/*
Copyright 2019 The Kubernetes 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 fi

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"

	"k8s.io/klog/v2"
	"k8s.io/kops/upup/pkg/fi/utils"
	"k8s.io/kops/util/pkg/hashing"
)

type asset struct {
	Key       string
	AssetPath string
	resource  Resource
	source    *Source
}

type Source struct {
	Parent             *Source
	URL                string
	Hash               *hashing.Hash
	ExtractFromArchive string
}

// Key builds a unique key for this source
func (s *Source) Key() string {
	var k string
	if s.Parent != nil {
		k = s.Parent.Key() + "/"
	}
	if s.URL != "" {
		k += s.URL
	} else if s.ExtractFromArchive != "" {
		k += s.ExtractFromArchive
	} else {
		klog.Fatalf("expected either URL or ExtractFromArchive to be set")
	}
	return k
}

func (s *Source) String() string {
	return "Source[" + s.Key() + "]"
}

type HasSource interface {
	GetSource() *Source
}

// assetResource implements Resource, but also implements HasFetchInstructions
type assetResource struct {
	Asset *asset
}

var (
	_ Resource  = &assetResource{}
	_ HasSource = &assetResource{}
)

func (r *assetResource) Open() (io.Reader, error) {
	return r.Asset.resource.Open()
}

func (r *assetResource) GetSource() *Source {
	return r.Asset.source
}

type AssetStore struct {
	cacheDir string
	assets   []*asset
}

func NewAssetStore(cacheDir string) *AssetStore {
	a := &AssetStore{
		cacheDir: cacheDir,
	}
	return a
}

func (a *AssetStore) FindMatches(expr *regexp.Regexp) map[string]Resource {
	matches := make(map[string]Resource)

	klog.Infof("Matching assets for %q:", expr.String())
	for _, a := range a.assets {
		if expr.MatchString(a.AssetPath) {
			klog.Infof("    %s", a.AssetPath)
			matches[a.Key] = &assetResource{Asset: a}
		}
	}

	return matches
}

func (a *AssetStore) FindMatch(expr *regexp.Regexp) (name string, res Resource, err error) {
	matches := a.FindMatches(expr)

	switch len(matches) {
	case 0:
		return "", nil, fmt.Errorf("found no matching assets for expr: %q", expr.String())
	case 1:
		var n string
		var r Resource
		for k, v := range matches {
			klog.Infof("Found single matching asset for expr %q: %q", expr.String(), k)
			n = k
			r = v
		}
		return n, r, nil
	default:
		return "", nil, fmt.Errorf("found multiple matching assets for expr: %q", expr.String())
	}
}

func (a *AssetStore) Find(key string, assetPath string) (Resource, error) {
	var matches []*asset
	for _, asset := range a.assets {
		if asset.Key != key {
			continue
		}

		if assetPath != "" {
			if !strings.HasSuffix(asset.AssetPath, assetPath) {
				continue
			}
		}

		matches = append(matches, asset)
	}

	if len(matches) == 0 {
		return nil, nil
	}
	if len(matches) == 1 {
		klog.Infof("Resolved asset %s:%s to %s", key, assetPath, matches[0].AssetPath)
		return &assetResource{Asset: matches[0]}, nil
	}

	klog.Infof("Matching assets:")
	for _, match := range matches {
		klog.Infof("    %s %s", match.Key, match.AssetPath)
	}
	return nil, fmt.Errorf("found multiple matching assets for key: %q", key)
}

// Add an asset into the store, in one of the recognized formats (see Assets in types package)
func (a *AssetStore) AddForTest(id string, path string, content string) {
	a.assets = append(a.assets, &asset{
		Key:       id,
		AssetPath: path,
		resource:  NewStringResource(content),
	})
}

func hashFromHTTPHeader(url string) (*hashing.Hash, error) {
	klog.Infof("Doing HTTP HEAD on %q", url)
	response, err := http.Head(url)
	if err != nil {
		return nil, fmt.Errorf("error doing HEAD on %q: %v", url, err)
	}
	defer response.Body.Close()

	etag := response.Header.Get("ETag")
	etag = strings.TrimSpace(etag)
	etag = strings.Trim(etag, "'\"")

	if etag != "" {
		if len(etag) == 32 {
			// Likely md5
			return hashing.HashAlgorithmMD5.FromString(etag)
		}
	}

