Increase selection and recording functionality

- Added a button to each delta for selection
- Updated the `session` store to return the first session if the sessionId is not found
- Updated the `previousSession` store to return the session before the current one if it exists
- Updated the `docsNext` derived store to include the `selection` store
- Added an `if` statement for `files` in `+page.svelte`

[src/routes/projects/[projectId]/sessions/[sessionId]/+page.ts]
- Changed the import of `svelte/store` to include `writable`
- Changed the `session` store to return the first session if the sessionId is not found
- Changed the `previousSession` store to return the session before the current one if it exists
[src/routes/projects/[projectId]/sessions/[sessionId]/+page.svelte]
- Move the `Timeline` component import from `+page.svelte`
- Initialize `selection` store in `+page.svelte`
- Update `docsNext` derived store to include the `selection` store
- Add a button to each delta for selection
- Add an `if` statement for `files` in `+page.svelte`
- Delete `contentWithDeltasApplied` function from `+page.

src/routes/projects/[projectId]/sessions/[sessionId]/+page.svelte

@@ -1,9 +1,8 @@
 <script lang="ts">
     import { Doc } from "yjs";
-    import { Timeline, CodeViewer } from "$lib/components";
+    import { CodeViewer } from "$lib/components";
     import { Operation } from "$lib/deltas";
-    import type { Delta } from "$lib/deltas";
-    import { derived, writable } from "svelte/store";
+    import { derived } from "svelte/store";
     import type { PageData } from "./$types";
     import SessionNav from "$lib/components/session/SessionNav.svelte";
     import { toHumanReadableTime } from "$lib/time";
@@ -15,21 +14,32 @@
     $: nextSession = data.nextSession;
     $: session = data.session;
     $: deltas = data.deltas;
-    $: files = data.files;
 
-    const value = writable(new Date().getTime());
+    $: selection = {} as Record<string, Record<string, number>>;
 
-    const docs = derived(value, (value) =>
+    $: docsNext = derived([data.deltas], ([deltas]) =>
         Object.fromEntries(
-            Object.entries($deltas).map(([filePath, deltas]) => {
+            Object.entries(deltas).map(([filePath, deltas]) => {
                 const doc = new Doc();
                 const text = doc.getText();
-                if (filePath in files) {
-                    text.insert(0, files[filePath]);
+                if (filePath in data.files) {
+                    text.insert(0, data.files[filePath]);
                 }
+                const contentAtStart = text.toString();
+
+                if (!selection.hasOwnProperty($session?.id)) {
+                    selection[$session.id] = {};
+                }
+                if (!selection[$session.id].hasOwnProperty(filePath)) {
+                    selection[$session?.id][filePath] = deltas.length - 1;
+                }
+
                 const operations = deltas
-                    .filter((delta) => delta.timestampMs <= value)
+                    .filter(
+                        (_, index) => index <= selection[$session.id][filePath]
+                    )
                     .flatMap((delta) => delta.operations);
+
                 operations.forEach((operation) => {
                     if (Operation.isInsert(operation)) {
                         text.insert(operation.insert[0], operation.insert[1]);
@@ -37,36 +47,12 @@
                         text.delete(operation.delete[0], operation.delete[1]);
                     }
                 });
-                return [filePath, text.toString()];
+
+                const contentAfterDeltas = text.toString();
+                return [filePath, { a: contentAtStart, b: contentAfterDeltas }];
             })
         )
     );
-
-    const contentWithDeltasApplied = (
-        contentAtSessionStart: string,
-        deltas: Delta[]
-    ) => {
-        const doc = new Doc();
-        const text = doc.getText();
-        text.insert(0, contentAtSessionStart);
-        const operations = deltas.flatMap((delta) => delta.operations);
-        operations.forEach((operation) => {
-            if (Operation.isInsert(operation)) {
-                text.insert(operation.insert[0], operation.insert[1]);
-            } else if (Operation.isDelete(operation)) {
-                text.delete(operation.delete[0], operation.delete[1]);
-            }
-        });
-        return text.toString();
-    };
-
-    // const timestamps = Object.values(deltas).flatMap((deltas) =>
-    //     Object.values(deltas).map((delta) => delta.timestampMs)
-    // );
-
-    // const min = Math.min(...timestamps);
-    // const max = Math.max(...timestamps);
-    // const showTimeline = isFinite(min) && isFinite(max);
 </script>
 
 <div class="flex flex-col w-full h-full overflow-hidden space-y-2">
@@ -78,36 +64,30 @@
             previousSesssion={$previousSesssion}
         />
     </div>
+
     <div class="overflow-auto h-2/3 mx-4">
-        {#each Object.entries(files) as [filepath, contentAtSessionStart]}
-            {#if $deltas[filepath]}
+        {#each Object.entries($docsNext) as [filepath, content]}
             <details open>
-                    <summary>
-                        {filepath}
-                    </summary>
-                    <CodeViewer
-                        value={contentAtSessionStart}
-                        newValue={contentWithDeltasApplied(
-                            contentAtSessionStart,
-                            $deltas[filepath]
-                        )}
-                    />
-                </details>
-            {/if}
-        {/each}
-    </div>
-    <div class="flex flex-col border-t border-zinc-700 mt-2">
-        {#each Object.entries($deltas) as [filepath, deltas]}
-            <div class="flex">
-                <div class="w-32">{filepath}</div>
-                <div class="flex space-x-2 items-center">
-                    {#each deltas as delta}
-                        <div class="cursor-pointer text-center items-center justify-center text-xs rounded-full h-4 w-4 bg-zinc-400 text-zinc-600 hover:bg-zinc-200" title="{toHumanReadableTime(delta.timestampMs)}">
+                <summary>{filepath}</summary>
+                <div class="flex flex-col">
+                    <div class="flex space-x-1">
+                        {#each $deltas[filepath] as delta, i}
+                            <button
+                                on:click={() => {
+                                    selection[$session.id][filepath] = i;
+                                }}
+                                class="{selection[$session.id][filepath] == i
+                                    ? 'bg-orange-300'
+                                    : ''} text-center items-center justify-center text-xs rounded-full h-4 w-4 bg-zinc-400 text-zinc-600 hover:bg-zinc-200"
+                                title={toHumanReadableTime(delta.timestampMs)}
+                            >
                                 <span>{delta.operations.length}</span>
-                        </div>
+                            </button>
                         {/each}
                     </div>
+                    <CodeViewer value={content.a} newValue={content.b} />
                 </div>
+            </details>
         {/each}
     </div>
 </div>

src/routes/projects/[projectId]/sessions/[sessionId]/+page.ts

@@ -1,5 +1,5 @@
 import type { PageLoad } from "./$types";
-import { derived, readable } from "svelte/store";
+import { derived, readable, writable } from "svelte/store";
 import { building } from "$app/environment";
 import type { Delta } from "$lib/deltas";
 
@@ -19,8 +19,10 @@ export const load: PageLoad = async ({ parent, params }) => {
               sessionId: params.sessionId,
           });
     return {
-        session: derived(sessions, (sessions) =>
-            sessions.find((session) => session.id === params.sessionId)
+        session: derived(sessions, (sessions) => {
+            const result = sessions.find((session) => session.id === params.sessionId)
+            return result ? result : sessions[0];
+        }
         ),
         previousSesssion: derived(sessions, (sessions) => {
             const currentSessionIndex = sessions.findIndex(