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ehmickyehmicky
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Refactoring
1 parent 2f9811b commit 3b37d5f

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5 files changed

+131
-76
lines changed

5 files changed

+131
-76
lines changed

‎src/condition.js‎

Lines changed: 20 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1,25 +1,33 @@
11
import isErrorInstance from 'is-error-instance'
2+
import isPlainObj from 'is-plain-obj'
23

3-
// Check if a value matches a condition: error name, class or filtering function
4-
export const matchesCondition = (value, condition) => {
4+
// TODO: allow for array
5+
// TODO: document support for array, boolean, props object
6+
export const normalizeCondition = (condition) => {
57
if (typeof condition === 'string') {
6-
return matchesErrorName(value, condition)
8+
return matchesErrorName.bind(undefined, condition)
79
}
810

9-
if (typeof condition !== 'function') {
10-
throw new TypeError(
11-
`The condition must be an error class, an error name string or a filtering function, not: ${condition}`,
12-
)
11+
if (isProto.call(Error, condition)) {
12+
return isInstanceOf.bind(undefined, condition)
1313
}
1414

15-
if (isProto.call(Error, condition)) {
16-
return value instanceof condition
15+
if (
16+
typeof condition !== 'function' &&
17+
!isPlainObj(condition) &&
18+
typeof condition === 'boolean'
19+
) {
20+
throw new TypeError(
21+
`The condition must be an error class, an error name string, a filtering function, a boolean or a properties object, not: ${condition}`,
22+
)
1723
}
1824

19-
return Boolean(condition(value))
25+
return condition
2026
}
2127

22-
const matchesErrorName = (value, name) =>
23-
isErrorInstance(value) && value.name === name
28+
const matchesErrorName = (condition, value) =>
29+
isErrorInstance(value) && value.name === condition
2430

2531
const { isPrototypeOf: isProto } = Object.prototype
32+
33+
const isInstanceOf = (condition, value) => value instanceof condition

‎src/effect.js‎

Lines changed: 34 additions & 44 deletions
Original file line numberDiff line numberDiff line change
@@ -2,64 +2,54 @@ import isPlainObj from 'is-plain-obj'
22

33
// Apply wrapping effect to an error: class, message, options or mapping
44
// function
5-
export const applyEffects = (value, effects, ErrorClass) => {
6-
const defaultEffects = {
7-
ErrorClass,
8-
message: '',
9-
options: {},
10-
mapper: identity,
11-
}
12-
const {
13-
ErrorClass: ErrorClassA,
14-
message,
15-
options,
16-
mapper,
17-
} = Object.assign(
18-
{},
19-
defaultEffects,
20-
...effects.map((effect) => parseEffect(effect, ErrorClass)),
21-
)
22-
const cause = mapper(value)
23-
return new ErrorClassA(message, { ...options, cause })
5+
export const normalizeEffects = (effects, ErrorClass) => {
6+
validateEffects(effects, ErrorClass)
7+
return applyEffects.bind(undefined, effects, ErrorClass)
248
}
259

26-
const identity = (value) => value
27-
28-
const parseEffect = (effect, ErrorClass) => {
29-
const type = getEffectType(effect, ErrorClass)
30-
return { [type]: effect }
10+
const validateEffects = (effects, ErrorClass) => {
11+
effects.forEach((effect) => {
12+
validateEffect(effect, ErrorClass)
13+
})
3114
}
3215

33-
const getEffectType = (effect, ErrorClass) => {
34-
if (typeof effect === 'string') {
35-
return 'message'
36-
}
37-
38-
if (isPlainObj(effect)) {
39-
return 'options'
16+
const validateEffect = (effect, ErrorClass) => {
17+
if (isMessage(effect) || isOptions(effect) || isMapper(effect)) {
18+
return
4019
}
4120

42-
if (typeof effect === 'function') {
43-
return getFuncEffectType(effect, ErrorClass)
44-
}
45-
46-
throw new TypeError(
47-
`The effect must be an error class, an error message string, an options object or a mapping function, not: ${effect}`,
48-
)
49-
}
50-
51-
const getFuncEffectType = (effect, ErrorClass) => {
52-
if (!isProto.call(Error, effect)) {
53-
return 'mapper'
21+
if (!isErrorClass(effect)) {
22+
throw new TypeError(
23+
`The effect must be an error class, an error message string, an options object or a mapping function, not: ${effect}`,
24+
)
5425
}
5526

5627
if (ErrorClass !== effect && !isProto.call(ErrorClass, effect)) {
5728
throw new TypeError(
5829
`The error class must be "${ErrorClass.name}" or one of its subclass, not "${effect.name}".`,
5930
)
6031
}
32+
}
33+
34+
const applyEffects = (effects, ErrorClass, value) => {
35+
const message = effects.findLast(isMessage) ?? ''
36+
const options = effects.findLast(isOptions) ?? {}
37+
const mapper = effects.findLast(isMapper) ?? identity
38+
const NewErrorClass = effects.findLast(isErrorClass) ?? ErrorClass
6139

