// Package repository contains helper methods for working with the Git repo.
package repository

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

	"github.com/go-git/go-billy/v5"
	"github.com/go-git/go-billy/v5/osfs"

	"github.com/MichaelMure/git-bug/util/lamport"
)

const (
	clockPath = "git-bug"
)

var _ ClockedRepo = &GitRepo{}
var _ TestedRepo = &GitRepo{}

// GitRepo represents an instance of a (local) git repository.
type GitRepo struct {
	gitCli
	path string

	clocksMutex sync.Mutex
	clocks      map[string]lamport.Clock

	keyring Keyring
}

// NewGitRepo determines if the given working directory is inside of a git repository,
// and returns the corresponding GitRepo instance if it is.
func NewGitRepo(path string, clockLoaders []ClockLoader) (*GitRepo, error) {
	k, err := defaultKeyring()
	if err != nil {
		return nil, err
	}

	repo := &GitRepo{
		gitCli:  gitCli{path: path},
		path:    path,
		clocks:  make(map[string]lamport.Clock),
		keyring: k,
	}

	// Check the repo and retrieve the root path
	stdout, err := repo.runGitCommand("rev-parse", "--absolute-git-dir")

	// Now dir is fetched with "git rev-parse --git-dir". May be it can
	// still return nothing in some cases. Then empty stdout check is
	// kept.
	if err != nil || stdout == "" {
		return nil, ErrNotARepo
	}

	// Fix the path to be sure we are at the root
	repo.path = stdout
	repo.gitCli.path = stdout

	for _, loader := range clockLoaders {
		allExist := true
		for _, name := range loader.Clocks {
			if _, err := repo.getClock(name); err != nil {
				allExist = false
			}
		}

		if !allExist {
			err = loader.Witnesser(repo)
			if err != nil {
				return nil, err
			}
		}
	}

	return repo, nil
}

// InitGitRepo create a new empty git repo at the given path
func InitGitRepo(path string) (*GitRepo, error) {
	repo := &GitRepo{
		gitCli: gitCli{path: path},
		path:   path + "/.git",
		clocks: make(map[string]lamport.Clock),
	}

	_, err := repo.runGitCommand("init", path)
	if err != nil {
		return nil, err
	}

	return repo, nil
}

// InitBareGitRepo create a new --bare empty git repo at the given path
func InitBareGitRepo(path string) (*GitRepo, error) {
	repo := &GitRepo{
		gitCli: gitCli{path: path},
		path:   path,
		clocks: make(map[string]lamport.Clock),
	}

	_, err := repo.runGitCommand("init", "--bare", path)
	if err != nil {
		return nil, err
	}

	return repo, nil
}

// LocalConfig give access to the repository scoped configuration
func (repo *GitRepo) LocalConfig() Config {
	return newGitConfig(repo.gitCli, false)
}

// GlobalConfig give access to the global scoped configuration
func (repo *GitRepo) GlobalConfig() Config {
	return newGitConfig(repo.gitCli, true)
}

// AnyConfig give access to a merged local/global configuration
func (repo *GitRepo) AnyConfig() ConfigRead {
	return mergeConfig(repo.LocalConfig(), repo.GlobalConfig())
}

// Keyring give access to a user-wide storage for secrets
func (repo *GitRepo) Keyring() Keyring {
	return repo.keyring
}

// GetPath returns the path to the repo.
func (repo *GitRepo) GetPath() string {
	return repo.path
}

// GetUserName returns the name the the user has used to configure git
func (repo *GitRepo) GetUserName() (string, error) {
	return repo.runGitCommand("config", "user.name")
}

// GetUserEmail returns the email address that the user has used to configure git.
func (repo *GitRepo) GetUserEmail() (string, error) {
	return repo.runGitCommand("config", "user.email")
}

// GetCoreEditor returns the name of the editor that the user has used to configure git.
func (repo *GitRepo) GetCoreEditor() (string, error) {
	return repo.runGitCommand("var", "GIT_EDITOR")
}

