package internal

import (
	"bytes"
	"cloud.google.com/go/storage"
	"context"
	"crypto/sha1"
	"encoding/hex"
	"fmt"
	"github.com/bluekeyes/go-gitdiff/gitdiff"
	"github.com/cavaliercoder/go-cpio"
	"github.com/cavaliercoder/go-rpm"
	"github.com/go-git/go-billy/v5/memfs"
	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/config"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/object"
	"github.com/go-git/go-git/v5/plumbing/transport/ssh"
	"github.com/go-git/go-git/v5/storage/memory"
	"io"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"os/user"
	"path/filepath"
	"strings"
	"time"
)

type ProcessData struct {
	RpmLocation       string
	UpstreamPrefix    string
	SshKeyLocation    string
	SshUser           string
	Branch            string
	Bucket            *storage.BucketHandle
	GitCommitterName  string
	GitCommitterEmail string
}

func strContains(a []string, b string) bool {
	for _, val := range a {
		if val == b {
			return true
		}
	}

	return false
}

// ProcessRPM checks the RPM specs and discards any remote files
// This functions also sorts files into directories
// .spec files goes into -> SPECS
// metadata files goes to root
// source files goes into -> SOURCES
// all files that are remote goes into .gitignore
// all ignored files' hash goes into .{name}.metadata
func ProcessRPM(pd *ProcessData) {
	cmd := exec.Command("rpm2cpio", pd.RpmLocation)
	cpioBytes, err := cmd.Output()
	if err != nil {
		log.Fatalf("could not convert to cpio (maybe rpm2cpio is missing): %v", err)
	}

	// create in memory git repository
	repo, err := git.Init(memory.NewStorage(), memfs.New())
	if err != nil {
		log.Fatalf("could not init git repo: %v", err)
	}

	// read the rpm in cpio format
	buf := bytes.NewReader(cpioBytes)
	r := cpio.NewReader(buf)
	fileWrites := map[string][]byte{}
	for {
		hdr, err := r.Next()
		if err == io.EOF {
			// end of cpio archive
			break
		}
		if err != nil {
			log.Fatalln(err)
		}

		bts, err := ioutil.ReadAll(r)
		if err != nil {
			log.Fatalf("could not copy file to virtual filesystem: %v", err)
		}
		fileWrites[hdr.Name] = bts
	}

	w, err := repo.Worktree()
	if err != nil {
		log.Fatalf("could not get worktree: %v", err)
	}

	// create structure
	err = w.Filesystem.MkdirAll("SPECS", 0755)
	if err != nil {
		log.Fatalf("could not create SPECS dir in vfs: %v", err)
	}
	err = w.Filesystem.MkdirAll("SOURCES", 0755)
	if err != nil {
		log.Fatalf("could not create SOURCES dir in vfs: %v", err)
	}

	f, err := os.Open(pd.RpmLocation)
	if err != nil {
		log.Fatalf("could not open the file again: %v", err)
	}
	rpmFile, err := rpm.ReadPackageFile(f)
	if err != nil {
		log.Fatalf("could not read package, invalid?: %v", err)
	}

	var sourcesToIgnore []string
	for _, source := range rpmFile.Source() {
		if strings.Contains(source, ".tar") {
			sourcesToIgnore = append(sourcesToIgnore, source)
		}
	}

	// create a new remote
	remoteUrl := fmt.Sprintf("%s/dist/%s.git", pd.UpstreamPrefix, rpmFile.Name())
	log.Printf("using remote: %s", remoteUrl)
	refspec := config.RefSpec(fmt.Sprintf("+refs/heads/%s:refs/remotes/origin/%s", pd.Branch, pd.Branch))
	log.Printf("using refspec: %s", refspec)

	_, err = repo.CreateRemote(&config.RemoteConfig{
		Name:  "origin",
		URLs:  []string{remoteUrl},
		Fetch: []config.RefSpec{refspec},
	})
	if err != nil {
		log.Fatalf("could not create remote: %v", err)
	}

	lastKeyLocation := pd.SshKeyLocation
	if lastKeyLocation == "" {
		usr, err := user.Current()
		if err != nil {
			log.Fatalf("could not get user: %v", err)
		}
		lastKeyLocation = filepath.Join(usr.HomeDir, ".ssh/id_rsa")
	}
	// create ssh key authenticator
	authenticator, err := ssh.NewPublicKeysFromFile(pd.SshUser, lastKeyLocation, "")
	if err != nil {
		log.Fatalf("could not get git authenticator: %v", err)
	}
	err = repo.Fetch(&git.FetchOptions{
		RemoteName: "origin",
		RefSpecs:   []config.RefSpec{refspec},
		Auth:       authenticator,
	})

