Implement undo and redo as forward commits

GitHistoryProvider is the second HistoryProviding implementation:
its stack IS HEAD's first-parent ancestry, reseeded on load (redo
empty), re-synced to HEAD before every crossing so agents'
self-commits become the top and ⌘Z steps back exactly one commit;
any arriving commit clears redo (a heal-only window deliberately
does not). Restores are forward commits through the ordinary
signature path — GitRestoreOperation materializes only the
current-vs-target diff as working-tree writes and resolves no
reset/checkout symbol at all; heal commits are transparent
in-session (pointer passes over, restores exclude heal-owned paths,
identity carried on landed windows via PlannedCommit.kind →
GitLandedCommit). Subjects "Undo:/Redo: <crossed subject>"; menu
labels never nest in-session; the root commit is not a step
(crossing it would restore the empty tree).

Provider binding flips: makeHistoryProvider(store, tier, git) —
free binds native everywhere, Pro binds the git provider on git
boards and NOTHING on mode-none/repo-nested (the pair disables
through existing validation); add-git mid-session live-binds via
HistoryStore.didAddGit → bindHistoryProvider (the flip only ever
adds).

SessionSettleGate is the reusable Save All / Discard / Cancel step:
restores whose diff touches an open Edit session or raw-source
buffer gate on it (Save All applies with validation — a refused
buffer cancels the whole restore focused on the offender; Discard
reverts via CardBodyEditSession.discardBuffer and reconciles against
the working tree, deliberately skipping the second flush); untouched
sessions ride through undisturbed. Built for the branch-switch card
to reuse. BoardStore gains the async performWholesale sibling.

CardHistorySection fills the m6 EmptyView slot: read-only, newest
first, follows the card across lane moves by folder-component match
(the UUID is the identity — no rename detection), absent off git
mode and off Pro.

2332 tests / 403 suites green; InertGitTests untouched.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY
This commit is contained in:
2026-07-31 15:54:22 -04:00
parent 563999655f
commit 142c6e75fe
19 changed files with 3126 additions and 82 deletions
+174 -17
View File
@@ -290,19 +290,30 @@ public final class AppModel {
/// can bind a fake without a second `AppModel` initializer, `@ObservationIgnored` because
/// nothing renders from it.
///
/// ### The `Tier` argument, and the one consumer it is still short
/// ### The three answers, and the `nil` among them
///
/// **`pro-m1` is the consumer that will switch on it.** The default closure ignores the tier
/// today and binds the native stack for both not because the seam is decorative, but because
/// the git provider it would bind does not exist yet (12 Tier matrix: git init/adoption,
/// git-backed undo and the history surfaces are all Pro-tier work, designed in 06-history-undo.md
/// and unbuilt). The argument is here now so that arriving milestone is one closure body rather
/// than a change to the composition root, and so that the tier a board actually composed under is
/// a recorded fact from today (`BoardSession.tier`) instead of something pro-m1 has to introduce
/// alongside its provider.
/// The closure is now the whole tier matrix, in three lines (12 Tier matrix; 06 Rules):
///
/// - **Free** the native stack, on every board. There is no `HistoryStore` at all off Pro, so
/// the absent git state *is* the tier test; nothing here reads a flag.
/// - **Pro, mode `git`** the git provider: undo as forward restore commits over HEAD's
/// first-parent ancestry.
/// - **Pro, mode `none` or `repoNested`** **no provider**. "A board without git has no
/// undo/redo", and a repo-nested board is one the app "leaves strictly alone" so Edit
/// Undo/Redo and the toolbar pair disable there ("the pair disabled on boards with no undo
/// provider in the composed tier under Pro, no-git and repo-nested boards, matching their menu
/// items", 03-board-ui.md Toolbar). Not the native stack: on Pro, a mode-none board's edits
/// are deliberately unhistoried, and half-undoing them from an in-memory stack would be a second
/// substrate the design does not have.
