// +build go1.9

// Copyright 2017 Microsoft Corporation and contributors
//
//  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.

// profileBuilder creates a series of packages filled entirely with alias types
// and functions supporting those alias types by directing traffic to the
// functions supporting the original types. This is useful associating a series
// of packages in separate API Versions for easier/safer use.
//
// The Azure-SDK-for-Go teams intends to use this tool to generated profiles
// that we will publish in this repository for general use. However, this tool
// in the case that one has their own list of Services at given API Versions,
// this may prove to be a useful tool for you.
package main

import (
	"bytes"
	"errors"
	"flag"
	"fmt"
	"go/ast"
	"go/parser"
	"go/printer"
	"go/token"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path"
	"path/filepath"
	"strings"
	"time"

	"github.com/marstr/collection"
	goalias "github.com/marstr/goalias/model"
	"github.com/marstr/randname"
)

var (
	profileName     string
	outputLocation  string
	inputRoot       string
	inputList       io.Reader
	packageStrategy collection.Enumerable
	outputLog       *log.Logger
	errLog          *log.Logger
)

// WellKnownStrategy is an Enumerable which lists all known strategies for choosing packages for a profile.
type WellKnownStrategy string

// This block declares the definitive list of WellKnownStrategies
const (
	WellKnownStrategyList    WellKnownStrategy = "list"
	WellKnownStrategyLatest  WellKnownStrategy = "latest"
	WellKnownStrategyPreview WellKnownStrategy = "preview"
)

const armPathModifier = "mgmt"

// If not the empty string, this string should be stamped into files generated by the profileBuilder.
// Note: This variable should be set by passing the argument "-X main.version=`{your value}`" to the Go linker. example: `go build -ldflags "-X main.version=f43d726b6e3f1e3eb7cbdba3982f0253000d5dc5"`
var version string

func main() {
	var packages collection.Enumerator

	type alias struct {
		*goalias.AliasPackage
		TargetPath string
	}

	// Find the names of all of the packages for inclusion in this profile.
	packages = packageStrategy.Enumerate(nil).Select(func(x interface{}) interface{} {
		if cast, ok := x.(string); ok {
			return cast
		}
		return nil
	})

	// Parse the packages that were selected for inclusion in this profile.
	packages = packages.SelectMany(func(x interface{}) collection.Enumerator {
		results := make(chan interface{})

		go func() {
			defer close(results)

			cast, ok := x.(string)
			if !ok {
				return
			}
			files := token.NewFileSet()
			parsed, err := parser.ParseDir(files, cast, nil, 0)
			if err != nil {
				errLog.Printf("Couldn't open %q because: %v", cast, err)
				return
			}

			for _, entry := range parsed {
				results <- entry
			}
		}()

		return results
	})

	// Generate the alias package from the originally parsed one.
	packages = packages.ParallelSelect(func(x interface{}) interface{} {
		var err error
		var subject *goalias.AliasPackage
		cast, ok := x.(*ast.Package)
		if !ok {
			return nil
		}

		var bundle alias
		for filename := range cast.Files {
			bundle.TargetPath = filepath.Dir(filename)
			bundle.TargetPath = trimGoPath(bundle.TargetPath)
			subject, err = goalias.NewAliasPackage(cast, bundle.TargetPath)
			if err != nil {
				errLog.Print(err)
				return nil
			}
			bundle.TargetPath, err = getAliasPath(bundle.TargetPath, profileName)
			if err != nil {
				errLog.Print(err)
				return nil
			}
			break
		}

		bundle.AliasPackage = subject
		return &bundle
	})
	packages = packages.Where(func(x interface{}) bool {
		return x != nil
	})

	// Update the "UserAgent" function in the generated profile, if it is present.
	packages = packages.Select(func(x interface{}) interface{} {
		cast := x.(*alias)

		var userAgent *ast.FuncDecl

		// Grab all functions in the alias package named "UserAgent"
		userAgentCandidates := collection.Where(collection.AsEnumerable(cast.Files["models.go"].Decls), func(x interface{}) bool {
			cast, ok := x.(*ast.FuncDecl)
			return ok && cast.Name.Name == "UserAgent"
		})

		// There should really only be one of them, otherwise bailout because we don't understand the world anymore.
		candidate, err := collection.Single(userAgentCandidates)
		if err != nil {
			return x
		}
		userAgent, ok := candidate.(*ast.FuncDecl)
		if !ok {
			return x
		}

		// Grab the expression being returned.
		retResults := &userAgent.Body.List[0].(*ast.ReturnStmt).Results[0]

		// Append a string literal to the result
		updated := &ast.BinaryExpr{
			Op: token.ADD,
			X:  *retResults,
			Y: &ast.BasicLit{
				Value: fmt.Sprintf("\" profiles/%s\"", profileName),
			},
		}

		*retResults = updated
		return x
	})

	// Add the MSFT Copyright Header, then write the alias package to disk.
	products := packages.ParallelSelect(func(x interface{}) interface{} {
		cast, ok := x.(*alias)
		if !ok {
			return false
		}

		files := token.NewFileSet()

		outputPath := filepath.Join(outputLocation, cast.TargetPath, "models.go")
		outputPath = strings.Replace(outputPath, `\`, `/`, -1)
		err := os.MkdirAll(path.Dir(outputPath), os.ModePerm|os.ModeDir)
		if err != nil {
			errLog.Print("error creating directory:", err)
			return false
		}

		outputFile, err := os.Create(outputPath)
		if err != nil {
			errLog.Print("error creating file: ", err)
			return false
		}

