import type { Field } from '@/types/field'

/** Whether form values carry raw File references (multipart submit). */
export function formSubmissionValuesContainFiles(values: Record<string, unknown>): boolean {
  for (const v of Object.values(values)) {
    if (v instanceof File) return true
    if (Array.isArray(v) && v.some((item) => item instanceof File)) return true
  }
  return false
}

function fileUploadMultipartSuffix(fieldKey: string, fileIndex: number): string {
  const base = fieldKey.replace(/[^a-zA-Z0-9]+/g, '_').replace(/^_+|_+$/g, '') || 'field'
  return fileIndex === 0 ? base : `${base}__${fileIndex}`
}

/**
 * multipart/form-data for form submission when file-upload fields carry File instances.
 */
export function buildMultipartFormSubmissionData(payload: {
  formId: string | number
  values: Record<string, unknown>
  nonce: string
  postId: unknown
  referer: string
  formFields: Field[]
}): FormData {
  const fd = new FormData()
  const valuesForJson: Record<string, unknown> = { ...payload.values }
  const paramToLogicalKey: Record<string, string> = {}

  for (const field of payload.formFields) {
    if (field.type !== 'file-upload') continue
    const key = `${field.type}_${field.fieldIndex}`
    const raw = valuesForJson[key]
    const files: File[] = []

    if (raw instanceof File) files.push(raw)
    else if (Array.isArray(raw)) {
      for (const item of raw) {
        if (item instanceof File) files.push(item)
      }
    }

    delete valuesForJson[key]

    if (files.length === 0) continue

    files.forEach((file, idx) => {
      const suffix = fileUploadMultipartSuffix(key, idx)
      const param = `ivyforms_fu_${suffix}`
      fd.append(param, file)
      paramToLogicalKey[param] = key
    })
  }

  fd.append('formId', String(payload.formId))
  fd.append('nonce', String(payload.nonce))
  fd.append('postId', String(payload.postId ?? ''))
  fd.append('referer', payload.referer ?? '')
  fd.append('values', JSON.stringify(valuesForJson))
  fd.append('ivyforms_fm', JSON.stringify(paramToLogicalKey))

  return fd
}