variant-match/optional-pair.ts at main · Mike96Angelo/variant-match · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
import { Optional, toOptional, None } from "./optional.js";
import { Func, nonNullable } from "./util.types.js";
import { Variant, variant, VariantTypeClass } from "./variant.js";

type OptionalPairVariants<A extends nonNullable, B extends nonNullable> =
  | Variant<"First", [first: A]>
  | Variant<"Second", [second: B]>
  | Variant<"Both", [first: A, second: B]>
  | Variant<"Neither">;

class OptionalPair<
  A extends nonNullable,
  B extends nonNullable
> extends VariantTypeClass<OptionalPairVariants<A, B>> {
  first(): Optional<A> {
    return this.match({
      First(first) {
        return toOptional(first);
      },
      Both(first) {
        return toOptional(first);
      },
      _() {
        return None;
      },
    });
  }

  second(): Optional<B> {
    return this.match({
      Second(value) {
        return toOptional(value);
      },
      Both(_, second) {
        return toOptional(second);
      },
      _() {
        return None;
      },
    });
  }

  both(): Optional<Readonly<[first: A, second: B]>> {
    return this.match({
      Both(first, second) {
        return toOptional([first, second] as const);
      },
      _() {
        return None;
      },
    });
  }

  combineBoth<C extends nonNullable>(
    combine: Func<[first: A, second: B], C>
  ): Optional<C> {
    return this.match({
      Both(first, second) {
        return toOptional(combine(first, second));
      },
      _() {
        return None;
      },
    });
  }
}

const Neither = new OptionalPair<never, never>(variant("Neither"));

const First = <A extends nonNullable, B extends nonNullable>(
  first: Optional<A>
): OptionalPair<A, B> =>
  first.match({
    Some(value) {
      return new OptionalPair<A, B>(variant("First", value));
    },
    None() {
      return Neither;
    },
  });

const Second = <A extends nonNullable, B extends nonNullable>(
  second: Optional<B>
): OptionalPair<A, B> =>
  second.match({
    Some(value) {
      return new OptionalPair<A, B>(variant("Second", value));
    },
    None() {
      return Neither;
    },
  });

const Both = <A extends nonNullable, B extends nonNullable>(
  first: Optional<A>,
  second: Optional<B>
): OptionalPair<A, B> =>
  first.match({
    Some(first) {
      return second.match({
        Some(second) {
          return new OptionalPair<A, B>(variant("Both", first, second));
        },
        None() {
          return new OptionalPair<A, B>(variant("First", first));
        },
      });
    },
    None() {
      return second.match({
        Some(second) {
          return new OptionalPair<A, B>(variant("Second", second));
        },
        None() {
          return Neither;
        },
      });
    },
  });

const toOptionalPair = <A, B>(
  first: A,
  second: B
): OptionalPair<NonNullable<A>, NonNullable<B>> =>
  Both(toOptional(first), toOptional(second));

export { type OptionalPair, Neither, First, Second, Both, toOptionalPair };