Add code package with Parse function (with tests)

internal/code/code.go

@@ -0,0 +1,35 @@
+package code
+
+import (
+	"errors"
+	"regexp"
+)
+
+type Block struct {
+	Code     string
+	Language string
+}
+
+// ?: means non-capture group
+var re = regexp.MustCompile("(?:```|~~~)(.*)\n(.*)\n(?:```|~~~)")
+
+var (
+	ErrParse = errors.New("Error: could not parse code block")
+)
+
+// Parse takes a block of markdown and returns an array of Block's with code
+// and associated languages
+func Parse(markdown string) (Block, error) {
+	match := re.FindStringSubmatch(markdown)
+
+	// There was either no language specified or no code block
+	// Either way, we cannot execute the expression
+	if len(match) < 3 {
+		return Block{}, ErrParse
+	}
+
+	return Block{
+		Language: match[1],
+		Code:     match[2],
+	}, nil
+}

internal/code/code_test.go

@@ -0,0 +1,79 @@
+package code_test
+
+import (
+	"testing"
+
+	"github.com/maaslalani/slides/internal/code"
+)
+
+func TestParse(t *testing.T) {
+	tt := []struct {
+		markdown string
+		expected code.Block
+	}{
+		// We can't put backticks ```
+		// in multi-line strings, ~~~ instead
+		{
+			markdown: `
+~~~ruby
+puts "Hello, world!"
+~~~
+`,
+			expected: code.Block{
+				Code:     `puts "Hello, world!"`,
+				Language: "ruby",
+			},
+		},
+		{
+			markdown: `
+~~~go
+fmt.Println("Hello, world!")
+~~~
+`,
+			expected: code.Block{
+				Code:     `fmt.Println("Hello, world!")`,
+				Language: "go",
+			},
+		},
+		{
+			markdown: `
+# Slide 1
+Just a regular slide, no code block
+`,
+			expected: code.Block{},
+		},
+		{
+			markdown: `
+# Multiple Code Blocks
+~~~go
+fmt.Println("Oh no!")
+~~~
+
+# Secondary Code Block
+~~~ruby
+puts "We will only parse the first code block"
+~~~
+`,
+			expected: code.Block{
+				Code:     `fmt.Println("Oh no!")`,
+				Language: "go",
+			},
+		},
+		{
+			markdown: ``,
+			expected: code.Block{},
+		},
+	}
+
+	for _, tc := range tt {
+		b, _ := code.Parse(tc.markdown)
+		if b.Code != tc.expected.Code {
+			t.Log(b.Code)
+			t.Log(tc.expected.Code)
+			t.Fatal("parse failed: incorrect code")
+		}
+		if b.Language != tc.expected.Language {
+			t.Fatalf("incorrect language, got %s, want %s", b.Language, tc.expected.Language)
+		}
+	}
+}