import { useState } from "react";
import { data, type ActionFunctionArgs, type LoaderFunctionArgs } from "@remix-run/node";
import { Form, useLoaderData, useNavigation, useSearchParams } from "@remix-run/react";
import {
  Page,
  Card,
  BlockStack,
  InlineStack,
  Text,
  Button,
  Select,
  TextField,
  IndexTable,
  EmptyState,
} from "@shopify/polaris";
import { TitleBar } from "@shopify/app-bridge-react";
import type { Method } from "@prisma/client";
import { authenticate } from "../shopify.server";
import db from "../db.server";
import { writeCheckoutSnapshot } from "../services/checkout-snapshot.server";

const WEEKDAY_NAMES = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
const METHODS: Method[] = ["SHIPPING", "LOCAL_DELIVERY", "PICKUP"];

function minutesToTime(min: number): string {
  const h = Math.floor(min / 60)
    .toString()
    .padStart(2, "0");
  const m = (min % 60).toString().padStart(2, "0");
  return `${h}:${m}`;
}

function timeToMinutes(time: string): number {
  const [h, m] = time.split(":").map(Number);
  return h * 60 + m;
}

export const loader = async ({ request }: LoaderFunctionArgs) => {
  const { session } = await authenticate.admin(request);
  const url = new URL(request.url);
  const locationId = url.searchParams.get("locationId");

  const locations = await db.location.findMany({
    where: { shopDomain: session.shop },
    orderBy: { createdAt: "asc" },
  });

  const activeLocationId = locationId || locations[0]?.id || null;

  const slotTemplates = activeLocationId
    ? await db.slotTemplate.findMany({
        where: { shopDomain: session.shop, locationId: activeLocationId },
        orderBy: [{ weekday: "asc" }, { startMin: "asc" }],
      })
    : [];

  return { locations, activeLocationId, slotTemplates };
};

export const action = async ({ request }: ActionFunctionArgs) => {
  const { session, admin } = await authenticate.admin(request);
  const formData = await request.formData();
  const intent = formData.get("intent");
  const locationId = String(formData.get("locationId") || "");

  if (intent === "delete") {
    const id = String(formData.get("id") || "");
    await db.slotTemplate.deleteMany({ where: { id, shopDomain: session.shop } });
    await writeCheckoutSnapshot(admin, session.shop);
    return data({ ok: true });
  }

  const method = formData.get("method") as Method;
  const weekday = Number(formData.get("weekday"));
  const startMin = timeToMinutes(String(formData.get("startTime")));
  const endMin = timeToMinutes(String(formData.get("endTime")));
  const capacity = Number(formData.get("capacity"));
  const cutoffMin = Number(formData.get("cutoffMin") || 0);
  const leadTimeMin = Number(formData.get("leadTimeMin") || 0);
  const transitMinDaysRaw = String(formData.get("transitMinDays") || "");
  const transitMaxDaysRaw = String(formData.get("transitMaxDays") || "");

  const errors: Record<string, string> = {};
  if (!locationId) errors.locationId = "Choose a location";
  if (startMin >= endMin) errors.endTime = "End time must be after start time";
  if (!capacity || capacity < 1) errors.capacity = "Capacity must be at least 1";
  if (transitMinDaysRaw && transitMaxDaysRaw && Number(transitMinDaysRaw) > Number(transitMaxDaysRaw)) {
    errors.transitMaxDays = "Max transit days must be at least the min";
  }
  if (Object.keys(errors).length > 0) {
    return data({ errors });
  }

  await db.slotTemplate.create({
    data: {
      shopDomain: session.shop,
      locationId,
      method,
      weekday,
      startMin,
      endMin,
      capacity,
      cutoffMin,
      leadTimeMin,
      // Only meaningful for SHIPPING (PRODUCT_STRATEGY.md §2 "date ranges") —
      // stored regardless of method since a merchant might switch a
      // template's method later, but only ever read for SHIPPING.
      transitMinDays: transitMinDaysRaw ? Number(transitMinDaysRaw) : null,
      transitMaxDays: transitMaxDaysRaw ? Number(transitMaxDaysRaw) : null,
    },
  });

  await writeCheckoutSnapshot(admin, session.shop);
  return data({ ok: true });
};

export default function SlotsIndex() {
  const { locations, activeLocationId, slotTemplates } = useLoaderData<typeof loader>();
  const [, setSearchParams] = useSearchParams();
  const navigation = useNavigation();
  const isSubmitting = navigation.state === "submitting";

  if (locations.length === 0) {
    return (
      <Page>
        <TitleBar title="Weekly slots" />
        <Card>
          <EmptyState
            heading="Add a location first"
            action={{ content: "Add location", url: "/app/locations/new" }}
            image="https://cdn.shopify.com/s/files/1/0757/9955/files/empty-state.svg"
          >
            <Text as="p">Weekly slot templates belong to a location.</Text>
          </EmptyState>
        </Card>
      </Page>
    );
  }

  return (
    <Page>
      <TitleBar title="Weekly slots" />
      <BlockStack gap="400">
        <Card>
          <Select
            label="Location"
            options={locations.map((l) => ({ label: l.name, value: l.id }))}
            value={activeLocationId ?? undefined}
            onChange={(value) => setSearchParams({ locationId: value })}
          />
        </Card>

