/*
Copyright (C) 2023-2026 QuantumNous

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.

For commercial licensing, please contact support@quantumnous.com
*/
import * as React from 'react'
import { Add01Icon } from '@hugeicons/core-free-icons'
import { HugeiconsIcon } from '@hugeicons/react'
import { useTranslation } from 'react-i18next'
import { cn } from '@/lib/utils'
import {
  Combobox,
  ComboboxChip,
  ComboboxChips,
  ComboboxChipsInput,
  ComboboxCollection,
  ComboboxContent,
  ComboboxEmpty,
  ComboboxItem,
  ComboboxList,
  ComboboxValue,
} from '@/components/ui/combobox'

export type Option = {
  label: string
  value: string
}

interface MultiSelectProps {
  options: Option[]
  selected: string[]
  onChange: (values: string[]) => void
  placeholder?: string
  className?: string
  allowCreate?: boolean
  /**
   * Label shown for the "create" item in the dropdown.
   * Supports the `{{value}}` placeholder which is replaced with the typed input.
   * Falls back to `Add "{{value}}"` when omitted.
   */
  createLabel?: string
  /** Empty state text. Defaults to "No matching items". */
  emptyText?: string
  /** Optional `id` to wire labels/aria-describedby to the input. */
  id?: string
  /** Disable the entire control. */
  disabled?: boolean
}

const COMMA_REGEX = /[,，\n]/

function splitDraft(value: string): { completed: string[]; draft: string } {
  if (!COMMA_REGEX.test(value)) {
    return { completed: [], draft: value }
  }
  const normalized = value.replaceAll('，', ',').replaceAll('\n', ',')
  const parts = normalized.split(',')
  const draft = parts.at(-1) ?? ''
  const completed = parts
    .slice(0, -1)
    .map((part) => part.trim())
    .filter(Boolean)
  return { completed, draft }
}

/**
 * MultiSelect — tags/chips style multi-select built on Base UI Combobox.
 *
 * Behaviour:
 * - Search filters built-in options (Base UI handles fuzzy filtering).
 * - When `allowCreate` is true, custom values can be added inline:
 *   - Type and press Enter / "," to add a single value.
 *   - Paste a comma- (or newline-) separated list to add many at once.
 *   - A "Add \"<value>\"" item appears at the top of the dropdown when the
 *     typed text doesn't match any option.
 * - Backspace on an empty input removes the last selected chip (Base UI default).
 *
 * Focus/border styling is inherited from `ComboboxChips`, which uses the same
 * tokens as `Input` so it stays visually consistent with other form fields.
 */
export function MultiSelect(props: MultiSelectProps) {
  const { t } = useTranslation()
  const placeholder = props.placeholder ?? t('Select items...')

  const [inputValue, setInputValue] = React.useState('')
  const [open, setOpen] = React.useState(false)

  const selectedSet = React.useMemo(
    () => new Set(props.selected),
    [props.selected]
  )

  // Lookup of value -> display label so chips and items can show friendly names
  // even when the underlying option list changes (e.g. custom-added values).
  const labelMap = React.useMemo(() => {
    const map = new Map<string, string>()
    for (const option of props.options) {
      map.set(option.value, option.label)
    }
    return map
  }, [props.options])

  const trimmedInput = inputValue.trim()
  const inputMatchesExisting =
    trimmedInput.length > 0 &&
    (selectedSet.has(trimmedInput) ||
      props.options.some(
        (option) =>
          option.value.toLowerCase() === trimmedInput.toLowerCase() ||
          option.label.toLowerCase() === trimmedInput.toLowerCase()
      ))

  const canCreate =
    props.allowCreate === true &&
    trimmedInput.length > 0 &&
    !inputMatchesExisting

