// Platform Shell API client. Identity is a server-controlled session cookie (rn_session,
// HttpOnly — this code can't read it, and doesn't need to; the browser sends it automatically
// on every same-origin request). Roster name-picking is classroom/pilot identification, not
// production authentication (see docs/PHASE3A_IDENTITY_AND_INSTRUCTOR_ACCESS.md §5) — what's
// hardened here is the session that results from it: persistent (survives an API restart),
// unforgeable, and checked on every request.
//
// display_name is still cached in sessionStorage purely for UI convenience (showing "Hi,
// Alice" without an extra round trip) — it carries no authority; every actual API call is
// authorized by the cookie alone, not by anything read from here.
//
// rn_csrf_s is a deliberately non-HttpOnly cookie (double-submit CSRF pattern) — this code
// reads it and echoes it back as a header on every state-changing request, proving the request
// came from our own origin's JS (a cross-origin attacker can trigger the cookie but can't read
// its value or attach a matching custom header without CORS, which we don't grant elsewhere).

const DISPLAY_CACHE_KEY = 'rootnode_student_display'
const CSRF_COOKIE = 'rn_csrf_s'

export function getCachedDisplay() {
  try { return JSON.parse(sessionStorage.getItem(DISPLAY_CACHE_KEY) || 'null') } catch { return null }
}
function cacheDisplay(student) {
  sessionStorage.setItem(DISPLAY_CACHE_KEY, JSON.stringify(student))
}
function clearCachedDisplay() {
  sessionStorage.removeItem(DISPLAY_CACHE_KEY)
}

function getCookie(name) {
  return document.cookie.split('; ').find((c) => c.startsWith(`${name}=`))?.split('=')[1]
}

async function json(res) {
  if (!res.ok) {
    const body = await res.json().catch(() => ({}))
    throw new Error(body.message || body.error || `Request failed (${res.status})`)
  }
  return res.json()
}

function mutate(path, body) {
  return fetch(path, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json', 'X-CSRF-Token': getCookie(CSRF_COOKIE) || '' },
    body: body ? JSON.stringify(body) : undefined,
  }).then(json)
}

export const api = {
  cohorts: () => fetch('/api/roster/cohorts').then(json),
  roster: (cohort) => fetch(`/api/roster?cohort=${encodeURIComponent(cohort)}`).then(json),
  login: async (student_id) => {
    // No CSRF token yet at login (nothing authenticated to forge into) — same reasoning as the
    // instructor login route.
    const student = await fetch('/api/login', {
      method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ student_id }),
    }).then(json)
    cacheDisplay(student)
    return student
  },
  logout: async () => {
    await mutate('/api/logout').catch(() => {})
    clearCachedDisplay()
  },
  whoami: () => fetch('/api/session/whoami').then(json),

  curriculumPath: () => fetch('/api/curriculum/path').then(json),
  curriculumState: () => fetch('/api/curriculum/state').then(json),

  environmentStatus: () => fetch('/api/environment/status').then(json),
  launchEnvironment: () => mutate('/api/environment/launch'),
  resetEnvironment: () => mutate('/api/environment/reset'),

  recentAttempts: () => fetch('/api/attempts/recent').then(json),

  assessments: () => fetch('/api/assessments').then(json),
  activeAssessment: () => fetch('/api/assessments/active').then(json),
  assessmentDetail: (sessionId) => fetch(`/api/assessments/${sessionId}`).then(json),
  startAssessment: (definitionId) => mutate(`/api/assessments/${definitionId}/start`),
  submitAssessment: (sessionId) => mutate(`/api/assessments/${sessionId}/submit`),

  capstone: () => fetch('/api/capstone').then(json),

  achievements: () => fetch('/api/achievements').then(json),
}