import type {
  BaseSeDto,
  DisplaySlot,
  SeDraftBase,
  SeGridConfig,
  SeGridState,
  SeRowState,
} from "./grid-types";

export function createLoadedRowKey(index: number, code: string): string {
  return `loaded-${index}-${code}`;
}

export function createDraftRowKey(): string {
  return `draft-${Date.now()}-${Math.random().toString(36).slice(2, 9)}`;
}

export function createSeGridUtils<
  TDto extends BaseSeDto,
  TBaseEntry extends TDto & { rowKey: string },
  TRow extends TBaseEntry & SeRowState,
  TDraft extends SeDraftBase,
  TPatch extends Partial<TDto>,
  TSaveDto,
>(config: SeGridConfig<TDto, TBaseEntry, TRow, TDraft, TPatch, TSaveDto>) {
  function createEmptyGridState(): SeGridState<TDto, TBaseEntry, TDraft, TPatch> {
    return {
      baseByKey: {},
      structure: [],
      drafts: {},
      patches: {},
      deletedKeys: new Set(),
    };
  }

  function toInitialRow(entry: TBaseEntry): TRow {
    return {
      ...entry,
      isNew: false,
      isDirty: false,
      isDeleted: false,
    } as unknown as TRow;
  }

  function buildStructureFromBaseRows(baseByKey: Record<string, TBaseEntry>): DisplaySlot[] {
    const rows = Object.values(baseByKey).map(toInitialRow);
    const display = config.buildDisplayRows(rows);
    const cdToRowKey = new Map(rows.map((row) => [config.getCode(row), row.rowKey]));

    return display.map(({ row, depth }) => ({
      rowKey: row.rowKey,
      depth,
      parentRowKey: config.getParentCode(row)?.trim()
        ? (cdToRowKey.get(config.getParentCode(row)!.trim()) ?? null)
        : null,
    }));
  }

  function hydrateGridFromServer(content: TDto[]): SeGridState<TDto, TBaseEntry, TDraft, TPatch> {
    const baseByKey: Record<string, TBaseEntry> = {};

    content.forEach((item, index) => {
      const rowKey = createLoadedRowKey(index, config.getCode(item));
      baseByKey[rowKey] = { ...item, rowKey } as TBaseEntry;
    });

    return {
      baseByKey,
      structure: buildStructureFromBaseRows(baseByKey),
      drafts: {},
      patches: {},
      deletedKeys: new Set(),
    };
  }

  function resolveParentCode(
    state: SeGridState<TDto, TBaseEntry, TDraft, TPatch>,
    parentRowKey: string | null,
  ): string | undefined {
    if (!parentRowKey) return undefined;
    const parent = mergeRow(state, parentRowKey);
    const code = parent ? config.getCode(parent).trim() : "";
    return code || undefined;
  }

  function mergeRow(
    state: SeGridState<TDto, TBaseEntry, TDraft, TPatch>,
    rowKey: string,
  ): TRow | null {
    const draft = state.drafts[rowKey];
    if (draft) {
      const parentCode = resolveParentCode(state, draft.parentRowKey);
      return config.assembleDraftRow(draft, parentCode);
    }

    const base = state.baseByKey[rowKey];
    if (!base) return null;

    const patch = state.patches[rowKey] ?? ({} as TPatch);
    const hasPatch = Object.keys(patch).length > 0;

    return {
      ...base,
      ...patch,
      rowKey,
      isNew: false,
      isDirty: hasPatch,
      isDeleted: state.deletedKeys.has(rowKey),
    } as unknown as TRow;
  }

  function mergeAllRows(state: SeGridState<TDto, TBaseEntry, TDraft, TPatch>): TRow[] {
    const keys = new Set([...Object.keys(state.baseByKey), ...Object.keys(state.drafts)]);

    return [...keys]
      .map((rowKey) => mergeRow(state, rowKey))
      .filter((row): row is TRow => row != null);
  }

  function hasGridPendingChanges(state: SeGridState<TDto, TBaseEntry, TDraft, TPatch>): boolean {
    return (
      state.deletedKeys.size > 0 ||
      Object.keys(state.drafts).length > 0 ||
      Object.keys(state.patches).length > 0
    );
  }

