import type { ColumnDef } from '@tanstack/react-table'

import type { GriddyColumn, SelectionConfig } from './types'

import { DEFAULTS, SELECTION_COLUMN_ID, SELECTION_COLUMN_SIZE } from './constants'

/**
 * Retrieves the original GriddyColumn from a TanStack column's meta.
 */
export function getGriddyColumn<T>(column: { columnDef: ColumnDef<T> }): GriddyColumn<T> | undefined {
  return (column.columnDef.meta as { griddy?: GriddyColumn<T> })?.griddy
}

/**
 * Maps Griddy's user-facing GriddyColumn<T> definitions to TanStack Table ColumnDef<T>[].
 * Optionally prepends a selection checkbox column.
 */
export function mapColumns<T>(
  columns: GriddyColumn<T>[],
  selection?: SelectionConfig,
): ColumnDef<T>[] {
  const mapped: ColumnDef<T>[] = columns.map((col) => {
    const isStringAccessor = typeof col.accessor !== 'function'

    const def: ColumnDef<T> = {
      id: col.id,
      // Use accessorKey for string keys (enables TanStack auto-detection of sort/filter),
      // accessorFn for function accessors
      ...(isStringAccessor
        ? { accessorKey: col.accessor as string }
        : { accessorFn: col.accessor as (row: T) => unknown }),
      enableColumnFilter: col.filterable ?? false,
      enableHiding: true,
      enableResizing: true,
      enableSorting: col.sortable ?? true,
      header: () => col.header,
      maxSize: col.maxWidth ?? DEFAULTS.maxColumnWidth,
      meta: { griddy: col },
      minSize: col.minWidth ?? DEFAULTS.minColumnWidth,
      size: col.width,
      // For function accessors, TanStack can't auto-detect the sort type, so default to 'auto'
      sortingFn: col.sortFn ?? (isStringAccessor ? undefined : 'auto') as any,
    }
    if (col.filterFn) def.filterFn = col.filterFn
    return def
  })

  // Prepend checkbox column if selection is enabled
  if (selection && selection.mode !== 'none' && selection.showCheckbox !== false) {
    const checkboxCol: ColumnDef<T> = {
      cell: 'select-row',  // Rendered by TableCell with actual checkbox
      enableColumnFilter: false,
      enableHiding: false,
      enableResizing: false,
      enableSorting: false,
      header: selection.mode === 'multi'
        ? 'select-all'  // Rendered by TableHeader with actual checkbox
        : '',
      id: SELECTION_COLUMN_ID,
      size: SELECTION_COLUMN_SIZE,
    }
    mapped.unshift(checkboxCol)
  }

  return mapped
}