/**
 * Who an uploaded sheet is for.
 *
 * A sheet becomes stock on one shelf, so the upload has to name a tenant and a
 * branch before it can do anything — and where those come from depends entirely
 * on who is signed in:
 *
 *   - A **Nearle Admin** works across every merchant. Nothing in their session
 *     says which one, so they are ASKED, and the upload stays blocked until
 *     they answer. Guessing here would put another merchant's products on a
 *     shop's shelf.
 *   - A **Store Admin or Store user** is already scoped by their login. Asking
 *     them to pick their own tenant would be offering a choice with one legal
 *     answer, and a chance to get it wrong.
 *
 * The branch matters as much as the tenant and is easier to forget: stock is
 * held per outlet, so a sheet uploaded against the wrong branch loads a shelf
 * nobody is standing at.
 *
 * A CATEGORY IS NOT ASKED FOR, and its absence is deliberate. It used to be the
 * third question here, and one answer was applied to every row in the sheet —
 * so a shop uploading its whole range had butter, bleach and biryani masala all
 * filed under the same aisle, and the app's category filter showed exactly that.
 * The category is now worked out per product from the catalogue team's ladder
 * (`productCategory.ts`) and resolved to an id at shelving time, which is a
 * classification and not a preference: there is nothing here for anyone to get
 * right or wrong.
 */

import { useEffect, useMemo } from 'react';
import { Selector } from '@astryxdesign/core/Selector';
import { Text } from '@astryxdesign/core/Text';
import { VStack } from '@astryxdesign/core/VStack';
import { useTenantLocations, useTenants } from '@/queries/hooks';

/** Everything an upload needs before it can be turned into stock. */
export interface ImportTarget {
  tenantid: number;
  locationid: number;
}

export interface ImportScopeProps {
  value: Partial<ImportTarget>;
  onChange: (next: Partial<ImportTarget>) => void;
  /**
   * True for a store login, whose tenant is fixed by the session.
   *
   * The tenant picker is then not merely disabled but absent: a control that
   * cannot be used is still a question, and this one has no question in it.
   */
  isTenantFixed?: boolean;
}

export function ImportScope({ value, onChange, isTenantFixed = false }: ImportScopeProps) {
  const tenants = useTenants({ pageno: 1, pagesize: 200 });
  const locations = useTenantLocations(value.tenantid);

  const tenantOptions = useMemo(
    () =>
      (tenants.data ?? [])
        .filter((tenant) => tenant.tenantid)
        .map((tenant) => ({
          value: String(tenant.tenantid),
          label: tenant.tenantname || `Tenant ${tenant.tenantid}`,
        })),
    [tenants.data],
  );

  const branchOptions = useMemo(
    () =>
      (locations.data ?? []).map((branch) => ({
        value: String(branch.locationid),
        label: branch.locationname || `Branch ${branch.locationid}`,
      })),
    [locations.data],
  );

  /**
   * A single branch is not a choice, so it is made rather than offered.
   *
   * Most merchants run one outlet. Leaving it unpicked would block the upload
   * behind a dropdown with one entry.
   */
  useEffect(() => {
    if (!value.tenantid) return;
    if (!value.locationid && branchOptions.length === 1) {
      onChange({ ...value, locationid: Number(branchOptions[0]!.value) });
    }
  }, [branchOptions, value, onChange]);

  return (
    <VStack gap={1.5}>
      {!isTenantFixed ? (
        <Selector
          label="Merchant"
          size="sm"
          options={tenantOptions}
          value={value.tenantid ? String(value.tenantid) : ''}
          placeholder={tenants.isLoading ? 'Loading merchants…' : 'Choose a merchant'}
          description="Whose catalogue this sheet is loading. Nothing is uploaded until this is set."
          onChange={(next) =>
            // Changing the merchant clears the branch with it. Keeping it
            // would leave another tenant's branch id attached to this one — an
            // id that is valid-looking and wrong.
            onChange({ tenantid: Number(next) || undefined })
          }
        />
      ) : null}

      <Selector
        label="Branch"
        size="sm"
        options={branchOptions}
        value={value.locationid ? String(value.locationid) : ''}
        placeholder={
          !value.tenantid
            ? 'Choose a merchant first'
            : locations.isLoading
              ? 'Loading branches…'
              : 'Choose a branch'
        }
        description="Where the opening stock lands. Stock is held per branch, so this decides which shelf fills."
        isDisabled={!value.tenantid}
        onChange={(next) => onChange({ ...value, locationid: Number(next) || undefined })}
      />

      {value.tenantid && branchOptions.length === 0 && !locations.isLoading ? (
        <Text type="body" size="sm" style={{ color: 'var(--color-warning, #b7860b)' }}>
          This merchant has no branches, so there is nowhere for stock to land. Create one first.
        </Text>
      ) : null}
    </VStack>
  );
}

/** True when every field an import needs has been answered. */
export function isTargetComplete(value: Partial<ImportTarget>): value is ImportTarget {
  return Boolean(value.tenantid && value.locationid);
}

/** What is still missing, in words, for a blocked-reason line. */
export function describeMissingTarget(value: Partial<ImportTarget>): string | null {
  const missing = [
    !value.tenantid ? 'a merchant' : null,
    !value.locationid ? 'a branch' : null,
  ].filter(Boolean);
  if (missing.length === 0) return null;
  return `Choose ${missing.join(', ')} before uploading — a sheet becomes stock on one shelf, and this is which.`;
}