Created
March 12, 2023 13:57
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Simple Rules Engine
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| // The engine | |
| type Rule<T> = (input: T) => boolean; | |
| const All = | |
| <T>(...rules: Rule<T>[]) => | |
| (input: T) => | |
| rules.every((r) => r(input)); | |
| const Some = | |
| <T>(...rules: Rule<T>[]) => | |
| (input: T) => | |
| rules.some((r) => r(input)); | |
| const One = | |
| <T>(...rules: Rule<T>[]) => | |
| (input: T) => | |
| rules.filter((r) => r(input)).length === 1; | |
| const None = | |
| <T>(...rules: Rule<T>[]) => | |
| (input: T) => | |
| rules.filter((r) => r(input)).length === 0; | |
| const ruleRunner = | |
| <T, R>(rules: [R, Rule<T>][]) => | |
| (input: T) => | |
| rules.filter(([_, rule]) => rule(input)).map(([output, _]) => output); | |
| // An example | |
| type Ingredient = | |
| | 'salami' | |
| | 'olives' | |
| | 'peppers' | |
| | 'mushrooms' | |
| | 'pineapple' | |
| | 'banana'; | |
| type Dough = 'thin' | 'fluffy'; | |
| type Source = 'dominos' | 'pizzahut'; | |
| type Pizza = { | |
| ingredients: Ingredient[]; | |
| dough: Dough; | |
| source: Source; | |
| }; | |
| const has = (ingredient: Ingredient) => (pizza: Pizza) => | |
| pizza.ingredients.includes(ingredient); | |
| const dough = (dough: Dough) => (pizza: Pizza) => pizza.dough === dough; | |
| const source = (source: Source) => (pizza: Pizza) => pizza.source === source; | |
| const rules: [string, Rule<Pizza>][] = [ | |
| ['Mario', None(has('salami'), has('olives'))], | |
| ['Yoshi', All(has('pineapple'), has('banana'), source('dominos'))], | |
| ['Luigi', Some(has('mushrooms'), has('peppers'), dough('fluffy'))], | |
| ['Princess Peach', One(has('salami'), has('peppers'))] | |
| ]; | |
| const pizzas: Pizza[] = [ | |
| { ingredients: ['salami'], dough: 'thin', source: 'dominos' }, | |
| { ingredients: ['salami'], dough: 'fluffy', source: 'dominos' }, | |
| { ingredients: ['mushrooms'], dough: 'thin', source: 'pizzahut' }, | |
| { ingredients: ['pineapple'], dough: 'thin', source: 'pizzahut' }, | |
| { ingredients: ['pineapple', 'banana'], dough: 'fluffy', source: 'dominos' }, | |
| { ingredients: ['salami', 'peppers'], dough: 'fluffy', source: 'pizzahut' } | |
| ]; | |
| for (const pizza of pizzas) { | |
| console.log(ruleRunner(rules)(pizza)); | |
| } |
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