From c2e1e223d16e7bf87117cd8d72ad3ba211a333d8 Mon Sep 17 00:00:00 2001
From: Pooya Parsa <pyapar@gmail.com>
Date: Thu, 26 Aug 2021 20:11:55 +0200
Subject: [PATCH] feat!: improve type checking

---
 src/hookable.ts | 38 +++++++++++++++++++++++---------------
 src/types.ts    | 13 +++++++------
 src/utils.ts    | 23 ++++++++++++-----------
 3 files changed, 42 insertions(+), 32 deletions(-)

diff --git a/src/hookable.ts b/src/hookable.ts
index 2e47edf..8973242 100644
--- a/src/hookable.ts
+++ b/src/hookable.ts
@@ -1,10 +1,14 @@
 import { serial, flatHooks, mergeHooks } from './utils'
-import { LoggerT, hookFnT, configHooksT, deprecatedHookT, deprecatedHooksT } from './types'
+import type { LoggerT, DeprecatedHook, NestedHooks, HookCallback, HookKeys } from './types'
 export * from './types'
 
-class Hookable {
-  private _hooks: { [name: string]: hookFnT[] }
-  private _deprecatedHooks: deprecatedHooksT
+class Hookable <
+  _HooksT = Record<string, HookCallback>,
+  HooksT = _HooksT & { error: (error: Error | any) => void },
+  HookNameT extends HookKeys<HooksT> = HookKeys<HooksT>
+> {
+  private _hooks: { [key: string]: HookCallback[] }
+  private _deprecatedHooks: Record<string, DeprecatedHook<HooksT>>
   private _logger: LoggerT | false
 
   static mergeHooks: typeof mergeHooks
@@ -20,7 +24,7 @@ class Hookable {
     this.callHook = this.callHook.bind(this)
   }
 
-  hook (name: string, fn: hookFnT) {
+  hook <NameT extends HookNameT>(name: NameT, fn: HooksT[NameT] & HookCallback) {
     if (!name || typeof fn !== 'function') {
       return () => {}
     }
@@ -56,7 +60,7 @@ class Hookable {
     }
   }
 
-  hookOnce (name: string, fn: hookFnT) {
+  hookOnce <NameT extends HookNameT>(name: NameT, fn: HooksT[NameT] & HookCallback) {
     let _unreg
     let _fn = (...args) => {
       _unreg()
@@ -64,11 +68,11 @@ class Hookable {
       _fn = null
       return fn(...args)
     }
-    _unreg = this.hook(name, _fn)
+    _unreg = this.hook(name, _fn as typeof fn)
     return _unreg
   }
 
-  removeHook (name: string, fn: hookFnT) {
+  removeHook <NameT extends HookNameT> (name: NameT, fn: HooksT[NameT] & HookCallback) {
     if (this._hooks[name]) {
       const idx = this._hooks[name].indexOf(fn)
 
@@ -82,16 +86,17 @@ class Hookable {
     }
   }
 
-  deprecateHook (name: string, deprecated: deprecatedHookT) {
+  deprecateHook <NameT extends HookNameT> (name: NameT, deprecated: DeprecatedHook<HooksT>) {
     this._deprecatedHooks[name] = deprecated
   }
 
-  deprecateHooks (deprecatedHooks: deprecatedHooksT) {
+  deprecateHooks (deprecatedHooks: Record<HookNameT, DeprecatedHook<HooksT>>) {
     Object.assign(this._deprecatedHooks, deprecatedHooks)
   }
 
-  addHooks (configHooks: configHooksT) {
-    const hooks = flatHooks(configHooks)
+  addHooks (configHooks: NestedHooks<HooksT>) {
+    const hooks = flatHooks<HooksT>(configHooks)
+    // @ts-ignore
     const removeFns = Object.keys(hooks).map(key => this.hook(key, hooks[key]))
 
     return () => {
@@ -101,14 +106,16 @@ class Hookable {
     }
   }
 
-  removeHooks (configHooks: configHooksT) {
-    const hooks = flatHooks(configHooks)
+  removeHooks (configHooks: NestedHooks<HooksT>) {
+    const hooks = flatHooks<HooksT>(configHooks)
     for (const key in hooks) {
+      // @ts-ignore
       this.removeHook(key, hooks[key])
     }
   }
 