///
/// The `HistoryStore` argument is what makes that decidable here, and it is why `beginSession`
/// composes the git state *before* the provider: which substrate a board gets is a question about
/// its repository, and a root that had to ask the disk itself would be a second detection.
@ObservationIgnored
public var makeHistoryProvider: (BoardStore, Tier) -> any HistoryProviding = { _, _ in
NativeHistoryProvider()
public var makeHistoryProvider: (BoardStore, Tier, HistoryStore?) -> (any HistoryProviding)? = { store, _, git in
guard let git else { return NativeHistoryProvider() }
guard git.mode == .git else { return nil }
return GitHistoryProvider(boardRoot: store.rootURL)
}
// MARK: Sessions
@@ -323,7 +334,16 @@ public final class AppModel {
///
/// Which implementation it is, is the tier's answer and nobody else's
/// (12-editions.md The provider seam) see `AppModel.makeHistoryProvider`.
public let history: any HistoryProviding
///
/// **`nil` is a board with no undo at all** under Pro, mode `none` and repo-nested boards
/// (06-history-undo.md Rules: "A board without git has **no undo/redo**"). The command
/// surface disables through `undoManager`, which answers the empty way over an absent
/// substrate.
///
/// A `var`, unlike `tier` beside it, and for one event only: **add-git**, the design's single
/// sanctioned mid-session mode flip, binds a provider here on the board it flips
/// (`bindHistoryProvider(for:)`). A tier lapse still cannot touch it `tier` has no setter.
public var history: (any HistoryProviding)?
/// **The tier this board composed under** (12-editions.md The entitlement).
///
@@ -724,10 +744,6 @@ public final class AppModel {
// also the *only* time this board asks: the answer becomes `BoardSession.tier` and nothing
// re-derives it.
let tier = currentTier()
// The board's stack is born here, with the session that owns it, and dies in `tearDown`
// below the whole of 13-native-undo.md's session-only persistence: "the stack lives with
// the board session and dies at close/quit ... standard macOS behavior".
let history = makeHistoryProvider(store, tier)
// **Mode detection** (06-history-undo.md Rules Detection: "checked at every board
// open"), on the same line as the tier that gates it. Under `.free` this returns `nil`
// without looking at the disk at all the inert posture is unconditional there and under
@@ -736,7 +752,17 @@ public final class AppModel {
//
// Deliberately *not* re-run anywhere: no reload path, no watcher event, nothing. "The
// running session keeps its mode, and the watcher does not scan for `.git` appearing."
//
// **Before the provider**, which is new in pro-m1: which substrate a board's undo is depends
// on the mode this line detects (`makeHistoryProvider`), and a root that had to look at the
// disk itself would be a second detection able to disagree with this one.
let git = HistoryStore.compose(boardRoot: store.rootURL, tier: tier)
// The board's stack is born here, with the session that owns it, and dies in `tearDown`
// below the whole of 13-native-undo.md's session-only persistence: "the stack lives with
// the board session and dies at close/quit ... standard macOS behavior". On Pro's git boards
// it is instead the repository's own trail, which survives everything (06 Rules Undo
// survives relaunch) the seam's whole point.
let history = makeHistoryProvider(store, tier, git)
// **The loader's earlier-occurrence-wins history rung** (01-storage-format.md Fractal
// layout Rules; `BoardLoader.IdentityHistoryRanker`): git-mode boards get a ranker,
// everything else keeps injecting nothing. A *provider* rather than a ranker because each
@@ -763,6 +789,20 @@ public final class AppModel {
store?.banners.clearHistorySuspension()
}
store.commitSeam = .binding(to: committer)
// **The undo stack's ear on the committer** every commit this engine lands, and
// which of it was heal work (06 Rules The stack is HEAD's first-parent ancestry,
// live; Heal commits are transparent to undo). Bound here rather than in
// `wireGitUndo` because add-git builds a *new* committer, and this wiring is what
// `activateAutoCommit` remembers on its behalf.
