Add SSH connections: saved hosts manager and hierarchical shell picker

src/lib/layout/tree.ts

@@ -10,13 +10,25 @@ export type NodeId = string;
 /** 'h' = side-by-side (a on left, b on right). 'v' = stacked (a on top, b below). */
 export type Orientation = "h" | "v";
 
+/** What kind of shell a leaf is running. Determines which fields on
+ *  LeafNode are meaningful at spawn time and which spawn-spec the backend
+ *  receives. Migration on deserialize backfills this for pre-shellKind
+ *  workspaces (PowerShell was previously a sentinel `distro` string). */
+export type ShellKind = "wsl" | "powershell" | "ssh";
+
 export interface LeafNode {
   kind: "leaf";
   id: NodeId;
-  /** WSL distro the pane was spawned against. */
+  /** Discriminator: which shell-type this pane runs. */
+  shellKind: ShellKind;
+  /** WSL distro the pane was spawned against. Only meaningful when
+   *  shellKind === "wsl". */
   distro?: string;
-  /** Working directory the pane was started in. Not currently used at spawn time but preserved for future. */
+  /** Working directory the pane was started in. Only meaningful when
+   *  shellKind === "wsl". */
   cwd?: string;
+  /** Saved-host id (see SshHost). Only meaningful when shellKind === "ssh". */
+  sshHostId?: string;
   /** Optional user label shown in the pane toolbar. */
   label?: string;
   /**
@@ -60,7 +72,47 @@ function newId(): NodeId {
 }
 
 export function newLeaf(props: Partial<Omit<LeafNode, "kind" | "id">> = {}): LeafNode {
-  return { kind: "leaf", id: newId(), ...props };
+  return { kind: "leaf", id: newId(), shellKind: "wsl", ...props };
+}
+
+/** Spec for switching a leaf's shell. Discriminated by shellKind. Used by
+ *  {@link setLeafShell}; the helper always swaps the leaf id so the renderer
+ *  remounts XtermPane (kills the old PTY → spawns a fresh one with the new
+ *  spec). */
+export type LeafShellSpec =
+  | { shellKind: "wsl"; distro?: string; cwd?: string }
+  | { shellKind: "powershell" }
+  | { shellKind: "ssh"; sshHostId: string };
+
+/**
+ * Replace the leaf's shell-kind and shell-specific fields, then swap its id
+ * so the renderer's `key={leaf.id}` block remounts XtermPane (kills the old
+ * PTY → spawns a fresh one). Metadata like label / broadcast / font-size
+ * survives.
+ */
+export function setLeafShell(
+  root: TreeNode,
+  leafId: NodeId,
+  spec: LeafShellSpec,
+): TreeNode {
+  return replaceById(root, leafId, (node) => {
+    if (node.kind !== "leaf") return node;
+    const base: LeafNode = {
+      kind: "leaf",
+      id: newId(),
+      shellKind: spec.shellKind,
+      label: node.label,
+      broadcast: node.broadcast,
+      fontSizeOffset: node.fontSizeOffset,
+    };
+    if (spec.shellKind === "wsl") {
+      if (spec.distro !== undefined) base.distro = spec.distro;
+      if (spec.cwd !== undefined) base.cwd = spec.cwd;
+    } else if (spec.shellKind === "ssh") {
+      base.sshHostId = spec.sshHostId;
+    }
+    return base;
+  });
 }
 
 export function newSplit(
@@ -128,19 +180,18 @@ export function findLeaf(root: TreeNode, leafId: NodeId): LeafNode | null {
 }
 
 /**
- * Swap the distro on a leaf. The leaf gets a **new id** so the rendering
- * layer's `{#key node.id}` block remounts XtermPane — the old PTY is killed
- * and a fresh one spawns with the new distro.
+ * Swap the WSL distro on a leaf. The leaf gets a **new id** so the rendering
+ * layer remounts XtermPane — the old PTY is killed and a fresh one spawns
+ * against the new distro. Also forces shellKind back to "wsl" if the leaf
+ * had been a non-WSL kind (which is what the existing per-pane dropdown
+ * does when the user picks a WSL distro entry).
  */
 export function changeDistro(
   root: TreeNode,
   leafId: NodeId,
   distro: string,
 ): TreeNode {
-  return replaceById(root, leafId, (node) => {
-    if (node.kind !== "leaf") return node;
-    return { ...node, id: newId(), distro };
-  });
+  return setLeafShell(root, leafId, { shellKind: "wsl", distro });
 }
 
 /** Set or clear a leaf's label. Does NOT remount (label is metadata only). */
@@ -293,8 +344,10 @@ export function reshapeToPreset(
     if (!src) break;
     const slot = slots[i];
     slot.id = src.id;
+    slot.shellKind = src.shellKind;
     if (src.distro !== undefined) slot.distro = src.distro;
     if (src.cwd !== undefined) slot.cwd = src.cwd;
+    if (src.sshHostId !== undefined) slot.sshHostId = src.sshHostId;
     if (src.label !== undefined) slot.label = src.label;
     if (src.broadcast !== undefined) slot.broadcast = src.broadcast;
     if (src.fontSizeOffset !== undefined) slot.fontSizeOffset = src.fontSizeOffset;
@@ -518,17 +571,38 @@ export function serialize(root: TreeNode): string {
   return JSON.stringify(root);
 }
 
-/** Parse JSON back to a tree. Returns null on invalid input. */
+/** Parse JSON back to a tree. Returns null on invalid input. Pre-shellKind
+ *  workspaces are migrated in place: leaves without `shellKind` get one
+ *  inferred from the legacy `distro` sentinel (`"PowerShell"` → powershell,
+ *  anything else → wsl). */
 export function deserialize(json: string): TreeNode | null {
   try {
     const parsed = JSON.parse(json);
     if (!isTreeNode(parsed)) return null;
-    return parsed;
+    return migrateLegacyLeaves(parsed);
   } catch {
     return null;
   }
 }
 
+/** Sentinel used in pre-shellKind workspaces to mark PowerShell panes. */
+const LEGACY_POWERSHELL_DISTRO = "PowerShell";
+
+function migrateLegacyLeaves(node: TreeNode): TreeNode {
+  if (node.kind === "leaf") {
+    if (node.shellKind) return node;
+    if (node.distro === LEGACY_POWERSHELL_DISTRO) {
+      const { distro: _distro, ...rest } = node;
+      return { ...rest, shellKind: "powershell" };
+    }
+    return { ...node, shellKind: "wsl" };
+  }
+  const a = migrateLegacyLeaves(node.a);
+  const b = migrateLegacyLeaves(node.b);
+  if (a === node.a && b === node.b) return node;
+  return { ...node, a, b };
+}
+
 function isTreeNode(x: unknown): x is TreeNode {
   if (typeof x !== "object" || x === null) return false;
   const o = x as Record<string, unknown>;