/* ============================================================
   apiClient.js — the one HTTP entry point.

   Attaches the bearer token, renews proactively inside the skew window, and
   retries exactly once on a 401. Never loops: if the retry also 401s, the
   session is over and the expired handler fires.
   ============================================================ */

import { ApiError, parseDetail, SessionExpiredError } from './errors'
import { getAccessToken, isExpiring } from './tokenStore'
import { refreshSession } from './refresh'

const API_BASE = import.meta.env.VITE_API_BASE ?? ''

// AuthProvider registers this so the module never has to import the router.
let onSessionExpired = () => {}
export function setSessionExpiredHandler(fn) {
  onSessionExpired = fn
}

function buildUrl(path, params) {
  const url = new URL(`${API_BASE}${path}`, window.location.origin)
  if (params) {
    for (const [k, v] of Object.entries(params)) {
      if (v !== undefined && v !== null && v !== '') url.searchParams.set(k, v)
    }
  }
  return url.toString()
}

/**
 * @param {object} opts
 * @param {boolean} [opts.auth=true]  attach the session bearer token
 * @param {string}  [opts.token]      an explicit token (the password-reset flow);
 *                                    suppresses all refresh behaviour
 */
export async function request(
  path,
  { method = 'GET', body, params, auth = true, token, signal } = {},
) {
  // PROACTIVE renewal. Coalesced by single-flight, so a screen firing six
  // queries at once on an expiring token still triggers exactly one refresh.
  if (auth && !token && isExpiring()) {
    try {
      await refreshSession()
    } catch {
      // Fall through — the 401 path below makes the final call. This keeps a
      // transient network blip from logging the user out.
    }
  }

  // Multipart uploads pass a FormData body. Content-Type is deliberately NOT
  // set for those: the browser has to write it itself so the generated boundary
  // token ends up in the header, and a hand-set value strips it and the server
  // reads an unparseable body. FormData is replayable, so the 401 retry below
  // can re-send the same object.
  const multipart = typeof FormData !== 'undefined' && body instanceof FormData

  const send = async () => {
    const headers = { Accept: 'application/json' }
    if (body != null && !multipart) headers['Content-Type'] = 'application/json'
    const bearer = token ?? (auth ? getAccessToken() : null)
    if (bearer) headers.Authorization = `Bearer ${bearer}`
    return fetch(buildUrl(path, params), {
      method,
      headers,
      signal,
      body: body == null ? undefined : multipart ? body : JSON.stringify(body),
    })
  }

  let res
  try {
    res = await send()
  } catch (err) {
    if (err?.name === 'AbortError') throw err
    throw new ApiError('Unable to reach the server. Check your connection.', 0, null)
  }

  // REACTIVE renewal — exactly one retry.
  if (res.status === 401 && auth && !token) {
    try {
      await refreshSession()
    } catch (err) {
      if (err instanceof SessionExpiredError) onSessionExpired()
      throw err
    }
    res = await send()
    if (res.status === 401) {
      // A fresh access token still 401s: the user was deactivated or soft-deleted
      // server-side (get_current_user rejects both). Signing them out is correct.
      onSessionExpired()
      throw new ApiError('Session expired', 401, null)
    }
  }

  let data = null
  const text = await res.text()
  if (text) {
    try {
      data = JSON.parse(text)
    } catch {
      data = null
    }
  }

  if (!res.ok) {
    throw new ApiError(
      parseDetail(data?.detail) || res.statusText || 'Request failed',
      res.status,
      data,
    )
  }
  return data
}

