refactor(Sheet): create parse method

Move `Frontmatter.Parse` to `Sheet.parse`, and delete the `frontmatter`
package. `Sheet.parse` more accurately describes the parser's behavior.

internal/sheet/parse.go

@@ -0,0 +1,45 @@
+package sheet
+
+import (
+	"fmt"
+	"runtime"
+	"strings"
+
+	"gopkg.in/yaml.v1"
+)
+
+// Parse parses cheatsheet frontmatter
+func parse(markdown string) (frontmatter, string, error) {
+
+	// determine the appropriate line-break for the platform
+	linebreak := "\n"
+	if runtime.GOOS == "windows" {
+		linebreak = "\r\n"
+	}
+
+	// specify the frontmatter delimiter
+	delim := fmt.Sprintf("---%s", linebreak)
+
+	// initialize a frontmatter struct
+	var fm frontmatter
+
+	// if the markdown does not contain frontmatter, pass it through unmodified
+	if !strings.HasPrefix(markdown, delim) {
+		return fm, markdown, nil
+	}
+
+	// otherwise, split the frontmatter and cheatsheet text
+	parts := strings.SplitN(markdown, delim, 3)
+
+	// return an error if the frontmatter parses into the wrong number of parts
+	if len(parts) != 3 {
+		return fm, markdown, fmt.Errorf("failed to delimit frontmatter")
+	}
+
+	// return an error if the YAML cannot be unmarshalled
+	if err := yaml.Unmarshal([]byte(parts[1]), &fm); err != nil {
+		return fm, markdown, fmt.Errorf("failed to unmarshal frontmatter: %v", err)
+	}
+
+	return fm, parts[2], nil
+}

internal/sheet/parse_test.go

@@ -0,0 +1,95 @@
+package sheet
+
+import (
+	"testing"
+)
+
+// TestHasFrontmatter asserts that markdown is properly parsed when it contains
+// frontmatter
+func TestHasFrontmatter(t *testing.T) {
+
+	// stub our cheatsheet content
+	markdown := `---
+syntax: go
+tags: [ test ]
+---
+To foo the bar: baz`
+
+	// parse the frontmatter
+	fm, text, err := parse(markdown)
+
+	// assert expectations
+	if err != nil {
+		t.Errorf("failed to parse markdown: %v", err)
+	}
+
+	want := "To foo the bar: baz"
+	if text != want {
+		t.Errorf("failed to parse text: want: %s, got: %s", want, text)
+	}
+
+	want = "go"
+	if fm.Syntax != want {
+		t.Errorf("failed to parse syntax: want: %s, got: %s", want, fm.Syntax)
+	}
+
+	want = "test"
+	if fm.Tags[0] != want {
+		t.Errorf("failed to parse tags: want: %s, got: %s", want, fm.Tags[0])
+	}
+	if len(fm.Tags) != 1 {
+		t.Errorf("failed to parse tags: want: len 0, got: len %d", len(fm.Tags))
+	}
+}
+
+// TestHasFrontmatter asserts that markdown is properly parsed when it does not
+// contain frontmatter
+func TestHasNoFrontmatter(t *testing.T) {
+
+	// stub our cheatsheet content
+	markdown := "To foo the bar: baz"
+
+	// parse the frontmatter
+	fm, text, err := parse(markdown)
+
+	// assert expectations
+	if err != nil {
+		t.Errorf("failed to parse markdown: %v", err)
+	}
+
+	if text != markdown {
+		t.Errorf("failed to parse text: want: %s, got: %s", markdown, text)
+	}
+
+	if fm.Syntax != "" {
+		t.Errorf("failed to parse syntax: want: '', got: %s", fm.Syntax)
+	}
+
+	if len(fm.Tags) != 0 {
+		t.Errorf("failed to parse tags: want: len 0, got: len %d", len(fm.Tags))
+	}
+}
+
+// TestHasInvalidFrontmatter asserts that markdown is properly parsed when it
+// contains invalid frontmatter
+func TestHasInvalidFrontmatter(t *testing.T) {
+
+	// stub our cheatsheet content (with invalid frontmatter)
+	markdown := `---
+syntax: go
+tags: [ test ]
+To foo the bar: baz`
+
+	// parse the frontmatter
+	_, text, err := parse(markdown)
+
+	// assert that an error was returned
+	if err == nil {
+		t.Error("failed to error on invalid frontmatter")
+	}
+
+	// assert that the "raw" markdown was returned
+	if text != markdown {
+		t.Errorf("failed to parse text: want: %s, got: %s", markdown, text)
+	}
+}

internal/sheet/sheet.go

@@ -4,10 +4,14 @@ import (
 	"fmt"
 	"os"
 	"sort"
-
-	"github.com/cheat/cheat/internal/frontmatter"
 )
 
+// Frontmatter encapsulates cheatsheet frontmatter data
+type frontmatter struct {
+	Tags   []string
+	Syntax string
+}
+
 // Sheet encapsulates sheet information
 type Sheet struct {
 	Title     string
@@ -34,8 +38,8 @@ func New(
 		return Sheet{}, fmt.Errorf("failed to read file: %s, %v", path, err)
 	}
 
-	// parse the cheatsheet frontmatter
-	text, fm, err := frontmatter.Parse(string(markdown))
+	// parse the raw cheatsheet text
+	fm, text, err := parse(string(markdown))
 	if err != nil {
 		return Sheet{}, fmt.Errorf("failed to parse front-matter: %v", err)
 	}