committer.reportLanded = { [weak self, ref] window in
guard let provider = self?.sessions[ref]?.history as? GitHistoryProvider else { return }
provider.noteLanded(window)
}
}
// **Add-git binds undo too** (06 Rules Detection the one commanded mid-session mode
// flip). See `bindHistoryProvider(for:)` for the judgment call this records.
git.didAddGit = { [weak self] in
self?.bindHistoryProvider(for: ref)
}
}
// **The binding 13-native-undo.md Rules' "registration at the Writer boundary" needs**: the
@@ -789,10 +829,127 @@ public final class AppModel {
cardRefs: [],
access: access
)
wireGitUndo(history, store: store, git: git, ref: ref)
clearLaunchFailures(naming: [ref.path, store.rootURL.path])
refreshRecents()
}
// MARK: - The git provider's wiring
/// Fills a `GitHistoryProvider`'s seams with the session it is the history of and does nothing
/// at all for any other substrate.
///
/// Everything the git provider needs is a fact about *this* board that neither a repository nor a
/// protocol could supply: which committer's debounce to settle first, whether the git surface is
/// held, which card windows a restore's diff would disturb, and the bracket a wholesale tree
/// change runs inside. Each arrives as a closure for `HistoryCommitSeam`'s reason the provider
/// stays a thing that knows about commits, and the model stays the only object that knows what a
/// window is.
private func wireGitUndo(
_ history: (any HistoryProviding)?,
store: BoardStore,
git: HistoryStore?,
ref: BoardWindowRef
) {
guard let provider = history as? GitHistoryProvider, let git else { return }
provider.flushPendingCommit = { [weak git] in
await git?.committer?.flushNow()
}
provider.isHeld = { [weak git] in git?.committer?.pause != nil }
provider.suspendCommitting = { [weak git] in git?.committer?.stop() }
provider.resumeCommitting = { [weak git] in git?.committer?.start() }
// **A restore that failed cleanly** (06 Interaction with external writers: "surfaces as a
// one-shot banner failure naming the operation and the error, the tree left as it was").
//
// Posted as a **loss row**, and the compromise is recorded rather than hidden: the true
// failure class (`OneShotBanner`) carries a `BoardWriteError`, whose `operation` is the closed
// `WriteOperation` vocabulary and a git operation is deliberately not one of those
// (`BoardStore.performWholesale`'s own note says so). The loss row is the nearest honest
// class: warning tone, one-shot lifecycle, never auto-expires, and a free-form message that
// can name both halves 06 asks for. A message-carrying failure class is the right fix and is
// a banner-surface change, not this card's.
provider.reportFailure = { [weak store] failure in
store?.banners.postLoss(failure.description)
}
provider.runBracketed = { [weak store] subject, work in
guard let store else { return await work() }
// The completion phrase 10-accessibility.md gives a bracketed operation is the restore's
// own subject the sentence the trail now carries, spoken once when the reload lands.
try? await store.performWholesale(announcing: subject) { await work() }
}
provider.settleSessions = { [weak self, weak provider] paths in
guard let self, let provider else { return .proceed }
return await self.settleGate(for: ref, provider: provider).settle(touching: paths)
}
provider.seed()
}
/// **The save-or-discard step for one board**, built from its open card windows
/// (06-history-undo.md Rules Undo restore vs open Edit sessions; Branch switching).
///
/// Built per ask rather than stored, because its whole content is "which card windows are open
/// right now" a set that changes under any operation slow enough to need the step at all.
func settleGate(for ref: BoardWindowRef, provider: GitHistoryProvider?) -> SessionSettleGate {
SessionSettleGate(
sessions: { [weak self] in
guard let self, let session = self.sessions[ref] else { return [] }
return session.cardRefs.compactMap { cardRef in
guard let flushing = self.cardSessions[cardRef],
let settlement = flushing.settlement else { return nil }
return SettleableSession(
id: cardRef.cardID,
cardFolderName: cardRef.cardID,
needsSettling: settlement.needsSettling,
saveAll: settlement.saveAll,
discard: { [weak provider] in
settlement.discard()
// The card's uncommitted on-disk saves are reverted by the restore
// itself, which compares this folder against the working tree rather
// than against HEAD see `GitRestoreOperation.plan`.
