refactor(contexts): I'm not sure how to write it (#166)

* refactor(provider): rename context to provider

Signed-off-by: Flc゛ <four_leaf_clover@foxmail.com>

* refactor(provider): split to contexts and provider

Signed-off-by: Flc゛ <four_leaf_clover@foxmail.com>

* refactor(provider): split to contexts and provider

Signed-off-by: Flc゛ <four_leaf_clover@foxmail.com>

---------

Signed-off-by: Flc゛ <four_leaf_clover@foxmail.com>

contexts/contexts.go

@@ -0,0 +1,33 @@
+package contexts
+
+import (
+	"context"
+)
+
+type Func func(ctx context.Context) (context.Context, error)
+
+// Pipe returns a Provider that chains the provided Providers.
+func Pipe(ctx context.Context, fns ...Func) (context.Context, error) {
+	var err error
+	for _, fn := range fns {
+		if fn != nil {
+			if ctx, err = fn(ctx); err != nil {
+				return ctx, err
+			}
+		}
+	}
+	return ctx, nil
+}
+
+// Chain is a reverse Pipe.
+func Chain(ctx context.Context, fns ...Func) (context.Context, error) {
+	var err error
+	for i := len(fns) - 1; i >= 0; i-- {
+		if fns[i] != nil {
+			if ctx, err = fns[i](ctx); err != nil {
+				return ctx, err
+			}
+		}
+	}
+	return ctx, nil
+}

contexts/contexts_test.go

@@ -0,0 +1,78 @@
+package contexts
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type (
+	mockProviderStruct1 struct{}
+	mockProviderStruct2 struct{}
+	mockProviderStruct3 struct{}
+)
+
+var result chan string
+
+var (
+	mockProvider1 = func(ctx context.Context) (context.Context, error) {
+		result <- "mockProvider1"
+		return context.WithValue(ctx, mockProviderStruct1{}, "mockProvider1"), nil
+	}
+
+	mockProvider2 = func(ctx context.Context) (context.Context, error) {
+		result <- "mockProvider2"
+		return context.WithValue(ctx, mockProviderStruct2{}, "mockProvider2"), nil
+	}
+
+	mockProvider3 = func(ctx context.Context) (context.Context, error) {
+		result <- "mockProvider3"
+		return ctx, errors.New("mockProvider3")
+	}
+)
+
+func TestPipe(t *testing.T) {
+	result = make(chan string, 2)
+	ctx1, err1 := Pipe(
+		context.Background(),
+		mockProvider1, mockProvider2,
+	)
+	assert.NoError(t, err1)
+	assert.Equal(t, "mockProvider1", ctx1.Value(mockProviderStruct1{}))
+	assert.Equal(t, "mockProvider2", ctx1.Value(mockProviderStruct2{}))
+	assert.Equal(t, "mockProvider1", <-result)
+	assert.Equal(t, "mockProvider2", <-result)
+
+	ctx2, err2 := Pipe(
+		context.Background(),
+		mockProvider1, mockProvider3,
+	)
+	assert.Error(t, err2)
+	assert.NotNil(t, ctx2)
+	assert.Equal(t, "mockProvider1", ctx2.Value(mockProviderStruct1{}))
+	assert.Nil(t, ctx2.Value(mockProviderStruct3{}))
+	assert.Equal(t, "mockProvider1", <-result)
+}
+
+func TestChain(t *testing.T) {
+	result = make(chan string, 2)
+	ctx1, err1 := Chain(
+		context.Background(),
+		mockProvider1, mockProvider2,
+	)
+	assert.NoError(t, err1)
+	assert.Equal(t, "mockProvider1", ctx1.Value(mockProviderStruct1{}))
+	assert.Equal(t, "mockProvider2", ctx1.Value(mockProviderStruct2{}))
+	assert.Equal(t, "mockProvider2", <-result)
+	assert.Equal(t, "mockProvider1", <-result)
+
+	ctx2, err2 := Chain(
+		context.Background(),
+		mockProvider3, mockProvider1,
+	)
+	assert.Error(t, err2)
+	assert.Equal(t, "mockProvider1", ctx2.Value(mockProviderStruct1{}))
+	assert.Equal(t, "mockProvider1", <-result)
+}