// GetRemotes returns the configured remotes repositories.
func (repo *GitRepo) GetRemotes() (map[string]string, error) {
	stdout, err := repo.runGitCommand("remote", "--verbose")
	if err != nil {
		return nil, err
	}

	lines := strings.Split(stdout, "\n")
	remotes := make(map[string]string, len(lines))

	for _, line := range lines {
		if strings.TrimSpace(line) == "" {
			continue
		}
		elements := strings.Fields(line)
		if len(elements) != 3 {
			return nil, fmt.Errorf("git remote: unexpected output format: %s", line)
		}

		remotes[elements[0]] = elements[1]
	}

	return remotes, nil
}

// LocalStorage return a billy.Filesystem giving access to $RepoPath/.git/git-bug
func (repo *GitRepo) LocalStorage() billy.Filesystem {
	return osfs.New(repo.path)
}

// FetchRefs fetch git refs from a remote
func (repo *GitRepo) FetchRefs(remote, refSpec string) (string, error) {
	stdout, err := repo.runGitCommand("fetch", remote, refSpec)

	if err != nil {
		return stdout, fmt.Errorf("failed to fetch from the remote '%s': %v", remote, err)
	}

	return stdout, err
}

// PushRefs push git refs to a remote
func (repo *GitRepo) PushRefs(remote string, refSpec string) (string, error) {
	stdout, stderr, err := repo.runGitCommandRaw(nil, "push", remote, refSpec)

	if err != nil {
		return stdout + stderr, fmt.Errorf("failed to push to the remote '%s': %v", remote, stderr)
	}
	return stdout + stderr, nil
}

// StoreData will store arbitrary data and return the corresponding hash
func (repo *GitRepo) StoreData(data []byte) (Hash, error) {
	var stdin = bytes.NewReader(data)

	stdout, err := repo.runGitCommandWithStdin(stdin, "hash-object", "--stdin", "-w")

	return Hash(stdout), err
}

// ReadData will attempt to read arbitrary data from the given hash
func (repo *GitRepo) ReadData(hash Hash) ([]byte, error) {
	var stdout bytes.Buffer
	var stderr bytes.Buffer

	err := repo.runGitCommandWithIO(nil, &stdout, &stderr, "cat-file", "-p", string(hash))

	if err != nil {
		return []byte{}, err
	}

	return stdout.Bytes(), nil
}

// StoreTree will store a mapping key-->Hash as a Git tree
func (repo *GitRepo) StoreTree(entries []TreeEntry) (Hash, error) {
	buffer := prepareTreeEntries(entries)

	stdout, err := repo.runGitCommandWithStdin(&buffer, "mktree")

	if err != nil {
		return "", err
	}

	return Hash(stdout), nil
}

// StoreCommit will store a Git commit with the given Git tree
func (repo *GitRepo) StoreCommit(treeHash Hash) (Hash, error) {
	stdout, err := repo.runGitCommand("commit-tree", string(treeHash))

	if err != nil {
		return "", err
	}

	return Hash(stdout), nil
}

// StoreCommitWithParent will store a Git commit with the given Git tree
func (repo *GitRepo) StoreCommitWithParent(treeHash Hash, parent Hash) (Hash, error) {
	stdout, err := repo.runGitCommand("commit-tree", string(treeHash),
		"-p", string(parent))

	if err != nil {
		return "", err
	}

	return Hash(stdout), nil
}

// UpdateRef will create or update a Git reference
func (repo *GitRepo) UpdateRef(ref string, hash Hash) error {
	_, err := repo.runGitCommand("update-ref", ref, string(hash))

	return err
}

// RemoveRef will remove a Git reference
func (repo *GitRepo) RemoveRef(ref string) error {
	_, err := repo.runGitCommand("update-ref", "-d", ref)

	return err
}

// ListRefs will return a list of Git ref matching the given refspec
func (repo *GitRepo) ListRefs(refPrefix string) ([]string, error) {
	stdout, err := repo.runGitCommand("for-each-ref", "--format=%(refname)", refPrefix)