	refName := plumbing.NewBranchReferenceName(pd.Branch)
	log.Printf("set reference to ref: %s", refName)

	if err != nil {
		h := plumbing.NewSymbolicReference(plumbing.HEAD, refName)
		if err := repo.Storer.CheckAndSetReference(h, nil); err != nil {
			log.Fatalf("could not set reference: %v", err)
		}
	} else {
		err = w.Checkout(&git.CheckoutOptions{
			Branch: plumbing.NewRemoteReferenceName("origin", pd.Branch),
			Force:  true,
		})
		if err != nil {
			log.Fatalf("could not checkout: %v", err)
		}
	}

	// TODO: Remove dangling files

	for fileName, contents := range fileWrites {
		var newPath string
		if filepath.Ext(fileName) == ".spec" {
			newPath = filepath.Join("SPECS", fileName)
		} else {
			newPath = filepath.Join("SOURCES", fileName)
		}

		mode := os.FileMode(0666)
		for _, file := range rpmFile.Files() {
			if file.Name() == fileName {
				mode = file.Mode()
			}
		}

		// add the file to the virtual filesystem
		// we will move it to correct destination later
		f, err := w.Filesystem.OpenFile(newPath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, mode)
		if err != nil {
			log.Fatalf("could not create file %s: %v", fileName, err)
		}

		_, err = f.Write(contents)
		if err != nil {
			log.Fatalf("could not write to file %s: %v", fileName, err)
		}

		_ = f.Close()

		// don't add ignored file to git
		if strContains(sourcesToIgnore, fileName) {
			continue
		}

		_, err = w.Add(newPath)
		if err != nil {
			log.Fatalf("could not add source file: %v", err)
		}
	}

	// add sources to ignore (remote sources)
	gitIgnore, err := w.Filesystem.Create(".gitignore")
	if err != nil {
		log.Fatalf("could not create .gitignore: %v", err)
	}
	for _, ignore := range sourcesToIgnore {
		line := fmt.Sprintf("SOURCES/%s\n", ignore)
		_, err := gitIgnore.Write([]byte(line))
		if err != nil {
			log.Fatalf("could not write line to .gitignore: %v", err)
		}
	}
	err = gitIgnore.Close()
	if err != nil {
		log.Fatalf("could not close .gitignore: %v", err)
	}

	// check if patches exist
	_, err = w.Filesystem.Stat("ROCKY")
	if err == nil {
		// check SRPM patches
		_, err = w.Filesystem.Stat("ROCKY/SRPM")
		if err == nil {
			// iterate through patches
			infos, err := w.Filesystem.ReadDir("ROCKY/SRPM")
			if err != nil {
				log.Fatalf("could not walk patches: %v", err)
			}

			for _, info := range infos {
				// can only process .patch files
				if !strings.HasSuffix(info.Name(), ".patch") {
					continue
				}

				log.Printf("applying %s", info.Name())
				filePath := filepath.Join("ROCKY/SRPM", info.Name())

				patch, err := w.Filesystem.Open(filePath)
				if err != nil {
					log.Fatalf("could not open patch file %s: %v", info.Name(), err)
				}
				files, _, err := gitdiff.Parse(patch)
				if err != nil {
					log.Fatalf("could not parse patch file: %v", err)
				}

				for _, patchedFile := range files {
					srcPath := patchedFile.NewName
					if !strings.HasPrefix(srcPath, "SPECS") {
						srcPath = filepath.Join("SOURCES", patchedFile.NewName)
					}
					var output bytes.Buffer
					if !patchedFile.IsDelete && !patchedFile.IsNew {
						patchSubjectFile, err := w.Filesystem.Open(srcPath)
						if err != nil {
							log.Fatalf("could not open patch subject: %v", err)
						}

						err = gitdiff.NewApplier(patchSubjectFile).ApplyFile(&output, patchedFile)
						if err != nil {
							log.Fatalf("could not apply patch: %v", err)
						}
					}

					oldName := filepath.Join("SOURCES", patchedFile.OldName)
					_ = w.Filesystem.Remove(oldName)
					_ = w.Filesystem.Remove(srcPath)

