From 95330e04deb3fbf76560a5c983d35f2043c79320 Mon Sep 17 00:00:00 2001
From: Reaper Gelera <ahoy@barelyhuman.dev>
Date: Wed, 6 Dec 2023 01:44:29 +0530
Subject: [PATCH] feat: add in build batcher

---
 src/index.ts           | 13 ++++++++----
 src/{ => lib}/hooks.ts |  0
 src/lib/promise.ts     | 45 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 4 deletions(-)
 rename src/{ => lib}/hooks.ts (100%)
 create mode 100644 src/lib/promise.ts

diff --git a/src/index.ts b/src/index.ts
index 21fc48b..4f1dc61 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,8 @@
 import esbuild from 'esbuild'
 import { defu } from 'defu'
 import glob from 'tiny-glob'
-import { createHook } from './hooks.js'
+import { createHook } from './lib/hooks.js'
+import { batcher } from './lib/promise.js'
 
 export type GlobOptions = {
   cwd?: string
@@ -60,10 +61,14 @@ class ContextManager {
     }
   }
 
-  async build() {
+  async build({ limit = Infinity } = {}) {
     await this.#createContext()
-    await Promise.all(this.#contexts.map(x => x.rebuild()))
-    await this.#eventBus.emit('complete', null)
+    const errors = await batcher(x => x.rebuild(), { limit })(this.#contexts)
+    if (errors.length > 0) {
+      await this.#eventBus.emit('error', errors)
+    } else {
+      await this.#eventBus.emit('complete', null)
+    }
   }
 
   async watch() {
diff --git a/src/hooks.ts b/src/lib/hooks.ts
similarity index 100%
rename from src/hooks.ts
rename to src/lib/hooks.ts
diff --git a/src/lib/promise.ts b/src/lib/promise.ts
new file mode 100644
index 0000000..f9d0ee4
--- /dev/null
+++ b/src/lib/promise.ts
@@ -0,0 +1,45 @@
+type BatchOptions = {
+  limit: number
+}
+
+/**
+ * TODO: can be faster
+ */
+export const batcher =
+  <T extends any[], K extends keyof T, Item extends T[K]>(
+    mapper: (item: Item) => Promise<void>,
+    { limit = Infinity }: BatchOptions
+  ) =>
+  async (collection: T) => {
+    const errors: Error[] = []
+    const pwindow: Item[] = []
+
+    const process = async () => {
+      let batch: any = []
+      while (pwindow.length > 0) {
+        const item = pwindow.shift()
+        if (item) {
+          batch.push(mapper(item))
+        }
+      }
+      const result = await Promise.allSettled(batch)
+      result.forEach(d => {
+        if (d.status === 'rejected') {
+          errors.push(new Error(d.reason))
+        }
+      })
+    }
+
+    for (let item of collection) {
+      pwindow.push(item)
+      if (pwindow.length >= limit) {
+        await process()
+      }
+    }
+
+    if (pwindow.length) {
+      await process()
+    }
+
+    return errors
+  }