provider?.noteDiscarded(cardFolderPath: cardRef.cardID)
}
)
}
},
ask: { await SessionSettleStep.ask() },
focus: { [weak self] id in
guard let self, let session = self.sessions[ref] else { return }
guard let cardRef = session.cardRefs.first(where: { $0.cardID == id }) else { return }
// Opening a window that is already open is how SwiftUI's value-addressed groups say
// "bring that one forward" the same call `BoardWindowHost` makes to open a card, and
// the reason reopening a live card focuses its window rather than making a second one.
self.windowOpener?(id: WindowID.card, value: cardRef)
}
)
}
/// **Binds the git provider onto an already-open session** add-git's one caller.
///
/// 06 Rules Detection sanctions exactly one mid-session mode flip, the app's own add-git:
/// "clicking it flips the open board into git mode immediately the popover flows straight into
/// the git controls, the first auto-commit follows". It does not mention undo, so this is a
/// judgment call and it is recorded here: **the flip binds undo too**, live, rather than waiting
/// for the next open. Three reasons point the same way the mode flip already carries the
/// *committer* through (`HistoryStore.activateAutoCommit` remembers its wiring for precisely this
/// board); 12-editions.md's "an open board finishes with the provider it composed" is a rule about
/// a **tier** lapsing, which cannot change a running session at all; and a board that visibly
/// starts accumulating commits while Z stays greyed out until it is closed and reopened would
/// read as a defect rather than as a policy.
///
/// It only ever adds. A board that already has a provider keeps it, and nothing here can take one
/// away there is no un-add-git.
func bindHistoryProvider(for ref: BoardWindowRef) {
guard var session = sessions[ref], session.history == nil,
let git = session.git, git.mode == .git else { return }
guard let history = makeHistoryProvider(session.store, session.tier, git) else { return }
session.history = history
sessions[ref] = session
session.store.history = history
session.undoManager.history = history
wireGitUndo(history, store: session.store, git: git, ref: ref)
}
/// Registers a card window with its board's session, so the close flush can find it.
///
/// A card window whose board has no session is a card window with no board the ownership rule
@@ -1112,7 +1269,7 @@ public final class AppModel {
// Cleared rather than merely dropped because the steps hold closures over the store
// this line is about to release, and a stack that outlived its board would be a
// retain cycle wearing an undo stack's clothes.
session.history.clear()
session.history?.clear()
storeRegistry.release(session.store)
session.access?.stop()
}
+87
View File
@@ -77,6 +77,14 @@ final class CardWindowSession: CardSessionFlushing {
/// window that has not joined its board holds nothing, which is true.
var rawSourceHoldsUnsavedText: (@MainActor () -> Bool)?
/// The window's raw-source outlet, as the save-or-discard step's two writes: **Apply** (which
/// validates, and answers `false` when it refuses) and **Cancel**. Wired by the host beside
/// `rawSourceHoldsUnsavedText`, and for its reason the outlet is window state living beside
/// this object rather than inside it.
var rawSourceApply: (@MainActor () -> Bool)?
var rawSourceCancel: (@MainActor () -> Void)?
var rawSourceIsActive: (@MainActor () -> Bool)?
/// The Edit buffer's dirty text, a typed-in raw-source outlet, or an inline comment edit session
/// holding keystrokes its file has not got see `CardSessionFlushing`.
///
@@ -89,6 +97,44 @@ final class CardWindowSession: CardSessionFlushing {
body.isDirty || rawSourceHoldsUnsavedText?() == true || comments.holdsUnsavedContent
}
/// **What a restore or a branch switch asks this window to settle** (06-history-undo.md Rules
/// Undo restore vs open Edit sessions).
