// api.js — every backend call lives here.
//
// All write requests pass {credentials: 'include'} implicitly because
// the dev proxy and the production deploy serve the API from the same
// origin as the frontend. If you split origins later, change here.

async function jsonOrThrow(res) {
  if (!res.ok) {
    let detail = ''
    try {
      const body = await res.json()
      detail = body.detail || JSON.stringify(body)
    } catch {
      detail = await res.text()
    }
    const error = new Error(detail || `HTTP ${res.status}`)
    error.status = res.status
    throw error
  }
  return res.json()
}

export async function getMe() {
  const res = await fetch('/api/auth/me')
  return jsonOrThrow(res)
}

export async function listRFCs() {
  return jsonOrThrow(await fetch('/api/rfcs'))
}

export async function getRFC(slug) {
  return jsonOrThrow(await fetch(`/api/rfcs/${slug}`))
}

export async function listProposals() {
  return jsonOrThrow(await fetch('/api/proposals'))
}

export async function getProposal(prNumber) {
  return jsonOrThrow(await fetch(`/api/proposals/${prNumber}`))
}

export async function proposeRFC({ title, slug, pitch, tags }) {
  const res = await fetch('/api/rfcs/propose', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ title, slug, pitch, tags: tags || [] }),
  })
  return jsonOrThrow(res)
}

export async function mergeProposal(prNumber) {
  const res = await fetch(`/api/proposals/${prNumber}/merge`, { method: 'POST' })
  return jsonOrThrow(res)
}

export async function declineProposal(prNumber, comment) {
  const res = await fetch(`/api/proposals/${prNumber}/decline`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ comment }),
  })
  return jsonOrThrow(res)
}

export async function withdrawProposal(prNumber) {
  const res = await fetch(`/api/proposals/${prNumber}/withdraw`, { method: 'POST' })
  return jsonOrThrow(res)
}

// ── Slice 2: active-RFC view (§8) ─────────────────────────────────────────

export async function listModels() {
  return jsonOrThrow(await fetch('/api/models'))
}

export async function getRFCMain(slug) {
  return jsonOrThrow(await fetch(`/api/rfcs/${slug}/main`))
}

export async function getBranch(slug, branch) {
  return jsonOrThrow(await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}`
  ))
}

export async function promoteToBranch(slug, body = {}) {
  const res = await fetch(`/api/rfcs/${slug}/branches/main/promote-to-branch`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(body),
  })
  return jsonOrThrow(res)
}

export async function acceptChange(slug, branch, changeId, { proposed, wasEdited, forceApplyStale }) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/changes/${changeId}/accept`,
    {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({
        proposed,
        was_edited_before_accept: !!wasEdited,
        force_apply_stale: !!forceApplyStale,
      }),
    },
  )
  return jsonOrThrow(res)
}

export async function declineChange(slug, branch, changeId) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/changes/${changeId}/decline`,
    { method: 'POST' },
  )
  return jsonOrThrow(res)
}

export async function reaskChange(slug, branch, changeId) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/changes/${changeId}/reask`,
    { method: 'POST' },
  )
  return jsonOrThrow(res)
}

export async function manualFlush(slug, branch, { newContent, paragraphCount }) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/manual-flush`,
    {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ new_content: newContent, paragraph_count: paragraphCount }),
    },
  )
  return jsonOrThrow(res)
}

export async function setBranchVisibility(slug, branch, { readPublic, contributeMode }) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/visibility`,
    {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({
        read_public: readPublic,
        contribute_mode: contributeMode,
      }),
    },
  )
  return jsonOrThrow(res)
}

export async function createThread(slug, branch, body) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/threads`,
    {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(body),
    },
  )
  return jsonOrThrow(res)
}

export async function listThreads(slug, branch) {
  return jsonOrThrow(await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/threads`,
  ))
}

export async function getThreadMessages(slug, branch, threadId) {
  return jsonOrThrow(await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/threads/${threadId}/messages`,
  ))
}

export async function postThreadMessage(slug, branch, threadId, { text, quote }) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/threads/${threadId}/messages`,
    {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ text, quote }),
    },
  )
  return jsonOrThrow(res)
}

export async function resolveThread(slug, branch, threadId) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/threads/${threadId}/resolve`,
    { method: 'POST' },
  )
  return jsonOrThrow(res)
}

// ── Slice 4: super-draft body editing (§9.5) ─────────────────────────────

export async function startEditBranch(slug, body = {}) {
  const res = await fetch(`/api/rfcs/${slug}/start-edit-branch`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(body),
  })
  return jsonOrThrow(res)
}

export async function editMetadata(slug, { title, tags, prDescription }) {
  const res = await fetch(`/api/rfcs/${slug}/metadata`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      title: title ?? null,
      tags: tags ?? null,
      pr_description: prDescription ?? null,
    }),
  })
  return jsonOrThrow(res)
}

