import { z } from "zod";
import { and, desc, eq, inArray } from "drizzle-orm";
import { createTRPCRouter, protectedProcedure, publicProcedure } from "../trpc";
import {
  invoices,
  invoiceItems,
  clients,
  businesses,
  platformSettings,
} from "~/server/db/schema";
import { TRPCError } from "@trpc/server";
import { generateInvoicePDFBlob } from "~/lib/pdf-export";
import { Resend } from "resend";
import { env } from "~/env";
import { generateReminderEmailTemplate } from "~/lib/email-templates/reminder-email";
import type { db } from "~/server/db";

type InvoiceRouterContext = {
  db: typeof db;
  session: { user: { id: string } };
};

const invoiceItemSchema = z.object({
  date: z.date(),
  description: z.string().min(1, "Description is required"),
  hours: z.number().min(0, "Hours must be positive"),
  rate: z.number().min(0, "Rate must be positive"),
});

const createInvoiceSchema = z.object({
  invoiceNumber: z.string().min(1, "Invoice number is required"),
  invoicePrefix: z.string().optional().default("#"),
  businessId: z
    .string()
    .min(1, "Business is required")
    .optional()
    .or(z.literal("")),
  clientId: z.string().min(1, "Client is required"),
  issueDate: z.date(),
  dueDate: z.date(),
  status: z.enum(["draft", "sent", "paid"]).default("draft"),
  notes: z.string().optional().or(z.literal("")),
  emailMessage: z.string().optional().or(z.literal("")),
  taxRate: z.number().min(0).max(100).default(0),
  currency: z.string().length(3).default("USD"),
  sendReminderAt: z.date().nullable().optional(),
  items: z.array(invoiceItemSchema).min(1, "At least one item is required"),
});

const updateInvoiceSchema = createInvoiceSchema.partial().extend({
  id: z.string(),
});

const updateStatusSchema = z.object({
  id: z.string(),
  status: z.enum(["draft", "sent", "paid"]),
});

async function verifyBusinessAccess(
  ctx: InvoiceRouterContext,
  businessId?: string | null,
) {
  if (!businessId) return null;

  const business = await ctx.db.query.businesses.findFirst({
    where: eq(businesses.id, businessId),
  });

  if (!business) {
    throw new TRPCError({
      code: "BAD_REQUEST",
      message: "Business not found",
    });
  }

  if (business.createdById !== ctx.session.user.id) {
    throw new TRPCError({
      code: "FORBIDDEN",
      message: "You don't have permission to use this business",
    });
  }

  return business;
}

async function verifyClientAccess(ctx: InvoiceRouterContext, clientId: string) {
  const client = await ctx.db.query.clients.findFirst({
    where: eq(clients.id, clientId),
  });

  if (!client) {
    throw new TRPCError({
      code: "BAD_REQUEST",
      message: "Client not found",
    });
  }

  if (client.createdById !== ctx.session.user.id) {
    throw new TRPCError({
      code: "FORBIDDEN",
      message: "You don't have permission to use this client",
    });
  }

  return client;
}

const calculateInvoiceTotal = (
  items: Array<z.infer<typeof invoiceItemSchema>>,
  taxRate: number,
) => {
  const subtotal = items.reduce((sum, item) => sum + item.hours * item.rate, 0);
  const taxAmount = (subtotal * taxRate) / 100;
  return subtotal + taxAmount;
};

export const invoicesRouter = createTRPCRouter({
  getAll: protectedProcedure
    .input(
      z.object({
        status: z.enum(["draft", "sent", "paid"]).optional(),
        clientId: z.string().optional(),
      }).optional(),
    )
    .query(async ({ ctx, input }) => {
      try {
        const conditions = [eq(invoices.createdById, ctx.session.user.id)];
        if (input?.status) conditions.push(eq(invoices.status, input.status));
        if (input?.clientId) conditions.push(eq(invoices.clientId, input.clientId));

        return await ctx.db.query.invoices.findMany({
          where: and(...conditions),
          with: {
            business: true,
            client: true,
            items: {
              orderBy: (items, { asc }) => [
                asc(items.date),
                asc(items.position),
                asc(items.createdAt),
              ],
            },
          },
          orderBy: (invoices, { desc }) => [
            desc(invoices.issueDate),
            desc(invoices.dueDate),
            desc(invoices.invoiceNumber),
          ],
        });
      } catch (error) {
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: "Failed to fetch invoices",
          cause: error,
        });
      }
    }),

