revdiff-relay

1import type { EngineInterface, HookStream, ProcessSpawnChunk, ProcessSpawnResult, Register } from 'claude-code'
2
3const COMMAND = 'revdiff'
4const LEAD_IN = 'Annotations from revdiff:'
5
6const GUIDANCE = `The user opened revdiff over the current diff in a floating Zellij pane. Each time they press O there, their annotations arrive in this session as a message beginning "${LEAD_IN}", on their own schedule: possibly interleaved with unrelated work, possibly never. Treat each one as the user handing you review comments: answer questions in conversation and make the changes they ask for. Don't wait on or poll for annotations.
7
8When the user reloads the diff, revdiff clears annotations on lines the reload changed and keeps the rest, so an annotation they send again is deliberately still standing.
9
10Annotations are \`## path/to/file:43 (+)\` headers followed by the comment text, where (+) is an added line, (-) a removed line, ( ) an unchanged context line, and no line number means a file-level comment.`
11
12// Prompts can't be submitted from command.run; the reader runs from session.start.
13// https://code.claude.com/docs/en/plugins/mods/api#start-a-turn-from-a-background-job
14let isStarted = false
15let pendingFifo: string | undefined
16let wakeLoop: (() => void) | undefined
17let reader: HookStream<ProcessSpawnChunk, ProcessSpawnResult> | undefined
18let sessionTitle: string | undefined
19
20async function nextFifo(): Promise<string> {
21  while (pendingFifo === undefined) await new Promise<void>(resolve => (wakeLoop = resolve))
22  const fifo = pendingFifo
23  pendingFifo = undefined
24  return fifo
25}
26
27function stopReader() {
28  pendingFifo = undefined
29  const stopping = reader
30  reader = undefined
31  void stopping?.return({ code: null, signal: 'SIGTERM' })
32}
33
34function requestReader(fifo: string) {
35  stopReader()
36  pendingFifo = fifo
37  wakeLoop?.()
38}
39
40function statePaths(sessionId: string) {
41  const dir = `/tmp/revdiff-${sessionId}`
42  return { dir, annotations: `${dir}/annotations`, fifo: `${dir}/flush.pipe` }
43}
44
45const shellQuote = (s: string) => `'${s.replaceAll("'", `'\\''`)}'`
46
47async function findOnPath($: EngineInterface, name: string) {
48  for (const dir of ((await $.env.get('PATH')) ?? '').split(':')) {
49    if (!dir) continue
50    const path = `${dir}/${name}`
51    const stat = await $.fs.stat(path).catch(() => undefined)
52    if (stat?.kind === 'file') return path
53  }
54  return undefined
55}
56
57function startReader($: EngineInterface, fifo: string) {
58  // Opened read-write so cat never sees EOF between flushes.
59  const child = $.process.spawn({ argv: ['sh', '-c', 'exec cat <>"$1"', 'sh', fifo] })
60  reader = child
61
62  void (async () => {
63    let pending = ''
64    try {
65      for await (const { stream, text } of child) {
66        // return() doesn't cancel a pending read.
67        if (reader !== child) break
68        if (stream === 'stderr') {
69          $.ui.log(`reader: ${text.trim()}`, { to: 'debug' })
70          continue
71        }
72        pending += text
73        for (let end = pending.indexOf('\0'); end !== -1; end = pending.indexOf('\0')) {
74          const record = pending.slice(0, end)
75          pending = pending.slice(end + 1)
76          if (record.trim()) await $.prompt.submit({ text: `${LEAD_IN}\n\n${record}`, asUser: true })
77        }
78      }
79    } catch (err) {
80      $.ui.log(`reader stopped: ${String(err)}`, { to: 'debug' })
81    }
82    if (reader === child) reader = undefined
83  })()
84}
85
86export const register: Register = on => {
87  on('session.start', async ($, e, next) => {
88    if (!e.isInteractive) return next(e)
89    await $.command.register({
90      name: COMMAND,
91      description: 'Annotate the current diff in a floating revdiff pane',
92      argumentHint: '[ref] [ref2] [--staged] [--only=<file>]',
93    })
94    const started = await next(e)
95    isStarted = true
96    void (async () => {
97      for (;;) startReader($, await nextFifo())
98    })()
99
100    // A reload kills the reader but not the pane; resume an existing FIFO.