/**
 * Authenticated file download. Document routes return a binary body, so they
 * cannot go through `request()` (that always JSON-parses). Same bearer /
 * refresh behaviour as `request`; 404s stay 404 (the download route never 403s).
 */
export async function downloadFile(path, { params, auth = true, filename } = {}) {
  if (auth && isExpiring()) {
    try {
      await refreshSession()
    } catch {
      /* fall through — the 401 path below makes the final call */
    }
  }

  const send = async () => {
    const headers = { Accept: '*/*' }
    const bearer = auth ? getAccessToken() : null
    if (bearer) headers.Authorization = `Bearer ${bearer}`
    return fetch(buildUrl(path, params), { method: 'GET', headers })
  }

  let res
  try {
    res = await send()
  } catch (err) {
    if (err?.name === 'AbortError') throw err
    throw new ApiError('Unable to reach the server. Check your connection.', 0, null)
  }

  if (res.status === 401 && auth) {
    try {
      await refreshSession()
    } catch (err) {
      if (err instanceof SessionExpiredError) onSessionExpired()
      throw err
    }
    res = await send()
    if (res.status === 401) {
      onSessionExpired()
      throw new ApiError('Session expired', 401, null)
    }
  }

  if (!res.ok) {
    let data = null
    const text = await res.text()
    if (text) {
      try {
        data = JSON.parse(text)
      } catch {
        data = null
      }
    }
    throw new ApiError(
      parseDetail(data?.detail) || res.statusText || 'Download failed',
      res.status,
      data,
    )
  }

  const blob = await res.blob()
  const fromHeader = filenameFromDisposition(res.headers.get('Content-Disposition'))
  const name = filename || fromHeader || 'download'
  const url = URL.createObjectURL(blob)
  const a = document.createElement('a')
  a.href = url
  a.download = name
  document.body.appendChild(a)
  a.click()
  a.remove()
  URL.revokeObjectURL(url)
}

/**
 * Authenticated binary GET returning an object URL for <img>/<video>/<iframe>
 * use — a plain src attribute cannot carry the bearer token. Returns null on
 * 404 (the resource legitimately not existing, e.g. a job with no cover
 * image). `type` re-wraps the blob with that MIME type: routes that send
 * application/octet-stream would otherwise trigger a download instead of the
 * browser's inline viewer. Callers own the URL: revoke it when done.
 */
export async function fetchBlobUrl(path, { params, auth = true, type } = {}) {
  if (auth && isExpiring()) {
    try {
      await refreshSession()
    } catch {
      /* fall through — the 401 path below makes the final call */
    }
  }

  const send = async () => {
    const headers = { Accept: '*/*' }
    const bearer = auth ? getAccessToken() : null
    if (bearer) headers.Authorization = `Bearer ${bearer}`
    return fetch(buildUrl(path, params), { method: 'GET', headers })
  }

  let res
  try {
    res = await send()
  } catch (err) {
    if (err?.name === 'AbortError') throw err
    throw new ApiError('Unable to reach the server. Check your connection.', 0, null)
  }

  if (res.status === 401 && auth) {
    try {
      await refreshSession()
    } catch (err) {
      if (err instanceof SessionExpiredError) onSessionExpired()
      throw err
    }
    res = await send()
    if (res.status === 401) {
      onSessionExpired()
      throw new ApiError('Session expired', 401, null)
    }
  }

  if (res.status === 404) return null
  if (!res.ok) {
    throw new ApiError(res.statusText || 'Request failed', res.status, null)
  }
  const blob = await res.blob()
  return URL.createObjectURL(type ? new Blob([blob], { type }) : blob)
}

function filenameFromDisposition(header) {
  if (!header) return null
  const star = /filename\*=UTF-8''([^;]+)/i.exec(header)
  if (star) {
    try {
      return decodeURIComponent(star[1])
    } catch {
      return star[1]
    }
  }
  const quoted = /filename="([^"]+)"/i.exec(header)
  if (quoted) return quoted[1]
  const plain = /filename=([^;]+)/i.exec(header)
  return plain ? plain[1].trim() : null
}

export const get = (path, params, opts) => request(path, { ...opts, params })
export const post = (path, body, opts) => request(path, { ...opts, method: 'POST', body })
export const put = (path, body, opts) => request(path, { ...opts, method: 'PUT', body })
export const del = (path, opts) => request(path, { ...opts, method: 'DELETE' })