  /** Draft invoices available for time-clock billing. */
  getBillable: protectedProcedure
    .input(z.object({ clientId: z.string().optional() }).optional())
    .query(async ({ ctx, input }) => {
      const conditions = [
        eq(invoices.createdById, ctx.session.user.id),
        eq(invoices.status, "draft"),
      ];
      if (input?.clientId) conditions.push(eq(invoices.clientId, input.clientId));

      return ctx.db.query.invoices.findMany({
        where: and(...conditions),
        columns: {
          id: true,
          invoiceNumber: true,
          invoicePrefix: true,
          status: true,
          clientId: true,
          issueDate: true,
          totalAmount: true,
        },
        with: {
          client: { columns: { id: true, name: true } },
        },
        orderBy: (invoices, { desc }) => [
          desc(invoices.issueDate),
          desc(invoices.dueDate),
          desc(invoices.invoiceNumber),
        ],
      });
    }),

  getLineItemHistory: protectedProcedure.query(async ({ ctx }) => {
    const userInvoices = await ctx.db
      .select({ id: invoices.id })
      .from(invoices)
      .where(eq(invoices.createdById, ctx.session.user.id));

    if (userInvoices.length === 0) return [];

    const invoiceIds = userInvoices.map((i) => i.id);
    const rows = await ctx.db
      .select({
        description: invoiceItems.description,
        hours: invoiceItems.hours,
        rate: invoiceItems.rate,
        createdAt: invoiceItems.createdAt,
      })
      .from(invoiceItems)
      .where(inArray(invoiceItems.invoiceId, invoiceIds))
      .orderBy(desc(invoiceItems.createdAt))
      .limit(500);

    // Deduplicate by description, keeping most recent occurrence
    const seen = new Set<string>();
    return rows
      .filter((r) => {
        const key = r.description.toLowerCase();
        if (seen.has(key)) return false;
        seen.add(key);
        return true;
      })
      .slice(0, 200)
      .map(({ description, hours, rate }) => ({ description, hours, rate }));
  }),

  getCurrentOpen: protectedProcedure.query(async ({ ctx }) => {
    try {
      // Get the most recent draft invoice
      const currentInvoice = await ctx.db.query.invoices.findFirst({
        where: eq(invoices.createdById, ctx.session.user.id),
        with: {
          business: true,
          client: true,
          items: {
            orderBy: (items, { asc }) => [
              asc(items.date),
              asc(items.position),
              asc(items.createdAt),
            ],
          },
        },
        orderBy: (invoices, { desc }) => [
          desc(invoices.issueDate),
          desc(invoices.dueDate),
          desc(invoices.invoiceNumber),
        ],
      });

      // Return null if no draft invoice exists
      if (currentInvoice?.status !== "draft") {
        return null;
      }

      return currentInvoice;
    } catch (error) {
      throw new TRPCError({
        code: "INTERNAL_SERVER_ERROR",
        message: "Failed to fetch current open invoice",
        cause: error,
      });
    }
  }),

  getById: protectedProcedure
    .input(z.object({ id: z.string() }))
    .query(async ({ ctx, input }) => {
      try {
        const invoice = await ctx.db.query.invoices.findFirst({
          where: eq(invoices.id, input.id),
          with: {
            business: true,
            client: true,
            items: {
              orderBy: (items, { asc }) => [
                asc(items.date),
                asc(items.position),
                asc(items.createdAt),
              ],
            },
          },
        });

        if (!invoice) {
          throw new TRPCError({
            code: "NOT_FOUND",
            message: "Invoice not found",
          });
        }

