// Copyright Istio Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package istioio

import (
	"fmt"
	"os"
	"path"
	"path/filepath"
	"strings"

	"istio.io/istio/pkg/test/env"
	"istio.io/istio/pkg/test/scopes"

	"istio.io/istio/pkg/test/framework"
)

const (
	snippetsFileExtension    = ".snippets.txt"
	snippetsFileHeaderFormat = `# Created by %s. DO NOT EDIT THIS FILE MANUALLY!

`
)

// Step builds a step of the test pipeline.
type Step interface {
	// run this step.
	run(ctx Context)
}

// Builder builds a test of a documented workflow from http://istio.io.
type Builder struct {
	snippetsFileName string
	steps            []Step
	cleanupSteps     []Step
}

// NewBuilder returns an instance of an example test. The name of the snippets file must be provided.
// If the snippets file name does not end with ".snippets.txt", the extension will be appended automatically.
func NewBuilder(snippetsFileName string) *Builder {
	if snippetsFileName == "" {
		panic("must provide the snippets file name")
	}

	// Add the appropriate suffix if it's missing.
	if !strings.HasSuffix(snippetsFileName, snippetsFileExtension) {
		snippetsFileName += snippetsFileExtension
	}

	return &Builder{
		snippetsFileName: snippetsFileName,
	}
}

// Add a step to be run.
func (b *Builder) Add(steps ...Step) *Builder {
	b.steps = append(b.steps, steps...)
	return b
}

// Defer registers a function to be executed when the test completes.
func (b *Builder) Defer(steps ...Step) *Builder {
	b.cleanupSteps = append(b.cleanupSteps, steps...)
	return b
}

// BuildAndRun is a utility method for building and running the test function in one step.
func (b *Builder) BuildAndRun(ctx framework.TestContext) {
	b.Build()(ctx)
}

// Build a run function for the test
func (b *Builder) Build() func(ctx framework.TestContext) {
	return func(ctx framework.TestContext) {
		scopes.CI.Infof("Executing test %s (%d steps)", ctx.Name(), len(b.steps))

		snippetFile, err := os.Create(filepath.Join(ctx.WorkDir(), b.snippetsFileName))
		if err != nil {
			ctx.Fatalf("failed creating snippets file: %v", err)
		}
		defer func() { _ = snippetFile.Close() }()

		// Write the header to the snippets file.
		if _, err := snippetFile.WriteString(fmt.Sprintf(snippetsFileHeaderFormat, ctx.Name())); err != nil {
			ctx.Fatalf("failed writing header to snippets file: %v", err)
		}

		eCtx := Context{
			TestContext: ctx,
			snippetFile: snippetFile,
			snippetMap:  make(map[string]string),
		}

		// create a symbolic link to samples/, for easy access
		samplesSymlink := path.Join(ctx.WorkDir(), "samples")
		if _, err := os.Stat(samplesSymlink); os.IsNotExist(err) {
			err = os.Symlink(path.Join(env.IstioSrc, "samples"), samplesSymlink)
			if err != nil {
				scopes.CI.Warnf("Could not create symlink to samples/ directory at %s", samplesSymlink)
			} else {
				defer func() {
					_ = os.Remove(samplesSymlink)
				}()
			}
		}

		// Run cleanup functions at the end.
		defer func() {
			for _, step := range b.cleanupSteps {
				step.run(eCtx)
			}
		}()

		for _, step := range b.steps {
			step.run(eCtx)
		}
	}
}