feat: add basic conversion combinators to enable greater chaining of combinators (#27)

Author: purpleclay

.gitignore

@@ -13,6 +13,7 @@
 !.github/**/*
 !flake.nix
 !flake.lock
+!.zed/*
 
 # Allow Go files
 !*.go

basic.go

@@ -22,7 +22,10 @@ SOFTWARE.
 
 package chomp
 
-import "strings"
+import (
+	"fmt"
+	"strings"
+)
 
 // Tag must match a series of characters at the beginning of the input text,
 // in the exact order and case provided.
@@ -182,3 +185,47 @@ func Opt[T Result](c Combinator[T]) Combinator[T] {
 		return rem, out, nil
 	}
 }
+
+// S wraps the result of the inner combinator within a string slice.
+// Combinators of differing return types can be successfully chained
+// together while using this conversion combinator.
+//
+//	chomp.S(chomp.Until(","))("Hello, World!")
+//	// (", World!", []string{"Hello"}, nil)
+func S(c Combinator[string]) Combinator[[]string] {
+	return func(s string) (string, []string, error) {
+		rem, ext, err := c(s)
+		if err != nil {
+			return rem, nil, err
+		}
+
+		return rem, []string{ext}, err
+	}
+}
+
+// I extracts and returns a single string from the result of the inner combinator.
+// Combinators of differing return types can be successfully chained together while
+// using this conversion combinator.
+//
+//	chomp.I(chomp.SepPair(
+//		chomp.Tag("Hello"),
+//		chomp.Tag(", "),
+//		chomp.Tag("World")), 1)("Hello, World!")
+//	// ("!", "World", nil)
+func I(c Combinator[[]string], i int) Combinator[string] {
+	return func(s string) (string, string, error) {
+		rem, ext, err := c(s)
+		if err != nil {
+			return rem, "", err
+		}
+
+		if i < 0 || i >= len(ext) {
+			return rem, "", ParserError{
+				Err:  fmt.Errorf("index %d is out of bounds within string slice of %d elements", i, len(ext)),
+				Type: "i",
+			}
+		}
+
+		return rem, ext[i], nil
+	}
+}

basic_test.go

@@ -27,6 +27,7 @@ import (
 
 	"github.com/purpleclay/chomp"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestTag(t *testing.T) {
@@ -274,3 +275,22 @@ func TestOpt(t *testing.T) {
 	assert.Equal(t, "", ext)
 	assert.NoError(t, err)
 }
+
+func TestS(t *testing.T) {
+	rem, ext, err := chomp.S(chomp.Tag("hello"))("hello and good morning")
+
+	assert.Equal(t, " and good morning", rem)
+	require.Len(t, ext, 1)
+	assert.Equal(t, "hello", ext[0])
+	assert.NoError(t, err)
+}
+
+func TestI(t *testing.T) {
+	rem, ext, err := chomp.I(
+		chomp.Repeat(chomp.All(chomp.Until(" "), chomp.Tag(" ")), 3),
+		2)("hello and good morning")
+
+	assert.Equal(t, "morning", rem)
+	assert.Equal(t, "and", ext)
+	assert.NoError(t, err)
+}

examples/gpg/main.go

@@ -51,7 +51,7 @@ func (d GpgKeyDetails) String() string {
 	buf.WriteString(fmt.Sprintf("key_id:          %s\n", d.KeyID))
 	buf.WriteString(fmt.Sprintf("created_on:      %d (%s)\n", d.CreationDate, unixToRFC3339(int64(d.CreationDate))))
 	if d.ExpirationDate > 0 {
-		buf.WriteString(fmt.Sprintf("expires_on:      %d\n", d.ExpirationDate)) // Formatted time
+		buf.WriteString(fmt.Sprintf("expires_on:      %d (%s)\n", d.ExpirationDate, unixToRFC3339(int64(d.ExpirationDate))))
 	}
 
 	return buf.String()
@@ -138,11 +138,9 @@ func key() chomp.Combinator[[]string] {
 		var rem string
 		var err error
 
-		if rem, _, err = chomp.First(chomp.Tag("sec"), chomp.Tag("ssb"))(s); err != nil {
-			return rem, nil, err
-		}
-
-		if rem, _, err = chomp.Repeat(colon(), 4)(rem); err != nil {
+		if rem, _, err = chomp.Pair(
+			chomp.First(chomp.Tag("sec"), chomp.Tag("ssb")),
+			chomp.Repeat(colon(), 4))(s); err != nil {
 			return rem, nil, err
 		}
 
@@ -254,11 +252,11 @@ func user() chomp.Combinator[[]string] {
 }
 
 func main() {
-	colonFmt := `sec:-:4096:1:AAC7E54CBD73F690:1664450926:::-:::scESC:::+:::23::0:
+	colonFmt := `sec:-:4096:1:AAC7E54CBD73F690:1664450926:1695986926::-:::scESC:::+:::23::0:
 fpr:::::::::28BF65E18407FD2966565284AAC7E54CBD73F690:
 grp:::::::::12E86CE47CEB942D2A65B4D02106657BA8D0C92B:
 uid:-::::1664450926::E6F81442C4BEE48D9ED3E6EE4CAC21231D3C25EB::albert.einstein <albert.einstein@emcsqua.red>::::::::::0:
-ssb:-:4096:1:17441D4227A0B812:1664450926::::::e:::+:::23:
+ssb:-:4096:1:17441D4227A0B812:1664450926:1695986926:::::e:::+:::23:
 fpr:::::::::26965E00791A52ECC33AE88917441D4227A0B812:
 grp:::::::::603DAFFC5AAE42C4B8BFCC99DD7CEDD5C443FFA0:
 `