Firebase Database Rules with TypeScript

typescript-firebase-database-rules.ts

// Use the TypeScript compiler to check your database rules.
// You'll get the most out of type checking if you define a database schema
// through interfaces and use it both in the web client and with the database rules.
// The compiler will catch misspellings and structural errors.
// It won't check for completeness since all properties are optional.
// Only works with TypeScript 2.1 and up because of mapped types being used.

interface DatabaseRuleSet {
  '.read'?: string | boolean
  '.write'?: string | boolean
  '.validate'?: string | boolean
  '.indexOn'?: string | string[]
}

// Union types of objects do not work as types for properties
// 16 levels since firebase allows max of 16 levels.
type RulesOf<A> = {
  [B in keyof A]?: {
  [C in keyof A[B]]?: {
  [D in keyof A[B][C]]?: {
  [E in keyof A[B][C][D]]?: {
  [F in keyof A[B][C][D][E]]?: {
  [G in keyof A[B][C][D][E][F]]?: {
  [H in keyof A[B][C][D][E][F][G]]?: {
  [I in keyof A[B][C][D][E][F][G][H]]?: {
  [J in keyof A[B][C][D][E][F][G][H][I]]?: {
  [K in keyof A[B][C][D][E][F][G][H][I][J]]?: {
  [L in keyof A[B][C][D][E][F][G][H][I][J][K]]?: {
  [M in keyof A[B][C][D][E][F][G][H][I][J][K][L]]?: {
  [N in keyof A[B][C][D][E][F][G][H][I][J][K][L][M]]?: {
  [O in keyof A[B][C][D][E][F][G][H][I][J][K][L][M][N]]?: {
  [P in keyof A[B][C][D][E][F][G][H][I][J][K][L][M][N][O]]?: DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet
  } & DatabaseRuleSet

export interface DatabaseRules<Schema> {
  rules: RulesOf<Schema>
}
  
// Define your database schema
  
interface UserData {
  userName: string
  email: string
  signedUpAt: number
}
  
interface DatabaseSchema {
  users: {
    [uid: string]: UserData
  }
}
  
// Use the DatabaseRules interface with your schema.

const rules: DatabaseRules<DatabaseSchema> = {
  rules: {
    users: {
      '.read': 'auth != null',
      '.write': 'auth.uid == $uid',
      $uid: {
        userName: {
          '.validate': 'newData.isString() && newData.val().length >= 2'
        },
        email: {
          '.validate': 'newData.isString()'
        },
        signedUpAt: {
          '.validate': 'newData.isNumber()'
        },
      }
    } 
  }
};

  
// Write the rules as json for deployment.
  
require('fs').writeFileSync('./database.rules.json', JSON.stringify(rules, null, 2));