        <Card padding="0">
          {slotTemplates.length === 0 ? (
            <div style={{ padding: 16 }}>
              <Text as="p" tone="subdued">
                No slot templates yet for this location. Add one below.
              </Text>
            </div>
          ) : (
            <IndexTable
              itemCount={slotTemplates.length}
              headings={[
                { title: "Weekday" },
                { title: "Method" },
                { title: "Window" },
                { title: "Capacity" },
                { title: "Cutoff (min)" },
                { title: "Lead time (min)" },
                { title: "Transit (days)" },
                { title: "" },
              ]}
              selectable={false}
            >
              {slotTemplates.map((slot, index) => (
                <IndexTable.Row id={slot.id} key={slot.id} position={index}>
                  <IndexTable.Cell>{WEEKDAY_NAMES[slot.weekday]}</IndexTable.Cell>
                  <IndexTable.Cell>{slot.method.replace("_", " ")}</IndexTable.Cell>
                  <IndexTable.Cell>
                    {minutesToTime(slot.startMin)}–{minutesToTime(slot.endMin)}
                  </IndexTable.Cell>
                  <IndexTable.Cell>{slot.capacity}</IndexTable.Cell>
                  <IndexTable.Cell>{slot.cutoffMin}</IndexTable.Cell>
                  <IndexTable.Cell>{slot.leadTimeMin}</IndexTable.Cell>
                  <IndexTable.Cell>
                    {slot.transitMinDays != null || slot.transitMaxDays != null
                      ? `${slot.transitMinDays ?? "—"}–${slot.transitMaxDays ?? "—"}`
                      : "—"}
                  </IndexTable.Cell>
                  <IndexTable.Cell>
                    <Form method="post">
                      <input type="hidden" name="intent" value="delete" />
                      <input type="hidden" name="id" value={slot.id} />
                      <Button submit variant="plain" tone="critical">
                        Remove
                      </Button>
                    </Form>
                  </IndexTable.Cell>
                </IndexTable.Row>
              ))}
            </IndexTable>
          )}
        </Card>

        <AddSlotForm key={activeLocationId} locationId={activeLocationId ?? ""} isSubmitting={isSubmitting} />
      </BlockStack>
    </Page>
  );
}

function AddSlotForm({ locationId, isSubmitting }: { locationId: string; isSubmitting: boolean }) {
  const [startTime, setStartTime] = useState("09:00");
  const [endTime, setEndTime] = useState("17:00");
  const [capacity, setCapacity] = useState("10");
  const [cutoffMin, setCutoffMin] = useState("60");
  const [leadTimeMin, setLeadTimeMin] = useState("0");
  const [transitMinDays, setTransitMinDays] = useState("");
  const [transitMaxDays, setTransitMaxDays] = useState("");

  return (
    <Card>
      <Form method="post">
        <input type="hidden" name="locationId" value={locationId} />
        <BlockStack gap="300">
          <Text as="h3" variant="headingSm">
            Add a slot template
          </Text>
          <InlineStack gap="300" wrap>
            <Select
              label="Weekday"
              name="weekday"
              options={WEEKDAY_NAMES.map((name, value) => ({ label: name, value: String(value) }))}
            />
            <Select
              label="Method"
              name="method"
              options={METHODS.map((m) => ({ label: m.replace("_", " "), value: m }))}
            />
            <TextField
              label="Start time"
              name="startTime"
              type="time"
              value={startTime}
              onChange={setStartTime}
              autoComplete="off"
            />
            <TextField
              label="End time"
              name="endTime"
              type="time"
              value={endTime}
              onChange={setEndTime}
              autoComplete="off"
            />
            <TextField
              label="Capacity"
              name="capacity"
              type="number"
              value={capacity}
              onChange={setCapacity}
              autoComplete="off"
            />
            <TextField
              label="Cutoff (min)"
              name="cutoffMin"
              type="number"
              value={cutoffMin}
              onChange={setCutoffMin}
              autoComplete="off"
            />
            <TextField
              label="Lead time (min)"
              name="leadTimeMin"
              type="number"
              value={leadTimeMin}
              onChange={setLeadTimeMin}
              autoComplete="off"
            />
            <TextField
              label="Min transit days (Shipping only)"
              name="transitMinDays"
              type="number"
              value={transitMinDays}
              onChange={setTransitMinDays}
              autoComplete="off"
              helpText="Shown as an estimated arrival range instead of a delivery time slot."
            />
            <TextField
              label="Max transit days (Shipping only)"
              name="transitMaxDays"
              type="number"
              value={transitMaxDays}
              onChange={setTransitMaxDays}
              autoComplete="off"
            />
          </InlineStack>
          <div>
            <Button submit variant="primary" loading={isSubmitting}>
              Add slot template
            </Button>
          </div>
        </BlockStack>
      </Form>
    </Card>
  );
}