-  async callHook (name: string, ...args: any) {
+  // @ts-ignore HooksT[NameT] & HookCallback prevents typechecking
+  async callHook <NameT extends HookNameT> (name: NameT, ...args: Parameters<HooksT[NameT]>) {
     if (!this._hooks[name]) {
       return
     }
@@ -116,6 +123,7 @@ class Hookable {
       await serial(this._hooks[name], fn => fn(...args))
     } catch (err) {
       if (name !== 'error') {
+        // @ts-ignore Stranger Things
         await this.callHook('error', err)
       }
       if (this._logger) {
diff --git a/src/types.ts b/src/types.ts
index b11b8bb..04adf21 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,9 +1,10 @@
-export type unregHookT = () => void
-export type hookFnT = (...args: any) => Promise<void> | void
-export type configHooksT = { [name: string]: configHooksT | hookFnT }
-export type deprecatedHookT = string | { message: string, to: string }
-export type deprecatedHooksT = { [name: string]: deprecatedHookT}
-export type flatHooksT = { [name: string]: hookFnT }
+export type HookCallback = (...args: any) => Promise<void> | void
+
+export interface Hooks { [key: string]: HookCallback }
+export type HookKeys<T> = keyof T & string
+export type NestedHooks<T> = { [name in HookKeys<T>]: NestedHooks<T> | HookCallback }
+export type DeprecatedHook<T> = string | { message: string, to: HookKeys<T> }
+export type DeprecatedHooks<T> = { [name in HookKeys<T>]: DeprecatedHook<T> }
 
 export interface LoggerT {
   error(...args: any): void,
diff --git a/src/utils.ts b/src/utils.ts
index b112a47..9d6c904 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,28 +1,29 @@
-import { configHooksT, flatHooksT } from './types'
+import { NestedHooks } from './types'
 
-export function flatHooks (configHooks: configHooksT, hooks: flatHooksT = {}, parentName?: string): flatHooksT {
+export function flatHooks<T> (configHooks: NestedHooks<T>, hooks: T = {} as T, parentName?: string): T {
   for (const key in configHooks) {
     const subHook = configHooks[key]
     const name = parentName ? `${parentName}:${key}` : key
     if (typeof subHook === 'object' && subHook !== null) {
       flatHooks(subHook, hooks, name)
     } else if (typeof subHook === 'function') {
+      // @ts-ignore
       hooks[name] = subHook
     }
   }
-  return hooks
+  return hooks as any
 }
 
-export function mergeHooks (...hooks: configHooksT[]): flatHooksT {
-  const finalHooks: any = {}
+export function mergeHooks<T> (...hooks: NestedHooks<T>[]): T {
+  const finalHooks = {} as any
 
-  for (let _hook of hooks) {
-    _hook = flatHooks(_hook)
-    for (const key in _hook) {
+  for (let hook of hooks) {
+    const flatenHook = flatHooks(hook)
+    for (const key in flatenHook) {
       if (finalHooks[key]) {
-        finalHooks[key].push(_hook[key])
+        finalHooks[key].push(flatenHook[key])
       } else {
-        finalHooks[key] = [_hook[key]]
+        finalHooks[key] = [flatenHook[key]]
       }
     }
   }
@@ -36,7 +37,7 @@ export function mergeHooks (...hooks: configHooksT[]): flatHooksT {
     }
   }
 
-  return finalHooks
+  return finalHooks as any
 }
 
 export function serial<T> (tasks: T[], fn: (task: T) => Promise<any> | any) {