					if patchedFile.IsNew {
						newFile, err := w.Filesystem.Create(srcPath)
						if err != nil {
							log.Fatalf("could not create new file: %v", err)
						}
						err = gitdiff.NewApplier(newFile).ApplyFile(&output, patchedFile)
						if err != nil {
							log.Fatalf("could not apply patch: %v", err)
						}
						_, err = newFile.Write(output.Bytes())
						if err != nil {
							log.Fatalf("could not write post-patch file: %v", err)
						}
						_, err = w.Add(srcPath)
						if err != nil {
							log.Fatalf("could not add file %s to git: %v", srcPath, err)
						}
						log.Printf("git add %s", srcPath)
					} else if !patchedFile.IsDelete {
						newFile, err := w.Filesystem.Create(srcPath)
						if err != nil {
							log.Fatalf("could not create post-patch file: %v", err)
						}
						_, err = newFile.Write(output.Bytes())
						if err != nil {
							log.Fatalf("could not write post-patch file: %v", err)
						}
						_, err = w.Add(srcPath)
						if err != nil {
							log.Fatalf("could not add file %s to git: %v", srcPath, err)
						}
						log.Printf("git add %s", srcPath)
					} else {
						_, err = w.Remove(oldName)
						if err != nil {
							log.Fatalf("could not remove file %s to git: %v", oldName, err)
						}
						log.Printf("git rm %s", oldName)
					}
				}

				_, err = w.Add(filePath)
				if err != nil {
					log.Fatalf("could not add file %s to git: %v", filePath, err)
				}
				log.Printf("git add %s", filePath)
			}
		}
	}

	// get ignored files sha1 hash and add to .{name}.metadata
	metadataFile := fmt.Sprintf(".%s.metadata", rpmFile.Name())
	metadata, err := w.Filesystem.Create(metadataFile)
	if err != nil {
		log.Fatalf("could not create metadata file: %v", err)
	}
	for _, source := range sourcesToIgnore {
		sourcePath := "SOURCES/" + source
		sourceFile, err := w.Filesystem.Open(sourcePath)
		if err != nil {
			log.Fatalf("could not open ignored source file %s: %v", sourcePath, err)
		}
		sourceFileBts, err := ioutil.ReadAll(sourceFile)
		if err != nil {
			log.Fatalf("could not read the whole of ignored source file: %v", err)
		}

		ctx := context.Background()
		gcsPath := fmt.Sprintf("%s-%s/%s", rpmFile.Name(), pd.Branch, source)
		obj := pd.Bucket.Object(gcsPath)
		w := obj.NewWriter(ctx)
		_, err = w.Write(sourceFileBts)
		if err != nil {
			log.Fatalf("could not write tarball to gcs: %v", err)
		}
		// Close, just like writing a file.
		if err := w.Close(); err != nil {
			log.Fatalf("could not close gcs writer to source %s: %v", source, err)
		}
		log.Printf("wrote %s to gcs", gcsPath)

		checksum := sha1.Sum(sourceFileBts)
		checksumLine := fmt.Sprintf("%s %s\n", hex.EncodeToString(checksum[:]), sourcePath)
		_, err = metadata.Write([]byte(checksumLine))
		if err != nil {
			log.Fatalf("could not write to metadata file: %v", err)
		}
	}

	lastFilesToAdd := []string{metadataFile, ".gitignore", "SPECS"}
	for _, f := range lastFilesToAdd {
		_, err := w.Add(f)
		if err != nil {
			log.Fatalf("could not add metadata file: %v", err)
		}
	}

	// show status
	status, _ := w.Status()
	log.Printf("successfully processed:\n%s", status)

	var hashes []plumbing.Hash
	var pushRefspecs []config.RefSpec

	head, err := repo.Head()
	if err != nil {
		hashes = nil
		pushRefspecs = nil
	} else {
		log.Printf("tip %s", head.String())
		hashes = append(hashes, head.Hash())
		refOrigin := "refs/heads/" + pd.Branch
		pushRefspecs = append(pushRefspecs, config.RefSpec(fmt.Sprintf("HEAD:%s", refOrigin)))
	}

	// we are now finished with the tree and are going to push it to the src repo
	// create import commit
	commit, err := w.Commit("import "+filepath.Base(pd.RpmLocation), &git.CommitOptions{
		Author: &object.Signature{
			Name:  pd.GitCommitterName,
			Email: pd.GitCommitterEmail,
			When:  time.Now(),
		},
		Parents: hashes,
	})
	if err != nil {
		log.Fatalf("could not commit object: %v", err)
	}

	obj, err := repo.CommitObject(commit)
	if err != nil {
		log.Fatalf("could not get commit object: %v", err)
	}

	log.Printf("committed:\n%s", obj.String())

	err = repo.Push(&git.PushOptions{
		RemoteName: "origin",
		Auth:       authenticator,
		RefSpecs:   pushRefspecs,
	})
	if err != nil {
		log.Fatalf("could not push to remote: %v", err)
	}
}