export type StoredFileAttachment = {
  /** Display filename */
  name: string
  /** Full URL when known (opens in new tab) */
  url: string
}

function safeDecodeUriComponent(value: string): string {
  try {
    return decodeURIComponent(value)
  } catch {
    return value
  }
}

function displayNameFromUploadUrl(url: string): string {
  try {
    const pathname = new URL(url).pathname
    const base = pathname.split('/').pop() || url
    return safeDecodeUriComponent(base)
  } catch {
    const parts = url.split('/').filter(Boolean)
    const last = parts[parts.length - 1]
    return safeDecodeUriComponent(last || url)
  }
}

/** Submission storage: single URL or JSON-encoded array (`SubmissionUploadService`). */
export function parseStoredFileUploadUrls(raw: unknown): StoredFileAttachment[] {
  if (raw === null || raw === undefined) return []

  const s = typeof raw === 'string' ? raw.trim() : ''
  if (s === '') return []

  const fromUrlCandidate = (value: unknown): StoredFileAttachment | null => {
    const url = typeof value === 'string' ? value.trim() : ''
    if (!url) return null
    const absolute = /^https?:\/\//i.test(url)
    const relative = url.startsWith('/') && !/\s/.test(url)
    if (!(absolute || relative)) return null
    return { url, name: displayNameFromUploadUrl(url) }
  }

  if (s.startsWith('[')) {
    try {
      const parsed = JSON.parse(s)
      if (Array.isArray(parsed)) {
        const out: StoredFileAttachment[] = []
        for (const item of parsed) {
          const att = fromUrlCandidate(item)
          if (att) out.push(att)
        }
        return out
      }
    } catch {
      /* treat as plain string below */
    }
  }

  const single = fromUrlCandidate(s)
  return single ? [single] : []
}