///
/// ### The predicate is *open*, not *dirty*
///
/// An **open** Edit session is what needs settling even with a clean buffer, because its ~700 ms
/// saves are on disk and deliberately uncommitted the stage-around rule's whole point so a
/// restore landing over them would either bury text no commit protects or leave the session's
/// next debounced save to write pre-restore bytes back over the restored card, "a Z that visibly
/// doesn't happen". Same reading `CardBodyEditSession.isEditing` records for staging, applied to
/// the same fact.
///
/// An **open raw-source outlet** counts whether or not it has been typed in, and 06 says why: its
/// Apply "would write the *entire* pre-switch `index.md` byte-for-byte onto the new branch's
/// card". A buffer read from before the restore is the hazard; typing is not required for it.
var settlement: CardSessionSettlement? {
CardSessionSettlement(
needsSettling: { [self] in
body.isEditing || body.isDirty || rawSourceIsActive?() == true
},
saveAll: { [self] in
// The Edit session ends with its normal commit "each card's EditPreview flip".
body.endEditSession()
// Apply validates; a refusal is the whole operation's cancellation, and the alert it
// raised is already on the offending window.
guard rawSourceIsActive?() == true else { return true }
return rawSourceApply?() ?? true
},
discard: { [self] in
// The buffer goes back to what disk says; the *disk* goes back to the target state as
// part of the restore itself, which reconciles this card's folder against the working
// tree rather than against HEAD (`GitRestoreOperation.plan`).
body.discardBuffer()
rawSourceCancel?()
}
)
}
private var hasEnded = false
/// Both `let`s, wired to each other through a local the guard's two closures need the buffer,
@@ -185,6 +231,9 @@ struct CardWindowHost: View {
/// snapshot the store applies a cache that died with the view would regenerate every thumbnail
/// on every reload (`AttachmentThumbnailCache`).
@State private var thumbnails = AttachmentThumbnailCache()
/// This card's commit trail (05-card-window.md History). Held here for `thumbnails`' reason
/// it must survive every snapshot and surfaced to the view only in git mode (`cardHistory`).
@State private var history = CardHistory()
/// Whether a close is waiting on the dirty-buffer modal. Set when `windowShouldClose` could not
/// flush; cleared by the resolution that lets the close resume.
@State private var isClosePending = false
@@ -311,6 +360,29 @@ struct CardWindowHost: View {
.onDisappear { finish() }
}
/// **This card's commit trail, or nothing at all** (05-card-window.md History).
///
/// `nil` is the section's absence rule, read from the board's own git state rather than from a
/// flag: no `HistoryStore` means the free tier (12-editions.md where the section never exists),
/// and a mode other than `git` means a board the app manages no history for. The object is held
/// by this host so it survives every snapshot, `thumbnails`' reason exactly.
private var cardHistory: CardHistory? {
guard appModel.session(for: ref.board)?.gitMode == .git else { return nil }
return history
}
/// What a trail re-read depends on: this card, and the number of commits the board has landed.
///
/// The count is the committer's own (`GitAutoCommitter.commitCount`), which advances for every
/// commit the app makes the debounced ones, the launch catch-up, and a restore's. A foreign
/// commit an agent made *itself* moves HEAD without touching it; the trail then refreshes at the
/// next commit or the next open, which is the same freshness bound the popover's branch line has
/// and a great deal cheaper than polling HEAD from a sidebar.
private func historyReloadKey(store: BoardStore) -> String {
let commits = appModel.session(for: ref.board)?.git?.committer?.commitCount ?? 0
return "\(ref.cardID)#\(commits)"
}
/// **The minimum grows only while the comments pane is beside the body** (05-card-window.md
/// Composition) which is the whole reason the stacked mount exists, so a narrow display keeps
/// the minimum it always had.
@@ -343,11 +415,20 @@ struct CardWindowHost: View {
attachments: attachments,
comments: session.comments,
thumbnails: thumbnails,
history: cardHistory,
fileDrop: CardWindowDropDelegate(store: store, cardID: placement.card.id),
onToggleTask: { offset, checked in
store.toggleTaskMarker(inCard: placement.card.id, bodyOffset: offset, checked: checked)
}
)
// **The trail, re-read when a commit lands** (05 History). The id is the pair of facts
// the answer depends on: which card this is, and how many commits this board has made
// so the section refreshes after the app's own commits, after an agent's that the watcher
// committed, and after a Z's restore, with nothing here knowing what a committer is.