  // We expose all known option values + every currently selected value to Base
  // UI's items list. This way Base UI filters them by the search query and the
  // user can still see the chip labels mapped correctly.
  const items = React.useMemo(() => {
    const set = new Set<string>(props.options.map((option) => option.value))
    for (const value of props.selected) {
      set.add(value)
    }
    if (canCreate) {
      set.add(trimmedInput)
    }
    return Array.from(set)
  }, [props.options, props.selected, canCreate, trimmedInput])

  const addValues = React.useCallback(
    (values: string[]) => {
      const next: string[] = []
      const seen = new Set<string>(props.selected)
      for (const raw of values) {
        const value = raw.trim()
        if (!value) continue
        if (seen.has(value)) continue
        seen.add(value)
        next.push(value)
      }
      if (next.length === 0) return
      props.onChange([...props.selected, ...next])
    },
    [props]
  )

  const handleInputValueChange = (value: string) => {
    if (!props.allowCreate) {
      setInputValue(value)
      return
    }
    const parsed = splitDraft(value)
    if (parsed.completed.length > 0) {
      addValues(parsed.completed)
      setInputValue(parsed.draft)
      return
    }
    setInputValue(value)
  }

  const handleValueChange = (next: string[]) => {
    props.onChange(next)
    // When an item is picked (multiple mode), Base UI keeps the input but most
    // UX patterns clear it. Clearing once a value is added makes batch picking
    // feel snappier and matches popular chip-style multiselects.
    if (next.length > props.selected.length) {
      setInputValue('')
    }
  }

  const handleKeyDown = (event: React.KeyboardEvent<HTMLInputElement>) => {
    // Enter without a highlighted option commits the typed value.
    if (event.key === 'Enter' && props.allowCreate && canCreate) {
      // Only fire when Base UI has no highlighted item to select. We rely on
      // the highlighted item's data attribute on the popup. If the popup is
      // closed or empty, manually commit the typed value.
      const popup = document.querySelector<HTMLElement>(
        '[data-slot="combobox-content"][data-open]'
      )
      const hasHighlight = popup?.querySelector('[data-highlighted]') != null
      if (!hasHighlight) {
        event.preventDefault()
        addValues([trimmedInput])
        setInputValue('')
      }
    }
  }

  return (
    <Combobox
      multiple
      items={items}
      value={props.selected}
      onValueChange={handleValueChange}
      inputValue={inputValue}
      onInputValueChange={handleInputValueChange}
      open={open}
      onOpenChange={setOpen}
      disabled={props.disabled}
    >
      <ComboboxChips className={cn('w-full', props.className)}>
        <ComboboxValue>
          {(values: string[]) =>
            values.map((value) => (
              <ComboboxChip key={value}>
                <span className='max-w-[16rem] truncate'>
                  {labelMap.get(value) ?? value}
                </span>
              </ComboboxChip>
            ))
          }
        </ComboboxValue>
        <ComboboxChipsInput
          id={props.id}
          placeholder={props.selected.length === 0 ? placeholder : undefined}
          onKeyDown={handleKeyDown}
          aria-label={placeholder}
        />
      </ComboboxChips>

      <ComboboxContent>
        <ComboboxList>
          <ComboboxCollection>
            {(item: string) => {
              const isCreate = canCreate && item === trimmedInput
              const label = labelMap.get(item) ?? item
              return (
                <ComboboxItem
                  key={item}
                  value={item}
                  className={isCreate ? 'text-foreground' : undefined}
                >
                  {isCreate ? (
                    <>
                      <HugeiconsIcon
                        icon={Add01Icon}
                        strokeWidth={2}
                        className='text-muted-foreground'
                        aria-hidden='true'
                      />
                      <span className='truncate'>
                        {props.createLabel
                          ? t(props.createLabel, { value: item })
                          : t('Add "{{value}}"', { value: item })}
                      </span>
                    </>
                  ) : (
                    <span className='truncate'>{label}</span>
                  )}
                </ComboboxItem>
              )
            }}
          </ComboboxCollection>
        </ComboboxList>
        <ComboboxEmpty>
          {props.emptyText ?? t('No matching items')}
        </ComboboxEmpty>
      </ComboboxContent>
    </Combobox>
  )
}
