems)
        .values(
          accumulated.map((a) => ({
            invoiceId: inv.id,
            description: a.description,
            quantity: a.quantity,
            rate: a.rate,
            amount: a.amount,
            sortOrder: a.sortOrder,
          })),
        )
        .returning();

      // Link the time entries (when generated from time) to their new invoice items
      const updates: Array<Promise<unknown>> = [];
      accumulated.forEach((a, i) => {
        if (!a.timeEntryId) return;
        const item = insertedItems[i];
        if (!item) return;
        updates.push(
          tx
            .update(timeEntries)
            .set({ invoiceItemId: item.id, updatedAt: new Date() })
            .where(eq(timeEntries.id, a.timeEntryId)),
        );
      });
      await Promise.all(updates);

      return inv;
    });

    return reply.code(201).send(created);
  });

  // Update (notes, dueAt, taxRate; only on drafts)
  app.patch('/api/invoices/:id', async (req, reply) => {
    const firmId = req.user!.firmId!;
    const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
    const body = updateBody.parse(req.body);
    const db = getDb();

    const [existing] = await db
      .select()
      .from(invoices)
      .where(and(eq(invoices.id, id), eq(invoices.firmId, firmId)))
      .limit(1);
    if (!existing) return reply.code(404).send({ error: 'not_found' });
    if (existing.status !== 'draft') return reply.code(409).send({ error: 'invoice_not_draft' });

    const patch: Record<string, unknown> = { updatedAt: new Date() };
    if (body.notes !== undefined) patch.notes = body.notes;
    if (body.dueAt !== undefined) patch.dueAt = body.dueAt ? new Date(body.dueAt) : null;

    if (body.taxRate !== undefined) {
      patch.taxRate = String(body.taxRate);
      const items = await db.select().from(invoiceItems).where(eq(invoiceItems.invoiceId, id));
      const totals = computeTotals(items, body.taxRate);
      patch.subtotal = String(totals.subtotal);
      patch.total = String(totals.total);
    }

    const [row] = await db.update(invoices).set(patch).where(eq(invoices.id, id)).returning();
    return row;
  });

  // Send (draft → sent, set issuedAt). Emails the client with the PDF attached if we have
  // their email on file. Email failure does not block the status change.
  app.post('/api/invoices/:id/send', async (req, reply) => {
    const firmId = req.user!.firmId!;
    const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
    const db = getDb();

    const [existing] = await db
      .select()
      .from(invoices)
      .where(and(eq(invoices.id, id), eq(invoices.firmId, firmId)))
      .limit(1);
    if (!existing) return reply.code(404).send({ error: 'not_found' });
    if (existing.status !== 'draft') return reply.code(409).send({ error: 'invoice_not_draft' });

    const now = new Date();
    const [row] = await db
      .update(invoices)
      .set({ status: 'sent', issuedAt: now, updatedAt: now })
      .where(eq(invoices.id, id))
      .returning();
    if (!row) return reply.code(500).send({ error: 'update_failed' });

    // Render PDF + email the client (best-effort).
    try {
      const [client] = await db.select().from(clients).where(eq(clients.id, row.clientId)).limit(1);
      const [firm] = await db.select().from(firms).where(eq(firms.id, firmId)).limit(1);
      if (!client?.email || !firm) {
        app.log.info({ invoiceId: id }, 'invoice sent, skipped email (no client email or firm missing)');
        return row;
      }

      const items = await db
        .select()
        .from(invoiceItems)
        .where(eq(invoiceItems.invoiceId, id))
        .orderBy(asc(invoiceItems.sortOrder));

      const pdfStream = renderInvoicePdf({
        number: row.number,
        status: row.status,
        issuedAt: row.issuedAt,
        dueAt: row.dueAt,
        notes: row.notes,
        subtotal: row.subtotal,
        taxRate: row.taxRate,
        total: row.total,
        firm: { name: firm.name },
        client: { name: client.name, email: client.email, address: client.address },
        items: items.map((it) => ({
          description: it.description,
          quantity: it.quantity,
          rate: it.rate,
          amount: it.amount,
        })),
        watermark: firm.watermarkEnabled,
      });

      // Collect the PDF stream into a buffer.
      const chunks: Buffer[] = [];
      for await (const chunk of pdfStream as AsyncIterable<Buffer | string>) {
        chunks.push(typeof chunk === 'string' ? Buffer.from(chunk) : chunk);
      }
      const pdfBuffer = Buffer.concat(chunks);

      const totalFmt = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(
        Number(row.total),
      );
      const dueDate = row.dueAt ? row.dueAt.toLocaleDateString('en-US', { year: 'numeric', month: 'short', day: 'numeric' }) : null;

      const tpl = invoiceEmail({
        clientName: client.name,
        firmName: firm.name,
        invoiceNumber: row.number,
        total: totalFmt,
        dueDate,
        notes: row.notes,
      });

      sendEmail({
        to: client.email,
        ...tpl,
        attachments: [{ filename: `${row.number}.pdf`, content: pdfBuffer }],
      }).catch((err) => app.log.warn({ err, invoiceId: id }, 'invoice email failed'));
    } catch (err) {
      app.log.warn({ err, invoiceId: id }, 'failed to render/send invoice email');
    }

    return row;
  });

