'use client'

import type { InlineMathDelimiter } from '@admin/utils/editor/inline-math-delimiter'
import { findUnescapedCharacter } from '@admin/utils/editor/find-unescaped-character'
import { findUnescapedSequence } from '@admin/utils/editor/find-unescaped-sequence'
import { isValidDollarInlineMath } from '@admin/utils/editor/is-valid-dollar-inline-math'

interface InlineMathMatch {
  raw: string
  text: string
  delimiter: InlineMathDelimiter
}

export function matchInlineMath(src: string): InlineMathMatch | null {
  if (src.startsWith('\\(')) {
    const closingIndex = findUnescapedSequence(src, '\\)', 2)
    if (closingIndex === -1) return null

    return {
      raw: src.slice(0, closingIndex + 2),
      text: src.slice(2, closingIndex),
      delimiter: '\\('
    }
  }

  if (!src.startsWith('$') || src.startsWith('$$')) return null

  if (src[1] && /\s/u.test(src[1])) return null

  let closingIndex = 1

  while (closingIndex < src.length) {
    closingIndex = findUnescapedCharacter(src, '$', closingIndex)
    if (closingIndex === -1) return null

    const text = src.slice(1, closingIndex)
    if (isValidDollarInlineMath(src, text, closingIndex)) {
      return {
        raw: src.slice(0, closingIndex + 1),
        text,
        delimiter: '$'
      }
    }

    closingIndex++
  }

  return null
}