	return nil, fmt.Errorf("unable to determine hash from HTTP HEAD: %q", url)
}

// Add an asset into the store, in one of the recognized formats (see Assets in types package)
func (a *AssetStore) Add(id string) error {
	if strings.HasPrefix(id, "http://") || strings.HasPrefix(id, "https://") {
		return a.addURLs(strings.Split(id, ","), nil)
	}
	i := strings.Index(id, "@http://")
	if i == -1 {
		i = strings.Index(id, "@https://")
	}
	if i != -1 {
		urls := strings.Split(id[i+1:], ",")
		hash, err := hashing.FromString(id[:i])
		if err != nil {
			return err
		}
		return a.addURLs(urls, hash)
	}
	// TODO: local files!
	return fmt.Errorf("unknown asset format: %q", id)
}

func (a *AssetStore) addURLs(urls []string, hash *hashing.Hash) error {
	if len(urls) == 0 {
		return fmt.Errorf("no urls were specified")
	}

	var err error
	if hash == nil {
		for _, url := range urls {
			hash, err = hashFromHTTPHeader(url)
			if err != nil {
				klog.Warningf("unable to get hash from %q: %v", url, err)
				continue
			} else {
				break
			}
		}
		if err != nil {
			return err
		}
	}

	// We assume the first url is the "main" url, and download to the base of that _name_, wherever we get it from
	primaryURL := urls[0]
	key := path.Base(primaryURL)
	localFile := path.Join(a.cacheDir, hash.String()+"_"+utils.SanitizeString(key))

	for _, url := range urls {
		_, err = DownloadURL(url, localFile, hash)
		if err != nil {
			klog.Warningf("error downloading url %q: %v", url, err)
			continue
		} else {
			break
		}
	}
	if err != nil {
		return err
	}

	assetPath := primaryURL
	r := NewFileResource(localFile)

	source := &Source{URL: primaryURL, Hash: hash}

	asset := &asset{
		Key:       key,
		AssetPath: assetPath,
		resource:  r,
		source:    source,
	}
	klog.V(2).Infof("added asset %q for %q", asset.Key, asset.resource)
	a.assets = append(a.assets, asset)

	// normalize filename suffix
	file := strings.ToLower(assetPath)
	// pickup both tar.gz and tgz files
	if strings.HasSuffix(file, ".tar.gz") || strings.HasSuffix(file, ".tgz") {
		err = a.addArchive(source, localFile)
		if err != nil {
			return err
		}
	}

	return nil
}

func (a *AssetStore) addArchive(archiveSource *Source, archiveFile string) error {
	extracted := path.Join(a.cacheDir, "extracted/"+path.Base(archiveFile))

	if _, err := os.Stat(extracted); os.IsNotExist(err) {
		// We extract to a temporary dir which we then rename so this is atomic
		// (untarring can be slow, and we might crash / be interrupted half-way through)
		extractedTemp := extracted + ".tmp-" + strconv.FormatInt(time.Now().UnixNano(), 10)
		err := os.MkdirAll(extractedTemp, 0o755)
		if err != nil {
			return fmt.Errorf("error creating directories %q: %v", path.Dir(extractedTemp), err)
		}

		args := []string{"tar", "zxf", archiveFile, "-C", extractedTemp}
		klog.Infof("running extract command %s", args)
		cmd := exec.Command(args[0], args[1:]...)
		output, err := cmd.CombinedOutput()
		if err != nil {
			return fmt.Errorf("error expanding asset file %q %v: %s", archiveFile, err, string(output))
		}

		if err := os.Rename(extractedTemp, extracted); err != nil {
			return fmt.Errorf("error renaming extracted temp dir %s -> %s: %v", extractedTemp, extracted, err)
		}
	}

	localBase := extracted
	assetBase := ""

	walker := func(localPath string, info os.FileInfo, err error) error {
		if err != nil {
			return fmt.Errorf("error descending into path %q: %v", localPath, err)
		}

		if info.IsDir() {
			return nil
		}

		relativePath, err := filepath.Rel(localBase, localPath)
		if err != nil {
			return fmt.Errorf("error finding relative path for %q: %v", localPath, err)
		}

		assetPath := path.Join(assetBase, relativePath)
		key := info.Name()
		r := NewFileResource(localPath)

		asset := &asset{
			Key:       key,
			AssetPath: assetPath,
			resource:  r,
			source:    &Source{Parent: archiveSource, ExtractFromArchive: assetPath},
		}
		klog.V(2).Infof("added asset %q for %q", asset.Key, asset.resource)
		a.assets = append(a.assets, asset)

		return nil
	}

	err := filepath.Walk(localBase, walker)
	if err != nil {
		return fmt.Errorf("error adding expanded asset files in %q: %v", extracted, err)
	}
	return nil
}