        // Check if user owns this invoice
        if (invoice.createdById !== ctx.session.user.id) {
          throw new TRPCError({
            code: "FORBIDDEN",
            message: "You don't have permission to view this invoice",
          });
        }

        return invoice;
      } catch (error) {
        if (error instanceof TRPCError) throw error;
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: "Failed to fetch invoice",
          cause: error,
        });
      }
    }),

  create: protectedProcedure
    .input(createInvoiceSchema)
    .mutation(async ({ ctx, input }) => {
      try {
        const { items, ...invoiceData } = input;
        const cleanInvoiceData = {
          ...invoiceData,
          businessId:
            !invoiceData.businessId || invoiceData.businessId.trim() === ""
              ? null
              : invoiceData.businessId,
          notes: invoiceData.notes === "" ? null : invoiceData.notes,
          emailMessage:
            invoiceData.emailMessage === "" ? null : invoiceData.emailMessage,
        };

        // Verify business exists and belongs to user (if provided)
        await verifyBusinessAccess(ctx, cleanInvoiceData.businessId);

        // Verify client exists and belongs to user
        await verifyClientAccess(ctx, cleanInvoiceData.clientId);

        const totalAmount = calculateInvoiceTotal(
          items,
          cleanInvoiceData.taxRate,
        );

        return await ctx.db.transaction(async (tx) => {
          const [invoice] = await tx
            .insert(invoices)
            .values({
              ...cleanInvoiceData,
              totalAmount,
              createdById: ctx.session.user.id,
            })
            .returning();

          if (!invoice) {
            throw new TRPCError({
              code: "INTERNAL_SERVER_ERROR",
              message: "Failed to create invoice",
            });
          }

          await tx.insert(invoiceItems).values(
            items.map((item, idx) => ({
              ...item,
              invoiceId: invoice.id,
              amount: item.hours * item.rate,
              position: idx,
            })),
          );

          return invoice;
        });
      } catch (error) {
        if (error instanceof TRPCError) throw error;
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: "Failed to create invoice",
          cause: error,
        });
      }
    }),

  update: protectedProcedure
    .input(updateInvoiceSchema)
    .mutation(async ({ ctx, input }) => {
      try {
        const { id, items, ...invoiceData } = input;

        // Clean up empty strings to null for optional string fields only
        const cleanInvoiceData = {
          ...invoiceData,
          ...(invoiceData.businessId !== undefined
            ? {
                businessId:
                  invoiceData.businessId.trim() === ""
                    ? null
                    : invoiceData.businessId,
              }
            : {}),
          ...(invoiceData.notes !== undefined
            ? { notes: invoiceData.notes === "" ? null : invoiceData.notes }
            : {}),
          ...(invoiceData.emailMessage !== undefined
            ? {
                emailMessage:
                  invoiceData.emailMessage === ""
                    ? null
                    : invoiceData.emailMessage,
              }
            : {}),
        };

        // Verify invoice exists and belongs to user
        const existingInvoice = await ctx.db.query.invoices.findFirst({
          where: eq(invoices.id, id),
        });

        if (!existingInvoice) {
          throw new TRPCError({
            code: "NOT_FOUND",
            message: "Invoice not found",
          });
        }

        if (existingInvoice.createdById !== ctx.session.user.id) {
          throw new TRPCError({
            code: "FORBIDDEN",
            message: "You don't have permission to update this invoice",
          });
        }

        if (items && existingInvoice.status !== "draft") {
          throw new TRPCError({
            code: "FORBIDDEN",
            message: "Line items can only be edited on draft invoices",
          });
        }

        if (
          cleanInvoiceData.sendReminderAt !== undefined &&
          existingInvoice.status !== "draft"
        ) {
          throw new TRPCError({
            code: "FORBIDDEN",
            message: "Send reminders can only be set on draft invoices",
          });
        }

        // If business is being updated, verify it belongs to user
        if (
          cleanInvoiceData.businessId &&
          cleanInvoiceData.businessId.trim() !== ""
        ) {
          await verifyBusinessAccess(ctx, cleanInvoiceData.businessId);
        }

