import { useMemo, useState } from 'react';
import { useMutation, useQueryClient } from '@tanstack/react-query';
import { VStack } from '@astryxdesign/core/VStack';
import { Bike, Check, Truck } from 'lucide-react';
import { errorMessage } from '@/api/client';
import { tenantsApi } from '@/api/tenants';
import { useAllPartners, useAppRegions } from '@/queries/hooks';
import { queryKeys } from '@/queries/keys';
import { Drawer } from '@/features/store-admin/Drawer';
import { Alert, DrawerButton, DrawerCard, Note, Row, Section } from '@/features/store-admin/drawerKit';

/**
 * Which delivery partner supplies a merchant's riders.
 *
 * ── Why this is the platform's decision ─────────────────────────────────────
 *
 * `partnerid` is kept out of the merchant-editable allowlist on the server, so
 * this cannot be done from the shop's own profile — a merchant who could set it
 * would move themselves under another partner's riders and billing. It is
 * changed here, by whoever is looking at that merchant's record.
 *
 * ── Why "own riders" is an option and not an absence ────────────────────────
 *
 * Sending `partnerid: 0` is a real instruction: it means the shop delivers with
 * riders it hired itself. The server reads a zero as sent rather than as a
 * missing field, which is exactly why the endpoint is separate — everywhere
 * else in the tenant API a zero means "not supplied", and there it would
 * silently unassign somebody.
 *
 * One partner per merchant, which is what `tenants.partnerid` allows and what
 * the assign picker later branches on. A partner serving several merchants is
 * the ordinary case in the other direction: 44 supplies 48 shops.
 */
export function PartnerAssignDrawer({
  tenantid,
  tenantname,
  currentPartnerId,
  onClose,
}: {
  tenantid: number;
  tenantname: string;
  currentPartnerId: number;
  onClose: () => void;
}) {
  const client = useQueryClient();
  const partners = useAllPartners();
  const regions = useAppRegions();
  const [chosen, setChosen] = useState<number>(currentPartnerId);
  const [error, setError] = useState<string | null>(null);

  const regionName = useMemo(() => {
    const map = new Map<number, string>();
    for (const region of regions.data ?? []) {
      map.set(region.applocationid, region.locationname ?? `Region ${region.applocationid}`);
    }
    return map;
  }, [regions.data]);

  const save = useMutation({
    mutationFn: () => tenantsApi.assignPartner(tenantid, chosen),
    onSuccess: async () => {
      await client.invalidateQueries({ queryKey: queryKeys.tenants.all });
      onClose();
    },
    onError: (cause) => setError(errorMessage(cause)),
  });

  const current = partners.data.find((p) => p.partnerid === currentPartnerId);

  return (
    <Drawer
      title="Delivery partner"
      subtitle={tenantname}
      width={460}
      onClose={onClose}
      isFooterSpread
      footer={
        <>
          <DrawerButton label="Cancel" variant="ghost" onClick={onClose} />
          <DrawerButton
            label={save.isPending ? 'Saving…' : 'Save'}
            variant="primary"
            icon={<Truck size={15} />}
            isDisabled={save.isPending || chosen === currentPartnerId}
            onClick={() => save.mutate()}
          />
        </>
      }
    >
      <VStack gap={2}>
        {error ? <Alert>{error}</Alert> : null}

        <Note icon={<Bike size={15} />}>
          A partner supplies riders to this shop. With one set, the assign screen offers the
          partner’s riders alongside any the shop hired itself; without one, only its own.
        </Note>

        <Section title="Currently">
          <DrawerCard>
            <Row
              label="Partner"
              value={current?.partnername ?? (currentPartnerId > 0 ? `Partner ${currentPartnerId}` : 'Own riders only')}
            />
          </DrawerCard>
        </Section>

        <Section title="Change to">
          <DrawerCard>
            {/* "Own riders" first and always present. It is not the empty state
                — a shop that hires its own riders is a real arrangement, and
                the option has to be as reachable as any partner. */}
            <Choice
              label="Own riders only"
              detail="This shop delivers with riders it hired itself."
              isChosen={chosen === 0}
              onChoose={() => setChosen(0)}
            />
            {partners.isLoading ? (
              <Row label="Partners" value="Reading…" />
            ) : (
              partners.data.map((partner) => (
                <Choice
                  key={partner.partnerid}
                  label={partner.partnername ?? `Partner ${partner.partnerid}`}
                  detail={
                    [
                      regionName.get(partner.applocationid ?? 0),
                      partner.companyname,
                    ]
                      .filter(Boolean)
                      .join(' · ') || 'No region recorded'
                  }
                  isChosen={chosen === partner.partnerid}
                  onChoose={() => setChosen(partner.partnerid)}
                />
              ))
            )}
          </DrawerCard>
        </Section>
      </VStack>
    </Drawer>
  );
}

function Choice({
  label,
  detail,
  isChosen,
  onChoose,
}: {
  label: string;
  detail: string;
  isChosen: boolean;
  onChoose: () => void;
}) {
  return (
    <button
      type="button"
      onClick={onChoose}
      style={{
        display: 'flex',
        alignItems: 'center',
        gap: 12,
        width: '100%',
        padding: '12px 14px',
        border: 0,
        borderTop: '1px solid var(--color-line)',
        background: isChosen ? 'var(--color-brand-tint)' : 'transparent',
        cursor: 'pointer',
        textAlign: 'left',
      }}
    >
      <span
        aria-hidden
        style={{
          width: 18,
          height: 18,
          flex: 'none',
          borderRadius: 999,
          display: 'grid',
          placeItems: 'center',
          border: isChosen ? 0 : '1.5px solid var(--color-line)',
          background: isChosen ? 'var(--color-brand)' : 'transparent',
          color: '#fff',
        }}
      >
        {isChosen ? <Check size={11} strokeWidth={3} /> : null}
      </span>
      <span style={{ display: 'flex', flexDirection: 'column', gap: 2, minWidth: 0 }}>
        <span
          style={{
            font: '500 13.5px/1.4 var(--font-sans)',
            color: isChosen ? 'var(--color-brand)' : 'var(--color-ink-1)',
          }}
        >
          {label}
        </span>
        <span style={{ font: '400 12px/1.4 var(--font-sans)', color: 'var(--color-ink-3)' }}>
          {detail}
        </span>
      </span>
    </button>
  );
}