Starts adding the first bounds checking asserts for cut

Author: Ciro S. Costa

Makefile

@@ -5,4 +5,4 @@ fmt:
 	go fmt ./...
 
 test:
-	go test ./cast -v
+	go test ./... -v

editor/cut.go

@@ -0,0 +1,37 @@
+package editor
+
+import (
+	"github.com/cirocosta/asciinema-edit/cast"
+	"github.com/pkg/errors"
+)
+
+// Cut removes a piece of the cast event stream as specified by
+// `from` and `to`.
+//
+// It assumes that the provided `cast` is entirely valid (see
+// `github.com/cirocosta/asciinema-edit/cast#Validate`).
+//
+// 1. search a time that is close to `from`; then
+// 2. search a time that is close to `to`; then
+// 3. remove all in between; then
+// 4. adjust the time of the remaining.
+func Cut(c *cast.Cast, from, to float64) (err error) {
+	if c == nil {
+		err = errors.Errorf("a cast must be specified")
+		return
+	}
+
+	if len(c.EventStream) == 0 {
+		err = errors.Errorf(
+			"a cast with non-empty event stream must be supplied")
+		return
+	}
+
+	if from > to {
+		err = errors.Errorf(
+			"`from` cant be bigger than `to`")
+		return
+	}
+
+	return
+}

editor/cut_test.go

@@ -0,0 +1,71 @@
+package editor_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"github.com/cirocosta/asciinema-edit/cast"
+	"github.com/cirocosta/asciinema-edit/editor"
+)
+
+var (
+	event1 = &cast.Event{
+		Time: 1,
+		Data: "event1",
+	}
+	event1_2 = &cast.Event{
+		Time: 1.2,
+		Data: "event1_2",
+	}
+	event1_6 = &cast.Event{
+		Time: 1.6,
+		Data: "event1_6",
+	}
+	event2 = &cast.Event{
+		Time: 2,
+		Data: "event2",
+	}
+)
+
+var _ = Describe("Cut", func() {
+	Context("with nil cast", func() {
+		It("fails", func() {
+			err := editor.Cut(nil, 1, 2)
+			Expect(err).ToNot(Succeed())
+		})
+	})
+
+	Context("with an empty event stream", func() {
+		var data = &cast.Cast{
+			EventStream: []*cast.Event{},
+		}
+
+		It("errors", func() {
+			err := editor.Cut(data, 1, 2)
+			Expect(err).ToNot(Succeed())
+		})
+	})
+
+	Context("with non-empty event stream", func() {
+		var (
+			err  error
+			data *cast.Cast
+		)
+
+		BeforeEach(func() {
+			data = &cast.Cast{
+				EventStream: []*cast.Event{
+					event1,
+					event1_2,
+					event1_6,
+					event2,
+				},
+			}
+		})
+
+		It("fails if `from` > `to`", func() {
+			err = editor.Cut(data, 3, 2)
+			Expect(err).ToNot(Succeed())
+		})
+	})
+})

editor/doc.go

@@ -0,0 +1,3 @@
+// Package editor provides a set of functions to transform and
+// deal with the post production of asciinema casts.
+package editor