runes: imported github.com/JamesOwenHall/json2.Scanner as Probe

Signed-off-by: Alejandro Mery <amery@jpi.io>

runes/probe.go

@@ -0,0 +1,124 @@
+package runes
+
+import (
+	"unicode"
+)
+
+// Probe was borrowed from https://github.com/JamesOwenHall/json2.Scanner
+//
+
+// Probe is a func that returns a subset of the input and a success bool.
+type Probe func([]rune) ([]rune, bool)
+
+// If returns a probe that accepts the a rune if it satisfies the condition.
+func If(condition func(rune) bool) Probe {
+	return func(input []rune) ([]rune, bool) {
+		if len(input) > 0 && condition(input[0]) {
+			return input[0:1], true
+		}
+
+		return nil, false
+	}
+}
+
+// Rune returns a probe that accepts r.
+func Rune(r rune) Probe {
+	return If(func(b rune) bool {
+		return r == b
+	})
+}
+
+// Space returns a probe that accepts whitespace as defined in the unicode
+// package.
+func Space() Probe {
+	return func(input []rune) ([]rune, bool) {
+		if len(input) > 0 && unicode.IsSpace(input[0]) {
+			return input[0:1], true
+		}
+
+		return nil, false
+	}
+}
+
+// And returns a probe that accepts all probes in sequence.
+func And(probes ...Probe) Probe {
+	return func(input []rune) ([]rune, bool) {
+		remaining := input
+		accumulated := []rune{}
+
+		for _, s := range probes {
+			if read, ok := s(remaining); !ok {
+				return nil, false
+			} else {
+				accumulated = append(accumulated, read...)
+				remaining = remaining[len(read):]
+			}
+		}
+
+		return accumulated, true
+	}
+}
+
+// Or returns a probe that accepts the first successful probe in probes.
+func Or(probes ...Probe) Probe {
+	return func(input []rune) ([]rune, bool) {
+		for _, s := range probes {
+			if read, ok := s(input); ok {
+				return read, true
+			}
+		}
+
+		return nil, false
+	}
+}
+
+// Maybe runs probe and returns true regardless of the output.
+func Maybe(probe Probe) Probe {
+	return func(input []rune) ([]rune, bool) {
+		read, _ := probe(input)
+		return read, true
+	}
+}
+
+// Any returns a probe that accepts any number of occurrences of probe,
+// including zero.
+func Any(probe Probe) Probe {
+	return func(input []rune) ([]rune, bool) {
+		remaining := input
+		accumulated := []rune{}
+
+		for {
+			if read, ok := probe(remaining); !ok {
+				return accumulated, true
+			} else {
+				accumulated = append(accumulated, read...)
+				remaining = remaining[len(read):]
+			}
+		}
+	}
+}
+
+// N returns a probe that accepts probe exactly n times.
+func N(n int, probe Probe) Probe {
+	return func(input []rune) ([]rune, bool) {
+		probes := make([]Probe, n)
+		for i := 0; i < n; i++ {
+			probes[i] = probe
+		}
+
+		return And(probes...)(input)
+	}
+}
+
+// AtLeast returns a probe that accepts probe at least n times.
+func AtLeast(n int, probe Probe) Probe {
+	return func(input []rune) ([]rune, bool) {
+		probes := make([]Probe, n, n+1)
+		for i := range probes {
+			probes[i] = probe
+		}
+
+		probes = append(probes, Any(probe))
+		return And(probes...)(input)
+	}
+}

runes/probe_test.go

@@ -0,0 +1,58 @@
+package runes
+
+import (
+	"testing"
+)
+
+func TestProbe(t *testing.T) {
+	type TestCase struct {
+		probe Probe
+		input string
+	}
+
+	tests := []TestCase{
+		{Rune('a'), "a"},
+		{Space(), " "},
+		{Space(), "\t"},
+		{Space(), "\n"},
+		{And(Rune('1'), Rune('2'), Space()), "12 "},
+		{Or(Rune('r'), Space(), Rune('x')), "r"},
+		{Or(Rune('r'), Space(), Rune('x')), " "},
+		{Or(Rune('r'), Space(), Rune('x')), "x"},
+		{Any(Rune('w')), ""},
+		{Any(Rune('w')), "w"},
+		{Any(Rune('w')), "ww"},
+		{Any(Rune('w')), "www"},
+		{N(6, Rune('w')), "wwwwww"},
+		{Maybe(Rune('w')), ""},
+		{Maybe(Rune('w')), "w"},
+	}
+
+	for _, test := range tests {
+		if read, ok := test.probe([]rune(test.input)); !ok {
+			t.Errorf("Expected to read %s", string(test.input))
+		} else if string(read) != test.input {
+			t.Errorf("Mismatch of input %s and read %s", test.input, string(read))
+		}
+	}
+}
+
+func TestProbeFail(t *testing.T) {
+	type TestCase struct {
+		probe Probe
+		input string
+	}
+
+	tests := []TestCase{
+		{Rune('a'), "b"},
+		{Space(), "a"},
+		{And(Rune('1'), Rune('2'), Space()), "12"},
+		{Or(Rune('r'), Space(), Rune('x')), "4"},
+	}
+
+	for _, test := range tests {
+		if read, ok := test.probe([]rune(test.input)); ok {
+			t.Errorf("Unexpectedly read %s with input %s", string(read), test.input)
+		}
+	}
+}