		// TODO: This should really be added by the `goalias` package itself. Doing it here is a work around
		fmt.Fprintln(outputFile, "// +build go1.9")
		fmt.Fprintln(outputFile)

		generatorStampBuilder := new(bytes.Buffer)

		fmt.Fprintf(generatorStampBuilder, "// Copyright %4d Microsoft Corporation\n", time.Now().Year())
		fmt.Fprintln(generatorStampBuilder, `//
// 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.`)

		fmt.Fprintln(outputFile, generatorStampBuilder.String())

		generatorStampBuilder.Reset()

		fmt.Fprintln(generatorStampBuilder, "// This code was auto-generated by:")
		fmt.Fprintln(generatorStampBuilder, "// github.com/Azure/azure-sdk-for-go/tools/profileBuilder")

		if version != "" {
			fmt.Fprintln(generatorStampBuilder, "// commit ID:", version)
		}
		fmt.Fprintln(generatorStampBuilder)
		fmt.Fprint(outputFile, generatorStampBuilder.String())

		outputLog.Printf("Writing File: %s", outputPath)
		printer.Fprint(outputFile, files, cast.ModelFile())

		return true
	})

	generated := 0

	// Write each aliased package that was found
	for entry := range products {
		if entry.(bool) {
			generated++
		}
	}

	outputLog.Print(generated, " packages generated.")

}

func init() {
	const defaultName = "{randomly generated}"

	var selectedStrategy string
	var inputListLocation string
	var useVerbose bool

	flag.StringVar(&profileName, "name", defaultName, "The name that should be given to the generated profile.")
	flag.StringVar(&outputLocation, "o", defaultOutputLocation(), "The output location for the package generated as a profile.")
	flag.StringVar(&inputRoot, "root", defaultInputRoot(), "The location of the Azure SDK for Go's service packages.")
	flag.StringVar(&inputListLocation, "l", "", "If the `list` strategy is chosen, -l is the location of the file to read for said list. If not present, stdin is used.")
	flag.StringVar(&selectedStrategy, "s", string(WellKnownStrategyLatest), "The strategy to employ for finding packages to put in a profile.")
	flag.BoolVar(&useVerbose, "v", false, "Write status to stderr as the program progresses")
	flag.Parse()

	// Setup Verbose Status Log and Error Log
	var logWriter io.Writer
	if useVerbose {
		logWriter = os.Stderr
	} else {
		logWriter = ioutil.Discard
	}
	outputLog = log.New(logWriter, "[STATUS] ", 0)
	outputLog.Print("Status Logging Enabled")

	errLog = log.New(logWriter, "[ERROR] ", 0)

	if version != "" {
		outputLog.Print("profileBuilder Version: ", version)
	}

	// Sort out the Profile Name to be used.
	if profileName == defaultName {
		profileName = randname.AdjNoun{}.Generate()
		outputLog.Print("Profile Name Set to: ", profileName)
	}

	inputList = os.Stdin
	if inputListLocation == "" {
		outputLog.Print("Reading input from standard input")
	} else {
		var err error
		outputLog.Print("Reading input from: ", inputListLocation)
		inputList, err = os.Open(inputListLocation)
		if err != nil {
			errLog.Print(err)
			os.Exit(1)
		}
	}

	wellKnownStrategies := map[WellKnownStrategy]collection.Enumerable{
		WellKnownStrategyList:    ListStrategy{Reader: inputList},
		WellKnownStrategyLatest:  LatestStrategy{Root: inputRoot, Predicate: IgnorePreview, VerboseOutput: outputLog},
		WellKnownStrategyPreview: LatestStrategy{Root: inputRoot, Predicate: AcceptAll},
	}

	if s, ok := wellKnownStrategies[WellKnownStrategy(selectedStrategy)]; ok {
		packageStrategy = s
		outputLog.Printf("Using Well Known Strategy: %s", selectedStrategy)
	} else {
		errLog.Printf("Unknown strategy for identifying packages: %s\n", selectedStrategy)
		os.Exit(1)
	}
}

// AzureSDKforGoLocation returns the default location for the Azure-SDK-for-Go to reside.
func AzureSDKforGoLocation() string {
	return path.Join(
		os.Getenv("GOPATH"),
		"src",
		"github.com",
		"Azure",
		"azure-sdk-for-go",
	)
}

func defaultOutputLocation() string {
	return path.Join(AzureSDKforGoLocation(), "profiles")
}

func defaultInputRoot() string {
	return path.Join(AzureSDKforGoLocation(), "services")
}

// getAliasPath takes an existing API Version path and a package name, and converts the path
// to a path which uses the new profile layout.
func getAliasPath(subject, profile string) (transformed string, err error) {
	subject = strings.TrimSuffix(subject, "/")
	subject = trimGoPath(subject)

	matches := packageName.FindAllStringSubmatch(subject, -1)
	if matches == nil {
		err = errors.New("path does not resemble a known package path")
		return
	}

	output := []string{
		profile,
		matches[0][1],
	}

	if matches[0][2] == armPathModifier {
		output = append(output, armPathModifier)
	}

	output = append(output, matches[0][4])

	transformed = strings.Join(output, "/")
	return
}

// trimGoPath removes the prefix defined in the environment variabe GOPATH if it is present in the string provided.
var trimGoPath = func() func(string) string {
	splitGo := strings.Split(os.Getenv("GOPATH"), string(os.PathSeparator))
	splitGo = append(splitGo, "src")

	return func(subject string) string {
		splitPath := strings.Split(subject, string(os.PathSeparator))
		for i, dir := range splitGo {
			if splitPath[i] != dir {
				return subject
			}
		}
		packageIdentifier := splitPath[len(splitGo):]
		return path.Join(packageIdentifier...)
	}
}()