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

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

import { createOperatorFilter } from '../features/filtering'
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
}

/**
 * Converts a single GriddyColumn to a TanStack ColumnDef
 */
function mapSingleColumn<T>(col: GriddyColumn<T>): ColumnDef<T> {
  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 }),
    aggregationFn: col.aggregationFn,
    enableColumnFilter: col.filterable ?? false,
    enableGrouping: col.groupable ?? false,
    enableHiding: true,
    enablePinning: 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 provide a default
  if (col.sortFn) {
    def.sortingFn = col.sortFn
  } else if (!isStringAccessor && col.sortable !== false) {
    // Use alphanumeric sorting for function accessors
    def.sortingFn = 'alphanumeric'
  }

  if (col.filterFn) {
    def.filterFn = col.filterFn
  } else if (col.filterable) {
    def.filterFn = createOperatorFilter()
  }
  return def
}

/**
 * Maps Griddy's user-facing GriddyColumn<T> definitions to TanStack Table ColumnDef<T>[].
 * Supports header grouping and optionally prepends a selection checkbox column.
 */
export function mapColumns<T>(
  columns: GriddyColumn<T>[],
  selection?: SelectionConfig,
): ColumnDef<T>[] {
  // Group columns by headerGroup
  const grouped = new Map<string, GriddyColumn<T>[]>()
  const ungrouped: GriddyColumn<T>[] = []

  columns.forEach(col => {
    if (col.headerGroup) {
      const existing = grouped.get(col.headerGroup) || []
      existing.push(col)
      grouped.set(col.headerGroup, existing)
    } else {
      ungrouped.push(col)
    }
  })

  // Build column definitions
  const mapped: ColumnDef<T>[] = []

  // Add ungrouped columns first
  ungrouped.forEach(col => {
    mapped.push(mapSingleColumn(col))
  })

  // Add grouped columns
  grouped.forEach((groupColumns, groupName) => {
    const groupDef: ColumnDef<T> = {
      header: groupName,
      id: `group-${groupName}`,
      columns: groupColumns.map(col => mapSingleColumn(col)),
    }
    mapped.push(groupDef)
  })

  // 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
}