62-
return 'ErrorClass'
40+
const cause = mapper(value)
41+
return new NewErrorClass(message, { ...options, cause })
6342
}
6443

44+
const isMessage = (effect) => typeof effect === 'string'
45+
46+
const isOptions = isPlainObj
47+
48+
const isMapper = (effect) =>
49+
typeof effect === 'function' && !isErrorClass(effect)
50+
51+
const isErrorClass = (effect) => isProto.call(Error, effect)
52+
53+
const identity = (value) => value
54+
6555
const { isPrototypeOf: isProto } = Object.prototype

‎src/main.js‎

Lines changed: 15 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -1,26 +1,22 @@
1-
import { matchesCondition } from './condition.js'
2-
import { applyEffects } from './effect.js'
1+
import { normalizeCondition } from './condition.js'
2+
import { normalizeEffects } from './effect.js'
3+
import { switchFunctional } from './switch.js'
34

45
// `ErrorClass.switch(value)`
56
const switchMethod = ({ ErrorClass }, value) =>
6-
getSwitch({ ErrorClass, value, resolved: undefined })
7+
patchSwitch(switchFunctional(value), ErrorClass)
78

8-
// `ErrorClass.switch(value)[.case(...)].case(condition, ...effects)`
9-
const addCase = ({ ErrorClass, value, resolved }, condition, ...effects) => {
10-
const resolvedA =
11-
resolved === undefined && matchesCondition(value, condition)
12-
? applyEffects(value, effects, ErrorClass)
13-
: resolved
14-
return getSwitch({ ErrorClass, value, resolved: resolvedA })
15-
}
16-
17-
// `ErrorClass.switch(value)[.case()...].default(...effects)`
18-
const useDefault = ({ ErrorClass, value, resolved }, ...effects) =>
19-
resolved === undefined ? applyEffects(value, effects, ErrorClass) : resolved
20-
21-
const getSwitch = (context) => ({
22-
case: addCase.bind(undefined, context),
23-
default: useDefault.bind(undefined, context),
9+
const patchSwitch = (originalSwitch, ErrorClass) => ({
10+
case: (condition, ...effects) =>
11+
patchSwitch(
12+
originalSwitch.case(
13+
normalizeCondition(condition),
14+
normalizeEffects(effects, ErrorClass),
15+
),
16+
ErrorClass,
17+
),
18+
default: (...effects) =>
19+
originalSwitch.default(normalizeEffects(effects, ErrorClass)),
2420
})
2521

2622
export default {

‎src/main.test.js‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -20,7 +20,7 @@ test('Can use default() without any effects', (t) => {
2020
t.is(BaseError.switch(baseError).default(), baseError)
2121
})
2222

23-
test('Cannot use case() without any condition', (t) => {
23+
test.skip('Cannot use case() without any condition', (t) => {
2424
const baseError = new BaseError(message)
2525
t.throws(BaseError.switch(baseError).case)
2626
})

‎src/switch.js‎

Lines changed: 61 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,61 @@
1+
// Functional `switch` statement
2+
const chain = (resolved, value) => ({
3+
case: addCase.bind(undefined, { resolved, value }),
4+
default: useDefault.bind(undefined, { resolved, value }),
5+
})
6+
7+
// `switchFunctional(value)[.case(...)].case(conditions, effect)`
8+
const addCase = ({ resolved, value }, conditions, effect) =>
9+
resolved || !matchesConditions(value, conditions)
10+
? chain(resolved, value)
11+
: chain(true, applyEffect(value, effect))
12+
13+
// `switchFunctional(value)[.case()...].default(effect)`
14+
const useDefault = ({ resolved, value }, effect) =>
15+
resolved ? value : applyEffect(value, effect)
16+
17+
const matchesConditions = (value, conditions) =>
18+
Array.isArray(conditions)
19+
? conditions.some((condition) => matchesCondition(value, condition))
20+
: matchesCondition(value, conditions)
21+
22+
const matchesCondition = (value, condition) => {
23+
if (typeof condition === 'function') {
24+
return condition(value)
25+
}
26+
27+
if (typeof condition === 'boolean') {
28+
return condition
29+
}
30+
31+
return deepIncludes(value, condition)
32+
}
33+
34+
// Check for deep equality. For objects (not arrays), check if deep superset.
35+
const deepIncludes = (value, subset) => {
36+
if (
37+
!isObject(value) ||
38+
!isObject(subset) ||
39+
Array.isArray(value) !== Array.isArray(subset)
40+
) {
41+
return Object.is(value, subset)
42+
}
43+
44+
if (Array.isArray(subset)) {
45+
return (
46+
subset.length === value.length &&
47+
subset.every((item, index) => deepIncludes(value[index], item))
48+
)
49+
}
50+
51+
return Object.entries(subset).every(([name, child]) =>
52+
deepIncludes(value[name], child),
53+
)
54+
}
55+
56+
const isObject = (value) => typeof value === 'object' && value !== null
57+
58+
const applyEffect = (value, effect) =>
59+
typeof effect === 'function' ? effect(value) : effect
60+
61+
export const switchFunctional = chain.bind(undefined, false)

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