function toHeadersObject(headers?: HeadersInit): Record<string, string> {
  if (!headers) {
    return {}
  }

  if (headers instanceof Headers) {
    return Object.fromEntries(headers.entries())
  }

  if (Array.isArray(headers)) {
    return Object.fromEntries(headers)
  }

  return { ...headers }
}

function getDownloadFileName(contentDisposition: string | null, fallback: string) {
  if (!contentDisposition) {
    return fallback
  }

  const utf8Match = contentDisposition.match(/filename\*=UTF-8''([^;]+)/i)
  if (utf8Match?.[1]) {
    return decodeURIComponent(utf8Match[1])
  }

  const asciiMatch = contentDisposition.match(/filename="([^"]+)"/i)
  if (asciiMatch?.[1]) {
    return asciiMatch[1]
  }

  return fallback
}

export function useApiAuthHeader() {
    const runtimeConfig = useRuntimeConfig()
    const token = runtimeConfig.public.apiSecretKey

    if (!token) {
        return {}
    }

    // Tous les appels frontend vers /api/* reutilisent ce header commun.
    return {
        Authorization: `Bearer ${token}`
    }
}

export const apiFetch = $fetch.create({})

export function apiRequest(input: RequestInfo | URL, init: RequestInit = {}) {
  return fetch(input, withApiAuth(init))
}

export async function downloadApiFile(url: string, fileNameFallback: string) {
  // Les telechargements passent aussi par fetch pour pouvoir recuperer
  // le contenu et le nom de fichier renvoye par l'API.
  const response = await apiRequest(url)

  if (!response.ok) {
    throw new Error(`HTTP ${response.status}`)
  }

  const blob = await response.blob()
  const objectUrl = URL.createObjectURL(blob)
  const fileName = getDownloadFileName(
    response.headers.get("content-disposition"),
    fileNameFallback
  )
  const link = document.createElement("a")

  link.href = objectUrl
  link.download = fileName
  link.style.display = "none"
  document.body.appendChild(link)
  link.click()
  link.remove()
  URL.revokeObjectURL(objectUrl)
}

export function withApiAuth(init: RequestInit = {}) {
    // Fusionne le header d'auth avec d'eventuels headers deja fournis.
    return {
        ...init,
        headers: {
            ...useApiAuthHeader(),
            ...toHeadersObject(init.headers)
        }
    }
}