        // If client is being updated, verify it belongs to user
        if (cleanInvoiceData.clientId) {
          await verifyClientAccess(ctx, cleanInvoiceData.clientId);
        }

        await ctx.db.transaction(async (tx) => {
          if (items) {
            const totalAmount = calculateInvoiceTotal(
              items,
              cleanInvoiceData.taxRate ?? existingInvoice.taxRate,
            );

            const [updatedInvoice] = await tx
              .update(invoices)
              .set({
                ...cleanInvoiceData,
                totalAmount,
                updatedAt: new Date(),
              })
              .where(eq(invoices.id, id))
              .returning();

            if (!updatedInvoice) {
              throw new TRPCError({
                code: "INTERNAL_SERVER_ERROR",
                message: "Failed to update invoice",
              });
            }

            await tx.delete(invoiceItems).where(eq(invoiceItems.invoiceId, id));

            await tx.insert(invoiceItems).values(
              items.map((item, idx) => ({
                ...item,
                invoiceId: id,
                amount: item.hours * item.rate,
                position: idx,
              })),
            );
          } else {
            const [updatedInvoice] = await tx
              .update(invoices)
              .set({
                ...cleanInvoiceData,
                updatedAt: new Date(),
              })
              .where(eq(invoices.id, id))
              .returning();

            if (!updatedInvoice) {
              throw new TRPCError({
                code: "INTERNAL_SERVER_ERROR",
                message: "Failed to update invoice",
              });
            }
          }
        });

        return { success: true };
      } catch (error) {
        if (error instanceof TRPCError) throw error;
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: "Failed to update invoice",
          cause: error,
        });
      }
    }),

  delete: protectedProcedure
    .input(z.object({ id: z.string() }))
    .mutation(async ({ ctx, input }) => {
      try {
        // Verify invoice exists and belongs to user
        const invoice = await ctx.db.query.invoices.findFirst({
          where: eq(invoices.id, input.id),
        });

        if (!invoice) {
          throw new TRPCError({
            code: "NOT_FOUND",
            message: "Invoice not found",
          });
        }

        if (invoice.createdById !== ctx.session.user.id) {
          throw new TRPCError({
            code: "FORBIDDEN",
            message: "You don't have permission to delete this invoice",
          });
        }

        // Items will be deleted automatically due to cascade
        await ctx.db.delete(invoices).where(eq(invoices.id, input.id));

        return { success: true };
      } catch (error) {
        if (error instanceof TRPCError) throw error;
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: "Failed to delete invoice",
          cause: error,
        });
      }
    }),

  updateStatus: protectedProcedure
    .input(updateStatusSchema)
    .mutation(async ({ ctx, input }) => {
      try {
        const invoice = await ctx.db.query.invoices.findFirst({
          where: eq(invoices.id, input.id),
        });

        if (!invoice) {
          throw new TRPCError({
            code: "NOT_FOUND",
            message: "Invoice not found",
          });
        }

        if (invoice.createdById !== ctx.session.user.id) {
          throw new TRPCError({
            code: "FORBIDDEN",
            message: "You don't have permission to update this invoice",
          });
        }

        await ctx.db
          .update(invoices)
          .set({ status: input.status, updatedAt: new Date() })
          .where(eq(invoices.id, input.id));

        return {
          success: true,
          message: `Invoice status updated to ${input.status}`,
        };
      } catch (error) {
        if (error instanceof TRPCError) throw error;
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: "Failed to update invoice status",
          cause: error,
        });
      }
    }),

  bulkUpdateStatus: protectedProcedure
    .input(
      z.object({
        ids: z.array(z.string()).min(1),
        status: z.enum(["draft", "sent", "paid"]),
      }),
    )
    .mutation(async ({ ctx, input }) => {
      // Only update invoices owned by this user
      const owned = await ctx.db.query.invoices.findMany({
        where: inArray(invoices.id, input.ids),
        columns: { id: true, createdById: true },
      });

