import type { ContentEditorInlineMathDelimiter } from '@admin/utils/editor/content-editor-inline-math-delimiter'
import type { ContentEditorMathKind } from '@admin/utils/editor/content-editor-math-kind'
import type { ContentEditorMathValue } from '@admin/utils/editor/content-editor-math-value'

const BLOCK_MATH_ENVIRONMENT_NAMES = new Set([
  'align',
  'align*',
  'aligned',
  'alignedat',
  'alignedat*',
  'array',
  'bmatrix',
  'cases',
  'equation',
  'equation*',
  'gather',
  'gather*',
  'gathered',
  'matrix',
  'multline',
  'multline*',
  'pmatrix',
  'smallmatrix',
  'split',
  'vmatrix'
])

export function parseContentEditorMathInput(
  input: string,
  preferredKind?: ContentEditorMathKind
): ContentEditorMathValue | null {
  const value = input.trim()

  if (!value) return null

  const inlineParen = /^\\\(([\s\S]*?)\\\)$/.exec(value)
  const inlineDollar = /^\$([^\n]*?)\$$/.exec(value)
  const displayBracket = /^\\\[([\s\S]*?)\\\]$/.exec(value)
  const displayDollar = /^\$\$([\s\S]*?)\$\$$/.exec(value)
  const environment = /^\\begin\{([^}]+)\}[\s\S]*\\end\{\1\}$/.exec(value)
  const isSupportedEnvironment = Boolean(
    environment && BLOCK_MATH_ENVIRONMENT_NAMES.has(environment[1])
  )
  const displayRaw =
    displayBracket || displayDollar || isSupportedEnvironment || value.includes('\n')

  if (preferredKind === 'inline') {
    const raw = (
      inlineParen?.[1] ??
      inlineDollar?.[1] ??
      displayBracket?.[1] ??
      displayDollar?.[1] ??
      value
    ).trim()

    if (!raw) return null

    const delimiter: ContentEditorInlineMathDelimiter = inlineParen ? '\\(' : '$'

    return {
      delimiter,
      kind: 'inline',
      markdown: delimiter === '\\(' ? `\\(${raw}\\)` : `$${raw}$`,
      raw
    }
  }

  if (preferredKind === 'display' || displayRaw) {
    if (displayBracket || displayDollar || isSupportedEnvironment) {
      return {
        kind: 'display',
        markdown: value,
        raw: value
      }
    }

    const raw = inlineParen?.[1] ?? inlineDollar?.[1] ?? value
    const markdown = raw.includes('\n') ? `$$\n${raw.trim()}\n$$` : `$$${raw.trim()}$$`

    return {
      kind: 'display',
      markdown,
      raw: markdown
    }
  }

  const raw = inlineParen?.[1] ?? inlineDollar?.[1] ?? value
  const delimiter: ContentEditorInlineMathDelimiter = inlineParen ? '\\(' : '$'

  if (!raw.trim()) return null

  return {
    delimiter,
    kind: 'inline',
    markdown: delimiter === '\\(' ? `\\(${raw.trim()}\\)` : `$${raw.trim()}$`,
    raw: raw.trim()
  }
}