feat: add convex state functions for snapshot persistence

convex/schema.ts

@@ -0,0 +1,9 @@
+import { defineSchema, defineTable } from "convex/server";
+import { v } from "convex/values";
+
+export default defineSchema({
+  state_snapshots: defineTable({
+    snapshot: v.any(),
+    updatedAt: v.string(),
+  }),
+});

convex/state.ts

@@ -0,0 +1,45 @@
+import { mutation, query } from "./_generated/server";
+import { v } from "convex/values";
+
+export const getLatestSnapshot = query({
+  args: {},
+  handler: async (ctx) => {
+    const latest = await ctx.db
+      .query("state_snapshots")
+      .order("desc")
+      .first();
+
+    return latest
+      ? {
+        snapshot: latest.snapshot,
+        updatedAt: latest.updatedAt,
+      }
+      : null;
+  },
+});
+
+export const saveSnapshot = mutation({
+  args: {
+    snapshot: v.any(),
+    updatedAt: v.string(),
+  },
+  handler: async (ctx, args) => {
+    const latest = await ctx.db
+      .query("state_snapshots")
+      .order("desc")
+      .first();
+
+    if (latest) {
+      await ctx.db.patch(latest._id, {
+        snapshot: args.snapshot,
+        updatedAt: args.updatedAt,
+      });
+      return latest._id;
+    }
+
+    return ctx.db.insert("state_snapshots", {
+      snapshot: args.snapshot,
+      updatedAt: args.updatedAt,
+    });
+  },
+});