	if err != nil {
		return nil, err
	}

	split := strings.Split(stdout, "\n")

	if len(split) == 1 && split[0] == "" {
		return []string{}, nil
	}

	return split, nil
}

// RefExist will check if a reference exist in Git
func (repo *GitRepo) RefExist(ref string) (bool, error) {
	stdout, err := repo.runGitCommand("for-each-ref", ref)

	if err != nil {
		return false, err
	}

	return stdout != "", nil
}

// CopyRef will create a new reference with the same value as another one
func (repo *GitRepo) CopyRef(source string, dest string) error {
	_, err := repo.runGitCommand("update-ref", dest, source)

	return err
}

// ListCommits will return the list of commit hashes of a ref, in chronological order
func (repo *GitRepo) ListCommits(ref string) ([]Hash, error) {
	stdout, err := repo.runGitCommand("rev-list", "--first-parent", "--reverse", ref)

	if err != nil {
		return nil, err
	}

	split := strings.Split(stdout, "\n")

	casted := make([]Hash, len(split))
	for i, line := range split {
		casted[i] = Hash(line)
	}

	return casted, nil

}

// ReadTree will return the list of entries in a Git tree
func (repo *GitRepo) ReadTree(hash Hash) ([]TreeEntry, error) {
	stdout, err := repo.runGitCommand("ls-tree", string(hash))

	if err != nil {
		return nil, err
	}

	return readTreeEntries(stdout)
}

// FindCommonAncestor will return the last common ancestor of two chain of commit
func (repo *GitRepo) FindCommonAncestor(hash1 Hash, hash2 Hash) (Hash, error) {
	stdout, err := repo.runGitCommand("merge-base", string(hash1), string(hash2))

	if err != nil {
		return "", err
	}

	return Hash(stdout), nil
}

// GetTreeHash return the git tree hash referenced in a commit
func (repo *GitRepo) GetTreeHash(commit Hash) (Hash, error) {
	stdout, err := repo.runGitCommand("rev-parse", string(commit)+"^{tree}")

	if err != nil {
		return "", err
	}

	return Hash(stdout), nil
}

// GetOrCreateClock return a Lamport clock stored in the Repo.
// If the clock doesn't exist, it's created.
func (repo *GitRepo) GetOrCreateClock(name string) (lamport.Clock, error) {
	c, err := repo.getClock(name)
	if err == nil {
		return c, nil
	}
	if err != ErrClockNotExist {
		return nil, err
	}

	repo.clocksMutex.Lock()
	defer repo.clocksMutex.Unlock()

	c, err = lamport.NewPersistedClock(repo.LocalStorage(), name+"-clock")
	if err != nil {
		return nil, err
	}

	repo.clocks[name] = c
	return c, nil
}

func (repo *GitRepo) getClock(name string) (lamport.Clock, error) {
	repo.clocksMutex.Lock()
	defer repo.clocksMutex.Unlock()

	if c, ok := repo.clocks[name]; ok {
		return c, nil
	}

	c, err := lamport.LoadPersistedClock(repo.LocalStorage(), name+"-clock")
	if err == nil {
		repo.clocks[name] = c
		return c, nil
	}
	if err == lamport.ErrClockNotExist {
		return nil, ErrClockNotExist
	}
	return nil, err
}

// AddRemote add a new remote to the repository
// Not in the interface because it's only used for testing
func (repo *GitRepo) AddRemote(name string, url string) error {
	_, err := repo.runGitCommand("remote", "add", name, url)

	return err
}

// GetLocalRemote return the URL to use to add this repo as a local remote
func (repo *GitRepo) GetLocalRemote() string {
	return repo.path
}

// EraseFromDisk delete this repository entirely from the disk
func (repo *GitRepo) EraseFromDisk() error {
	path := filepath.Clean(strings.TrimSuffix(repo.path, string(filepath.Separator)+".git"))

	// fmt.Println("Cleaning repo:", path)
	return os.RemoveAll(path)
}