Dependency Injection

Share tools between handlers, hooks and plugins without globals.

The problem it solves

// ❌ Bad: global variable
const db = new Database()

bot.when('visitas', async (ctx) => {
  const user = await db.touch(ctx.from)  // db is global
})

// ✅ Good: injected
bot.provide('db', new Database())

bot.when('visitas', async (ctx) => {
  const user = await ctx.tools.db.touch(ctx.from)  // db is in ctx.tools
})

How it works

1. Register a tool

bot.provide('db', {
  users: new Map(),
  async touch(jid: string) {
    const u = this.users.get(jid) ?? { visits: 0 }
    u.visits++
    this.users.set(jid, u)
    return u
  },
})

bot.provide(name, value) returns this, so calls can be chained:

bot
  .provide('db', myDatabase)
  .provide('cache', myCache)

2. Use it in any handler

bot.when('visitas', async (ctx) => {
  const db = ctx.tools.db
  const user = await db.touch(ctx.from)
  await ctx.reply(`📊 You have visited ${user.visits} times.`)
})

3. Available in hooks and plugins too

bot.before('message', async (ctx, next) => {
  const db = ctx.tools.db
  await db.touch(ctx.from)
  await next()
})

A plugin's install(ctx) also receives ctx.tools, so plugins can consume tools registered elsewhere (or register their own with bot.provide).

Multiple tools

bot.provide('db', myDatabase)
bot.provide('cache', myCache)
bot.provide('api', myApiClient)

bot.when('test', async (ctx) => {
  await ctx.tools.db.query(/* ... */)
  await ctx.tools.cache.get(/* ... */)
  await ctx.tools.api.fetch(/* ... */)
})

Next steps

• Plugins — access tools from a plugin
• Scheduler — scheduled tasks