      const ownedIds = owned
        .filter((inv) => inv.createdById === ctx.session.user.id)
        .map((inv) => inv.id);

      if (ownedIds.length === 0) {
        throw new TRPCError({
          code: "NOT_FOUND",
          message: "No matching invoices found",
        });
      }

      await ctx.db
        .update(invoices)
        .set({ status: input.status, updatedAt: new Date() })
        .where(inArray(invoices.id, ownedIds));

      return { success: true, updated: ownedIds.length };
    }),

  bulkDelete: protectedProcedure
    .input(z.object({ ids: z.array(z.string()).min(1) }))
    .mutation(async ({ ctx, input }) => {
      const owned = await ctx.db.query.invoices.findMany({
        where: inArray(invoices.id, input.ids),
        columns: { id: true, createdById: true },
      });

      const ownedIds = owned
        .filter((inv) => inv.createdById === ctx.session.user.id)
        .map((inv) => inv.id);

      if (ownedIds.length === 0) {
        throw new TRPCError({
          code: "NOT_FOUND",
          message: "No matching invoices found",
        });
      }

      await ctx.db.delete(invoices).where(inArray(invoices.id, ownedIds));

      return { success: true, deleted: ownedIds.length };
    }),

  previewPdf: protectedProcedure
    .input(createInvoiceSchema)
    .query(async ({ ctx, input }) => {
      try {
        const businessId =
          input.businessId && input.businessId.trim() !== ""
            ? input.businessId
            : null;
        const [client, business, settings] = await Promise.all([
          verifyClientAccess(ctx, input.clientId),
          verifyBusinessAccess(ctx, businessId),
          ctx.db.query.platformSettings.findFirst({
            where: eq(platformSettings.id, "global"),
          }),
        ]);

        const totalAmount = calculateInvoiceTotal(input.items, input.taxRate);
        const pdfBlob = await generateInvoicePDFBlob(
          {
            invoiceNumber: input.invoiceNumber,
            invoicePrefix: input.invoicePrefix,
            issueDate: input.issueDate,
            dueDate: input.dueDate,
            status: input.status,
            totalAmount,
            taxRate: input.taxRate,
            currency: input.currency,
            notes: input.notes,
            client,
            business,
            items: input.items.map((item) => ({
              date: item.date,
              description: item.description,
              hours: item.hours,
              rate: item.rate,
              amount: item.hours * item.rate,
            })),
          },
          {
            pdfTemplate: settings?.pdfTemplate as
              | "classic"
              | "minimal"
              | undefined,
            pdfAccentColor: settings?.pdfAccentColor,
            pdfFooterText: settings?.pdfFooterText,
            pdfShowLogo: settings?.pdfShowLogo,
            pdfShowPageNumbers: settings?.pdfShowPageNumbers,
          },
        );

        const buffer = Buffer.from(await pdfBlob.arrayBuffer());
        return {
          contentType: "application/pdf",
          base64: buffer.toString("base64"),
        };
      } catch (error) {
        if (error instanceof TRPCError) throw error;
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: "Failed to generate PDF preview",
          cause: error,
        });
      }
    }),

  // ── Public token (shareable link) ──────────────────────────────────────────

  generatePublicToken: protectedProcedure
    .input(z.object({ id: z.string(), ttlHours: z.number().positive().optional() }))
    .mutation(async ({ ctx, input }) => {
      const invoice = await ctx.db.query.invoices.findFirst({
        where: eq(invoices.id, input.id),
      });
      if (invoice?.createdById !== ctx.session.user.id) {
        throw new TRPCError({ code: "NOT_FOUND" });
      }
      const token = crypto.randomUUID();
      const expiresAt = input.ttlHours
        ? new Date(Date.now() + input.ttlHours * 3_600_000)
        : null;
      await ctx.db
        .update(invoices)
        .set({ publicToken: token, publicTokenExpiresAt: expiresAt })
        .where(eq(invoices.id, input.id));
      return { token, expiresAt };
    }),