101    const { fifo } = statePaths(await $.session.id())
102    const stat = await $.fs.stat(fifo).catch(() => undefined)
103    if (stat?.kind === 'other') requestReader(fifo)
104
105    return started
106  })
107
108  // A pane belongs to its session; /clear and /resume end it without a reload.
109  on('session.end', async (_$, e, next) => {
110    stopReader()
111    sessionTitle = undefined
112    return next(e)
113  })
114
115  // Title only: classic.* hooks are skipped under managed settings.
116  // https://code.claude.com/docs/en/plugins/mods/admin#know-what-happens-by-default
117  on('classic.SessionStart', async (_$, e, next) => {
118    sessionTitle = e.session_title
119    return next(e)
120  })
121
122  on('classic.UserPromptSubmit', async (_$, e, next) => {
123    if (e.session_title) sessionTitle = e.session_title
124    return next(e)
125  })
126
127  on('command.run', { command: COMMAND }, async ($, e) => {
128    if (!isStarted) return { text: 'The session has not started yet.' }
129    if (!(await $.env.get('ZELLIJ'))) return { text: 'Not inside a Zellij session.' }
130
131    // The pane runs in the Zellij server's environment, whose PATH may differ.
132    const revdiff = await findOnPath($, 'revdiff')
133    if (!revdiff) return { text: 'revdiff not found on PATH.' }
134
135    const sessionId = await $.session.id()
136    const { dir, annotations, fifo } = statePaths(sessionId)
137
138    stopReader()
139    await $.process.run(['mkdir', '-p', dir])
140    await $.process.run(['rm', '-f', annotations, fifo])
141    await $.process.run(['mkfifo', fifo])
142    requestReader(fifo)
143
144    const flush = `${$.plugin.root}/scripts/flush.sh`
145    const postFlush = `${shellQuote(flush)} --annotations ${shellQuote(annotations)} --fifo ${shellQuote(fifo)}`
146    let cmd = [
147      revdiff,
148      `--output=${annotations}`,
149      `--post-flush-command=${postFlush}`,
150      ...e.args.split(/\s+/).filter(Boolean),
151    ]
152
153    const editors: string[] = []
154    const editor = await $.env.get('EDITOR')
155    const visual = await $.env.get('VISUAL')
156    if (editor) editors.push(`EDITOR=${editor}`)
157    if (visual) editors.push(`VISUAL=${visual}`)
158    if (editors.length > 0) cmd = ['/usr/bin/env', ...editors, ...cmd]
159
160    const cwd = await $.session.cwd()
161    const owner = sessionTitle
162      ? sessionTitle.length > 60 ? `${sessionTitle.slice(0, 59)}…` : sessionTitle
163      : `${cwd.split('/').pop()} · ${sessionId.slice(0, 8)}`
164    const opened = await $.process.run([
165      'zellij', 'run', '--floating', '--close-on-exit',
166      '--width', (await $.env.get('REVDIFF_POPUP_WIDTH')) ?? '90%',
167      '--height', (await $.env.get('REVDIFF_POPUP_HEIGHT')) ?? '90%',
168      '--x', '5%', '--y', '5%',
169      '--name', `revdiff: ${owner}`, '--cwd', cwd,
170      '--', ...cmd,
171    ])
172    if (opened.exitCode !== 0) {
173      stopReader()
174      return { text: `zellij could not open the pane: ${opened.stderr.trim()}` }
175    }
176
177    return {
178      text: 'revdiff is open. Press O in the pane to send annotations here, R to reload the diff.',
179      context: [GUIDANCE],
180    }
181  })
182}
183