  function collectDescendantRowKeys(structure: DisplaySlot[], rootRowKey: string): Set<string> {
    const result = new Set<string>([rootRowKey]);
    const queue = [rootRowKey];

    while (queue.length > 0) {
      const parentKey = queue.shift()!;
      for (const slot of structure) {
        if (slot.parentRowKey === parentKey && !result.has(slot.rowKey)) {
          result.add(slot.rowKey);
          queue.push(slot.rowKey);
        }
      }
    }

    return result;
  }

  function insertRootSlot(structure: DisplaySlot[], slot: DisplaySlot): DisplaySlot[] {
    const firstRootIndex = structure.findIndex((item) => item.parentRowKey === null);
    if (firstRootIndex === -1) return [slot, ...structure];
    return [...structure.slice(0, firstRootIndex), slot, ...structure.slice(firstRootIndex)];
  }

  function insertChildSlot(
    structure: DisplaySlot[],
    parentRowKey: string,
    slot: DisplaySlot,
  ): DisplaySlot[] {
    const parentIndex = structure.findIndex((item) => item.rowKey === parentRowKey);
    if (parentIndex === -1) return [...structure, slot];

    const insertAt = parentIndex + 1;
    return [...structure.slice(0, insertAt), slot, ...structure.slice(insertAt)];
  }

  function removeSlotsFromStructure(
    structure: DisplaySlot[],
    rowKeysToRemove: Set<string>,
  ): DisplaySlot[] {
    return structure.filter((slot) => !rowKeysToRemove.has(slot.rowKey));
  }

  function patchGridRow(
    state: SeGridState<TDto, TBaseEntry, TDraft, TPatch>,
    rowKey: string,
    patch: Partial<TRow>,
  ): SeGridState<TDto, TBaseEntry, TDraft, TPatch> {
    const draft = state.drafts[rowKey];
    if (draft) {
      return {
        ...state,
        drafts: {
          ...state.drafts,
          [rowKey]: config.applyDraftPatch(draft, patch),
        },
      };
    }

    const { rowKey: _rk, isNew: _n, isDirty: _d, isDeleted: _del, ...dtoPatch } = patch;

    return {
      ...state,
      patches: {
        ...state.patches,
        [rowKey]: { ...state.patches[rowKey], ...dtoPatch } as TPatch,
      },
    };
  }

  function markRowsDeleted(
    state: SeGridState<TDto, TBaseEntry, TDraft, TPatch>,
    rootRowKey: string,
  ): SeGridState<TDto, TBaseEntry, TDraft, TPatch> {
    const keysToDelete = collectDescendantRowKeys(state.structure, rootRowKey);
    const deletedKeys = new Set(state.deletedKeys);
    for (const key of keysToDelete) {
      deletedKeys.add(key);
    }
    return { ...state, deletedKeys };
  }

  function validateDraftParentCode(
    state: SeGridState<TDto, TBaseEntry, TDraft, TPatch>,
    rowKey: string,
  ): string | null {
    const draft = state.drafts[rowKey];
    if (!draft?.parentRowKey) return null;

    const parent = mergeRow(state, draft.parentRowKey);
    if (!parent || !config.getCode(parent).trim()) {
      return "하위 항목을 추가하려면 상위 코드를 먼저 입력하세요.";
    }

    return null;
  }

  function removeDraftFromGrid(
    state: SeGridState<TDto, TBaseEntry, TDraft, TPatch>,
    rowKey: string,
  ): SeGridState<TDto, TBaseEntry, TDraft, TPatch> {
    const { [rowKey]: _removed, ...restDrafts } = state.drafts;
    const keysToRemove = collectDescendantRowKeys(state.structure, rowKey);

    return {
      ...state,
      drafts: restDrafts,
      structure: removeSlotsFromStructure(state.structure, keysToRemove),
    };
  }

  return {
    createEmptyGridState,
    hydrateGridFromServer,
    mergeRow,
    mergeAllRows,
    hasGridPendingChanges,
    collectDescendantRowKeys,
    insertRootSlot,
    insertChildSlot,
    removeSlotsFromStructure,
    patchGridRow,
    markRowsDeleted,
    validateDraftParentCode,
    removeDraftFromGrid,
    resolveParentCode,
  };
}