/**
 * 功能：为资源表单和详情页加载、缓存并搜索关联资源选项。
 * 版本：v1.1.0
 */
import { Message } from '@arco-design/web-vue';
import { onBeforeUnmount, reactive } from 'vue';
import { resourceApi } from '@/api/resource';
import {
  staffRelationFilters,
  type StaffRelationContext,
} from '@/api/resource-staff-relation';
import type { ResourceField } from '@/api/resources';
import type { ResourceRow } from '@/api/resource-page-rules';
import { fieldRelationResource } from '@/api/resource-display';
import { relationDisplayName } from '../shared/resource-list-field-display';
import { createRelationRequestVersionGuard } from './resource-relation-linkage-policy';

export type ResourceRelationLoadOptions = {
  filters?: Record<string, string>;
  preserveIdentities?: string[];
};

export function useResourceRelations(
  context: () => StaffRelationContext = () => ({}),
) {
  const options = reactive<Record<string, ResourceRow[]>>({});
  const loading = reactive<Record<string, boolean>>({});
  const timers = new Map<string, ReturnType<typeof setTimeout>>();
  const requestGuard = createRelationRequestVersionGuard();

  /** 合并需要保留的当前选项，搜索和筛选时不让下拉框退回显示原始标识。 */
  function mergePreserved(
    resource: string,
    rows: ResourceRow[],
    identities: string[] = [],
  ) {
    const merged = [...rows];
    const seen = new Set(rows.map((row) => String(row.identity ?? '')));
    for (const identity of identities.filter(Boolean)) {
      if (seen.has(identity)) continue;
      const current = (options[resource] ?? []).find(
        (row) => String(row.identity ?? '') === identity,
      );
      if (current) {
        merged.push(current);
        seen.add(identity);
      }
    }
    return merged;
  }

  /** 加载一类关联资源，并丢弃已经过期的搜索或筛选响应。 */
  async function load(
    resource: string,
    keyword = '',
    request: ResourceRelationLoadOptions = {},
  ) {
    const version = requestGuard.begin(resource);
    loading[resource] = true;
    try {
      const filters: Record<string, string> = {
        ...(request.filters ?? {}),
        ...(keyword ? { keyword } : {}),
      };
      const rows = (
        await resourceApi.list<ResourceRow>(resource, 1, 100, filters)
      ).list;
      if (!requestGuard.isLatest(resource, version)) return;
      options[resource] = mergePreserved(
        resource,
        rows,
        request.preserveIdentities,
      );
    } catch (error) {
      if (!requestGuard.isLatest(resource, version)) return;
      Message.error(`关联数据加载失败：${(error as Error).message}`);
    } finally {
      if (requestGuard.isLatest(resource, version)) {
        loading[resource] = false;
      }
    }
  }

  /** 按字段的显式关系策略加载选项，工作人员字段不得依赖全局默认值。 */
  function loadField(
    field: ResourceField,
    keyword = '',
    request: ResourceRelationLoadOptions = {},
  ) {
    if (!field.relation) return Promise.resolve();
    return load(field.relation, keyword, {
      ...request,
      filters: {
        ...(field.relationFilters ?? {}),
        ...staffRelationFilters(field, context()),
        ...(request.filters ?? {}),
      },
    });
  }

  /** 按唯一标识补载当前选项，解决编辑记录不在列表前 100 条时的回显。 */
  async function ensure(resource: string, identity: string) {
    if (!identity) return undefined;
    const current = (options[resource] ?? []).find(
      (row) => String(row.identity ?? '') === identity,
    );
    if (current) return current;
    try {
      const row = await resourceApi.detail<ResourceRow>(resource, identity);
      const resolved = (options[resource] ?? []).find(
        (item) => String(item.identity ?? '') === identity,
      );
      if (resolved) return resolved;
      options[resource] = [...(options[resource] ?? []), row];
      return row;
    } catch (error) {
      Message.error(`关联数据加载失败：${(error as Error).message}`);
      return undefined;
    }
  }

  /** 预加载当前页面实际使用的全部关系字段。 */
  async function preload(fields: ResourceField[]) {
    const fieldsByResource = new Map<string, ResourceField>();
    for (const field of fields) {
      if (field.relation && !fieldsByResource.has(field.relation)) {
        fieldsByResource.set(field.relation, field);
      }
    }
    await Promise.all(
      [...fieldsByResource.values()].map((field) => loadField(field)),
    );
  }

  /** 补载表单或详情中已经保存的关系值，避免分页和筛选导致回显裸标识。 */
  async function ensureValues(fields: ResourceField[], values: ResourceRow) {
    const requests = fields.flatMap((field) => {
      // 服务端已在当前业务记录范围内返回名称时，不再重复补载关联用户。
      if (relationDisplayName(field, values)) return [];
      const resource = fieldRelationResource(field, values);
      if (!resource) return [];
      const value = values[field.key];
      const identities = Array.isArray(value) ? value : [value];
      return identities
        .map((identity) => String(identity ?? ''))
        .filter(Boolean)
        .map((identity) => ensure(resource, identity));
    });
    await Promise.all(requests);
  }

  /** 对远程关系选项进行防抖搜索。 */
  function search(
    resource: string | undefined,
    keyword: string,
    request: ResourceRelationLoadOptions = {},
  ) {
    if (!resource) return;
    cancelSearch(resource);
    timers.set(
      resource,
      setTimeout(() => {
        timers.delete(resource);
        void load(resource, keyword.trim(), request);
      }, 250),
    );
  }

  /** 按字段的显式关系策略执行防抖搜索。 */
  function searchField(
    field: ResourceField,
    keyword: string,
    request: ResourceRelationLoadOptions = {},
  ) {
    if (!field.relation) return;
    search(field.relation, keyword, {
      ...request,
      filters: {
        ...(field.relationFilters ?? {}),
        ...staffRelationFilters(field, context()),
        ...(request.filters ?? {}),
      },
    });
  }

  /** 取消关联资源尚未触发的防抖搜索。 */
  function cancelSearch(resource: string) {
    const timer = timers.get(resource);
    if (timer) clearTimeout(timer);
    timers.delete(resource);
  }

  /** 清空依赖父级但当前尚无有效父级的候选项。 */
  function clear(resource: string | undefined) {
    if (!resource) return;
    cancelSearch(resource);
    requestGuard.begin(resource);
    options[resource] = [];
    loading[resource] = false;
  }

  onBeforeUnmount(() => {
    for (const resource of timers.keys()) cancelSearch(resource);
  });

  return {
    options,
    loading,
    load,
    loadField,
    ensure,
    ensureValues,
    preload,
    search,
    searchField,
    cancelSearch,
    clear,
  };
}

export type ResourceRelations = ReturnType<typeof useResourceRelations>;