// ── Slice 5: §13 graduation + §13.1 claim ────────────────────────────────

export async function claimOwnership(slug) {
  const res = await fetch(`/api/rfcs/${slug}/claim`, { method: 'POST' })
  return jsonOrThrow(res)
}

export async function listBlockingPRs(slug) {
  return jsonOrThrow(await fetch(`/api/rfcs/${slug}/blocking-prs`))
}

export async function graduateCheck(slug, { id, repo }) {
  const params = new URLSearchParams()
  if (id != null) params.set('id', id)
  if (repo != null) params.set('repo', repo)
  return jsonOrThrow(await fetch(`/api/rfcs/${slug}/graduate/check?${params}`))
}

export async function startGraduation(slug, { rfcId, repoName, owners }) {
  const res = await fetch(`/api/rfcs/${slug}/graduate`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ rfc_id: rfcId, repo_name: repoName, owners }),
  })
  return jsonOrThrow(res)
}

// Open an EventSource on the §13.3 progress stream. Returns the
// EventSource so the caller can close() on dialog dismiss. Calls
// onUpdate with the parsed state payload for every event.
export function openGraduationProgress(slug, { onUpdate, onDone, onError }) {
  const es = new EventSource(`/api/rfcs/${slug}/graduate/progress`)
  const handle = (e) => {
    try {
      const payload = JSON.parse(e.data)
      onUpdate?.(payload, e.type)
      if (e.type === 'done' && payload?.finished) onDone?.(payload)
    } catch (err) {
      onError?.(err)
    }
  }
  for (const name of ['snapshot', 'step', 'rollback_step', 'completed', 'rolled_back', 'done']) {
    es.addEventListener(name, handle)
  }
  es.onerror = (e) => { onError?.(e); es.close() }
  return es
}

// ── Slice 3: the §10 PR flow ─────────────────────────────────────────────

export async function draftPRText(slug, branch) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/pr-draft`,
    { method: 'POST' },
  )
  return jsonOrThrow(res)
}

export async function openPR(slug, branch, { title, description }) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/open-pr`,
    {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ title, description }),
    },
  )
  return jsonOrThrow(res)
}

export async function getPR(slug, prNumber) {
  return jsonOrThrow(await fetch(`/api/rfcs/${slug}/prs/${prNumber}`))
}

export async function advancePRSeen(slug, prNumber, { lastSeenCommitSha, lastSeenMessageId }) {
  const res = await fetch(`/api/rfcs/${slug}/prs/${prNumber}/seen`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      last_seen_commit_sha: lastSeenCommitSha,
      last_seen_message_id: lastSeenMessageId,
    }),
  })
  return jsonOrThrow(res)
}

export async function postPRReview(slug, prNumber, { text, anchorPayload, quote }) {
  const res = await fetch(`/api/rfcs/${slug}/prs/${prNumber}/review`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ text, anchor_payload: anchorPayload || {}, quote: quote || null }),
  })
  return jsonOrThrow(res)
}

export async function mergePR(slug, prNumber) {
  const res = await fetch(`/api/rfcs/${slug}/prs/${prNumber}/merge`, { method: 'POST' })
  return jsonOrThrow(res)
}

export async function withdrawPR(slug, prNumber) {
  const res = await fetch(`/api/rfcs/${slug}/prs/${prNumber}/withdraw`, { method: 'POST' })
  return jsonOrThrow(res)
}

export async function editPRDescription(slug, prNumber, { title, description }) {
  const res = await fetch(`/api/rfcs/${slug}/prs/${prNumber}/description`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ title, description }),
  })
  return jsonOrThrow(res)
}

export async function startResolutionBranch(slug, prNumber) {
  const res = await fetch(`/api/rfcs/${slug}/prs/${prNumber}/resolution-branch`, {
    method: 'POST',
  })
  return jsonOrThrow(res)
}

// Stream a chat turn into a per-branch thread. Calls onChunk for each
// text fragment, onChanges when the trailing `changes` event arrives,
// and onDone at the terminal DONE marker. Returns the response headers
// (so the caller can pull X-Assistant-Message-Id without re-streaming).
export async function streamChatTurn(slug, branch, threadId, { text, quote, model }, { onChunk, onChanges, onDone }) {
  const res = await fetch(
    `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/threads/${threadId}/chat`,
    {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ text, quote, model }),
    },
  )
  if (!res.ok) {
    const detail = await res.text()
    throw new Error(`Chat failed: ${detail || res.status}`)
  }
  const assistantId = res.headers.get('X-Assistant-Message-Id')
  const userMsgId = res.headers.get('X-User-Message-Id')
  const reader = res.body.getReader()
  const decoder = new TextDecoder()
  let buffer = ''
  let currentEvent = null
  while (true) {
    const { done, value } = await reader.read()
    if (done) break
    buffer += decoder.decode(value, { stream: true })
    const parts = buffer.split('\n\n')
    buffer = parts.pop()
    for (const part of parts) {
      const lines = part.split('\n')
      let dataLine = null
      let event = null
      for (const line of lines) {
        if (line.startsWith('event: ')) event = line.slice(7).trim()
        if (line.startsWith('data: ')) dataLine = line.slice(6).trim()
      }
      if (dataLine === null) continue
      if (event === 'changes') {
        try { onChanges?.(JSON.parse(dataLine)) } catch {}
        continue
      }
      if (dataLine === 'DONE') { onDone?.(); break }
      try {
        const text = new TextDecoder().decode(
          Uint8Array.from(atob(dataLine), c => c.charCodeAt(0))
        )
        onChunk?.(text)
      } catch {
        // partial chunk
      }
    }
  }
  onDone?.()
  return { assistantId, userMsgId }
}