.task(id: historyReloadKey(store: store)) {
guard let cardHistory else { return }
await cardHistory.load(boardRoot: store.rootURL, cardFolderName: ref.cardID)
}
// **The listing is the snapshot's, republished** `Card.attachments`, which the loader
// fills from `attachments/`'s top-level files in Finder order. Every write in the
// section is bracketed, so the reload that refreshes this arrives by itself and the
@@ -544,6 +625,12 @@ struct CardWindowHost: View {
// The other half of the outlet's wiring: the session answers for this window's unsaved
// content, and the outlet is the half that does not live inside it (`CardWindowSession`).
session.rawSourceHoldsUnsavedText = { [rawSource] in rawSource.holdsUnsavedText }
// The save-or-discard step's half of the same wiring (06-history-undo.md Branch switching):
// Save All *applies* an open outlet validation included, so a refusal cancels the whole
// operation and Discard leaves it without writing.
session.rawSourceIsActive = { [rawSource] in rawSource.isActive }
session.rawSourceApply = { [rawSource] in rawSource.applyAndLeave() }
session.rawSourceCancel = { [rawSource] in rawSource.cancel() }
Self.configureAttachments(attachments, store: store, cardID: cardID)
Self.configureComments(session.comments, store: store, cardID: cardID)
}
+12
View File
@@ -42,11 +42,23 @@ public protocol CardSessionFlushing: AnyObject {
/// template that silently missed those keystrokes would break 09's never-misses-keystrokes
/// guarantee, which outranks the item's availability.
var holdsUnsavedContent: Bool { get }
/// **This window's answers to the save-or-discard step** (06-history-undo.md Rules Undo
/// restore vs open Edit sessions; Branch switching), or `nil` for a window with nothing a
/// wholesale tree operation could disturb.
///
/// Beside `holdsUnsavedContent` and deliberately not folded into it: that property answers "would
/// a *template copy* miss keystrokes", which is a read; this one carries the two writes Save
/// All and Discard that a restore or a branch switch needs the window to perform before it can
/// run on a settled tree. Same window, two different questions, and collapsing them would give
/// the settle step the draft-composer exemption `holdsUnsavedContent` deliberately makes.
var settlement: CardSessionSettlement? { get }
}
public extension CardSessionFlushing {
func endSession() async {}
var holdsUnsavedContent: Bool { false }
var settlement: CardSessionSettlement? { nil }
}
// MARK: - CloseFlushCoordinator
+253
View File
@@ -0,0 +1,253 @@
import AppKit
import Foundation
// MARK: - Vocabulary
/// What the user chose at the save-or-discard step (06-history-undo.md Branch switching: "**Save
/// All** ends every session with its normal commit , **Discard** reverts buffers and uncommitted
/// saves to HEAD, **Cancel** keeps the current branch and the sessions").
public enum SessionSettleChoice: Sendable, Equatable {
case saveAll
case discard
case cancel
}
/// What the gate concluded the only thing the operation behind it branches on.
public enum SessionSettleOutcome: Sendable, Equatable {
/// Nothing needed settling, or everything did and did. The tree is settled; run.
case proceed
/// The user chose Cancel. "Cancel keeps everything" nothing was written, nothing reverted.
case cancelled
/// **Save All met a raw-source buffer that would not validate.** "Since Apply validates, a buffer
/// that fails validation cancels the whole switch with focus on the offending window, nothing
/// half-switched" (06 Branch switching). The payload is that window's session id, already
/// focused by the gate.
case failed(String)
}
// MARK: - What one card window offers the step
/// **A card window's three answers to the save-or-discard step**, handed over as closures.