  // Mark paid
  app.post('/api/invoices/:id/mark-paid', async (req, reply) => {
    const firmId = req.user!.firmId!;
    const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
    const db = getDb();

    const [existing] = await db
      .select()
      .from(invoices)
      .where(and(eq(invoices.id, id), eq(invoices.firmId, firmId)))
      .limit(1);
    if (!existing) return reply.code(404).send({ error: 'not_found' });
    if (!['sent', 'overdue'].includes(existing.status)) {
      return reply.code(409).send({ error: 'invoice_not_sent' });
    }

    const now = new Date();
    const [row] = await db
      .update(invoices)
      .set({ status: 'paid', paidAt: now, updatedAt: now })
      .where(eq(invoices.id, id))
      .returning();

    // Payment receipt to the client (best-effort).
    if (row) {
      try {
        const [client] = await db.select().from(clients).where(eq(clients.id, row.clientId)).limit(1);
        const [firm] = await db.select().from(firms).where(eq(firms.id, firmId)).limit(1);
        if (client?.email && firm) {
          const totalFmt = new Intl.NumberFormat('en-US', {
            style: 'currency',
            currency: 'USD',
          }).format(Number(row.total));
          const tpl = invoicePaidEmail({
            clientName: client.name,
            firmName: firm.name,
            invoiceNumber: row.number,
            total: totalFmt,
          });
          sendEmail({ to: client.email, ...tpl }).catch((err) =>
            app.log.warn({ err, invoiceId: id }, 'invoice paid email failed'),
          );
        }
      } catch (err) {
        app.log.warn({ err, invoiceId: id }, 'failed to send invoice paid email');
      }
    }

    return row;
  });

  // Void
  app.post('/api/invoices/:id/void', async (req, reply) => {
    const firmId = req.user!.firmId!;
    const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
    const db = getDb();

    const [existing] = await db
      .select()
      .from(invoices)
      .where(and(eq(invoices.id, id), eq(invoices.firmId, firmId)))
      .limit(1);
    if (!existing) return reply.code(404).send({ error: 'not_found' });
    if (existing.status === 'paid') return reply.code(409).send({ error: 'invoice_already_paid' });

    const [row] = await db
      .update(invoices)
      .set({ status: 'void', updatedAt: new Date() })
      .where(eq(invoices.id, id))
      .returning();
    return row;
  });

  // Delete (drafts only) — also unlinks time entries
  app.delete('/api/invoices/:id', async (req, reply) => {
    const firmId = req.user!.firmId!;
    const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
    const db = getDb();

    const [existing] = await db
      .select()
      .from(invoices)
      .where(and(eq(invoices.id, id), eq(invoices.firmId, firmId)))
      .limit(1);
    if (!existing) return reply.code(404).send({ error: 'not_found' });
    if (existing.status !== 'draft') return reply.code(409).send({ error: 'invoice_not_draft' });

    await db.transaction(async (tx) => {
      const items = await tx
        .select({ id: invoiceItems.id })
        .from(invoiceItems)
        .where(eq(invoiceItems.invoiceId, id));
      const itemIds = items.map((i) => i.id);
      if (itemIds.length) {
        await tx
          .update(timeEntries)
          .set({ invoiceItemId: null, updatedAt: new Date() })
          .where(inArray(timeEntries.invoiceItemId, itemIds));
      }
      await tx.delete(invoiceItems).where(eq(invoiceItems.invoiceId, id));
      await tx.delete(invoices).where(eq(invoices.id, id));
    });

    return { ok: true };
  });

  // PDF download
  app.get(
    '/api/invoices/:id/pdf',
    { config: { rateLimit: { max: 60, timeWindow: '1 hour' } } },
    async (req, reply) => {
    const firmId = req.user!.firmId!;
    const { id } = z.object({ id: z.string().uuid() }).parse(req.params);
    const db = getDb();

    const [inv] = await db
      .select({
        invoice: invoices,
        client: clients,
        firm: firms,
      })
      .from(invoices)
      .innerJoin(clients, eq(clients.id, invoices.clientId))
      .innerJoin(firms, eq(firms.id, invoices.firmId))
      .where(and(eq(invoices.id, id), eq(invoices.firmId, firmId)))
      .limit(1);
    if (!inv) return reply.code(404).send({ error: 'not_found' });

    const items = await db
      .select()
      .from(invoiceItems)
      .where(eq(invoiceItems.invoiceId, id))
      .orderBy(asc(invoiceItems.sortOrder));

    const stream = renderInvoicePdf({
      number: inv.invoice.number,
      status: inv.invoice.status,
      issuedAt: inv.invoice.issuedAt,
      dueAt: inv.invoice.dueAt,
      notes: inv.invoice.notes,
      subtotal: inv.invoice.subtotal,
      taxRate: inv.invoice.taxRate,
      total: inv.invoice.total,
      firm: { name: inv.firm.name },
      client: { name: inv.client.name, email: inv.client.email, address: inv.client.address },
      items: items.map((it) => ({
        description: it.description,
        quantity: it.quantity,
        rate: it.rate,
        amount: it.amount,
      })),
      watermark: inv.firm.watermarkEnabled,
    });

    reply
      .header('Content-Type', 'application/pdf')
      .header('Content-Disposition', `inline; filename="${inv.invoice.number}.pdf"`);
    return reply.send(stream);
  });
}