  revokePublicToken: protectedProcedure
    .input(z.object({ id: z.string() }))
    .mutation(async ({ ctx, input }) => {
      const invoice = await ctx.db.query.invoices.findFirst({
        where: eq(invoices.id, input.id),
      });
      if (invoice?.createdById !== ctx.session.user.id) {
        throw new TRPCError({ code: "NOT_FOUND" });
      }
      await ctx.db
        .update(invoices)
        .set({ publicToken: null })
        .where(eq(invoices.id, input.id));
      return { success: true };
    }),

  getByPublicToken: publicProcedure
    .input(z.object({ token: z.string() }))
    .query(async ({ ctx, input }) => {
      const invoice = await ctx.db.query.invoices.findFirst({
        where: eq(invoices.publicToken, input.token),
        with: {
          client: true,
          business: true,
          items: {
            orderBy: (i, { asc }) => [
              asc(i.date),
              asc(i.position),
              asc(i.createdAt),
            ],
          },
        },
      });
      if (!invoice) throw new TRPCError({ code: "NOT_FOUND" });
      if (invoice.publicTokenExpiresAt && new Date(invoice.publicTokenExpiresAt) < new Date()) {
        throw new TRPCError({ code: "FORBIDDEN", message: "This link has expired" });
      }
      return invoice;
    }),

  // ── Send reminder ──────────────────────────────────────────────────────────

  sendReminder: protectedProcedure
    .input(z.object({ id: z.string(), customMessage: z.string().optional() }))
    .mutation(async ({ ctx, input }) => {
      const invoice = await ctx.db.query.invoices.findFirst({
        where: eq(invoices.id, input.id),
        with: { client: true, business: true },
      });
      if (invoice?.createdById !== ctx.session.user.id) {
        throw new TRPCError({ code: "NOT_FOUND" });
      }
      if (!invoice.client?.email) {
        throw new TRPCError({ code: "BAD_REQUEST", message: "Client has no email address" });
      }

      const userName =
        invoice.business?.emailFromName ?? invoice.business?.name ?? ctx.session.user.name ?? "";
      const userEmail = invoice.business?.email ?? ctx.session.user.email ?? "";

      const { html, text, subject } = generateReminderEmailTemplate({
        invoice: {
          invoiceNumber: invoice.invoiceNumber,
          issueDate: invoice.issueDate,
          dueDate: invoice.dueDate,
          totalAmount: invoice.totalAmount,
          currency: invoice.currency,
          client: { name: invoice.client.name, email: invoice.client.email },
          business: invoice.business,
        },
        customMessage: input.customMessage,
        userName,
        userEmail,
      });

      // Resolve Resend instance (same two-tier logic as email router)
      let resendInstance: Resend;
      let fromEmail: string;
      if (invoice.business?.resendApiKey && invoice.business?.resendDomain) {
        resendInstance = new Resend(invoice.business.resendApiKey);
        const fromName = invoice.business.emailFromName ?? invoice.business.name;
        fromEmail = `${fromName} <noreply@${invoice.business.resendDomain}>`;
      } else if (env.RESEND_API_KEY && env.RESEND_DOMAIN) {
        resendInstance = new Resend(env.RESEND_API_KEY);
        fromEmail = `noreply@${env.RESEND_DOMAIN}`;
      } else if (env.RESEND_API_KEY) {
        resendInstance = new Resend(env.RESEND_API_KEY);
        fromEmail = invoice.business?.email ?? "noreply@example.com";
      } else {
        throw new TRPCError({
          code: "BAD_REQUEST",
          message: "Email delivery is not configured. Add a Resend API key.",
        });
      }

      const result = await resendInstance.emails.send({
        from: fromEmail,
        to: [invoice.client.email],
        subject,
        html,
        text,
      });

      if (result.error) {
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: result.error.message,
        });
      }

      await ctx.db
        .update(invoices)
        .set({ lastReminderSentAt: new Date() })
        .where(eq(invoices.id, input.id));

      return { sent: true };
    }),
});