///
/// A type of its own rather than three members on `CardSessionFlushing` because it is optional as a
/// unit: a window with nothing settleable in it has no settlement, and the gate should not have to
/// ask three questions to find that out. `nil` is also every window in a build with no card session
/// at all, which is what the protocol's default supplies.
@MainActor
public struct CardSessionSettlement {
/// Whether this window is holding state a wholesale tree operation would disturb.
public let needsSettling: @MainActor () -> Bool
/// Ends the Edit session with its normal commit and *applies* the raw buffer. `false` means the
/// raw buffer failed validation.
public let saveAll: @MainActor () -> Bool
/// Reverts the Edit buffer and leaves raw source without writing.
public let discard: @MainActor () -> Void
public init(
needsSettling: @escaping @MainActor () -> Bool,
saveAll: @escaping @MainActor () -> Bool,
discard: @escaping @MainActor () -> Void
) {
self.needsSettling = needsSettling
self.saveAll = saveAll
self.discard = discard
}
}
// MARK: - One settleable session
/// **A card window, as the save-or-discard step sees it** three closures and the card it is over.
///
/// A value of closures rather than a protocol over `CardWindowSession`, for `CloseFlushCoordinator`'s
/// reason exactly: what this gate is *about* is a decision procedure, and a procedure written against
/// a live window is verifiable only by running the app. The production values come from the card
/// windows; a test builds them from a counter.
@MainActor
public struct SettleableSession {
/// The window's identity `CardWindowRef.cardID` is what production passes. Opaque to the gate,
/// and only ever handed back to `focus`.
public let id: String
/// The **card's folder name** its id, which is its folder on disk (01-storage-format.md).
///
/// Matched component-wise against the paths a wholesale operation would write, which is what
/// makes the match survive a lane move: a card's own folder component never changes, only the
/// lane above it (`GitHistoryWalk.path(_:isInsideFolderNamed:)`, the same trick, same reason).
public let cardFolderName: String
/// Whether this session is holding state a wholesale tree operation would disturb: unsaved
/// keystrokes, an **open** Edit session whose ~700 ms saves are deliberately uncommitted, or a
/// raw-source outlet that is open at all.
public let needsSettling: @MainActor () -> Bool
/// **Save All** for this one session: end the Edit session with its normal commit, and *apply*
/// the raw buffer. `false` means the raw buffer failed validation the whole operation is off.
public let saveAll: @MainActor () -> Bool
/// **Discard** for this one session: revert the buffer and leave raw source without writing. The
/// on-disk uncommitted saves are reverted by the operation itself, which is comparing this card's
/// folder against the working tree rather than against HEAD for exactly that reason
/// (`GitRestoreOperation.plan(at:target:excluding:reconciling:)`).
public let discard: @MainActor () -> Void
public init(
id: String,
cardFolderName: String,
needsSettling: @escaping @MainActor () -> Bool,
saveAll: @escaping @MainActor () -> Bool,
discard: @escaping @MainActor () -> Void
) {
self.id = id
self.cardFolderName = cardFolderName
self.needsSettling = needsSettling
self.saveAll = saveAll
self.discard = discard
}
}
// MARK: - SessionSettleGate
/// **The save-or-discard step**, as one reusable decision procedure (06-history-undo.md Rules
/// Undo restore vs open Edit sessions; Branch switching).
///
/// ### One machinery, two callers, by design
///
/// 06 does not describe two gates. It describes the branch-switch step and then hands undo the same
/// one by name: "When the diff *does* touch a session card, the restore **gates on the branch-switch
/// save-or-discard step** (Branch switching below Save All / Discard / Cancel, same machinery, same
/// rationale)." So this object is written for both from the start; the undo provider is its first
/// caller and the branch controls will be its second, passing the paths a checkout would write
/// instead of the paths a restore would.
///
/// ### The diff decides whether it appears at all
///
/// "A restore materializes only the diff between the current tree and the target state, so a card
/// whose open Edit session the diff doesn't touch is simply unaffected its uncommitted ~700 ms
/// saves and the stage-around rule continue undisturbed, and most undos never meet an editor at all."
/// That is `settle(touching:)`'s first line, and it is why the gate takes paths rather than a
/// yes/no: a modal that appeared on every Z because *some* window somewhere was in Edit would be a
/// different, much worse feature.
///
/// ### Why the ask is a closure
///
/// Presenting three buttons is AppKit's job and cannot be asserted without a display. The rule this
/// file exists to hold which sessions are asked about, what each answer does to them, and that a
/// failing raw buffer stops everything with focus on the offender is decidable from values, so the
/// presentation is a seam and the decision is testable.
@MainActor
public struct SessionSettleGate {
/// Every open card session on this board, read live: a window can open or close between the
/// moment an operation starts and the moment it asks.
public var sessions: () -> [SettleableSession]
/// Presents the three-button step and answers what the user chose.
public var ask: () async -> SessionSettleChoice
/// Brings one session's window forward the "focus on the offending window" half of the
/// validation-failure rule.
public var focus: (String) -> Void
public init(
sessions: @escaping () -> [SettleableSession],
ask: @escaping () async -> SessionSettleChoice,
focus: @escaping (String) -> Void = { _ in }
) {
self.sessions = sessions
self.ask = ask
self.focus = focus
}
// MARK: The decision
/// Settles whatever the operation's paths reach, and answers whether it may run.
///
/// - Parameter paths: board-root-relative paths the operation would write.
public func settle(touching paths: Set<String>) async -> SessionSettleOutcome {
let candidates = Self.reached(by: paths, among: sessions()).filter { $0.needsSettling() }
guard !candidates.isEmpty else { return .proceed }
switch await ask() {
case .cancel:
return .cancelled
case .discard:
for session in candidates { session.discard() }
return .proceed
case .saveAll:
for session in candidates {
guard session.saveAll() else {
// "Nothing half-switched": the sessions saved before this one are saved, which is
// an ordinary Save and loses nothing, but the operation itself does not run.
focus(session.id)
return .failed(session.id)
}
}
return .proceed
}
}
/// **Which sessions a set of paths reaches** pure, and the whole of "the diff touches a session
/// card".
///
/// Component-exact folder matching, so a card whose id happens to be a prefix of another's cannot
/// drag that other card's window into the step.
public static func reached(
by paths: Set<String>,
among sessions: [SettleableSession]
) -> [SettleableSession] {
guard !paths.isEmpty else { return [] }
return sessions.filter { session in
paths.contains { GitHistoryWalk.path($0, isInsideFolderNamed: session.cardFolderName) }
}
}
}
// MARK: - The presented step
/// **The three buttons**, as an `NSAlert` the production `SessionSettleGate.ask`.
///
/// One of 02-architecture.md's sanctioned modal moments, and it is modal for `DirtyBufferGuard`'s
/// reason exactly: the operation behind it cannot proceed until the user has decided what happens to
/// text no commit protects, and there is no non-modal shape for a question whose three answers are
/// mutually exclusive and immediate.
///
/// The wording is 06's own vocabulary. The default is **Cancel**, deliberately: a Return pressed
/// reflexively at a dialog nobody read must be the answer that changes nothing, and both other
/// answers write.
public enum SessionSettleStep {
public static let title = "Unsaved card edits"
public static let message = """
Restoring an earlier state would change cards you are editing. \
Save them, discard the changes, or cancel.
"""
@MainActor
public static func ask() async -> SessionSettleChoice {
let alert = NSAlert()
alert.alertStyle = .warning
alert.messageText = title
alert.informativeText = message
// Order matters for the key equivalents AppKit assigns: the first button takes Return, so
// Cancel leads and the two writing answers follow. Escape reaches Cancel either way.
alert.addButton(withTitle: "Cancel")
alert.addButton(withTitle: "Save All")
alert.addButton(withTitle: "Discard")
switch alert.runModal() {
case .alertSecondButtonReturn: return .saveAll
case .alertThirdButtonReturn: return .discard
default: return .cancel
}
}
}